1
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Apken LH, Barz H, Beel S, Michalke E, Rasche R, Verma A, Ricker A, Nüsse H, Klingauf J, Kerl K, Wardelmann E, Kümmel D, Steinestel K, Pethő Z, Meisterernst M, Oeckinghaus A. RalGAP complexes control secretion and primary cilia in pancreatic disease. Life Sci Alliance 2025; 8:e202403123. [PMID: 40490362 DOI: 10.26508/lsa.202403123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2024] [Revised: 05/26/2025] [Accepted: 05/27/2025] [Indexed: 06/11/2025] Open
Abstract
κB-Ras/RalGAP complexes limit the activity of Ral GTPases, which function in EGFR/Ras signaling. RalGAP expression is down-regulated in pancreatic cancer; however, the role of RalGAP and Ral GTPases in tumor development in vivo remained unclear. Here, we show that pancreatic RalGAPβ deficiency alone is sufficient to induce inflammation and neoplasia in vivo. We identify that this phenotype is triggered by disturbance of the secretory pathway and polarized exocytosis in acinar cells, demonstrating that RalGAP complexes uphold spatial control of Ral activity. We furthermore show that RALGAPβ deficiency results in defective primary cilium assembly, a process required for efficient acinar regeneration upon inflammation. Only primary cilium formation depends on κB-Ras proteins, suggesting that κB-Ras proteins are not essential for all RalGAP complex-controlled processes. In combination with an oncogenic KRAS G12D mutation, RalGAPβ deficiency leads to a dramatic shortening of tumor latency and median survival. Our results highlight an important role of RalGAP/Ral signaling in upholding acinar cell identity and preventing pancreatic cancer development.
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Affiliation(s)
- Lisa H Apken
- Institute of Molecular Tumor Biology, Faculty of Medicine, University Münster, Münster, Germany
| | - Hannah Barz
- Institute of Biochemistry, University Münster, Münster, Germany
| | - Stephanie Beel
- Institute of Molecular Tumor Biology, Faculty of Medicine, University Münster, Münster, Germany
| | - Esther Michalke
- Institute of Molecular Tumor Biology, Faculty of Medicine, University Münster, Münster, Germany
| | - René Rasche
- Institute of Biochemistry, University Münster, Münster, Germany
| | - Archana Verma
- Department of Pediatric Hematology and Oncology, University Children's Hospital Münster, Münster, Germany
| | - Andrea Ricker
- Institute of Medical Physics and Biophysics, University Münster, Münster, Germany
| | - Harald Nüsse
- Institute of Medical Physics and Biophysics, University Münster, Münster, Germany
| | - Jürgen Klingauf
- Institute of Medical Physics and Biophysics, University Münster, Münster, Germany
| | - Kornelius Kerl
- Department of Pediatric Hematology and Oncology, University Children's Hospital Münster, Münster, Germany
| | - Eva Wardelmann
- Gerhard-Domagk-Institute of Pathology, Faculty of Medicine, University Münster, Münster, Germany
| | - Daniel Kümmel
- Institute of Biochemistry, University Münster, Münster, Germany
| | - Konrad Steinestel
- Institute of Pathology and Molecular Pathology, Bundeswehrkrankenhaus Ulm, Ulm, Germany
| | - Zoltán Pethő
- Institute of Physiology II, University Münster, Münster, Germany
| | - Michael Meisterernst
- Institute of Molecular Tumor Biology, Faculty of Medicine, University Münster, Münster, Germany
| | - Andrea Oeckinghaus
- Institute of Molecular Tumor Biology, Faculty of Medicine, University Münster, Münster, Germany
- Department of Metabolism, Senescence and Autophagy, Research Center One Health Ruhr, University Alliance Ruhr and University Hospital Essen, University Duisburg-Essen, Essen, Germany
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2
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Zhou D, Zeng Y, Luo W, Leng C, Li C. Senior-Loken Syndrome: Ocular Perspectives on Genetics, Pathogenesis, and Management. Biomolecules 2025; 15:667. [PMID: 40427560 PMCID: PMC12109206 DOI: 10.3390/biom15050667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2025] [Revised: 05/02/2025] [Accepted: 05/03/2025] [Indexed: 05/29/2025] Open
Abstract
Senior-Loken syndrome (SLSN) is a group of rare autosomal recessive disorders caused by dysfunction of the primary cilium, primarily affecting the kidneys (typically leading to nephronophthisis) and eyes (typically leading to retinal degeneration). Moreover, patients with SLSN may experience additional multisystemic symptoms, such as developmental delay, intellectual disability, ataxia, and nystagmus. To date, eight genes have been demonstrated to cause SLSN, all encoding for proteins involved in the structure and functions of the primary cilium. This places SLSN within an expanding category of diseases known as "ciliopathies". Due to the genetic heterogeneity and significant phenotypic overlap with other ciliopathies, establishing a definitive diagnosis during the initial consultation remains a challenge for clinicians. Furthermore, current research on SLSN-related ciliopathies predominantly focuses on renal involvement, while the ocular manifestations remain insufficiently explored and lack a comprehensive review. Therefore, with the goal of offering practical guidance for clinical practice, this review aims to provide a comprehensive overview of the clinical features, along with an ocular perspective on the molecular mechanisms, genetic underpinnings, and advances in the treatment of SLSN.
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Affiliation(s)
- Di Zhou
- Center for Drug Evaluation, National Medical Products Administration, Beijing 100076, China;
| | - Yi Zeng
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (Y.Z.); (W.L.)
| | - Weihan Luo
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (Y.Z.); (W.L.)
| | - Chenyang Leng
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (Y.Z.); (W.L.)
| | - Chen Li
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (Y.Z.); (W.L.)
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3
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Huang W, Chen ZA, Li QY, Huang CF, Lin YX, Lan YM, Zhang ZP, Jiang YF, Qin QW, Sun HY. EXOC8 of Epinephelus coioides involved in SGIV infection via innate immunity and apoptosis. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2025; 166:105368. [PMID: 40189122 DOI: 10.1016/j.dci.2025.105368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2024] [Revised: 03/30/2025] [Accepted: 03/31/2025] [Indexed: 04/14/2025]
Abstract
The exocyst complex (EXOC) plays a major role in the extracellular secretion of organisms. In this study, EXOC8, a member of the EXOC family, was characterized from Epinephelus coioides,an important economical important fish in southern China and Southeast Asia, and its role response to viral infection was explored. The full length of E. coioides EXOC8 is 3091 bp including a 2061 bp open reading frame (ORF) encoding 686 amino acids, with a molecular mass of 79037.42 Da. The mRNA of E. coioides EXOC8 can be detected in all of the tissues examined with different levels. E. coioides EXOC8 is distributed in the cytoplasm. The expression of E. coioides EXOC8 was up-regulated during Singapore grouper iridovirus (SGIV) infection, an important pathogen of E. coioides. Overexpressing E. coioides EXOC8 significantly promoted the formation of cytopathic effects (CPE) caused by SGIV infection and the expressions of SGIV key genes MCP, VP19, LITAF and ICP18; but significantly inhibited the activities of NF-κB/AP-1 promoter, apoptosis induced by SGIV, and the expressions of inflammatory factors (IL-6,IL-8, IL-1β and TNF-α) in E. coioides. The results demonstrated that E. coioides EXOC8 may be involved in SGIV infection, providing a theoretical basis for clearing the mechanisms of viral infection in fish.
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Affiliation(s)
- Wei Huang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Zi-An Chen
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Qi-Yin Li
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Cui-Fen Huang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Yun-Xiang Lin
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Yin-Mei Lan
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Ze-Peng Zhang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Yu-Feng Jiang
- Department of Laboratory, Jining No.1 People's Hospital, Shandong, 272111, PR China.
| | - Qi-Wei Qin
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Hong-Yan Sun
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China.
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Volpiana MW, Nenadic A, Beh CT. Regulation of yeast polarized exocytosis by phosphoinositide lipids. Cell Mol Life Sci 2024; 81:457. [PMID: 39560727 DOI: 10.1007/s00018-024-05483-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2024] [Revised: 10/01/2024] [Accepted: 10/18/2024] [Indexed: 11/20/2024]
Abstract
Phosphoinositides help steer membrane trafficking routes within eukaryotic cells. In polarized exocytosis, which targets vesicular cargo to sites of polarized growth at the plasma membrane (PM), the two phosphoinositides phosphatidylinositol 4-phosphate (PI4P) and its derivative phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) pave the pathway for vesicle transport from the Golgi to the PM. PI4P is a critical regulator of mechanisms that shape late Golgi membranes for vesicle biogenesis and release. Although enriched in vesicle membranes, PI4P is inexplicably removed from post-Golgi vesicles during their transit to the PM, which drives subsequent steps in exocytosis. At the PM, PI(4,5)P2 recruits effectors that establish polarized membrane sites for targeting the vesicular delivery of secretory cargo. The budding yeast Saccharomyces cerevisiae provides an elegant model to unravel the complexities of phosphoinositide regulation during polarized exocytosis. Here, we review how PI4P and PI(4,5)P2 promote yeast vesicle biogenesis, exocyst complex assembly and vesicle docking at polarized cortical sites, and suggest how these steps might impact related mechanisms of human disease.
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Affiliation(s)
- Matthew W Volpiana
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
- Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, BC, Canada.
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5
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Lei YR, He JY, Fu XM, Huang CF, Lin YX, Dai LL, Chen ZA, Zhang ZP, Liu FM, Qin QW, Sun HY. Epinephelus coioides Sec3 promotes Singapore grouper iridovirus infection by negatively regulates immune response. FISH & SHELLFISH IMMUNOLOGY 2024; 152:109784. [PMID: 39067495 DOI: 10.1016/j.fsi.2024.109784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2024] [Revised: 06/19/2024] [Accepted: 07/19/2024] [Indexed: 07/30/2024]
Abstract
Exocyst, a protein complex, plays a crucial role in various cellular functions, including cell polarization, migration, invasion, cytokinesis, and autophagy. Sec3, known as Exoc1, is a key subunit of the Exocyst complex and can be involved in cell survival and apoptosis. In this study, two subtypes of Sec3 were isolated from Epinephelus coioides, an important marine fish in China. The role of E. coioides Sec3 was explored during Singapore grouper iridovirus (SGIV) infection, an important pathogen of marine fish which could induce 90 % mortality. E. coioides Sec3 sequences showed a high similarity with that from other species, indicating the presence of a conserved Sec3 superfamily domain. E. coioides Sec3 mRNA could be detected in all examined tissues, albeit at varying expression levels. SGIV infection could upregulate E. coioides Sec3 mRNA. Upregulated Sec3 significantly promoted SGIV-induced CPE, and the expressions of viral key genes. E. coioides Sec3 could inhibit the activation of NF-κB and AP-1, as well as SGIV-induced cell apoptosis. The results illustrated that E. coioides Sec3 promotes SGIV infection by regulating the innate immune response.
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Affiliation(s)
- Yu-Rong Lei
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Jia-Yang He
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Xue-Mei Fu
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Cui-Fen Huang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Yun-Xiang Lin
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Li-Ling Dai
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Zi-An Chen
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Ze-Peng Zhang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Fu-Min Liu
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China
| | - Qi-Wei Qin
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China.
| | - Hong-Yan Sun
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong Province, PR China.
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Wu H, Nguyen H, Hashim PH, Fogelgren B, Duncan FE, Ward WS. Oocyte-specific EXOC5 expression is required for mouse oogenesis and folliculogenesis. Mol Hum Reprod 2024; 30:gaae026. [PMID: 39037927 PMCID: PMC11299862 DOI: 10.1093/molehr/gaae026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Revised: 07/11/2024] [Indexed: 07/24/2024] Open
Abstract
EXOC5 is a crucial component of a large multi-subunit tethering complex, the exocyst complex, that is required for fusion of secretory vesicles with the plasma membrane. Exoc5 deleted mice die as early embryos. Therefore, to determine the role of EXOC5 in follicular and oocyte development, it was necessary to produce a conditional knockout (cKO), Zp3-Exoc5-cKO, in which Exoc5 was deleted only in oocytes. The first wave of folliculogenesis appeared histologically normal and progressed to the antral stage. However, after IVF with normal sperm, oocytes collected from the first wave (superovulated 21-day-old cKO mice) were shown to be developmentally incompetent. Adult follicular waves did not progress beyond the secondary follicle stage where they underwent apoptosis. Female cKO mice were infertile. Overall, these data suggest that the first wave of folliculogenesis is less sensitive to oocyte-specific loss of Exoc5, but the resulting gametes have reduced developmental competence. In contrast, subsequent waves of folliculogenesis require oocyte-specific Exoc5 for development past the preantral follicle stage. The Zp3-Exoc5-cKO mouse provides a model for disrupting folliculogenesis that also enables the separation between the first and subsequent waves of folliculogenesis.
