1
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Sacharidou A, Chambliss K, Peng J, Barrera J, Tanigaki K, Luby-Phelps K, Özdemir İ, Khan S, Sirsi SR, Kim SH, Katzenellenbogen BS, Katzenellenbogen JA, Kanchwala M, Sathe AA, Lemoff A, Xing C, Hoyt K, Mineo C, Shaul PW. Endothelial ERα promotes glucose tolerance by enhancing endothelial insulin transport to skeletal muscle. Nat Commun 2023; 14:4989. [PMID: 37591837 PMCID: PMC10435471 DOI: 10.1038/s41467-023-40562-w] [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: 08/12/2021] [Accepted: 08/01/2023] [Indexed: 08/19/2023] Open
Abstract
The estrogen receptor (ER) designated ERα has actions in many cell and tissue types that impact glucose homeostasis. It is unknown if these include mechanisms in endothelial cells, which have the potential to influence relative obesity, and processes in adipose tissue and skeletal muscle that impact glucose control. Here we show that independent of impact on events in adipose tissue, endothelial ERα promotes glucose tolerance by enhancing endothelial insulin transport to skeletal muscle. Endothelial ERα-deficient male mice are glucose intolerant and insulin resistant, and in females the antidiabetogenic actions of estradiol (E2) are absent. The glucose dysregulation is due to impaired skeletal muscle glucose disposal that results from attenuated muscle insulin delivery. Endothelial ERα activation stimulates insulin transcytosis by skeletal muscle microvascular endothelial cells. Mechanistically this involves nuclear ERα-dependent upregulation of vesicular trafficking regulator sorting nexin 5 (SNX5) expression, and PI3 kinase activation that drives plasma membrane recruitment of SNX5. Thus, coupled nuclear and non-nuclear actions of ERα promote endothelial insulin transport to skeletal muscle to foster normal glucose homeostasis.
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Affiliation(s)
- Anastasia Sacharidou
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Ken Chambliss
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jun Peng
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jose Barrera
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Keiji Tanigaki
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Katherine Luby-Phelps
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - İpek Özdemir
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Sohaib Khan
- University of Cincinnati Cancer Institute, Department of Cancer and Cell Biology, University of Cincinnati College of Medicine, Cincinnati, OH, 45219, USA
| | - Shashank R Sirsi
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Sung Hoon Kim
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Benita S Katzenellenbogen
- Departments of Physiology and Cell Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | | | - Mohammed Kanchwala
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Adwait A Sathe
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Andrew Lemoff
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Chao Xing
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
- Lyda Hill Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Kenneth Hoyt
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Chieko Mineo
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
| | - Philip W Shaul
- Center for Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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2
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Tornero-Écija A, Zapata-Del-Baño A, Antón-Esteban L, Vincent O, Escalante R. The association of lipid transfer protein VPS13A with endosomes is mediated by sorting nexin SNX5. Life Sci Alliance 2023; 6:e202201852. [PMID: 36977596 PMCID: PMC10053439 DOI: 10.26508/lsa.202201852] [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: 11/25/2022] [Revised: 03/17/2023] [Accepted: 03/17/2023] [Indexed: 03/30/2023] Open
Abstract
Human VPS13 proteins are implicated in severe neurological diseases. These proteins play an important role in lipid transport at membrane contact sites between different organelles. Identification of adaptors that regulate the subcellular localization of these proteins at specific membrane contact sites is essential to understand their function and role in disease. We have identified the sorting nexin SNX5 as an interactor of VPS13A that mediates its association with endosomal subdomains. As for the yeast sorting nexin and Vps13 endosomal adaptor Ypt35, this association involves the VPS13 adaptor-binding (VAB) domain in VPS13A and a PxP motif in SNX5. Notably, this interaction is impaired by mutation of a conserved asparagine residue in the VAB domain, which is also required for Vps13-adaptor binding in yeast and is pathogenic in VPS13D. VPS13A fragments containing the VAB domain co-localize with SNX5, whereas the more C-terminal part of VPS13A directs its localization to the mitochondria. Overall, our results suggest that a fraction of VPS13A localizes to junctions between the endoplasmic reticulum, mitochondria, and SNX5-containing endosomes.
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Affiliation(s)
- Alba Tornero-Écija
- Instituto de Investigaciones Biomédicas Alberto Sols, C.S.I.C./U.A.M., Madrid, Spain
| | | | - Laura Antón-Esteban
- Instituto de Investigaciones Biomédicas Alberto Sols, C.S.I.C./U.A.M., Madrid, Spain
| | - Olivier Vincent
- Instituto de Investigaciones Biomédicas Alberto Sols, C.S.I.C./U.A.M., Madrid, Spain
| | - Ricardo Escalante
- Instituto de Investigaciones Biomédicas Alberto Sols, C.S.I.C./U.A.M., Madrid, Spain
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3
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Zhou C, Wu Z, Du W, Que H, Wang Y, Ouyang Q, Jian F, Yuan W, Zhao Y, Tian R, Li Y, Chen Y, Gao S, Wong CCL, Rong Y. Recycling of autophagosomal components from autolysosomes by the recycler complex. Nat Cell Biol 2022; 24:497-512. [PMID: 35332264 DOI: 10.1038/s41556-022-00861-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 02/04/2022] [Indexed: 11/09/2022]
Abstract
Autolysosomes contain components from autophagosomes and lysosomes. The contents inside the autolysosomal lumen are degraded during autophagy, while the fate of autophagosomal components on the autolysosomal membrane remains unknown. Here we report that the autophagosomal membrane components are not degraded, but recycled from autolysosomes through a process coined in this study as autophagosomal components recycling (ACR). We further identified a multiprotein complex composed of SNX4, SNX5 and SNX17 essential for ACR, which we termed 'recycler'. In this, SNX4 and SNX5 form a heterodimer that recognizes autophagosomal membrane proteins and is required for generating membrane curvature on autolysosomes, both via their BAR domains, to mediate the cargo sorting process. SNX17 interacts with both the dynein-dynactin complex and the SNX4-SNX5 dimer to facilitate the retrieval of autophagosomal membrane components. Our discovery of ACR and identification of the recycler reveal an important retrieval and recycling pathway on autolysosomes.
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Affiliation(s)
- Chuchu Zhou
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhe Wu
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wanqing Du
- The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Huilin Que
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yufen Wang
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qinqin Ouyang
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Fenglei Jian
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Weigang Yuan
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yuan Zhao
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Rui Tian
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ying Li
- The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yang Chen
- Center for Precision Medicine Multi-Omics Research, Peking University Health Science Center, Peking University, Beijing, China.,School of Basic Medical Sciences, Peking University Health Science Center, Peking University, Beijing, China
| | - Shuaixin Gao
- Center for Precision Medicine Multi-Omics Research, Peking University Health Science Center, Peking University, Beijing, China.,School of Basic Medical Sciences, Peking University Health Science Center, Peking University, Beijing, China
| | - Catherine C L Wong
- Center for Precision Medicine Multi-Omics Research, Peking University Health Science Center, Peking University, Beijing, China.,School of Basic Medical Sciences, Peking University Health Science Center, Peking University, Beijing, China
| | - Yueguang Rong
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. .,Cell Architecture Research Center, Huazhong University of Science and Technology, Wuhan, China.