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Affiliation(s)
- Hongwen Wu
- Department of Anatomy, Biochemistry & Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
- Department of Obstetrics, Gynecology & Women’s Health, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Hieu Nguyen
- Department of Anatomy, Biochemistry & Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
- Department of Obstetrics, Gynecology & Women’s Health, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Prianka H Hashim
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry & Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
- Department of Obstetrics, Gynecology & Women’s Health, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Francesca E Duncan
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - W Steven Ward
- Department of Anatomy, Biochemistry & Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
- Department of Obstetrics, Gynecology & Women’s Health, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI, USA
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Zuo X, Winkler B, Lerner K, Ilatovskaya DV, Zamaro AS, Dang Y, Su Y, Deng P, Fitzgibbon W, Hartman J, Park KM, Lipschutz JH. Cilia-deficient renal tubule cells are primed for injury with mitochondrial defects and aberrant tryptophan metabolism. Am J Physiol Renal Physiol 2024; 327:F61-F76. [PMID: 38721661 PMCID: PMC11390130 DOI: 10.1152/ajprenal.00225.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 04/11/2024] [Accepted: 04/24/2024] [Indexed: 06/21/2024] Open
Abstract
The exocyst and Ift88 are necessary for primary ciliogenesis. Overexpression of Exoc5 (OE), a central exocyst component, resulted in longer cilia and enhanced injury recovery. Mitochondria are involved in acute kidney injury (AKI). To investigate cilia and mitochondria, basal respiration and mitochondrial maximal and spare respiratory capacity were measured in Exoc5 OE, Exoc5 knockdown (KD), Exoc5 ciliary targeting sequence mutant (CTS-mut), control Madin-Darby canine kidney (MDCK), Ift88 knockout (KO), and Ift88 rescue cells. In Exoc5 KD, Exoc5 CTS-mut, and Ift88 KO cells, these parameters were decreased. In Exoc5 OE and Ift88 rescue cells they were increased. Reactive oxygen species were higher in Exoc5 KD, Exoc5 CTS-mut, and Ift88 KO cells compared with Exoc5 OE, control, and Ift88 rescue cells. By electron microscopy, mitochondria appeared abnormal in Exoc5 KD, Exoc5 CTS-mut, and Ift88 KO cells. A metabolomics screen of control, Exoc5 KD, Exoc5 CTS-mut, Exoc5 OE, Ift88 KO, and Ift88 rescue cells showed a marked increase in tryptophan levels in Exoc5 CTS-mut (113-fold) and Exoc5 KD (58-fold) compared with control cells. A 21% increase was seen in Ift88 KO compared with rescue cells. In Exoc5 OE compared with control cells, tryptophan was decreased 59%. To determine the effects of ciliary loss on AKI, we generated proximal tubule-specific Exoc5 and Ift88 KO mice. These mice had loss of primary cilia, decreased mitochondrial ATP synthase, and increased tryptophan in proximal tubules with greater injury following ischemia-reperfusion. These data indicate that cilia-deficient renal tubule cells are primed for injury with mitochondrial defects in tryptophan metabolism.NEW & NOTEWORTHY Mitochondria are centrally involved in acute kidney injury (AKI). Here, we show that cilia-deficient renal tubule cells both in vitro in cell culture and in vivo in mice are primed for injury with mitochondrial defects and aberrant tryptophan metabolism. These data suggest therapeutic strategies such as enhancing ciliogenesis or improving mitochondrial function to protect patients at risk for AKI.
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Affiliation(s)
- Xiaofeng Zuo
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Brennan Winkler
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Kasey Lerner
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Daria V Ilatovskaya
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, United States
| | - Aleksandra S Zamaro
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, United States
| | - Yujing Dang
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Yanhui Su
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Peifeng Deng
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Wayne Fitzgibbon
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Jessica Hartman
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Kwon Moo Park
- Department of Anatomy, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
- Department of Medicine, Ralph H. Johnson Veterans Affairs Health Care System, Charleston, South Carolina, United States
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Kong MJ, Han SJ, Seu SY, Han KH, Lipschutz JH, Park KM. High water intake induces primary cilium elongation in renal tubular cells. Kidney Res Clin Pract 2024; 43:313-325. [PMID: 37933114 PMCID: PMC11181044 DOI: 10.23876/j.krcp.23.087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 07/25/2023] [Accepted: 07/27/2023] [Indexed: 11/08/2023] Open
Abstract
BACKGROUND The primary cilium protrudes from the cell surface and functions as a mechanosensor. Recently, we found that water intake restriction shortens the primary cilia of renal tubular cells, and a blockage of the shortening disturbs the ability of the kidneys to concentrate urine. Here, we investigate whether high water intake (HWI) alters primary cilia length, and if so, what is its underlying mechanism and its role on kidney urine production. METHODS Experimental mice were given free access to normal water (normal water intake) or 3% sucrose-containing water for HWI for 2 days. Some mice were administered with U0126 (10 mg/kg body weight), an inhibitor of MEK kinase, from 2 days before HWI, daily. The primary cilium length and urine amount and osmolality were investigated. RESULTS HWI-induced diluted urine production and primary cilium elongation in renal tubular cells. HWI increased the expression of α-tubulin acetyltransferase 1 (αTAT1), leading to the acetylation of α-tubulins, a core protein of the primary cilia. HWI also increased phosphorylated ERK1/2 (p-ERK1/2) and exocyst complex component 5 (Exoc5) expression in the kidneys. U0126 blocked HWI-induced increases in αTAT1, p-ERK1/2, and Exoc5 expression. U0126 inhibited HWI-induced α-tubulin acetylation, primary cilium elongation, urine amount increase, and urine osmolality decrease. CONCLUSION These results show that increased water intake elongates the primary cilia via ERK1/2 activation and that ERK inhibition prevents primary cilium elongation and diluted urine production. These data suggest that the elongation of primary cilium length is associated with the production of diluted urine.
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Affiliation(s)
- Min Jung Kong
- Department of Anatomy, BK21 Plus, and Cardiovascular Research Institute, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Sang Jun Han
- Department of Anatomy, BK21 Plus, and Cardiovascular Research Institute, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
- Department of Biotechnology, College of Fisheries Science, Pukyong National University, Busan, Republic of Korea
| | - Sung Young Seu
- Department of Anatomy, BK21 Plus, and Cardiovascular Research Institute, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Ki-Hwan Han
- Department of Anatomy, Ewha Womans University School of Medicine, Seoul, Republic of Korea
| | - Joshua H. Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC, USA
- Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA
| | - Kwon Moo Park
- Department of Anatomy, BK21 Plus, and Cardiovascular Research Institute, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
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9
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Niedziółka SM, Datta S, Uśpieński T, Baran B, Skarżyńska W, Humke EW, Rohatgi R, Niewiadomski P. The exocyst complex and intracellular vesicles mediate soluble protein trafficking to the primary cilium. Commun Biol 2024; 7:213. [PMID: 38378792 PMCID: PMC10879184 DOI: 10.1038/s42003-024-05817-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 01/15/2024] [Indexed: 02/22/2024] Open
Abstract
The efficient transport of proteins into the primary cilium is a crucial step for many signaling pathways. Dysfunction of this process can lead to the disruption of signaling cascades or cilium assembly, resulting in developmental disorders and cancer. Previous studies on the protein delivery to the cilium were mostly focused on the membrane-embedded receptors. In contrast, how soluble proteins are delivered into the cilium is poorly understood. In our work, we identify the exocyst complex as a key player in the ciliary trafficking of soluble Gli transcription factors. In line with the known function of the exocyst in intracellular vesicle transport, we demonstrate that soluble proteins, including Gli2/3 and Lkb1, can use the endosome recycling machinery for their delivery to the primary cilium. Finally, we identify GTPases: Rab14, Rab18, Rab23, and Arf4 that are involved in vesicle-mediated Gli protein ciliary trafficking. Our data pave the way for a better understanding of ciliary transport and uncover transport mechanisms inside the cell.
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Affiliation(s)
- S M Niedziółka
- Centre of New Technologies, University of Warsaw, Warsaw, Poland
- Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - S Datta
- Centre of New Technologies, University of Warsaw, Warsaw, Poland
| | - T Uśpieński
- Centre of New Technologies, University of Warsaw, Warsaw, Poland
- Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - B Baran
- Centre of New Technologies, University of Warsaw, Warsaw, Poland
- Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - W Skarżyńska
- Centre of New Technologies, University of Warsaw, Warsaw, Poland
| | - E W Humke
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
- IGM Biosciences, Inc, Mountain View, CA, USA
| | - R Rohatgi
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA
| | - P Niewiadomski
- Centre of New Technologies, University of Warsaw, Warsaw, Poland.
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10
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Guleria VS, Quadri N, Prasad K, Das R, Upadhyai P. Early insights into the role of Exoc6B associated with spondyloepimetaphyseal dysplasia with joint laxity type 3 in primary ciliogenesis and chondrogenic differentiation in vitro. Mol Biol Rep 2024; 51:274. [PMID: 38305850 DOI: 10.1007/s11033-023-09114-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 12/06/2023] [Indexed: 02/03/2024]
Abstract
BACKGROUND Spondyloepimetaphyseal dysplasia with joint laxity type 3 (SEMDJL3) is a rare skeletal dysplasia associated with EXOC6B, a component of the exocyst complex, involved in vesicle tethering and exocytosis at the plasma membrane. So far, EXOC6B and the pathomechanisms underlying SEMDJL3 remain obscure. METHODS AND RESULTS Exoc6b was detected largely at the perinuclear regions and the primary cilia base in ATDC5 prechondrocytes. Its shRNA lentiviral knockdown impeded primary ciliogenesis. In Exoc6b silenced prechondrocytes, Hedgehog signaling was attenuated, including when stimulated with Smoothened agonist. Exoc6b knockdown deregulated the mRNA and protein levels of Col2a1, a marker of chondrocyte proliferation at 7- and 14-days following differentiation. It led to the upregulation of Ihh another marker of proliferative chondrocytes. The levels of Col10a1, a marker of chondrocyte hypertrophy was enhanced at 14 days of differentiation. Congruently, Axin2, a canonical Wnt pathway modulator that inhibits chondrocyte hypertrophy was repressed. The expression of Mmp13 and Adamts4 that are terminal chondrocyte hypertrophy markers involved in extracellular matrix (ECM) remodelling were downregulated at 7 and 14 days of chondrogenesis. Bglap that encodes for the most abundant non-collagenous bone matrix constituent and promotes ECM calcification was suppressed at 14 days of chondrocyte differentiation. ECM mineralization was assessed by Alizarin Red staining. Gene expression and ciliogenesis were investigated by reverse transcription quantitative real-time PCR, immunoblotting, and immunocytochemistry. CONCLUSIONS These findings provide initial insights into the potential role of Exoc6b in primary ciliogenesis and chondrogenic differentiation, contributing towards a preliminary understanding of the molecular pathomechanisms underlying SEMDJL3.
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Affiliation(s)
- Vishal Singh Guleria
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Neha Quadri
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Keshava Prasad
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, India
| | - Ranajit Das
- Division of Data Analytics, Bioinformatics and Structural Biology, Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, India
| | - Priyanka Upadhyai
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India.
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11
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Pazos I, Puig‐Tintó M, Betancur L, Cordero J, Jiménez‐Menéndez N, Abella M, Hernández AC, Duran AG, Adachi‐Fernández E, Belmonte‐Mateos C, Sabido‐Bozo S, Tosi S, Nezu A, Oliva B, Colombelli J, Graham TR, Yoshimori T, Muñiz M, Hamasaki M, Gallego O. The P4-ATPase Drs2 interacts with and stabilizes the multisubunit tethering complex TRAPPIII in yeast. EMBO Rep 2023; 24:e56134. [PMID: 36929574 PMCID: PMC10157312 DOI: 10.15252/embr.202256134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 02/10/2023] [Accepted: 02/17/2023] [Indexed: 03/17/2023] Open
Abstract
Multisubunit Tethering Complexes (MTCs) are a set of conserved protein complexes that tether vesicles at the acceptor membrane. Interactions with other components of the trafficking machinery regulate MTCs through mechanisms that are partially understood. Here, we systematically investigate the interactome that regulates MTCs. We report that P4-ATPases, a family of lipid flippases, interact with MTCs that participate in the anterograde and retrograde transport at the Golgi, such as TRAPPIII. We use the P4-ATPase Drs2 as a paradigm to investigate the mechanism and biological relevance of this interplay during transport of Atg9 vesicles. Binding of Trs85, the sole-specific subunit of TRAPPIII, to the N-terminal tail of Drs2 stabilizes TRAPPIII on membranes loaded with Atg9 and is required for Atg9 delivery during selective autophagy, a role that is independent of P4-ATPase canonical functions. This mechanism requires a conserved I(S/R)TTK motif that also mediates the interaction of the P4-ATPases Dnf1 and Dnf2 with MTCs, suggesting a broader role of P4-ATPases in MTC regulation.