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4
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Zhou Q, Li J, Ge C, Chen J, Tian W, Tian H. SNX5 suppresses clear cell renal cell carcinoma progression by inducing CD44 internalization and epithelial-to-mesenchymal transition. Mol Ther Oncolytics 2022; 24:87-100. [PMID: 35024436 PMCID: PMC8717386 DOI: 10.1016/j.omto.2021.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 12/04/2021] [Indexed: 01/06/2023] Open
Abstract
Aberrant expression of SNX5 can contribute to tumorigenesis, invasion, and metastasis of several human cancers. However, the clinicopathological and biological significance of SNX5 in clear cell renal cell carcinoma (ccRCC) remain unclear. In this study, we found that SNX5 expression was downregulated and negatively correlated with tumor size, American Joint Committee on Cancer stage, tumor thrombus of inferior vena cava, and poor prognosis in human ccRCC. Ectopic expression of SNX5 inhibited ccRCC cell proliferation and metastasis, whereas knockdown of SNX5 increased these activities both in vitro and in vivo. Mechanistically, overexpression of SNX5 blocked internalization and intracellular trafficking of CD44 in ccRCC cells. Knockdown of SNX5 was associated with epithelial-to-mesenchymal transition (EMT) in ccRCC cells. Overexpression of SNX5 inhibited TGF-β-induced migration, invasion, and EMT in ccRCC cells. KLF9 directly bound to the SNX5 promoter and increased SNX5 transcription. Moreover, we found that the combination of SNX5 and CD44 or E-cadherin or KLF9 was a more powerful predictor of poor prognosis than either parameter alone. Collectively, our data reveal a mechanism that KLF9-mediated SNX5 expression was associated with poor prognosis via trafficking of CD44 and promoting EMT in ccRCC. SNX5 may be a potential prognostic biomarker and therapeutic target for patients with ccRCC.
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Affiliation(s)
- Qingqing Zhou
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jiajun Li
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chao Ge
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jinsi Chen
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei Tian
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hua Tian
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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5
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Kervin TA, Wiseman BC, Overduin M. Phosphoinositide Recognition Sites Are Blocked by Metabolite Attachment. Front Cell Dev Biol 2021; 9:690461. [PMID: 34368138 PMCID: PMC8340361 DOI: 10.3389/fcell.2021.690461] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 06/18/2021] [Indexed: 12/16/2022] Open
Abstract
Membrane readers take part in trafficking and signaling processes by localizing proteins to organelle surfaces and transducing molecular information. They accomplish this by engaging phosphoinositides (PIs), a class of lipid molecules which are found in different proportions in various cellular membranes. The prototypes are the PX domains, which exhibit a range of specificities for PIs. Our meta-analysis indicates that recognition of membranes by PX domains is specifically controlled by modification of lysine and arginine residues including acetylation, hydroxyisobutyrylation, glycation, malonylation, methylation and succinylation of sidechains that normally bind headgroups of phospholipids including organelle-specific PI signals. Such metabolite-modulated residues in lipid binding elements are named MET-stops here to highlight their roles as erasers of membrane reader functions. These modifications are concentrated in the membrane binding sites of half of all 49 PX domains in the human proteome and correlate with phosphoregulatory sites, as mapped using the Membrane Optimal Docking Area (MODA) algorithm. As these motifs are mutated and modified in various cancers and the responsible enzymes serve as potential drug targets, the discovery of MET-stops as a widespread inhibitory mechanism may aid in the development of diagnostics and therapeutics aimed at the readers, writers and erasers of the PI code.
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Affiliation(s)
- Troy A Kervin
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | - Brittany C Wiseman
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.,Molecular and Cellular Biology, MacEwan University, Edmonton, AB, Canada.,SMALP Network, Edmonton, AB, Canada
| | - Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.,SMALP Network, Edmonton, AB, Canada
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6
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Kervin TA, Overduin M. Regulation of the Phosphoinositide Code by Phosphorylation of Membrane Readers. Cells 2021; 10:cells10051205. [PMID: 34069055 PMCID: PMC8156045 DOI: 10.3390/cells10051205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/07/2021] [Accepted: 05/09/2021] [Indexed: 02/07/2023] Open
Abstract
The genetic code that dictates how nucleic acids are translated into proteins is well known, however, the code through which proteins recognize membranes remains mysterious. In eukaryotes, this code is mediated by hundreds of membrane readers that recognize unique phosphatidylinositol phosphates (PIPs), which demark organelles to initiate localized trafficking and signaling events. The only superfamily which specifically detects all seven PIPs are the Phox homology (PX) domains. Here, we reveal that throughout evolution, these readers are universally regulated by the phosphorylation of their PIP binding surfaces based on our analysis of existing and modelled protein structures and phosphoproteomic databases. These PIP-stops control the selective targeting of proteins to organelles and are shown to be key determinants of high-fidelity PIP recognition. The protein kinases responsible include prominent cancer targets, underscoring the critical role of regulated membrane readership.
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7
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Vieira N, Rito T, Correia-Neves M, Sousa N. Sorting Out Sorting Nexins Functions in the Nervous System in Health and Disease. Mol Neurobiol 2021; 58:4070-4106. [PMID: 33931804 PMCID: PMC8280035 DOI: 10.1007/s12035-021-02388-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/05/2021] [Indexed: 12/18/2022]
Abstract
Endocytosis is a fundamental process that controls protein/lipid composition of the plasma membrane, thereby shaping cellular metabolism, sensing, adhesion, signaling, and nutrient uptake. Endocytosis is essential for the cell to adapt to its surrounding environment, and a tight regulation of the endocytic mechanisms is required to maintain cell function and survival. This is particularly significant in the central nervous system (CNS), where composition of neuronal cell surface is crucial for synaptic functioning. In fact, distinct pathologies of the CNS are tightly linked to abnormal endolysosomal function, and several genome wide association analysis (GWAS) and biochemical studies have identified intracellular trafficking regulators as genetic risk factors for such pathologies. The sorting nexins (SNXs) are a family of proteins involved in protein trafficking regulation and signaling. SNXs dysregulation occurs in patients with Alzheimer’s disease (AD), Down’s syndrome (DS), schizophrenia, ataxia and epilepsy, among others, establishing clear roles for this protein family in pathology. Interestingly, restoration of SNXs levels has been shown to trigger synaptic plasticity recovery in a DS mouse model. This review encompasses an historical and evolutionary overview of SNXs protein family, focusing on its organization, phyla conservation, and evolution throughout the development of the nervous system during speciation. We will also survey SNXs molecular interactions and highlight how defects on SNXs underlie distinct pathologies of the CNS. Ultimately, we discuss possible strategies of intervention, surveying how our knowledge about the fundamental processes regulated by SNXs can be applied to the identification of novel therapeutic avenues for SNXs-related disorders.
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Affiliation(s)
- Neide Vieira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus Gualtar, 4710-057, Braga, Portugal. .,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Teresa Rito
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus Gualtar, 4710-057, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Margarida Correia-Neves
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus Gualtar, 4710-057, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus Gualtar, 4710-057, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
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8
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Abstract
Autophagy, a process of degradation that occurs via the lysosomal pathway, has an essential role in multiple aspects of immunity, including immune system development, regulation of innate and adaptive immune and inflammatory responses, selective degradation of intracellular microorganisms, and host protection against infectious diseases1,2. Autophagy is known to be induced by stimuli such as nutrient deprivation and suppression of mTOR, but little is known about how autophagosomal biogenesis is initiated in mammalian cells in response to viral infection. Here, using genome-wide short interfering RNA screens, we find that the endosomal protein sorting nexin 5 (SNX5)3,4 is essential for virus-induced, but not for basal, stress- or endosome-induced, autophagy. We show that SNX5 deletion increases cellular susceptibility to viral infection in vitro, and that Snx5 knockout in mice enhances lethality after infection with several human viruses. Mechanistically, SNX5 interacts with beclin 1 and ATG14-containing class III phosphatidylinositol-3-kinase (PI3KC3) complex 1 (PI3KC3-C1), increases the lipid kinase activity of purified PI3KC3-C1, and is required for endosomal generation of phosphatidylinositol-3-phosphate (PtdIns(3)P) and recruitment of the PtdIns(3)P-binding protein WIPI2 to virion-containing endosomes. These findings identify a context- and organelle-specific mechanism-SNX5-dependent PI3KC3-C1 activation at endosomes-for initiation of autophagy during viral infection.
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9
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Review of PIP2 in Cellular Signaling, Functions and Diseases. Int J Mol Sci 2020; 21:ijms21218342. [PMID: 33172190 PMCID: PMC7664428 DOI: 10.3390/ijms21218342] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/30/2020] [Accepted: 11/03/2020] [Indexed: 12/27/2022] Open
Abstract
Phosphoinositides play a crucial role in regulating many cellular functions, such as actin dynamics, signaling, intracellular trafficking, membrane dynamics, and cell-matrix adhesion. Central to this process is phosphatidylinositol bisphosphate (PIP2). The levels of PIP2 in the membrane are rapidly altered by the activity of phosphoinositide-directed kinases and phosphatases, and it binds to dozens of different intracellular proteins. Despite the vast literature dedicated to understanding the regulation of PIP2 in cells over past 30 years, much remains to be learned about its cellular functions. In this review, we focus on past and recent exciting results on different molecular mechanisms that regulate cellular functions by binding of specific proteins to PIP2 or by stabilizing phosphoinositide pools in different cellular compartments. Moreover, this review summarizes recent findings that implicate dysregulation of PIP2 in many diseases.
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10
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Colin M, Delporte C, Janky R, Lechon AS, Renard G, Van Antwerpen P, Maltese WA, Mathieu V. Dysregulation of Macropinocytosis Processes in Glioblastomas May Be Exploited to Increase Intracellular Anti-Cancer Drug Levels: The Example of Temozolomide. Cancers (Basel) 2019; 11:cancers11030411. [PMID: 30909495 PMCID: PMC6468498 DOI: 10.3390/cancers11030411] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 03/15/2019] [Accepted: 03/20/2019] [Indexed: 12/16/2022] Open
Abstract
Macropinocytosis is a clathrin-independent endocytosis of extracellular fluid that may contribute to cancer aggressiveness through nutrient supply, recycling of plasma membrane and receptors, and exosome internalization. Macropinocytosis may be notably triggered by epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR), two well-known markers for glioblastoma aggressiveness. Therefore, we studied whether the expression of key actors of macropinocytosis is modified in human glioma datasets. Strong deregulation has been evidenced at the mRNA level according to the grade of the tumor, and 38 macropinocytosis-related gene signatures allowed discrimination of the glioblastoma (GBM) samples. Honokiol-induced vacuolization was then compared to vacquinol-1 and MOMIPP, two known macropinocytosis inducers. Despite high phase-contrast morphological similarities, honokiol-induced vacuoles appeared to originate from both endocytosis and ER. Also, acridine orange staining suggested differences in the macropinosomes’ fate: their fusion with lysosomes appeared very limited in 3-(5-methoxy -2-methyl-1H-indol-3-yl)-1-(4-pyridinyl)-2-propen-1-one (MOMIPP)-treated cells. Nevertheless, each of the compounds markedly increased temozolomide uptake by glioma cells, as evidenced by LC-MS. In conclusion, the observed deregulation of macropinocytosis in GBM makes them prone to respond to various compounds affecting their formation and/or intracellular fate. Considering that sustained macropinocytosis may also trigger cell death of both sensitive and resistant GBM cells, we propose to envisage macropinocytosis inducers in combination approaches to obtain dual benefits: increased drug uptake and additive/synergistic effects.
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Affiliation(s)
- Margaux Colin
- Department of Pharmacotherapy and Pharmaceuticals, Faculty of Pharmacy, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium.
| | - Cédric Delporte
- RD3-Pharmacognosy, Bioanalysis and Drug Discovery Unit and Analytical Platform, Faculty of Pharmacy, Université libre de Bruxelles (ULB), 1050 Brussels, Belgium.
| | | | - Anne-Sophie Lechon
- Department of Pharmacotherapy and Pharmaceuticals, Faculty of Pharmacy, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium.
| | - Gwendoline Renard
- Department of Pharmacotherapy and Pharmaceuticals, Faculty of Pharmacy, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium.
| | - Pierre Van Antwerpen
- RD3-Pharmacognosy, Bioanalysis and Drug Discovery Unit and Analytical Platform, Faculty of Pharmacy, Université libre de Bruxelles (ULB), 1050 Brussels, Belgium.
| | - William A Maltese
- Department of Cancer Biology, University of Toledo College of Medicine, Toledo, OH 43614, USA.
| | - Véronique Mathieu
- Department of Pharmacotherapy and Pharmaceuticals, Faculty of Pharmacy, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium.
- ULB Cancer Research Center, Université libre de Bruxelles (ULB), 1050 Bruxelles, Belgium.