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Affiliation(s)
- Irene Pazos
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Marta Puig‐Tintó
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Laura Betancur
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Jorge Cordero
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | | | - Marc Abella
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Altair C Hernández
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Ana G Duran
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Emi Adachi‐Fernández
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Carla Belmonte‐Mateos
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
| | - Susana Sabido‐Bozo
- Department of Cell BiologyUniversity of SevilleSevilleSpain
- Instituto de Biomedicina de Sevilla (IBiS)Hospital Universitario Virgen del Rocío/CSIC/Universidad de SevillaSevilleSpain
| | - Sébastien Tosi
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST)BarcelonaSpain
| | - Akiko Nezu
- Department of Genetics, Graduate School of MedicineOsaka UniversityOsakaJapan
- Department of Intracellular Membrane Dynamics, Graduate School of Frontier BiosciencesOsaka UniversityOsakaJapan
| | - Baldomero Oliva
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
- Structural Bioinformatics Lab (GRIB‐IMIM)BarcelonaSpain
| | - Julien Colombelli
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST)BarcelonaSpain
| | - Todd R Graham
- Department of Biological SciencesVanderbilt UniversityNashvilleTNUSA
| | - Tamotsu Yoshimori
- Department of Genetics, Graduate School of MedicineOsaka UniversityOsakaJapan
- Department of Intracellular Membrane Dynamics, Graduate School of Frontier BiosciencesOsaka UniversityOsakaJapan
| | - Manuel Muñiz
- Department of Cell BiologyUniversity of SevilleSevilleSpain
- Instituto de Biomedicina de Sevilla (IBiS)Hospital Universitario Virgen del Rocío/CSIC/Universidad de SevillaSevilleSpain
| | - Maho Hamasaki
- Department of Genetics, Graduate School of MedicineOsaka UniversityOsakaJapan
- Department of Intracellular Membrane Dynamics, Graduate School of Frontier BiosciencesOsaka UniversityOsakaJapan
| | - Oriol Gallego
- Department of Medicine and Life Sciences (MELIS)Pompeu Fabra University (UPF)BarcelonaSpain
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12
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Pereira C, Stalder D, Anderson GS, Shun-Shion AS, Houghton J, Antrobus R, Chapman MA, Fazakerley DJ, Gershlick DC. The exocyst complex is an essential component of the mammalian constitutive secretory pathway. J Cell Biol 2023; 222:e202205137. [PMID: 36920342 PMCID: PMC10041652 DOI: 10.1083/jcb.202205137] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 11/11/2022] [Accepted: 02/01/2023] [Indexed: 03/16/2023] Open
Abstract
Secreted proteins fulfill a vast array of functions, including immunity, signaling, and extracellular matrix remodeling. In the trans-Golgi network, proteins destined for constitutive secretion are sorted into post-Golgi carriers which fuse with the plasma membrane. The molecular machinery involved is poorly understood. Here, we have used kinetic trafficking assays and transient CRISPR-KO to study biosynthetic sorting from the Golgi to the plasma membrane. Depletion of all canonical exocyst subunits causes cargo accumulation in post-Golgi carriers. Exocyst subunits are recruited to and co-localize with carriers. Exocyst abrogation followed by kinetic trafficking assays of soluble cargoes results in intracellular cargo accumulation. Unbiased secretomics reveals impairment of soluble protein secretion after exocyst subunit knockout. Importantly, in specialized cell types, the loss of exocyst prevents constitutive secretion of antibodies in lymphocytes and of leptin in adipocytes. These data identify exocyst as the functional tether of secretory post-Golgi carriers at the plasma membrane and an essential component of the mammalian constitutive secretory pathway.
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Affiliation(s)
- Conceição Pereira
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Danièle Stalder
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | | | - Amber S. Shun-Shion
- Metabolic Research Laboratory, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Jack Houghton
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Robin Antrobus
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | | | - Daniel J. Fazakerley
- Metabolic Research Laboratory, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - David C. Gershlick
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
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13
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Safavian D, Kim MS, Xie H, El-Zeiry M, Palander O, Dai L, Collins RF, Froese C, Shannon R, Nagata KI, Trimble WS. Septin-mediated RhoA activation engages the exocyst complex to recruit the cilium transition zone. J Cell Biol 2023; 222:e201911062. [PMID: 36912772 PMCID: PMC10039714 DOI: 10.1083/jcb.201911062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 01/25/2022] [Accepted: 01/05/2023] [Indexed: 03/14/2023] Open
Abstract
Septins are filamentous GTPases that play important but poorly characterized roles in ciliogenesis. Here, we show that SEPTIN9 regulates RhoA signaling at the base of cilia by binding and activating the RhoA guanine nucleotide exchange factor, ARHGEF18. GTP-RhoA is known to activate the membrane targeting exocyst complex, and suppression of SEPTIN9 causes disruption of ciliogenesis and mislocalization of an exocyst subunit, SEC8. Using basal body-targeted proteins, we show that upregulating RhoA signaling at the cilium can rescue ciliary defects and mislocalization of SEC8 caused by global SEPTIN9 depletion. Moreover, we demonstrate that the transition zone components, RPGRIP1L and TCTN2, fail to accumulate at the transition zone in cells lacking SEPTIN9 or depleted of the exocyst complex. Thus, SEPTIN9 regulates the recruitment of transition zone proteins on Golgi-derived vesicles by activating the exocyst via RhoA to allow the formation of primary cilia.
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Affiliation(s)
- Darya Safavian
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Moshe S. Kim
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Hong Xie
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Maha El-Zeiry
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Oliva Palander
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Lu Dai
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Richard F. Collins
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Carol Froese
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Rachel Shannon
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Koh-ichi Nagata
- Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan
| | - William S. Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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14
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Bigge BM, Rosenthal NE, Avasthi P. Initial ciliary assembly in Chlamydomonas requires Arp2/3 complex-dependent endocytosis. Mol Biol Cell 2023; 34:ar24. [PMID: 36753382 PMCID: PMC10092647 DOI: 10.1091/mbc.e22-09-0443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Ciliary assembly, trafficking, and regulation are dependent on microtubules, but the mechanisms of ciliary assembly also require the actin cytoskeleton. Here, we dissect subcellular roles of actin in ciliogenesis by focusing on actin networks nucleated by the Arp2/3 complex in the powerful ciliary model, Chlamydomonas. We find that the Arp2/3 complex is required for the initial stages of ciliary assembly when protein and membrane are in high demand but cannot yet be supplied from the Golgi complex. We provide evidence for Arp2/3 complex-dependent endocytosis of ciliary proteins, an increase in endocytic activity upon induction of ciliary growth, and relocalization of plasma membrane proteins to newly formed cilia.
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Affiliation(s)
- Brae M Bigge
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755; Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS 66103
| | - Nicholas E Rosenthal
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755; Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS 66103
| | - Prachee Avasthi
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755; Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS 66103
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15
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Zhao H, Khan Z, Westlake CJ. Ciliogenesis membrane dynamics and organization. Semin Cell Dev Biol 2023; 133:20-31. [PMID: 35351373 PMCID: PMC9510604 DOI: 10.1016/j.semcdb.2022.03.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/17/2022] [Accepted: 03/18/2022] [Indexed: 12/28/2022]
Abstract
Ciliogenesis is a complex multistep process used to describe assembly of cilia and flagella. These organelles play essential roles in motility and signaling on the surface of cells. Cilia are built at the distal ends of centrioles through the formation of an axoneme that is surrounded by the ciliary membrane. As is the case in the biogenesis of other cellular organelles, regulators of membrane trafficking play essential roles in ciliogenesis, albeit with a unique feature that membranes are organized around microtubule-based structures. Membrane association with the distal end of the centriole is a critical initiating step for ciliogenesis. Studies of this process in different cell types suggests that a singular mechanism may not be utilized to initiate cilium assembly. In this review, we focus on recent insights into cilium biogenesis and the roles membrane trafficking regulators play in described ciliogenesis mechanisms with relevance to human disease.
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Affiliation(s)
- Huijie Zhao
- Center for Cancer Research, NCI Frederick, Laboratory of Cellular and Developmental, Signaling, Frederick, MD 21702, USA
| | - Ziam Khan
- Center for Cancer Research, NCI Frederick, Laboratory of Cellular and Developmental, Signaling, Frederick, MD 21702, USA
| | - Christopher J Westlake
- Center for Cancer Research, NCI Frederick, Laboratory of Cellular and Developmental, Signaling, Frederick, MD 21702, USA.
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16
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Simsek-Kiper PO, Jacob P, Upadhyai P, Taşkıran ZE, Guleria VS, Karaosmanoglu B, Imren G, Gocmen R, Bhavani GS, Kausthubham N, Shah H, Utine GE, Boduroglu K, Girisha KM. Biallelic loss-of-function variants in EXOC6B are associated with impaired primary ciliogenesis and cause spondylo-epi-metaphyseal dysplasia with joint laxity type 3. Hum Mutat 2022; 43:2116-2129. [PMID: 36150098 PMCID: PMC7615863 DOI: 10.1002/humu.24478] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 08/30/2022] [Accepted: 09/21/2022] [Indexed: 01/25/2023]
Abstract
Spondylo-epi-metaphyseal dysplasias with joint laxity, type 3 (SEMDJL3) is a genetic skeletal disorder characterized by multiple joint dislocations, caused by biallelic pathogenic variants in the EXOC6B gene. Only four individuals from two families have been reported to have this condition to date. The molecular pathogenesis related to primary ciliogenesis has not been enumerated in subjects with SEMDJL3. In this study, we report two additional affected individuals from unrelated families with biallelic pathogenic variants, c.2122+15447_2197-59588del and c.401T>G in EXOC6B identified by exome sequencing. One of the affected individuals had an intellectual disability and central nervous system anomalies, including hydrocephalus, hypoplastic mesencephalon, and thin corpus callosum. Using the fibroblast cell lines, we demonstrate the primary evidence for the abrogation of exocytosis in an individual with SEMDLJ3 leading to impaired primary ciliogenesis. Osteogenesis differentiation and pathways related to the extracellular matrix were also found to be reduced. Additionally, we provide a review of the clinical and molecular profile of all the mutation-proven patients reported hitherto, thereby further characterizing SEMDJL3. SEMDJL3 with biallelic pathogenic variants in EXOC6B might represent yet another ciliopathy with central nervous system involvement and joint dislocations.
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Affiliation(s)
| | - Prince Jacob
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Priyanka Upadhyai
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Zihni Ekim Taşkıran
- Department of Medical Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Vishal S. Guleria
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Beren Karaosmanoglu
- Department of Medical Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Gozde Imren
- Department of Medical Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Rahsan Gocmen
- Department of Radiology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Gandham S. Bhavani
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Neethukrishna Kausthubham
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Hitesh Shah
- Department of Pediatric Orthopaedics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Gulen Eda Utine
- Department of Pediatric Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Koray Boduroglu
- Department of Pediatric Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Katta M. Girisha
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
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17
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Luxmi R, King SM. Isolation of ciliary ectosomes and analysis of amidated peptide-mediated chemotaxis in Chlamydomonas. Methods Cell Biol 2022; 175:163-175. [PMID: 36967139 DOI: 10.1016/bs.mcb.2022.09.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Ciliary ectosomes are vesicles that bud from the ciliary membrane. Isolation and analysis of these structures can shed light on their bioactive cargoes and identify proteins and biomolecules involved in intercellular communication and various physiological processes. Most published methods to isolate ciliary ectosomes are based on their size (100nm to 1μm) to separate cilia-derived vesicles from isolated cilia and/or intact cells. However, it is often difficult to determine the origin of extracellular vesicles and to distinguish ciliary ectosomes from ectosomes budded from the plasma membrane or from exosomes that derive from multivesicular bodies. Here, we describe procedures to isolate and purify ciliary ectosomes from the unicellular green alga, Chlamydomonas reinhardtii, through differential and iodixanol density gradient ultracentrifugation; in this organism, the ciliary membrane is the only membrane directly exposed to the environment and thus ectosomes are of known origin. Ciliary ectosomes contain enzymes and α-amidated peptide products required to mediate peptidergic-signaling cascades; one identified amidated peptide acts as a chemotactic modulator for C. reinhardtii gametes. Classical methods used to assess chemotaxis do not provide quantitative measurements of the chemotactic gradient or the real-time effects on the migration of fast moving cells. Consequently, we developed a chemotaxis assay protocol using microfluidic channel slides that provides quantitative and qualitative measurements of the chemotactic gradient and cell migration. Here, we describe how to establish a stable gradient of a bioactive substance in microfluidic channel slides and perform quantitative assays to assess chemotaxis of both individual cells and populations of C. reinhardtii.
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Affiliation(s)
- Raj Luxmi
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, United States.
| | - Stephen M King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, United States.
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18
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Luxmi R, King SM. Cilia-derived vesicles: An ancient route for intercellular communication. Semin Cell Dev Biol 2022; 129:82-92. [PMID: 35346578 PMCID: PMC9378432 DOI: 10.1016/j.semcdb.2022.03.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/10/2022] [Accepted: 03/10/2022] [Indexed: 12/11/2022]
Abstract
Extracellular vesicles (EVs) provide a mechanism for intercellular communication that transports complex signals in membrane delimited structures between cells, tissues and organisms. Cells secrete EVs of various subtypes defined by the pathway leading to release and by the pathological condition of the cell. Cilia are evolutionarily conserved organelles that can act as sensory structures surveilling the extracellular environment. Here we discuss the secretory functions of cilia and their biological implications. Studies in multiple species - from the nematode Caenorhabditis elegans and the chlorophyte alga Chlamydomonas reinhardtii to mammals - have revealed that cilia shed bioactive EVs (ciliary EVs or ectosomes) by outward budding of the ciliary membrane. The content of ciliary EVs is distinct from that of other vesicles released by cells. Peptides regulate numerous aspects of metazoan physiology and development through evolutionarily conserved mechanisms. Intriguingly, cilia-derived vesicles have recently been found to mediate peptidergic signaling. C. reinhardtii releases the peptide α-amidating enzyme (PAM), bioactive amidated products and components of the peptidergic signaling machinery in ciliary EVs in a developmentally regulated manner. Considering the origin of cilia in early eukaryotes, it is likely that release of peptidergic signals in ciliary EVs represents an alternative and ancient mode of regulated secretion that cells can utilize in the absence of dedicated secretory granules.
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Affiliation(s)
- Raj Luxmi
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3305, USA.
| | - Stephen M King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3305, USA.