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11
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Shabrish S, Kelkar M, Chavan N, Desai M, Bargir U, Gupta M, Mehta P, Chichra A, S C, Taur P, Saxena V, Vundinti BR, Madkaikar M. Natural Killer Cell Degranulation Defect: A Cause for Impaired NK-Cell Cytotoxicity and Hyperinflammation in Fanconi Anemia Patients. Front Immunol 2019; 10:490. [PMID: 30949167 PMCID: PMC6438155 DOI: 10.3389/fimmu.2019.00490] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 02/22/2019] [Indexed: 12/17/2022] Open
Abstract
Fanconi anemia (FA) is a rare inherited syndrome characterized by progressive bone marrow failure (BMF), abnormal skin pigmentation, short stature, and increased cancer risk. BMF in FA is multifactorial and largely results from the death of hematopoietic stem cells due to genomic instability. Also, inflammatory pathology in FA has been previously reported, however the mechanism is still not clear. In literature, decreased NK-cell count and/or impaired NK-cell activity, along with other immunological abnormalities have been described in FA-patients (1). However, to the best of our knowledge, this is the first report showing a defective degranulation mechanism leading to abnormal NK-cell cytotoxicity in FA-patients, which may explain the development of a hyperinflammatory response in these patients. This may predispose some patients to develop Hemophagocytic lymphohistiocytosis (HLH) which manifests with prolonged fever, progressive cytopenias and organomegaly. Early diagnosis and initiation of immunosuppressive therapy in these patients will help to better manage these patients. We also propose FA genes to be listed as a cause of familial HLH.
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Affiliation(s)
- Snehal Shabrish
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
| | - Madhura Kelkar
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
| | - Niranjan Chavan
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
| | - Mukesh Desai
- Division of Immunology, Bai Jerbai Wadia Hospital for Children, Mumbai, India
| | - Umair Bargir
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
| | - Maya Gupta
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
| | | | | | - Chandrakala S
- Department of Haematology, Seth G. S. Medical College and KEM Hospital, Mumbai, India
| | - Prasad Taur
- Division of Immunology, Bai Jerbai Wadia Hospital for Children, Mumbai, India
| | - Vinay Saxena
- National Institute of Virology, Mumbai Unit, Haffkine Institute, Mumbai, India
| | - Babu Rao Vundinti
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
| | - Manisha Madkaikar
- Department of Paediatric Immunology and Leukocyte Biology, National Institute of Iummunohematology (ICMR), KEM Hospital, Mumbai, India
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Comparative Characterization of the Sindbis Virus Proteome from Mammalian and Invertebrate Hosts Identifies nsP2 as a Component of the Virion and Sorting Nexin 5 as a Significant Host Factor for Alphavirus Replication. J Virol 2018; 92:JVI.00694-18. [PMID: 29743363 PMCID: PMC6026752 DOI: 10.1128/jvi.00694-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Accepted: 04/27/2018] [Indexed: 01/08/2023] Open
Abstract
Recent advances in mass spectrometry methods and instrumentation now allow for more accurate identification of proteins in low abundance. This technology was applied to Sindbis virus, the prototypical alphavirus, to investigate the viral proteome. To determine if host proteins are specifically packaged into alphavirus virions, Sindbis virus (SINV) was grown in multiple host cells representing vertebrate and mosquito hosts, and total protein content of purified virions was determined. This analysis identified host factors not previously associated with alphavirus entry, replication, or egress. One host protein, sorting nexin 5 (SNX5), was shown to be critical for the replication of three different alphaviruses, Sindbis, Mayaro, and Chikungunya viruses. The most significant finding was that in addition to the host proteins, SINV nonstructural protein 2 (nsP2) was detected within virions grown in all host cells examined. The protein and RNA-interacting capabilities of nsP2 coupled with its presence in the virion support a role for nsP2 during packaging and/or entry of progeny virus. This function has not been identified for this protein. Taken together, this strategy identified at least one host factor integrally involved in alphavirus replication. Identification of other host proteins provides insight into alphavirus-host interactions during viral replication in both vertebrate and invertebrate hosts. This method of virus proteome analysis may also be useful for the identification of protein candidates for host-based therapeutics. IMPORTANCE Pathogenic alphaviruses, such as Chikungunya and Mayaro viruses, continue to plague public health in developing and developed countries alike. Alphaviruses belong to a group of viruses vectored in nature by hematophagous (blood-feeding) insects and are termed arboviruses (arthropod-borne viruses). This group of viruses contains many human pathogens, such as dengue fever, West Nile, and Yellow fever viruses. With few exceptions, there are no vaccines or prophylactics for these agents, leaving one-third of the world population at risk of infection. Identifying effective antivirals has been a long-term goal for combating these diseases not only because of the lack of vaccines but also because they are effective during an ongoing epidemic. Mass spectrometry-based analysis of the Sindbis virus proteome can be effective in identifying host genes involved in virus replication and novel functions for virus proteins. Identification of these factors is invaluable for the prophylaxis of this group of viruses.
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De Craene JO, Bertazzi DL, Bär S, Friant S. Phosphoinositides, Major Actors in Membrane Trafficking and Lipid Signaling Pathways. Int J Mol Sci 2017; 18:ijms18030634. [PMID: 28294977 PMCID: PMC5372647 DOI: 10.3390/ijms18030634] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 03/02/2017] [Accepted: 03/06/2017] [Indexed: 11/30/2022] Open
Abstract
Phosphoinositides are lipids involved in the vesicular transport of proteins and lipids between the different compartments of eukaryotic cells. They act by recruiting and/or activating effector proteins and thus are involved in regulating various cellular functions, such as vesicular budding, membrane fusion and cytoskeleton dynamics. Although detected in small concentrations in membranes, their role is essential to cell function, since imbalance in their concentrations is a hallmark of many cancers. Their synthesis involves phosphorylating/dephosphorylating positions D3, D4 and/or D5 of their inositol ring by specific lipid kinases and phosphatases. This process is tightly regulated and specific to the different intracellular membranes. Most enzymes involved in phosphoinositide synthesis are conserved between yeast and human, and their loss of function leads to severe diseases (cancer, myopathy, neuropathy and ciliopathy).
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Affiliation(s)
- Johan-Owen De Craene
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Dimitri L Bertazzi
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Séverine Bär
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
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14
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Pathogenic Huntington Alters BMP Signaling and Synaptic Growth through Local Disruptions of Endosomal Compartments. J Neurosci 2017; 37:3425-3439. [PMID: 28235896 DOI: 10.1523/jneurosci.2752-16.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/07/2017] [Accepted: 02/13/2017] [Indexed: 01/05/2023] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by expansion of a polyglutamine (polyQ) stretch within the Huntingtin (Htt) protein. Pathogenic Htt disrupts multiple neuronal processes, including gene expression, axonal trafficking, proteasome and mitochondrial activity, and intracellular vesicle trafficking. However, the primary pathogenic mechanism and subcellular site of action for mutant Htt are still unclear. Using a Drosophila HD model, we found that pathogenic Htt expression leads to a profound overgrowth of synaptic connections that correlates directly with the levels of Htt at nerve terminals. Branches of the same nerve containing different levels of Htt show distinct phenotypes, indicating that Htt acts locally to disrupt synaptic growth. The effects of pathogenic Htt on synaptic growth arise from defective synaptic endosomal trafficking, leading to expansion of a recycling endosomal signaling compartment containing Sorting Nexin 16 and a reduction in late endosomes containing Rab11. The disruption of endosomal compartments leads to elevated BMP signaling within nerve terminals, driving excessive synaptic growth. Blocking aberrant signaling from endosomes or reducing BMP activity ameliorates the severity of HD pathology and improves viability. Pathogenic Htt is present largely in a nonaggregated form at synapses, indicating that cytosolic forms of the protein are likely to be the toxic species that disrupt endosomal signaling. Our data indicate that pathogenic Htt acts locally at nerve terminals to alter trafficking between endosomal compartments, leading to defects in synaptic structure that correlate with pathogenesis and lethality in the Drosophila HD model.SIGNIFICANCE STATEMENT Huntington's disease (HD) is the most commonly inherited polyglutamine expansion disorder, but how mutant Huntingtin (Htt) disrupts neuronal function is unclear. In particular, it is unknown within what subcellular compartment pathogenic Htt acts and whether the pathogenesis is associated with aggregated or more soluble forms of the protein. Using a Drosophila HD model, we find that nonaggregated pathogenic Htt acts locally at synaptic terminals to disrupt endosomal compartments, leading to aberrant wiring defects. Genetic manipulations to increase endosomal trafficking of synaptic growth receptors from signaling endosomes or to reduce BMP signaling reduce pathology in this HD model. These data indicate that pathogenic Htt can act locally within nerve terminals to disrupt synaptic endosomal signaling and induce neuropathology.
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15
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Chu YJ, Chen X, Xue HW. Ins(1,4,5)P 3 Suppresses Protein Degradation in Plant Vacuoles by Regulating SNX-Mediated Protein Sorting. MOLECULAR PLANT 2016; 9:1440-1443. [PMID: 27477682 DOI: 10.1016/j.molp.2016.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 07/10/2016] [Accepted: 07/22/2016] [Indexed: 06/06/2023]
Affiliation(s)
- Yu-Jia Chu
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China
| | - Xu Chen
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China
| | - Hong-Wei Xue
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
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16
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Lim JP, Gosavi P, Mintern JD, Ross EM, Gleeson PA. Sorting nexin 5 selectively regulates dorsal-ruffle-mediated macropinocytosis in primary macrophages. J Cell Sci 2015; 128:4407-19. [PMID: 26459636 DOI: 10.1242/jcs.174359] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 10/05/2015] [Indexed: 02/01/2023] Open
Abstract
The regulation of macropinocytosis, a specialised endocytosis pathway, is important for immune cell function. However, it is not known whether the biogenesis of macropinosomes involves one or more distinct pathways. We previously identified sorting nexin 5 (SNX5) as a regulator of macropinocytosis in macrophages. Here, we show that bone-marrow-derived macrophages from SNX5-knockout mice had a 60-70% reduction in macropinocytic uptake of dextran or ovalbumin, whereas phagocytosis and retrograde transport from the plasma membrane to the Golgi was unaffected. In contrast, deficiency of SNX5 had no effect on macropinocytosis or antigen presentation by dendritic cells. Activation of macrophages with CSF-1 resulted in a localisation of SNX5 to actin-rich ruffles in a manner dependent on receptor tyrosine kinases. SNX5-deficient macrophages showed a dramatic reduction in ruffling on the dorsal surface following CSF-1 receptor activation, whereas peripheral ruffling and cell migration were unaffected. We demonstrate that SNX5 is acting upstream of actin polymerisation following CSF-1 receptor activation. Overall, our findings reveal the important contribution of dorsal ruffing to receptor-activated macropinocytosis in primary macrophages and show that SNX5 selectively regulates macropinosomes derived from the dorsal ruffles.
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Affiliation(s)
- Jet Phey Lim
- The Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Prajakta Gosavi
- The Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Justine D Mintern
- The Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Ellen M Ross
- The Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Paul A Gleeson
- The Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
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17
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Rizopoulos Z, Balistreri G, Kilcher S, Martin CK, Syedbasha M, Helenius A, Mercer J. Vaccinia Virus Infection Requires Maturation of Macropinosomes. Traffic 2015; 16:814-31. [PMID: 25869659 PMCID: PMC4973667 DOI: 10.1111/tra.12290] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 04/08/2015] [Accepted: 04/09/2015] [Indexed: 01/11/2023]
Abstract
The prototypic poxvirus, vaccinia virus (VACV), occurs in two infectious forms, mature virions (MVs) and extracellular virions (EVs). Both enter HeLa cells by inducing macropinocytic uptake. Using confocal microscopy, live-cell imaging, targeted RNAi screening and perturbants of endosome maturation, we analyzed the properties and maturation pathway of the macropinocytic vacuoles containing VACV MVs in HeLa cells. The vacuoles first acquired markers of early endosomes [Rab5, early endosome antigen 1 and phosphatidylinositol(3)P]. Prior to release of virus cores into the cytoplasm, they contained markers of late endosomes and lysosomes (Rab7a, lysosome-associated membrane protein 1 and sorting nexin 3). RNAi screening of endocytic cell factors emphasized the importance of late compartments for VACV infection. Follow-up perturbation analysis showed that infection required Rab7a and PIKfyve, confirming that VACV is a late-penetrating virus dependent on macropinosome maturation. VACV EV infection was inhibited by depletion of many of the same factors, indicating that both infectious particle forms share the need for late vacuolar conditions for penetration.
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Affiliation(s)
- Zaira Rizopoulos
- ETH Zürich Institute of Biochemistry, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Giuseppe Balistreri
- ETH Zürich Institute of Biochemistry, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Samuel Kilcher
- MRC-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Caroline K Martin
- MRC-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | | | - Ari Helenius
- ETH Zürich Institute of Biochemistry, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Jason Mercer
- MRC-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
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18
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Inflammatory stimuli reprogram macrophage phagocytosis to macropinocytosis for the rapid elimination of pathogens. PLoS Pathog 2014; 10:e1003879. [PMID: 24497827 PMCID: PMC3907376 DOI: 10.1371/journal.ppat.1003879] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 11/18/2013] [Indexed: 12/17/2022] Open
Abstract
Following an infectious challenge, macrophages have to be activated in order to allow efficient clearance of infectious pathogens, but how macrophage activation is coupled to increased clearance remains largely unknown. We here describe that inflammatory stimuli induced the reprogramming of the macrophage endocytic machinery from receptor-mediated phagocytosis to macropinocytosis, allowing the rapid transfer of internalized cargo to lysosomes in a receptor-independent manner. Reprogramming occurred through protein kinase C-mediated phosphorylation of the macrophage protein coronin 1, thereby activating phosphoinositol (PI)-3-kinase activity necessary for macropinocytic uptake. Expression of a phosphomimetic form of coronin 1 was sufficient to induce PI3-kinase activation and macropinocytosis even in the absence of inflammatory stimuli. Together these results suggest a hitherto unknown mechanism to regulate the internalization and degradation of infectious material during inflammation. The main cells that are involved in cleaning up microbial pathogens are macrophages. Upon an infection, macrophages are being recruited to the site of infection by a number of different stimuli. In addition, during an infection, macrophages are also activated by cytokines such as interferon-γ and tumor necrosis factor-α that is released from other immune cells. Such macrophage activation is important to achieve a rapid and efficient clearance of microbial pathogens. In this study, we found that macrophage activation induces uptake through macropinocytosis rather than receptor-mediate phagocytosis. As a consequence, microbial material as well as particles can be internalized far more efficiently; In addition, the internalized cargo is rapidly destroyed within lysosomes. We also provide the mechanisms for the switch from phagocytosis to macropinocytosis, which turned out to be the cytokine-induced phosphorylation of the host protein coronin 1. Phosphorylated coronin 1 activated the lipid kinase phosphoinositide 3-kinase, which is known to be responsible for the entry of cargo through macropinocytosis. Together these results provide evidence for a hitherto unrecognized mechanisms to regulate the internalization and degradation of infectious material during an infection.