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19
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Nakamura NK, Tokunaga DS, Ha HY, Polgar N. The Exocyst Is Required for CD36 Fatty Acid Translocase Trafficking and Free Fatty Acid Uptake in Skeletal Muscle Cells. Cells 2022; 11:2440. [PMID: 35954283 PMCID: PMC9368548 DOI: 10.3390/cells11152440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 07/31/2022] [Accepted: 08/03/2022] [Indexed: 11/26/2022] Open
Abstract
In obesity, chronic membrane-localization of CD36 free fatty acid (FFA) translocase, but not other FFA transporters, enhances FFA uptake and intracellular lipid accumulation. This ectopic lipid accumulation promotes insulin resistance by inhibiting insulin-induced GLUT4 glucose transporter trafficking and glucose uptake. GLUT4 and CD36 cell surface delivery is triggered by insulin- and contraction-induced signaling, which share conserved downstream effectors. While we have gathered detailed knowledge on GLUT4 trafficking, the mechanisms regulating CD36 membrane delivery and subsequent FFA uptake in skeletal muscle are not fully understood. The exocyst trafficking complex facilitates the docking of membrane-bound vesicles, a process underlying the controlled surface delivery of fuel transporters. The exocyst regulates insulin-induced glucose uptake via GLUT4 membrane trafficking in adipocytes and skeletal muscle cells and plays a role in lipid uptake in adipocytes. Based on the high degree of conservation of the GLUT4 and CD36 trafficking mechanisms in adipose and skeletal muscle tissue, we hypothesized that the exocyst also contributes to lipid uptake in skeletal muscle and acts through the targeted plasma membrane delivery of CD36 in response to insulin and contraction. Here, we show that the exocyst complex is necessary for insulin- and contraction-induced CD36 membrane trafficking and FFA uptake in muscle cells.
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Affiliation(s)
| | | | | | - Noemi Polgar
- Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA
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20
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Zebrafish and inherited photoreceptor disease: Models and insights. Prog Retin Eye Res 2022; 91:101096. [PMID: 35811244 DOI: 10.1016/j.preteyeres.2022.101096] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/20/2022] [Accepted: 06/23/2022] [Indexed: 11/21/2022]
Abstract
Photoreceptor dysfunctions and degenerative diseases are significant causes of vision loss in patients, with few effective treatments available. Targeted interventions to prevent or reverse photoreceptor-related vision loss are not possible without a thorough understanding of the underlying mechanism leading to disease, which is exceedingly difficult to accomplish in the human system. Cone diseases are particularly challenging to model, as some popular genetically modifiable model animals are nocturnal with a rod-dominant visual system and cones that have dissimilarities to human cones. As a result, cone diseases, which affect visual acuity, colour perception, and central vision in patients, are generally poorly understood in terms of pathology and mechanism. Zebrafish (Danio rerio) provide the opportunity to model photoreceptor diseases in a diurnal vertebrate with a cone-rich retina which develops many macular degeneration-like pathologies. Zebrafish undergo external development, allowing early-onset retinal diseases to be detected and studied, and many ophthalmic tools are available for zebrafish visual assessment during development and adulthood. There are numerous zebrafish models of photoreceptor disease, spanning the various types of photoreceptor disease (developmental, rod, cone, and mixed photoreceptor diseases) and genetic/molecular cause. In this review, we explore the features of zebrafish that make them uniquely poised to model cone diseases, summarize the established zebrafish models of inherited photoreceptor disease, and discuss how disease in these models compares to the human presentation, where applicable. Further, we highlight the contributions of these zebrafish models to our understanding of photoreceptor biology and disease, and discuss future directions for utilising and investigating these diverse models.
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21
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Abstract
Primary cilia play a key role in the ability of cells to respond to extracellular stimuli, such as signaling molecules and environmental cues. These sensory organelles are crucial to the development of many organ systems, and defects in primary ciliogenesis lead to multisystemic genetic disorders, known as ciliopathies. Here, we review recent advances in the understanding of several key aspects of the regulation of ciliogenesis. Primary ciliogenesis is thought to take different pathways depending on cell type, and some recent studies shed new light on the cell-type-specific mechanisms regulating ciliogenesis at the apical surface in polarized epithelial cells, which are particularly relevant for many ciliopathies. Furthermore, recent findings have demonstrated the importance of actin cytoskeleton dynamics in positively and negatively regulating multiple stages of ciliogenesis, including the vesicular trafficking of ciliary components and the positioning and docking of the basal body. Finally, studies on the formation of motile cilia in multiciliated epithelial cells have revealed requirements for actin remodeling in this process too, as well as showing evidence of an additional alternative ciliogenesis pathway.
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Affiliation(s)
| | - Rytis Prekeris
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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22
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Han SJ, Kim JI, Lipschutz JH, Park KM. Hydrogen sulfide, a gaseous signaling molecule, elongates primary cilia on kidney tubular epithelial cells by activating extracellular signal-regulated kinase. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2021; 25:593-601. [PMID: 34697270 PMCID: PMC8552824 DOI: 10.4196/kjpp.2021.25.6.593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/28/2021] [Accepted: 09/28/2021] [Indexed: 11/22/2022]
Abstract
Primary cilia on kidney tubular cells play crucial roles in maintaining structure and physiological function. Emerging evidence indicates that the absence of primary cilia, and their length, are associated with kidney diseases. The length of primary cilia in kidney tubular epithelial cells depends, at least in part, on oxidative stress and extracellular signal-regulated kinase 1/2 (ERK) activation. Hydrogen sulfide (H2S) is involved in antioxidant systems and the ERK signaling pathway. Therefore, in this study, we investigated the role of H2S in primary cilia elongation and the downstream pathway. In cultured Madin-Darby Canine Kidney cells, the length of primary cilia gradually increased up to 4 days after the cells were grown to confluent monolayers. In addition, the expression of H2S-producing enzyme increased concomitantly with primary cilia length. Treatment with NaHS, an exogenous H2S donor, accelerated the elongation of primary cilia whereas DL-propargylglycine (a cystathionine γ-lyase inhibitor) and hydroxylamine (a cystathionine-β-synthase inhibitor) delayed their elongation. NaHS treatment increased ERK activation and Sec10 and Arl13b protein expression, both of which are involved in cilia formation and elongation. Treatment with U0126, an ERK inhibitor, delayed elongation of primary cilia and blocked the effect of NaHS-mediated primary cilia elongation and Sec10 and Arl13b upregulation. Finally, we also found that H2S accelerated primary cilia elongation after ischemic kidney injury. These results indicate that H2S lengthens primary cilia through ERK activation and a consequent increase in Sec10 and Arl13b expression, suggesting that H2S and its downstream targets could be novel molecular targets for regulating primary cilia.
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Affiliation(s)
- Sang Jun Han
- Department of Biotechnology, College of Fisheries Sciences, Pukyong National University, Busan 48513, Korea
| | - Jee In Kim
- Department of Molecular Medicine, Keimyung University School of Medicine, Daegu 42601, Korea
| | - Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, SC 29425, USA.,Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29425, USA
| | - Kwon Moo Park
- Department of Anatomy, BK21 Plus, Cardiovascular Research Institute, School of Medicine, Kyungpook National University, Daegu 41944, Korea
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23
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Rivera-Molina FE, Xi Z, Reales E, Wang B, Toomre D. Exocyst complex mediates recycling of internal cilia. Curr Biol 2021; 31:5580-5589.e5. [PMID: 34678163 DOI: 10.1016/j.cub.2021.09.067] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 07/22/2021] [Accepted: 09/23/2021] [Indexed: 12/23/2022]
Abstract
Primary cilia are slender, cellular antennae that sense extracellular stimuli, and their absence or dysfunction plays a role in numerous human diseases. Prior work has indicated a role of the exocyst tethering complex in cilia biogenesis and maintenance,1-6 with the underlying paradigm that the exocyst targets vesicles to the ciliary base to deliver ciliary cargoes.7-9 However, the role of the exocyst vis-à-vis to primary cilia in living cells and during stimulation is unknown. Herein, using advanced imaging and quantitative analysis reveals that serum stimulation increases the exocyst's localization to cilia by three-fold. This serum-stimulated localization is highly dynamic, and FRAP experiments show that exocysts at the cilia are highly mobile (60%-80%). Super resolution imaging reveals that the xocyst extends past the cilia base to the entire ciliary pocket. To visualize cilia exocytosis, we conducted live cell imaging with pH-sensitive cilia reporters in combination with extracellular pH switching. Strikingly, we observed that an exocyst-positive internal cilia fuses with the cell surface. These live cell results support a novel and dynamic role of the exocyst complex in the delivery of internalized cilia to the cell surface. Moreover, they suggest a novel pathway may be used to recycle primary cilia to the cell surface that engages the exocyst in response to stimuli. This new remarkable plasticity in cilia presence on the surface in response to extracellular stimuli suggest new means to potentially modulate cilia signaling.
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Affiliation(s)
- Félix E Rivera-Molina
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA.
| | - Zhiqun Xi
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA
| | - Elena Reales
- Department of Regeneration and Cell Therapy, Andalusian Molecular Biology and Regenerative Medicine Centre (CABIMER), Seville, Spain
| | - Bryan Wang
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA
| | - Derek Toomre
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA.
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24
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An SJ, Rivera-Molina F, Anneken A, Xi Z, McNellis B, Polejaev VI, Toomre D. An active tethering mechanism controls the fate of vesicles. Nat Commun 2021; 12:5434. [PMID: 34521845 PMCID: PMC8440521 DOI: 10.1038/s41467-021-25465-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 08/05/2021] [Indexed: 11/09/2022] Open
Abstract
Vesicle tethers are thought to underpin the efficiency of intracellular fusion by bridging vesicles to their target membranes. However, the interplay between tethering and fusion has remained enigmatic. Here, through optogenetic control of either a natural tether-the exocyst complex-or an artificial tether, we report that tethering regulates the mode of fusion. We find that vesicles mainly undergo kiss-and-run instead of full fusion in the absence of functional exocyst. Full fusion is rescued by optogenetically restoring exocyst function, in a manner likely dependent on the stoichiometry of tether engagement with the plasma membrane. In contrast, a passive artificial tether produces mostly kissing events, suggesting that kiss-and-run is the default mode of vesicle fusion. Optogenetic control of tethering further shows that fusion mode has physiological relevance since only full fusion could trigger lamellipodial expansion. These findings demonstrate that active coupling between tethering and fusion is critical for robust membrane merger.
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Affiliation(s)
- Seong J An
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Alexander Anneken
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Zhiqun Xi
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Brian McNellis
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Vladimir I Polejaev
- International Science and Technology Center, Yale University School of Medicine, New Haven, CT, USA
| | - Derek Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
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25
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Mecklenburg N, Kowalczyk I, Witte F, Görne J, Laier A, Mamo TM, Gonschior H, Lehmann M, Richter M, Sporbert A, Purfürst B, Hübner N, Hammes A. Identification of disease-relevant modulators of the SHH pathway in the developing brain. Development 2021; 148:272000. [PMID: 34463328 DOI: 10.1242/dev.199307] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 07/19/2021] [Indexed: 12/13/2022]
Abstract
Pathogenic gene variants in humans that affect the sonic hedgehog (SHH) pathway lead to severe brain malformations with variable penetrance due to unknown modifier genes. To identify such modifiers, we established novel congenic mouse models. LRP2-deficient C57BL/6N mice suffer from heart outflow tract defects and holoprosencephaly caused by impaired SHH activity. These defects are fully rescued on a FVB/N background, indicating a strong influence of modifier genes. Applying comparative transcriptomics, we identified Pttg1 and Ulk4 as candidate modifiers upregulated in the rescue strain. Functional analyses showed that ULK4 and PTTG1, both microtubule-associated proteins, are positive regulators of SHH signaling, rendering the pathway more resilient to disturbances. In addition, we characterized ULK4 and PTTG1 as previously unidentified components of primary cilia in the neuroepithelium. The identification of genes that powerfully modulate the penetrance of genetic disturbances affecting the brain and heart is likely relevant to understanding the variability in human congenital disorders.