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19
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Sun Y, Hedman AC, Tan X, Schill NJ, Anderson RA. Endosomal type Iγ PIP 5-kinase controls EGF receptor lysosomal sorting. Dev Cell 2013; 25:144-55. [PMID: 23602387 DOI: 10.1016/j.devcel.2013.03.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Revised: 01/24/2013] [Accepted: 03/15/2013] [Indexed: 12/24/2022]
Abstract
Endosomal trafficking and degradation of epidermal growth factor receptor (EGFR) play an essential role in the control of its signaling. Phosphatidylinositol-4,5-bisphosphate (PtdIns4,5P(2)) is an established regulator of endocytosis, whereas PtdIns3P modulates endosomal trafficking. However, we demonstrate here that type I gamma phosphatidylinositol phosphate 5-kinase i5 (PIPKIγi5), an enzyme that synthesizes PtdIns4,5P(2), controls endosome-to-lysosome sorting of EGFR. In this pathway, PIPKIγi5 interacts with sorting nexin 5 (SNX5), a protein that binds PtdIns4,5P(2) and other phosphoinositides. PIPKIγi5 and SNX5 localize to endosomes, and loss of either protein blocks EGFR sorting into intraluminal vesicles (ILVs) of the multivesicular body. Loss of ILV sorting greatly enhances and prolongs EGFR signaling. PIPKIγi5 and SNX5 prevent Hrs ubiquitination, and this facilitates the Hrs association with EGFR that is required for ILV sorting. These findings reveal that PIPKIγi5 and SNX5 form a signaling nexus that controls EGFR endosomal sorting, degradation, and signaling.
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Affiliation(s)
- Yue Sun
- University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706, USA
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20
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Im SK, Jeong H, Jeong HW, Kim KT, Hwang D, Ikegami M, Kong YY. Disruption of sorting nexin 5 causes respiratory failure associated with undifferentiated alveolar epithelial type I cells in mice. PLoS One 2013; 8:e58511. [PMID: 23526992 PMCID: PMC3602295 DOI: 10.1371/journal.pone.0058511] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 02/05/2013] [Indexed: 01/16/2023] Open
Abstract
Sorting nexin 5 (Snx5) has been posited to regulate the degradation of epidermal growth factor receptor and the retrograde trafficking of cation-independent mannose 6-phosphate receptor/insulin-like growth factor II receptor. Snx5 has also been suggested to interact with Mind bomb-1, an E3 ubiquitin ligase that regulates the activation of Notch signaling. However, the in vivo functions of Snx5 are largely unknown. Here, we report that disruption of the Snx5 gene in mice (Snx5-/- mice) resulted in partial perinatal lethality; 40% of Snx5-/- mice died shortly after birth due to cyanosis, reduced air space in the lungs, and respiratory failure. Histological analysis revealed that Snx5-/- mice exhibited thickened alveolar walls associated with undifferentiated alveolar epithelial type I cells. In contrast, alveolar epithelial type II cells were intact, exhibiting normal surfactant synthesis and secretion. Although the expression levels of surfactant proteins and saturated phosphatidylcholine in the lungs of Snx5-/- mice were comparable to those of Snx5+/+ mice, the expression levels of T1α, Aqp5, and Rage, markers for distal alveolar epithelial type I cells, were significantly decreased in Snx5-/- mice. These results demonstrate that Snx5 is necessary for the differentiation of alveolar epithelial type I cells, which may underlie the adaptation to air breathing at birth.
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Affiliation(s)
- Sun-Kyoung Im
- School of Biological Science, College of Natural Sciences, Seoul National University, Seoul, South Korea
- Department of Life Science, Division of Molecular and Life Science, POSTECH, Pohang, South Korea
| | - HyoBin Jeong
- School of Interdisciplinary Biosciences and Bioengineering, POSTECH, Pohang, South Korea
| | - Hyun-Woo Jeong
- School of Biological Science, College of Natural Sciences, Seoul National University, Seoul, South Korea
| | - Kyong-Tai Kim
- Department of Life Science, Division of Molecular and Life Science, POSTECH, Pohang, South Korea
| | - Daehee Hwang
- School of Interdisciplinary Biosciences and Bioengineering, POSTECH, Pohang, South Korea
| | - Machiko Ikegami
- Division of Pulmonary Biology, Cincinnati Children’s Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Young-Yun Kong
- School of Biological Science, College of Natural Sciences, Seoul National University, Seoul, South Korea
- * E-mail:
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21
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Aubry L, Klein G. True arrestins and arrestin-fold proteins: a structure-based appraisal. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:21-56. [PMID: 23764049 DOI: 10.1016/b978-0-12-394440-5.00002-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Arrestin-clan proteins are folded alike, a feature responsible for their recent grouping in a single clan. In human, it includes the well-characterized visual and β-arrestins, the arrestin domain-containing proteins (ARRDCs), isoforms of the retromer subunit VPS26, and DSCR3, a protein involved in Down syndrome. A new arrestin-fold-predicted protein, RGP1, described here may join the clan. Unicellular organisms like the yeast Saccharomyces cerevisiae or the amoeba Dictyostelium discoideum harbor VPS26, DSCR3, and RGP1 isoforms as well as arrestin-related trafficking adaptors or ADCs, but true arrestins are missing. Functionally, members of the arrestin clan have generally a scaffolding role in various membrane protein trafficking events. Despite their similar structure, the mechanism of cargo recognition and internalization and the nature of recruited partners differ for the different members. Based on the recent literature, true arrestins (visual and β-arrestins), ARRDCs, and yeast ARTS are the closest from a functional point of view.