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Affiliation(s)
- Nora Mecklenburg
- Disorders of the Nervous System, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Izabela Kowalczyk
- Disorders of the Nervous System, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Franziska Witte
- Cardiovascular and Metabolic Sciences, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Jessica Görne
- Disorders of the Nervous System, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Alena Laier
- Disorders of the Nervous System, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Tamrat M Mamo
- Disorders of the Nervous System, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Hannes Gonschior
- Cellular Imaging, Light Microscopy, Leibniz-Research Institute for Molecular Pharmacology (FMP), 13125 Berlin, Germany
| | - Martin Lehmann
- Cellular Imaging, Light Microscopy, Leibniz-Research Institute for Molecular Pharmacology (FMP), 13125 Berlin, Germany
| | - Matthias Richter
- Advanced Light Microscopy Technology Platform, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Anje Sporbert
- Advanced Light Microscopy Technology Platform, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Bettina Purfürst
- Electron microscopy technology platform, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
| | - Norbert Hübner
- Cardiovascular and Metabolic Sciences, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Berlin, 10785 Berlin, Germany.,Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany.,Berlin Institute of Health (BIH), 10178 Berlin, Germany
| | - Annette Hammes
- Disorders of the Nervous System, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), 13125 Berlin, Germany
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26
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Loss of the exocyst complex component EXOC3 promotes hemostasis and accelerates arterial thrombosis. Blood Adv 2021; 5:674-686. [PMID: 33560379 DOI: 10.1182/bloodadvances.2020002515] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 12/28/2020] [Indexed: 11/20/2022] Open
Abstract
The exocyst is an octameric complex comprising 8 distinct protein subunits, exocyst complex components (EXOC) 1 to 8. It has an established role in tethering secretory vesicles to the plasma membrane, but its relevance to platelet granule secretion and function remains to be determined. Here, EXOC3 conditional knockout (KO) mice in the megakaryocyte/platelet lineage were generated to assess exocyst function in platelets. Significant defects in platelet aggregation, integrin activation, α-granule (P-selectin and platelet factor 4), dense granule, and lysosomal granule secretion were detected in EXOC3 KO platelets after treatment with a glycoprotein VI (GPVI)-selective agonist, collagen-related peptide (CRP). Except for P-selectin exposure, these defects were completely recovered by maximal CRP concentrations. GPVI surface levels were also significantly decreased by 14.5% in KO platelets, whereas defects in proximal GPVI signaling responses, Syk and LAT phosphorylation, and calcium mobilization were also detected, implying an indirect mechanism for these recoverable defects due to decreased surface GPVI. Paradoxically, dense granule secretion, integrin activation, and changes in surface expression of integrin αIIb (CD41) were significantly increased in KO platelets after protease-activated receptor 4 activation, but calcium responses were unaltered. Elevated integrin activation responses were completely suppressed with a P2Y12 receptor antagonist, suggesting enhanced dense granule secretion of adenosine 5'-diphosphate as a critical mediator of these responses. Finally, arterial thrombosis was significantly accelerated in KO mice, which also displayed improved hemostasis determined by reduced tail bleeding times. These findings reveal a regulatory role for the exocyst in controlling critical aspects of platelet function pertinent to thrombosis and hemostasis.
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27
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Rohrer B, Biswal MR, Obert E, Dang Y, Su Y, Zuo X, Fogelgren B, Kondkar AA, Lobo GP, Lipschutz JH. Conditional Loss of the Exocyst Component Exoc5 in Retinal Pigment Epithelium (RPE) Results in RPE Dysfunction, Photoreceptor Cell Degeneration, and Decreased Visual Function. Int J Mol Sci 2021; 22:5083. [PMID: 34064901 PMCID: PMC8151988 DOI: 10.3390/ijms22105083] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 04/29/2021] [Accepted: 05/07/2021] [Indexed: 11/17/2022] Open
Abstract
To characterize the mechanisms by which the highly conserved exocyst trafficking complex regulates eye physiology in zebrafish and mice, we focused on Exoc5 (also known as sec10), a central exocyst component. We analyzed both exoc5 zebrafish mutants and retinal pigmented epithelium (RPE)-specific Exoc5 knockout mice. Exoc5 is present in both the non-pigmented epithelium of the ciliary body and in the RPE. In this study, we set out to establish an animal model to study the mechanisms underlying the ocular phenotype and to establish if loss of visual function is induced by postnatal RPE Exoc5-deficiency. Exoc5-/- zebrafish had smaller eyes, with decreased number of melanocytes in the RPE and shorter photoreceptor outer segments. At 3.5 days post-fertilization, loss of rod and cone opsins were observed in zebrafish exoc5 mutants. Mice with postnatal RPE-specific loss of Exoc5 showed retinal thinning associated with compromised visual function and loss of visual photoreceptor pigments. Abnormal levels of RPE65 together with a reduced c-wave amplitude indicate a dysfunctional RPE. The retinal phenotype in Exoc5-/- mice was present at 20 weeks, but was more pronounced at 27 weeks, indicating progressive disease phenotype. We previously showed that the exocyst is necessary for photoreceptor ciliogenesis and retinal development. Here, we report that exoc5 mutant zebrafish and mice with RPE-specific genetic ablation of Exoc5 develop abnormal RPE pigmentation, resulting in retinal cell dystrophy and loss of visual pigments associated with compromised vision. Together, these data suggest that exocyst-mediated signaling in the RPE is required for RPE structure and function, indirectly leading to photoreceptor degeneration.
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Affiliation(s)
- Bärbel Rohrer
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA; (B.R.); (E.O.)
- Ralph H. Johnson VA Medical Center, Division of Research, Charleston, SC 29401, USA
| | - Manas R. Biswal
- Department of Pharmaceutical Sciences, Taneja College of Pharmacy, University of South Florida, Tampa, FL 33612, USA;
| | - Elisabeth Obert
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA; (B.R.); (E.O.)
| | - Yujing Dang
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (Y.D.); (Y.S.); (X.Z.); (J.H.L.)
| | - Yanhui Su
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (Y.D.); (Y.S.); (X.Z.); (J.H.L.)
| | - Xiaofeng Zuo
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (Y.D.); (Y.S.); (X.Z.); (J.H.L.)
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, HI 96813, USA;
| | - Altaf A. Kondkar
- Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia;
| | - Glenn P. Lobo
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA; (B.R.); (E.O.)
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (Y.D.); (Y.S.); (X.Z.); (J.H.L.)
- Department of Ophthalmology and Visual Neurosciences, Lions Research Building, 2001 6th Street SE., Room 225, University of Minnesota, Minneapolis, MN 55455, USA
| | - Joshua H. Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (Y.D.); (Y.S.); (X.Z.); (J.H.L.)
- Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29425, USA
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28
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Mohieldin AM, Pala R, Beuttler R, Moresco JJ, Yates JR, Nauli SM. Ciliary extracellular vesicles are distinct from the cytosolic extracellular vesicles. J Extracell Vesicles 2021; 10:e12086. [PMID: 33936569 PMCID: PMC8077156 DOI: 10.1002/jev2.12086] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 03/25/2021] [Accepted: 04/06/2021] [Indexed: 12/28/2022] Open
Abstract
Extracellular vesicles (EVs) are cell‐derived membrane vesicles that are released into the extracellular space. EVs encapsulate key proteins and mediate intercellular signalling pathways. Recently, primary cilia have been shown to release EVs under fluid‐shear flow, but many proteins encapsulated in these vesicles have never been identified. Primary cilia are ubiquitous mechanosensory organelles that protrude from the apical surface of almost all human cells. Primary cilia also serve as compartments for signalling pathways, and their defects have been associated with a wide range of human genetic diseases called ciliopathies. To better understand the mechanism of ciliopathies, it is imperative to know the distinctive protein profiles of the differently sourced EVs (cilia vs cytosol). Here, we isolated EVs from ciliated wild‐type (WT) and non‐ciliated IFT88 knockout (KO) mouse endothelial cells using fluid‐shear flow followed by a conventional method of EV isolation. EVs isolated from WT and KO exhibited distinctive sizes. Differences in EV protein contents were studied using liquid chromatography with tandem mass spectrometry (LC‐MS‐MS) and proteomic comparative analysis, which allowed us to classify proteins between ciliary EVs and cytosolic EVs derived from WT and KO, respectively. A total of 79 proteins were exclusively expressed in WT EVs, 145 solely in KO EVs, and 524 in both EVs. Our bioinformatics analyses revealed 29% distinct protein classes and 75% distinct signalling pathways between WT and KO EVs. Based on our statistical analyses and in vitro studies, we identified NADPH‐cytochrome P450 reductase (POR), and CD166 antigen (CD166) as potential biomarkers for ciliary and cytosolic EVs, respectively. Our protein‐protein interaction network analysis revealed that POR, but not CD166, interacted with either established or strong ciliopathy gene candidates. This report shows the unique differences between EVs secreted from cilia and the cytosol. These results will be important in advancing our understanding of human genetic diseases.
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Affiliation(s)
- Ashraf M Mohieldin
- Department of Biomedical & Pharmaceutical Sciences Chapman University Irvine California USA.,Department of Medicine University of California Irvine Irvine California USA
| | - Rajasekharreddy Pala
- Department of Biomedical & Pharmaceutical Sciences Chapman University Irvine California USA
| | - Richard Beuttler
- Department of Biomedical & Pharmaceutical Sciences Chapman University Irvine California USA
| | - James J Moresco
- Department of Molecular Medicine The Scripps Research Institute La Jolla California USA
| | - John R Yates
- Department of Molecular Medicine The Scripps Research Institute La Jolla California USA
| | - Surya M Nauli
- Department of Biomedical & Pharmaceutical Sciences Chapman University Irvine California USA.,Department of Medicine University of California Irvine Irvine California USA
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29
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Functional compartmentalization of photoreceptor neurons. Pflugers Arch 2021; 473:1493-1516. [PMID: 33880652 DOI: 10.1007/s00424-021-02558-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/15/2021] [Accepted: 03/22/2021] [Indexed: 12/16/2022]
Abstract
Retinal photoreceptors are neurons that convert dynamically changing patterns of light into electrical signals that are processed by retinal interneurons and ultimately transmitted to vision centers in the brain. They represent the essential first step in seeing without which the remainder of the visual system is rendered moot. To support this role, the major functions of photoreceptors are segregated into three main specialized compartments-the outer segment, the inner segment, and the pre-synaptic terminal. This compartmentalization is crucial for photoreceptor function-disruption leads to devastating blinding diseases for which therapies remain elusive. In this review, we examine the current understanding of the molecular and physical mechanisms underlying photoreceptor functional compartmentalization and highlight areas where significant knowledge gaps remain.
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30
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Van Bergen NJ, Ahmed SM, Collins F, Cowley M, Vetro A, Dale RC, Hock DH, de Caestecker C, Menezes M, Massey S, Ho G, Pisano T, Glover S, Gusman J, Stroud DA, Dinger M, Guerrini R, Macara IG, Christodoulou J. Mutations in the exocyst component EXOC2 cause severe defects in human brain development. J Exp Med 2021; 217:151928. [PMID: 32639540 PMCID: PMC7537385 DOI: 10.1084/jem.20192040] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/03/2020] [Accepted: 04/03/2020] [Indexed: 12/30/2022] Open
Abstract
The exocyst, an octameric protein complex, is an essential component of the membrane transport machinery required for tethering and fusion of vesicles at the plasma membrane. We report pathogenic variants in an exocyst subunit, EXOC2 (Sec5). Affected individuals have severe developmental delay, dysmorphism, and brain abnormalities; variability associated with epilepsy; and poor motor skills. Family 1 had two offspring with a homozygous truncating variant in EXOC2 that leads to nonsense-mediated decay of EXOC2 transcript, a severe reduction in exocytosis and vesicle fusion, and undetectable levels of EXOC2 protein. The patient from Family 2 had a milder clinical phenotype and reduced exocytosis. Cells from both patients showed defective Arl13b localization to the primary cilium. The discovery of mutations that partially disable exocyst function provides valuable insight into this essential protein complex in neural development. Since EXOC2 and other exocyst complex subunits are critical to neuronal function, our findings suggest that EXOC2 variants are the cause of the patients’ neurological disorders.
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Affiliation(s)
- Nicole J Van Bergen
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - Syed Mukhtar Ahmed
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN
| | - Felicity Collins
- Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Medical Genomics Department, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Mark Cowley
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.,St Vincent's Clinical School, University of New South Wales Sydney, Sydney, New South Wales, Australia.,Children's Cancer Institute, Kensington, New South Wales, Australia
| | - Annalisa Vetro
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy
| | - Russell C Dale
- Department of Paediatric Neurology, The Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Kids Neuroscience Centre, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Daniella H Hock
- Department of Biochemistry and Molecular Biology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Christian de Caestecker
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN
| | - Minal Menezes
- Kids Research, The Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Sean Massey
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Gladys Ho
- Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Tiziana Pisano
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy
| | - Seana Glover
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - Jovanka Gusman
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - David A Stroud
- Department of Biochemistry and Molecular Biology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Marcel Dinger
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.,School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington Campus, Sydney, New South Wales, Australia
| | - Renzo Guerrini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy
| | - Ian G Macara
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN
| | - John Christodoulou
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.,Victorian Clinical Genetics Services, Royal Children's Hospital, Parkville, Victoria, Australia
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31
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Abrams J, Nance J. A polarity pathway for exocyst-dependent intracellular tube extension. eLife 2021; 10:65169. [PMID: 33687331 PMCID: PMC8021397 DOI: 10.7554/elife.65169] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 03/08/2021] [Indexed: 12/25/2022] Open
Abstract
Lumen extension in intracellular tubes can occur when vesicles fuse with an invading apical membrane. Within the Caenorhabditis elegans excretory cell, which forms an intracellular tube, the exocyst vesicle-tethering complex is enriched at the lumenal membrane and is required for its outgrowth, suggesting that exocyst-targeted vesicles extend the lumen. Here, we identify a pathway that promotes intracellular tube extension by enriching the exocyst at the lumenal membrane. We show that PAR-6 and PKC-3/aPKC concentrate at the lumenal membrane and promote lumen extension. Using acute protein depletion, we find that PAR-6 is required for exocyst membrane recruitment, whereas PAR-3, which can recruit the exocyst in mammals, appears dispensable for exocyst localization and lumen extension. Finally, we show that CDC-42 and RhoGEF EXC-5/FGD regulate lumen extension by recruiting PAR-6 and PKC-3 to the lumenal membrane. Our findings reveal a pathway that connects CDC-42, PAR proteins, and the exocyst to extend intracellular tubes.