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Affiliation(s)
- Laurence Aubry
- CEA, IRTSV, Laboratoire Biologie à Grande Echelle, F-38054, Grenoble, France
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22
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Lim JP, Teasdale RD, Gleeson PA. SNX5 is essential for efficient macropinocytosis and antigen processing in primary macrophages. Biol Open 2012; 1:904-14. [PMID: 23213485 PMCID: PMC3507233 DOI: 10.1242/bio.20122204] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 06/19/2012] [Indexed: 12/14/2022] Open
Abstract
Macropinocytosis mediates the bulk endocytosis of solute molecules, nutrients and antigens. As this endocytic pathway is considered important in functions associated with immune responses, the molecular mechanisms regulating this pathway in immune cells is of particular significance. However, the regulators of macropinocytosis in primary cells remain poorly defined. Members of the sorting nexin (SNX) family have been implicated in macropinosome biogenesis in cultured cells and here we have analyzed the role of two SNX family members, SNX1 and its binding partner SNX5, in macropinocytosis of mouse primary macrophages. We show that endogenous SNX1 and SNX5 are localised to newly-formed macropinosomes in primary mouse macrophages and, moreover, demonstrate that SNX5 plays an essential role in macropinosome biogenesis. Depletion of SNX5 in bone marrow-derived macrophages dramatically decreased both the number and size of macropinosomes. Depletion of SNX5 also resulted in dramatic reduction in uptake and processing of soluble ovalbumin in macrophages, indicating that the majority of antigen uptake and delivery to late endosomes is via macropinocytosis. By contrast, the absence of SNX1 had no effect on endogenous SNX5 localisation and macropinosome biogenesis using macrophages from SNX1 knockout mice. Therefore, SNX5 can function independently of SNX1 and is a modulator of macropinocytosis that influences the uptake and processing of soluble antigen in primary mouse macrophages.
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Affiliation(s)
- Jet Phey Lim
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Victoria 3010 , Australia
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23
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Mercer J, Helenius A. Gulping rather than sipping: macropinocytosis as a way of virus entry. Curr Opin Microbiol 2012; 15:490-9. [PMID: 22749376 DOI: 10.1016/j.mib.2012.05.016] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 05/25/2012] [Accepted: 05/31/2012] [Indexed: 12/18/2022]
Abstract
Macropinocytosis has emerged as a major endocytic mechanism in the cell entry of animal viruses. The process differs fundamentally from other endocytic mechanisms involved in virus internalization. By activating growth factor receptors or other signaling molecules, plasma membrane-bound viruses trigger the activation of a signaling pathway. When amplified, this causes a transient, global change in cell behavior. The consequences of this change include the actin-dependent formation of membrane protrusions, the elevation of non-specific uptake of fluid, and the internalization of membrane together with surface-bound ligands and particles including viruses. Recent studies show that this strategy is used by a variety of enveloped and non-enveloped viruses.
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Affiliation(s)
- Jason Mercer
- ETH Zürich, Institute of Biochemistry, Zürich, Switzerland.
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24
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Zhang J, Reiling C, Reinecke JB, Prislan I, Marky LA, Sorgen PL, Naslavsky N, Caplan S. Rabankyrin-5 interacts with EHD1 and Vps26 to regulate endocytic trafficking and retromer function. Traffic 2012; 13:745-57. [PMID: 22284051 DOI: 10.1111/j.1600-0854.2012.01334.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 01/24/2012] [Accepted: 01/27/2012] [Indexed: 12/13/2022]
Abstract
Rabankyrin-5 (Rank-5) has been implicated as an effector of the small GTPase Rab5 and plays an important role in macropinocytosis. We have now identified Rank-5 as an interaction partner for the recycling regulatory protein, Eps15 homology domain 1 (EHD1). We have demonstrated this interaction by glutathione S-transferase-pulldown, yeast two-hybrid assay, isothermal calorimetry and co-immunoprecipitation, and found that the binding occurs between the EH domain of EHD1 and the NPFED motif of Rank-5. Similar to EHD1, we found that Rank-5 colocalizes and interacts with components of the retromer complex such as vacuolar protein sorting 26 (Vps26), suggesting a role for Rank-5 in retromer-based transport. Indeed, depletion of Rank-5 causes mislocalization of Vps26 and affects both the retrieval of mannose 6-phosphate receptor transport to the Golgi from endosomes and biosynthetic transport. Moreover, Rank-5 is required for normal retromer distribution, as overexpression of a wild-type Rank-5-small interfering RNA-resistant construct rescues retromer mislocalization. Finally, we show that depletion of either Rank-5 or EHD1 impairs secretion of vesicular stomatitis virus glycoprotein. Overall, our data identify a new interaction between Rank-5 and EHD1, and novel endocytic regulatory roles that include retromer-based transport and secretion.
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Affiliation(s)
- Jing Zhang
- Department of Biochemistry and Molecular Biology and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198-5870, USA
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25
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Insights into the PX (phox-homology) domain and SNX (sorting nexin) protein families: structures, functions and roles in disease. Biochem J 2011; 441:39-59. [DOI: 10.1042/bj20111226] [Citation(s) in RCA: 212] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The mammalian genome encodes 49 proteins that possess a PX (phox-homology) domain, responsible for membrane attachment to organelles of the secretory and endocytic system via binding of phosphoinositide lipids. The PX domain proteins, most of which are classified as SNXs (sorting nexins), constitute an extremely diverse family of molecules that play varied roles in membrane trafficking, cell signalling, membrane remodelling and organelle motility. In the present review, we present an overview of the family, incorporating recent functional and structural insights, and propose an updated classification of the proteins into distinct subfamilies on the basis of these insights. Almost all PX domain proteins bind PtdIns3P and are recruited to early endosomal membranes. Although other specificities and localizations have been reported for a select few family members, the molecular basis for binding to other lipids is still not clear. The PX domain is also emerging as an important protein–protein interaction domain, binding endocytic and exocytic machinery, transmembrane proteins and many other molecules. A comprehensive survey of the molecular interactions governed by PX proteins highlights the functional diversity of the family as trafficking cargo adaptors and membrane-associated scaffolds regulating cell signalling. Finally, we examine the mounting evidence linking PX proteins to different disorders, in particular focusing on their emerging importance in both pathogen invasion and amyloid production in Alzheimer's disease.