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Affiliation(s)
- Joshua Abrams
- Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, United States
| | - Jeremy Nance
- Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, United States.,Department of Cell Biology, NYU Grossman School of Medicine, New York, United States
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32
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Wiegering A, Dildrop R, Vesque C, Khanna H, Schneider-Maunoury S, Gerhardt C. Rpgrip1l controls ciliary gating by ensuring the proper amount of Cep290 at the vertebrate transition zone. Mol Biol Cell 2021; 32:675-689. [PMID: 33625872 PMCID: PMC8108517 DOI: 10.1091/mbc.e20-03-0190] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A range of severe human diseases called ciliopathies is caused by the dysfunction of primary cilia. Primary cilia are cytoplasmic protrusions consisting of the basal body (BB), the axoneme, and the transition zone (TZ). The BB is a modified mother centriole from which the axoneme, the microtubule-based ciliary scaffold, is formed. At the proximal end of the axoneme, the TZ functions as the ciliary gate governing ciliary protein entry and exit. Since ciliopathies often develop due to mutations in genes encoding proteins that localize to the TZ, the understanding of the mechanisms underlying TZ function is of eminent importance. Here, we show that the ciliopathy protein Rpgrip1l governs ciliary gating by ensuring the proper amount of Cep290 at the vertebrate TZ. Further, we identified the flavonoid eupatilin as a potential agent to tackle ciliopathies caused by mutations in RPGRIP1L as it rescues ciliary gating in the absence of Rpgrip1l.
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Affiliation(s)
- Antonia Wiegering
- Institute for Animal Developmental and Molecular Biology, Heinrich Heine University, 40225 Düsseldorf, Germany.,Sorbonne Université, CNRS UMR7622, INSERM U1156, Institut de Biologie Paris Seine (IBPS) - Developmental Biology Unit, 75005 Paris, France
| | - Renate Dildrop
- Institute for Animal Developmental and Molecular Biology, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Christine Vesque
- Sorbonne Université, CNRS UMR7622, INSERM U1156, Institut de Biologie Paris Seine (IBPS) - Developmental Biology Unit, 75005 Paris, France
| | - Hemant Khanna
- Department of Ophthalmology and Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Sylvie Schneider-Maunoury
- Sorbonne Université, CNRS UMR7622, INSERM U1156, Institut de Biologie Paris Seine (IBPS) - Developmental Biology Unit, 75005 Paris, France
| | - Christoph Gerhardt
- Institute for Animal Developmental and Molecular Biology, Heinrich Heine University, 40225 Düsseldorf, Germany
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Abstract
Ciliogenesis describes the assembly of cilia in interphase cells. Several hundred proteins have been linked to ciliogenesis, which proceeds through a highly coordinated multistage process at the distal end of centrioles requiring membranes. In this short review, we focus on recently reported insights into the biogenesis of the primary cilium membrane and its association with other ciliogenic processes in the intracellular ciliogenesis pathway.
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Affiliation(s)
- Saurabh Shakya
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, Laboratory of Cellular and Developmental Signaling, Frederick, MD 21702, USA
| | - Christopher J Westlake
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, Laboratory of Cellular and Developmental Signaling, Frederick, MD 21702, USA
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34
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Partisani M, Baron CL, Ghossoub R, Fayad R, Pagnotta S, Abélanet S, Macia E, Brau F, Lacas-Gervais S, Benmerah A, Luton F, Franco M. EFA6A, an exchange factor for Arf6, regulates early steps in ciliogenesis. J Cell Sci 2021; 134:237326. [PMID: 33483367 DOI: 10.1242/jcs.249565] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 11/20/2020] [Indexed: 12/13/2022] Open
Abstract
Ciliogenesis is a coordinated process initiated by the recruitment and fusion of pre-ciliary vesicles at the distal appendages of the mother centriole through mechanisms that remain unclear. Here, we report that EFA6A (also known as PSD), an exchange factor for the small G protein Arf6, is involved in early stage of ciliogenesis by promoting the fusion of distal appendage vesicles forming the ciliary vesicle. EFA6A is present in the vicinity of the mother centriole before primary cilium assembly and prior to the arrival of Arl13B-containing vesicles. During ciliogenesis, EFA6A initially accumulates at the mother centriole and later colocalizes with Arl13B along the ciliary membrane. EFA6A depletion leads to the inhibition of ciliogenesis, the absence of centrosomal Rab8-positive structures and the accumulation of Arl13B-positive vesicles around the distal appendages. Our results uncover a novel fusion machinery, comprising EFA6A, Arf6 and Arl13B, that controls the coordinated fusion of ciliary vesicles docked at the distal appendages of the mother centriole.
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Affiliation(s)
- Mariagrazia Partisani
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Carole L Baron
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Rania Ghossoub
- Centre de Recherche en Cancérologie de Marseille (CRCM), Inserm, U1068-CNRS UMR7258, Aix-Marseille Université, Institut Paoli-Calmettes, 13009 Marseille, France
| | - Racha Fayad
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Sophie Pagnotta
- Centre Commun de Microscopie Appliquée (CCMA), Université Côte d'Azur Parc Valrose, 06103 Nice cedex 2, France
| | - Sophie Abélanet
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Eric Macia
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Frédéric Brau
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Sandra Lacas-Gervais
- Centre Commun de Microscopie Appliquée (CCMA), Université Côte d'Azur Parc Valrose, 06103 Nice cedex 2, France
| | - Alexandre Benmerah
- Université de Paris, Imagine Institute, Laboratory of Inherited Kidney Diseases, INSERM UMR 1163, F-75015, Paris, France
| | - Frédéric Luton
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Michel Franco
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
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35
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Hu J, Harris PC. Regulation of polycystin expression, maturation and trafficking. Cell Signal 2020; 72:109630. [PMID: 32275942 PMCID: PMC7269868 DOI: 10.1016/j.cellsig.2020.109630] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/03/2020] [Accepted: 04/04/2020] [Indexed: 12/26/2022]
Abstract
The major autosomal dominant polycystic kidney disease (ADPKD) genes, PKD1 and PKD2, are wildly expressed at the organ and tissue level. PKD1 encodes polycystin 1 (PC1), a large membrane associated receptor-like protein that can complex with the PKD2 product, PC2. Various cellular locations have been described for both PC1, including the plasma membrane and extracellular vesicles, and PC2, especially the endoplasmic reticulum (ER), but compelling evidence indicates that the primary cilium, a sensory organelle, is the key site for the polycystin complex to prevent PKD. As with other membrane proteins, the ER biogenesis pathway is key to appropriately folding, performing quality control, and exporting fully folded PC1 to the Golgi apparatus. There is a requirement for binding with PC2 and cleavage of PC1 at the GPS for this folding and export to occur. Six different monogenic defects in this pathway lead to cystic disease development, with PC1 apparently particularly sensitive to defects in this general protein processing pathway. Trafficking of membrane proteins, and the polycystins in particular, through the Golgi to the primary cilium have been analyzed in detail, but at this time, there is no clear consensus on a ciliary targeting sequence required to export proteins to the cilium. After transitioning though the trans-Golgi network, polycystin-bearing vesicles are likely sorted to early or recycling endosomes and then transported to the ciliary base, possibly via docking to transition fibers (TF). The membrane-bound polycystin complex then undergoes facilitated trafficking through the transition zone, the diffusion barrier at the base of the cilium, before entering the cilium. Intraflagellar transport (IFT) may be involved in moving the polycystins along the cilia, but data also indicates other mechanisms. The ciliary polycystin complex can be ubiquitinated and removed from cilia by internalization at the ciliary base and may be sent back to the plasma membrane for recycling or to lysosomes for degradation. Monogenic defects in processes regulating the protein composition of cilia are associated with syndromic disorders involving many organ systems, reflecting the pleotropic role of cilia during development and for tissue maintenance. Many of these ciliopathies have renal involvement, likely because of faulty polycystin signaling from cilia. Understanding the expression, maturation and trafficking of the polycystins helps understand PKD pathogenesis and suggests opportunities for therapeutic intervention.
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Affiliation(s)
- Jinghua Hu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA; Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA.
| | - Peter C Harris
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA; Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA.
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36
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Coulter ME, Musaev D, DeGennaro EM, Zhang X, Henke K, James KN, Smith RS, Hill RS, Partlow JN, Muna Al-Saffar, Kamumbu AS, Hatem N, Barkovich AJ, Aziza J, Chassaing N, Zaki MS, Sultan T, Burglen L, Rajab A, Al-Gazali L, Mochida GH, Harris MP, Gleeson JG, Walsh CA. Regulation of human cerebral cortical development by EXOC7 and EXOC8, components of the exocyst complex, and roles in neural progenitor cell proliferation and survival. Genet Med 2020; 22:1040-1050. [PMID: 32103185 PMCID: PMC7272323 DOI: 10.1038/s41436-020-0758-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 01/16/2020] [Accepted: 01/27/2020] [Indexed: 01/31/2023] Open
Abstract
PURPOSE The exocyst complex is a conserved protein complex that mediates fusion of intracellular vesicles to the plasma membrane and is implicated in processes including cell polarity, cell migration, ciliogenesis, cytokinesis, autophagy, and fusion of secretory vesicles. The essential role of these genes in human genetic disorders, however, is unknown. METHODS We performed homozygosity mapping and exome sequencing of consanguineous families with recessively inherited brain development disorders. We modeled an EXOC7 splice variant in vitro and examined EXOC7 messenger RNA (mRNA) expression in developing mouse and human cortex. We modeled exoc7 loss-of-function in a zebrafish knockout. RESULTS We report variants in exocyst complex members, EXOC7 and EXOC8, in a novel disorder of cerebral cortex development. In EXOC7, we identified four independent partial loss-of-function (LOF) variants in a recessively inherited disorder characterized by brain atrophy, seizures, and developmental delay, and in severe cases, microcephaly and infantile death. In EXOC8, we found a homozygous truncating variant in a family with a similar clinical disorder. We modeled exoc7 deficiency in zebrafish and found the absence of exoc7 causes microcephaly. CONCLUSION Our results highlight the essential role of the exocyst pathway in normal cortical development and how its perturbation causes complex brain disorders.
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Affiliation(s)
- Michael E Coulter
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Program in Neuroscience and Harvard/MIT MD-PHD Program, Harvard Medical School, Boston, MA, USA
| | - Damir Musaev
- Department of Neurosciences and Howard Hughes Medical Institute, University of San Diego, La Jolla, CA, USA
| | - Ellen M DeGennaro
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Xiaochang Zhang
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - Katrin Henke
- Division of Orthopedic Research, Boston Children's Hospital, Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Kiely N James
- Department of Neurosciences and Howard Hughes Medical Institute, University of San Diego, La Jolla, CA, USA
| | - Richard S Smith
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - R Sean Hill
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - Jennifer N Partlow
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - Muna Al-Saffar
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Department of Paediatrics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - A Stacy Kamumbu
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - Nicole Hatem
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - A James Barkovich
- Benioff Children's Hospital, Departments of Radiology, Pediatrics, Neurology, and Neurological Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Jacqueline Aziza
- Département de Pathologie, Institut Universitaire du Cancer de Toulouse-Oncopole-CHU Toulouse, Toulouse, France
| | - Nicolas Chassaing
- Service de Génétique Médicale, CHU Toulouse, Toulouse, France
- UDEAR; UMR 1056 Inserm-Université de Toulouse, Toulouse, France
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Tipu Sultan
- Department of Pediatric Neurology, Institute of Child Health & The Children's Hospital, Lahore, Pakistan
| | - Lydie Burglen
- Centre de référence des malformations et maladies congénitales du cervelet, Département de génétique, AP-HP.Sorbonne Université, Paris, France
- Hôpital Trousseau and Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, Paris, France
| | - Anna Rajab
- National Genetics Center, Directorate General of Health Affairs, Ministry of Health, Muscat, Oman
| | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Ganeshwaran H Mochida
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Matthew P Harris
- Division of Orthopedic Research, Boston Children's Hospital, Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Joseph G Gleeson
- Department of Neurosciences and Howard Hughes Medical Institute, University of San Diego, La Jolla, CA, USA.
| | - Christopher A Walsh
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA.
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Wen P, Zhang F, Fu Y, Zhu JY, Han Z. Exocyst Genes Are Essential for Recycling Membrane Proteins and Maintaining Slit Diaphragm in Drosophila Nephrocytes. J Am Soc Nephrol 2020; 31:1024-1034. [PMID: 32238475 DOI: 10.1681/asn.2019060591] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 02/17/2020] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Studies have linked mutations in genes encoding the eight-protein exocyst protein complex to kidney disease, but the underlying mechanism is unclear. Because Drosophila nephrocytes share molecular and structural features with mammalian podocytes, they provide an efficient model for studying this issue. METHODS We silenced genes encoding exocyst complex proteins specifically in Drosophila nephrocytes and studied the effects on protein reabsorption by lacuna channels and filtration by the slit diaphragm. We performed nephrocyte functional assays, carried out super-resolution confocal microscopy of slit diaphragm proteins, and used transmission electron microscopy to analyze ultrastructural changes. We also examined the colocalization of slit diaphragm proteins with exocyst protein Sec15 and with endocytosis and recycling regulators Rab5, Rab7, and Rab11. RESULTS Silencing exocyst genes in nephrocytes led to profound changes in structure and function. Abolition of cellular accumulation of hemolymph proteins with dramatically reduced lacuna channel membrane invaginations offered a strong indication of reabsorption defects. Moreover, the slit diaphragm's highly organized surface structure-essential for filtration-was disrupted, and key proteins were mislocalized. Ultrastructural analysis revealed that exocyst gene silencing led to the striking appearance of novel electron-dense structures that we named "exocyst rods," which likely represent accumulated membrane proteins following defective exocytosis or recycling. The slit diaphragm proteins partially colocalized with Sec15, Rab5, and Rab11. CONCLUSIONS Our findings suggest that the slit diaphragm of Drosophila nephrocytes requires balanced endocytosis and recycling to maintain its structural integrity and that impairment of the exocyst complex leads to disruption of the slit diaphragm and nephrocyte malfunction. This model may help identify therapeutic targets for treating kidney diseases featuring molecular defects in vesicle endocytosis, exocytosis, and recycling.
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Affiliation(s)
- Pei Wen
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland.,Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Fujian Zhang
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Yulong Fu
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Jun-Yi Zhu
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland.,Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Zhe Han
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland .,Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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38
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Regulation of the Extracellular Matrix by Ciliary Machinery. Cells 2020; 9:cells9020278. [PMID: 31979260 PMCID: PMC7072529 DOI: 10.3390/cells9020278] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/13/2020] [Accepted: 01/19/2020] [Indexed: 12/14/2022] Open
Abstract
The primary cilium is an organelle involved in cellular signalling. Mutations affecting proteins involved in cilia assembly or function result in diseases known as ciliopathies, which cause a wide variety of phenotypes across multiple tissues. These mutations disrupt various cellular processes, including regulation of the extracellular matrix. The matrix is important for maintaining tissue homeostasis through influencing cell behaviour and providing structural support; therefore, the matrix changes observed in ciliopathies have been implicated in the pathogenesis of these diseases. Whilst many studies have associated the cilium with processes that regulate the matrix, exactly how these matrix changes arise is not well characterised. This review aims to bring together the direct and indirect evidence for ciliary regulation of matrix, in order to summarise the possible mechanisms by which the ciliary machinery could regulate the composition, secretion, remodelling and organisation of the matrix.
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Zuo X, Kwon SH, Janech MG, Dang Y, Lauzon SD, Fogelgren B, Polgar N, Lipschutz JH. Primary cilia and the exocyst are linked to urinary extracellular vesicle production and content. J Biol Chem 2019; 294:19099-19110. [PMID: 31694916 PMCID: PMC6916495 DOI: 10.1074/jbc.ra119.009297] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 10/29/2019] [Indexed: 12/13/2022] Open
Abstract
The recently proposed idea of "urocrine signaling" hypothesizes that small secreted extracellular vesicles (EVs) contain proteins that transmit signals to distant cells. However, the role of renal primary cilia in EV production and content is unclear. We previously showed that the exocyst, a highly conserved trafficking complex, is necessary for ciliogenesis; that it is present in human urinary EVs; that knockdown (KD) of exocyst complex component 5 (EXOC5), a central exocyst component, results in very short or absent cilia; and that human EXOC5 overexpression results in longer cilia. Here, we show that compared with control Madin-Darby canine kidney (MDCK) cells, EXOC5 overexpression increases and KD decreases EV numbers. Proteomic analyses of isolated EVs from EXOC5 control, KD, and EXOC5-overexpressing MDCK cells revealed significant alterations in protein composition. Using immunoblotting to specifically examine the expression levels of ADP-ribosylation factor 6 (ARF6) and EPS8-like 2 (EPS8L2) in EVs, we found that EXOC5 KD increases ARF6 levels and decreases EPS8L2 levels, and that EXOC5 overexpression increases EPS8L2. Knockout of intraflagellar transport 88 (IFT88) confirmed that the changes in EV number/content were due to cilia loss: similar to EXOC5, the IFT88 loss resulted in very short or absent cilia, decreased EV numbers, increased EV ARF6 levels, and decreased Eps8L2 levels compared with IFT88-rescued EVs. Compared with control animals, urine from proximal tubule-specific EXOC5-KO mice contained fewer EVs and had increased ARF6 levels. These results indicate that perturbations in exocyst and primary cilia affect EV number and protein content.
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Affiliation(s)
- Xiaofeng Zuo
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Sang-Ho Kwon
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, Georgia 30912
| | - Michael G Janech
- Department of Biology, College of Charleston, Charleston, South Carolina 29424
| | - Yujing Dang
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Steven D Lauzon
- Department of Public Health Sciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | - Noemi Polgar
- Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | - Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
- Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425
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40
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Fujimoto BA, Young M, Carter L, Pang APS, Corley MJ, Fogelgren B, Polgar N. The exocyst complex regulates insulin-stimulated glucose uptake of skeletal muscle cells. Am J Physiol Endocrinol Metab 2019; 317:E957-E972. [PMID: 31593505 PMCID: PMC6962504 DOI: 10.1152/ajpendo.00109.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/02/2019] [Accepted: 10/02/2019] [Indexed: 01/16/2023]
Abstract
Skeletal muscle handles ~80-90% of the insulin-induced glucose uptake. In skeletal muscle, insulin binding to its cell surface receptor triggers redistribution of intracellular glucose transporter GLUT4 protein to the cell surface, enabling facilitated glucose uptake. In adipocytes, the eight-protein exocyst complex is an indispensable constituent in insulin-induced glucose uptake, as it is responsible for the targeted trafficking and plasma membrane-delivery of GLUT4. However, the role of the exocyst in skeletal muscle glucose uptake has never been investigated. Here we demonstrate that the exocyst is a necessary factor in insulin-induced glucose uptake in skeletal muscle cells as well. The exocyst complex colocalizes with GLUT4 storage vesicles in L6-GLUT4myc myoblasts at a basal state and associates with these vesicles during their translocation to the plasma membrane after insulin signaling. Moreover, we show that the exocyst inhibitor endosidin-2 and a heterozygous knockout of Exoc5 in skeletal myoblast cells both lead to impaired GLUT4 trafficking to the plasma membrane and hinder glucose uptake in response to an insulin stimulus. Our research is the first to establish that the exocyst complex regulates insulin-induced GLUT4 exocytosis and glucose metabolism in muscle cells. A deeper knowledge of the role of the exocyst complex in skeletal muscle tissue may help our understanding of insulin resistance in type 2 diabetes.
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Affiliation(s)
- Brent A Fujimoto
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
| | - Madison Young
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
| | - Lamar Carter
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
| | - Alina P S Pang
- Department of Native Hawaiian Health, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
| | - Michael J Corley
- Department of Native Hawaiian Health, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
| | - Noemi Polgar
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii
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41
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Boehm C, Field MC. Evolution of late steps in exocytosis: conservation and specialization of the exocyst complex. Wellcome Open Res 2019; 4:112. [PMID: 31633057 PMCID: PMC6784791 DOI: 10.12688/wellcomeopenres.15142.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2019] [Indexed: 01/09/2023] Open
Abstract
Background: The eukaryotic endomembrane system most likely arose via paralogous expansions of genes encoding proteins that specify organelle identity, coat complexes and govern fusion specificity. While the majority of these gene families were established by the time of the last eukaryotic common ancestor (LECA), subsequent evolutionary events has moulded these systems, likely reflecting adaptations retained for increased fitness. As well as sequence evolution, these adaptations include loss of otherwise canonical components, the emergence of lineage-specific proteins and paralog expansion. The exocyst complex is involved in late exocytosis and additional trafficking pathways and a member of the complexes associated with tethering containing helical rods (CATCHR) tethering complex family. CATCHR includes the conserved oligomeric Golgi (COG) complex, homotypic fusion and vacuole protein sorting (HOPS)/class C core vacuole/endosome tethering (CORVET) complexes and several others. The exocyst is integrated into a complex GTPase signalling network in animals, fungi and other lineages. Prompted by discovery of Exo99, a non-canonical subunit in the excavate protist Trypanosoma brucei, and availability of significantly increased genome sequence data, we re-examined evolution of the exocyst. Methods: We examined the evolution of exocyst components by comparative genomics, phylogenetics and structure prediction. Results: The exocyst composition is highly conserved, but with substantial losses of subunits in the Apicomplexa and expansions in Streptophyta plants, Metazoa and land plants, where for the latter, massive paralog expansion of Exo70 represents an extreme and unique example. Significantly, few taxa retain a partial complex, suggesting that, in general, all subunits are probably required for functionality. Further, the ninth exocyst subunit, Exo99, is specific to the Euglenozoa with a distinct architecture compared to the other subunits and which possibly represents a coat system. Conclusions: These data reveal a remarkable degree of evolutionary flexibility within the exocyst complex, suggesting significant diversity in exocytosis mechanisms.
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Affiliation(s)
- Cordula Boehm
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovic, 37005, Czech Republic
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42
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Lipschutz JH. The role of the exocyst in renal ciliogenesis, cystogenesis, tubulogenesis, and development. Kidney Res Clin Pract 2019; 38:260-266. [PMID: 31284362 PMCID: PMC6727897 DOI: 10.23876/j.krcp.19.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/13/2019] [Accepted: 05/20/2019] [Indexed: 12/23/2022] Open
Abstract
The exocyst is a highly conserved eight-subunit protein complex (EXOC1–8) involved in the targeting and docking of exocytic vesicles translocating from the trans-Golgi network to various sites in renal cells. EXOC5 is a central exocyst component because it connects EXOC6, bound to the vesicles exiting the trans-Golgi network via the small GTPase RAB8, to the rest of the exocyst complex at the plasma membrane. In the kidney, the exocyst complex is involved in primary ciliognesis, cystogenesis, and tubulogenesis. The exocyst, and its regulators, have also been found in urinary extracellular vesicles, and may be centrally involved in urocrine signaling and repair following acute kidney injury. The exocyst is centrally involved in the development of other organs, including the eye, ear, and heart. The exocyst is regulated by many different small GTPases of the RHO, RAL, RAB, and ARF families. The small GTPases, and their guanine nucleotide exchange factors and GTPase-activating proteins, likely give the exocyst specificity of function. The recent development of a floxed Exoc5 mouse line will aid researchers in studying the role of the exocyst in multiple cells and organ types by allowing for tissue-specific knockout, in conjunction with Cre-driver mouse lines.
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Affiliation(s)
- Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC, USA.,Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA
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43
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Fulmer D, Toomer K, Guo L, Moore K, Glover J, Moore R, Stairley R, Lobo G, Zuo X, Dang Y, Su Y, Fogelgren B, Gerard P, Chung D, Heydarpour M, Mukherjee R, Body SC, Norris RA, Lipschutz JH. Defects in the Exocyst-Cilia Machinery Cause Bicuspid Aortic Valve Disease and Aortic Stenosis. Circulation 2019; 140:1331-1341. [PMID: 31387361 DOI: 10.1161/circulationaha.119.038376] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND Bicuspid aortic valve (BAV) disease is a congenital defect that affects 0.5% to 1.2% of the population and is associated with comorbidities including ascending aortic dilation and calcific aortic valve stenosis. To date, although a few causal genes have been identified, the genetic basis for the vast majority of BAV cases remains unknown, likely pointing to complex genetic heterogeneity underlying this phenotype. Identifying genetic pathways versus individual gene variants may provide an avenue for uncovering additional BAV causes and consequent comorbidities. METHODS We performed genome-wide association Discovery and Replication Studies using cohorts of 2131 patients with BAV and 2728 control patients, respectively, which identified primary cilia genes as associated with the BAV phenotype. Genome-wide association study hits were prioritized based on P value and validated through in vivo loss of function and rescue experiments, 3-dimensional immunohistochemistry, histology, and morphometric analyses during aortic valve morphogenesis and in aged animals in multiple species. Consequences of these genetic perturbations on cilia-dependent pathways were analyzed by Western and immunohistochemistry analyses, and assessment of aortic valve and cardiac function were determined by echocardiography. RESULTS Genome-wide association study hits revealed an association between BAV and genetic variation in human primary cilia. The most associated single-nucleotide polymorphisms were identified in or near genes that are important in regulating ciliogenesis through the exocyst, a shuttling complex that chaperones cilia cargo to the membrane. Genetic dismantling of the exocyst resulted in impaired ciliogenesis, disrupted ciliogenic signaling and a spectrum of cardiac defects in zebrafish, and aortic valve defects including BAV, valvular stenosis, and valvular calcification in murine models. CONCLUSIONS These data support the exocyst as required for normal ciliogenesis during aortic valve morphogenesis and implicate disruption of ciliogenesis and its downstream pathways as contributory to BAV and associated comorbidities in humans.
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Affiliation(s)
- Diana Fulmer
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston.,Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Katelynn Toomer
- Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Lilong Guo
- Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Kelsey Moore
- Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Janiece Glover
- Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Reece Moore
- Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Rebecca Stairley
- Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Glenn Lobo
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston.,Ophthalmology (G.L.), Medical University of South Carolina, Charleston
| | - Xiaofeng Zuo
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston
| | - Yujing Dang
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston
| | - Yanhui Su
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu (B.F.)
| | - Patrick Gerard
- Department of Mathematical Sciences, Clemson University, SC (P.G.)
| | - Dongjun Chung
- Public Health Sciences (D.C.), Medical University of South Carolina, Charleston
| | - Mahyar Heydarpour
- Department of Anesthesiology, Brigham and Women's Hospital (M.H.), Harvard Medical School, Boston, MA
| | - Rupak Mukherjee
- Surgery (R. Mukherjee), Medical University of South Carolina, Charleston.,Departments of Research (R. Mukherjee), Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC
| | - Simon C Body
- Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center (S.C.B.), Harvard Medical School, Boston, MA
| | - Russell A Norris
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston.,Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston
| | - Joshua H Lipschutz
- Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston.,Medicine (J.H.L.), Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC
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44
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Cassioli C, Baldari CT. A Ciliary View of the Immunological Synapse. Cells 2019; 8:E789. [PMID: 31362462 PMCID: PMC6721628 DOI: 10.3390/cells8080789] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 07/15/2019] [Accepted: 07/25/2019] [Indexed: 12/28/2022] Open
Abstract
The primary cilium has gone from being a vestigial organelle to a crucial signaling hub of growing interest given the association between a group of human disorders, collectively known as ciliopathies, and defects in its structure or function. In recent years many ciliogenesis proteins have been observed at extraciliary sites in cells and likely perform cilium-independent functions ranging from regulation of the cytoskeleton to vesicular trafficking. Perhaps the most striking example is the non-ciliated T lymphocyte, in which components of the ciliary machinery are repurposed for the assembly and function of the immunological synapse even in the absence of a primary cilium. Furthermore, the specialization traits described at the immunological synapse are similar to those seen in the primary cilium. Here, we review common regulators and features shared by the immunological synapse and the primary cilium that document the remarkable homology between these structures.
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Affiliation(s)
- Chiara Cassioli
- Department of Life Sciences, University of Siena, 53100 Siena, Italy
| | - Cosima T Baldari
- Department of Life Sciences, University of Siena, 53100 Siena, Italy.
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45
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Boehm C, Field MC. Evolution of late steps in exocytosis: conservation, specialization. Wellcome Open Res 2019; 4:112. [PMID: 31633057 PMCID: PMC6784791 DOI: 10.12688/wellcomeopenres.15142.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/11/2019] [Indexed: 01/05/2025] Open
Abstract
Background: The eukaryotic endomembrane system likely arose via paralogous expansion of genes encoding proteins specifying organelle identity, coat complexes and government of fusion specificity. While the majority of these gene families were established by the time of the last eukaryotic common ancestor (LECA), subsequent evolutionary events molded these systems, likely reflecting adaptations retained for increased fitness. As well as sequence evolution, these adaptations include loss of otherwise canonical subunits, emergence of lineage-specific proteins and paralog expansion. The exocyst complex is involved in late exocytosis, and possibly additional pathways, and is a member of the complexes associated with tethering containing helical rods (CATCHR) tethering complex family, which includes conserved oligomeric Golgi (COG), homotypic fusion and vacuole protein sorting (HOPS), class C core vacuole/endosome tethering (CORVET) and others. The exocyst is integrated into a complex GTPase signaling network in animals, fungi and other lineages. Prompted by discovery of Exo99, a non-canonical subunit in the excavate protist Trypanosoma brucei, and significantly increased genome sequence data, we examined evolution of the exocyst. Methods: We examined evolution of the exocyst by comparative genomics, phylogenetics and structure prediction. Results: The exocyst is highly conserved, but with substantial losses of subunits in the Apicomplexa and expansions in Streptophyta plants and Metazoa. Significantly, few taxa retain a partial complex, suggesting that, in the main, all subunits are required for functionality. Further, the ninth exocyst subunit Exo99 is specific to the Euglenozoa with a distinct architecture compared to the other subunits and which possibly represents a coat system. Conclusions: These data reveal a remarkable degree of evolutionary flexibility within the exocyst complex, suggesting significant diversity in exocytosis mechanisms.
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Affiliation(s)
- Cordula Boehm
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovic, 37005, Czech Republic
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46
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Nihalani D, Solanki AK, Arif E, Srivastava P, Rahman B, Zuo X, Dang Y, Fogelgren B, Fermin D, Gillies CE, Sampson MG, Lipschutz JH. Disruption of the exocyst induces podocyte loss and dysfunction. J Biol Chem 2019; 294:10104-10119. [PMID: 31073028 PMCID: PMC6664173 DOI: 10.1074/jbc.ra119.008362] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/06/2019] [Indexed: 11/06/2022] Open
Abstract
Although the slit diaphragm proteins in podocytes are uniquely organized to maintain glomerular filtration assembly and function, little is known about the underlying mechanisms that participate in trafficking these proteins to the correct location for development and homeostasis. Identifying these mechanisms will likely provide novel targets for therapeutic intervention to preserve podocyte function following glomerular injury. Analysis of structural variation in cases of human nephrotic syndrome identified rare heterozygous deletions of EXOC4 in two patients. This suggested that disruption of the highly-conserved eight-protein exocyst trafficking complex could have a role in podocyte dysfunction. Indeed, mRNA profiling of injured podocytes identified significant exocyst down-regulation. To test the hypothesis that the exocyst is centrally involved in podocyte development/function, we generated homozygous podocyte-specific Exoc5 (a central exocyst component that interacts with Exoc4) knockout mice that showed massive proteinuria and died within 4 weeks of birth. Histological and ultrastructural analysis of these mice showed severe glomerular defects with increased fibrosis, proteinaceous casts, effaced podocytes, and loss of the slit diaphragm. Immunofluorescence analysis revealed that Neph1 and Nephrin, major slit diaphragm constituents, were mislocalized and/or lost. mRNA profiling of Exoc5 knockdown podocytes showed that vesicular trafficking was the most affected cellular event. Mapping of signaling pathways and Western blot analysis revealed significant up-regulation of the mitogen-activated protein kinase and transforming growth factor-β pathways in Exoc5 knockdown podocytes and in the glomeruli of podocyte-specific Exoc5 KO mice. Based on these data, we propose that exocyst-based mechanisms regulate Neph1 and Nephrin signaling and trafficking, and thus podocyte development and function.
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Affiliation(s)
- Deepak Nihalani
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425,
| | - Ashish K Solanki
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ehtesham Arif
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Pankaj Srivastava
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Bushra Rahman
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Xiaofeng Zuo
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Yujing Dang
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ben Fogelgren
- the Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | | | | | - Matthew G Sampson
- the Department of Pediatrics-Nephrology and.,Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Joshua H Lipschutz
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425.,the Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401
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47
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Zuo X, Lobo G, Fulmer D, Guo L, Dang Y, Su Y, Ilatovskaya DV, Nihalani D, Rohrer B, Body SC, Norris RA, Lipschutz JH. The exocyst acting through the primary cilium is necessary for renal ciliogenesis, cystogenesis, and tubulogenesis. J Biol Chem 2019; 294:6710-6718. [PMID: 30824539 DOI: 10.1074/jbc.ra118.006527] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 02/25/2019] [Indexed: 11/06/2022] Open
Abstract
The exocyst is a highly conserved protein complex found in most eukaryotic cells and is associated with many functions, including protein translocation in the endoplasmic reticulum, vesicular basolateral targeting, and ciliogenesis in the kidney. To investigate the exocyst functions, here we exchanged proline for alanine in the highly conserved VXPX ciliary targeting motif of EXOC5 (exocyst complex component 5), a central exocyst gene/protein, and generated stable EXOC5 ciliary targeting sequence-mutated (EXOC5CTS-m) Madin-Darby canine kidney (MDCK) cells. The EXOC5CTS-m protein was stable and could bind other members of the exocyst complex. Culturing stable control, EXOC5-overexpressing (OE), Exoc5-knockdown (KD), and EXOC5CTS-m MDCK cells on Transwell filters, we found that primary ciliogenesis is increased in EXOC5 OE cells and inhibited in Exoc5-KD and EXOC5CTS-m cells. Growing cells in collagen gels until the cyst stage, we noted that EXOC5-OE cells form mature cysts with single lumens more rapidly than control cysts, whereas Exoc5-KD and EXOC5CTS-m MDCK cells failed to form mature cysts. Adding hepatocyte growth factor to induce tubulogenesis, we observed that EXOC5-OE cell cysts form tubules more efficiently than control MDCK cell cysts, EXOC5CTS-m MDCK cell cysts form significantly fewer tubules than control cell cysts, and Exoc5-KD cysts did not undergo tubulogenesis. Finally, we show that EXOC5 mRNA almost completely rescues the ciliary phenotypes in exoc5-mutant zebrafish, unlike the EXOC5CTS-m mRNA, which could not efficiently rescue the phenotypes. Taken together, these results indicate that the exocyst, acting through the primary cilium, is necessary for renal ciliogenesis, cystogenesis, and tubulogenesis.
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Affiliation(s)
| | - Glenn Lobo
- From the Departments of Medicine.,Ophthalmology, and
| | - Diana Fulmer
- From the Departments of Medicine.,Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Lilong Guo
- From the Departments of Medicine.,Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | | | | | | | | | | | - Simon C Body
- the Department of Anesthesiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - Russell A Norris
- From the Departments of Medicine.,Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Joshua H Lipschutz
- From the Departments of Medicine, .,the Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401, and
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48
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Rangel L, Bernabé-Rubio M, Fernández-Barrera J, Casares-Arias J, Millán J, Alonso MA, Correas I. Caveolin-1α regulates primary cilium length by controlling RhoA GTPase activity. Sci Rep 2019; 9:1116. [PMID: 30718762 PMCID: PMC6362014 DOI: 10.1038/s41598-018-38020-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 10/26/2018] [Indexed: 11/08/2022] Open
Abstract
The primary cilium is a single non-motile protrusion of the plasma membrane of most types of mammalian cell. The structure, length and function of the primary cilium must be tightly controlled because their dysfunction is associated with disease. Caveolin 1 (Cav1), which is best known as a component of membrane invaginations called caveolae, is also present in non-caveolar membrane domains whose function is beginning to be understood. We show that silencing of α and β Cav1 isoforms in different cell lines increases ciliary length regardless of the route of primary ciliogenesis. The sole expression of Cav1α, which is distributed at the apical membrane, restores normal cilium size in Cav1 KO MDCK cells. Cells KO for only Cav1α, which also show long cilia, have a disrupted actin cytoskeleton and reduced RhoA GTPase activity at the apical membrane, and a greater accumulation of Rab11 vesicles at the centrosome. Subsequent experiments showed that DIA1 and ROCK help regulate ciliary length. Since MDCK cells lack apical caveolae, our results imply that non-caveolar apical Cav1α is an important regulator of ciliary length, exerting its effect via RhoA and its effectors, ROCK and DIA1.
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Affiliation(s)
- Laura Rangel
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid, Madrid, Spain
| | - Miguel Bernabé-Rubio
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Jaime Fernández-Barrera
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Javier Casares-Arias
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Jaime Millán
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Miguel A Alonso
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain.
| | - Isabel Correas
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain.
- Department of Molecular Biology, Universidad Autónoma de Madrid, Madrid, Spain.
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49
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Sacher M, Shahrzad N, Kamel H, Milev MP. TRAPPopathies: An emerging set of disorders linked to variations in the genes encoding transport protein particle (TRAPP)-associated proteins. Traffic 2018; 20:5-26. [PMID: 30152084 DOI: 10.1111/tra.12615] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 08/23/2018] [Accepted: 08/26/2018] [Indexed: 02/06/2023]
Abstract
The movement of proteins between cellular compartments requires the orchestrated actions of many factors including Rab family GTPases, Soluble NSF Attachment protein REceptors (SNAREs) and so-called tethering factors. One such tethering factor is called TRAnsport Protein Particle (TRAPP), and in humans, TRAPP proteins are distributed into two related complexes called TRAPP II and III. Although thought to act as a single unit within the complex, in the past few years it has become evident that some TRAPP proteins function independently of the complex. Consistent with this, variations in the genes encoding these proteins result in a spectrum of human diseases with diverse, but partially overlapping, phenotypes. This contrasts with other tethering factors such as COG, where variations in the genes that encode its subunits all result in an identical phenotype. In this review, we present an up-to-date summary of all the known disease-related variations of genes encoding TRAPP-associated proteins and the disorders linked to these variations which we now call TRAPPopathies.
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Affiliation(s)
- Michael Sacher
- Department of Biology, Concordia University, Montreal, Quebec, Canada.,Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Nassim Shahrzad
- Department of Medicine, University of California, San Francisco, California
| | - Hiba Kamel
- Department of Biology, Concordia University, Montreal, Quebec, Canada
| | - Miroslav P Milev
- Department of Biology, Concordia University, Montreal, Quebec, Canada
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50
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Gupta A, Fabian L, Brill JA. Phosphatidylinositol 4,5-bisphosphate regulates cilium transition zone maturation in Drosophila melanogaster. J Cell Sci 2018; 131:jcs.218297. [PMID: 30054387 DOI: 10.1242/jcs.218297] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 07/11/2018] [Indexed: 01/06/2023] Open
Abstract
Cilia are cellular antennae that are essential for human development and physiology. A large number of genetic disorders linked to cilium dysfunction are associated with proteins that localize to the ciliary transition zone (TZ), a structure at the base of cilia that regulates trafficking in and out of the cilium. Despite substantial effort to identify TZ proteins and their roles in cilium assembly and function, processes underlying maturation of TZs are not well understood. Here, we report a role for the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) in TZ maturation in the Drosophila melanogaster male germline. We show that reduction of cellular PIP2 levels through ectopic expression of a phosphoinositide phosphatase or mutation of the type I phosphatidylinositol phosphate kinase Skittles induces formation of longer than normal TZs. These hyperelongated TZs exhibit functional defects, including loss of plasma membrane tethering. We also report that the onion rings (onr) allele of DrosophilaExo84 decouples TZ hyperelongation from loss of cilium-plasma membrane tethering. Our results reveal a requirement for PIP2 in supporting ciliogenesis by promoting proper TZ maturation.
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Affiliation(s)
- Alind Gupta
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada
| | - Lacramioara Fabian
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada
| | - Julie A Brill
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, M5S 1A8, Canada .,Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
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