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Identification of components of the host type IA phosphoinositide 3-kinase pathway that promote internalization of Listeria monocytogenes. Infect Immun 2011; 80:1252-66. [PMID: 22158742 DOI: 10.1128/iai.06082-11] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The bacterial pathogen Listeria monocytogenes causes food-borne illnesses resulting in gastroenteritis, meningitis, or abortion. Listeria promotes its internalization into some human cells through binding of the bacterial surface protein InlB to the host receptor tyrosine kinase Met. The interaction of InlB with the Met receptor stimulates host signaling pathways that promote cell surface changes driving bacterial uptake. One human signaling protein that plays a critical role in Listeria entry is type IA phosphoinositide 3-kinase (PI 3-kinase). The molecular mechanism by which PI 3-kinase promotes bacterial internalization is not understood. Here we perform an RNA interference (RNAi)-based screen to identify components of the type IA PI 3-kinase pathway that control the entry of Listeria into the human cell line HeLa. The 64 genes targeted encode known upstream regulators or downstream effectors of type IA PI 3-kinase. The results of this screen indicate that at least 9 members of the PI 3-kinase pathway play important roles in Listeria uptake. These 9 human proteins include a Rab5 GTPase, several regulators of Arf or Rac1 GTPases, and the serine/threonine kinases phosphoinositide-dependent kinase 1 (PDK1), mammalian target of rapamycin (mTor), and protein kinase C-ζ. These findings represent a key first step toward understanding the mechanism by which type IA PI 3-kinase controls bacterial internalization.
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Abstract
From the pioneering work of Mabel and Lowell Hokin in the 1950s, the biology of this specific isomer of hexahydroxycyclohexane and its phosphorylated derivatives, in the form of inositol phosphates and phosphoinositides, has expanded to fill virtually every corner of cell biology, whole-organism physiology and development. In the present paper, I give a personal view of the role played by phosphoinositides in regulating the function of the endosomal network, and, in so doing, highlight some of the basic properties through which phosphoinositides regulate cell function.
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Bugarcic A, Zhe Y, Kerr MC, Griffin J, Collins BM, Teasdale RD. Vps26A and Vps26B Subunits Define Distinct Retromer Complexes. Traffic 2011; 12:1759-73. [DOI: 10.1111/j.1600-0854.2011.01284.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Abstract
Macropinocytosis is a regulated form of endocytosis that mediates the non-selective uptake of solute molecules, nutrients and antigens. It is an actin-dependent process initiated from surface membrane ruffles that give rise to large endocytic vacuoles called macropinosomes. Macropinocytosis is important in a range of physiological processes; it is highly active in macrophages and dendritic cells where it is a major pathway for the capture of antigens, it is relevant to cell migration and tumour metastasis and it represents a portal of cell entry exploited by a range of pathogens. The molecular basis for the formation and maturation of macropinosomes has only recently begun to be defined. Here, we review the general characteristics of macropinocytosis, describe some of the regulators of this pathway, which have been identified to date and highlight strategies to explore the relevance of this endocytosis pathway in vivo.
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Wang JTH, Kerr MC, Karunaratne S, Jeanes A, Yap AS, Teasdale RD. The SNX-PX-BAR family in macropinocytosis: the regulation of macropinosome formation by SNX-PX-BAR proteins. PLoS One 2010; 5:e13763. [PMID: 21048941 PMCID: PMC2966440 DOI: 10.1371/journal.pone.0013763] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 10/08/2010] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Macropinocytosis is an actin-driven endocytic process, whereby membrane ruffles fold back onto the plasma membrane to form large (>0.2 µm in diameter) endocytic organelles called macropinosomes. Relative to other endocytic pathways, little is known about the molecular mechanisms involved in macropinocytosis. Recently, members of the Sorting Nexin (SNX) family have been localized to the cell surface and early macropinosomes, and implicated in macropinosome formation. SNX-PX-BAR proteins form a subset of the SNX family and their lipid-binding (PX) and membrane-curvature sensing (BAR) domain architecture further implicates their functional involvement in macropinosome formation. METHODOLOGY/PRINCIPAL FINDINGS We exploited the tractability of macropinosomes through image-based screening and systematic overexpression of SNX-PX-BAR proteins to quantitate their effect on macropinosome formation. SNX1 (40.9+/-3.19 macropinosomes), SNX5 (36.99+/-4.48 macropinosomes), SNX9 (37.55+/-2.4 macropinosomes), SNX18 (88.2+/-8 macropinosomes), SNX33 (65.25+/-6.95 macropinosomes) all exhibited statistically significant (p<0.05) increases in average macropinosome numbers per 100 transfected cells as compared to control cells (24.44+/-1.81 macropinosomes). SNX1, SNX5, SNX9, and SNX18 were also found to associate with early-stage macropinosomes within 5 minutes following organelle formation. The modulation of intracellular PI(3,4,5)P(3) levels through overexpression of PTEN or a lipid phosphatase-deficient mutant PTEN(G129E) was also observed to significantly reduce or elevate macropinosome formation respectively; coexpression of PTEN(G129E) with SNX9 or SNX18 synergistically elevated macropinosome formation to 119.4+/-7.13 and 91.4+/-6.37 macropinosomes respectively (p<0.05). CONCLUSIONS/SIGNIFICANCE SNX1, SNX5, SNX9, SNX18, and SNX33 were all found to elevate macropinosome formation and (with the exception of SNX33) associate with early-stage macropinosomes. Moreover the effects of SNX9 and SNX18 overexpression in elevating macropinocytosis is likely to be synergistic with the increase in PI(3,4,5)P(3) levels, which is known to accumulate on the cell surface and early-stage macropinocytic cups. Together these findings represent the first systematic functional study into the impact of the SNX-PX-BAR family on macropinocytosis.
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Affiliation(s)
- Jack T. H. Wang
- Institute for Molecular Bioscience and Australia Research Council (ARC) Centre of Excellence in Bioinformatics, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Markus C. Kerr
- Institute for Molecular Bioscience and Australia Research Council (ARC) Centre of Excellence in Bioinformatics, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Seetha Karunaratne
- Institute for Molecular Bioscience and Australia Research Council (ARC) Centre of Excellence in Bioinformatics, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Angela Jeanes
- Institute for Molecular Bioscience and Australia Research Council (ARC) Centre of Excellence in Bioinformatics, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Alpha S. Yap
- Institute for Molecular Bioscience and Australia Research Council (ARC) Centre of Excellence in Bioinformatics, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Rohan D. Teasdale
- Institute for Molecular Bioscience and Australia Research Council (ARC) Centre of Excellence in Bioinformatics, The University of Queensland, St. Lucia, Brisbane, Australia
- * E-mail:
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Choi JH, Banks AS, Estall JL, Kajimura S, Boström P, Laznik D, Ruas JL, Chalmers MJ, Kamenecka TM, Blüher M, Griffin PR, Spiegelman BM. Anti-diabetic drugs inhibit obesity-linked phosphorylation of PPARgamma by Cdk5. Nature 2010; 466:451-6. [PMID: 20651683 PMCID: PMC2987584 DOI: 10.1038/nature09291] [Citation(s) in RCA: 679] [Impact Index Per Article: 48.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Accepted: 06/24/2010] [Indexed: 12/22/2022]
Abstract
Obesity induced in mice by high-fat feeding activates the protein kinase cdk5 in adipose tissues. This results in phosphorylation of the nuclear receptor PPARγ, a dominant regulator of adipogenesis and fat cell gene expression, at serine 273. This modification of PPARγ does not alter its adipogenic capacity, but leads to dysregulation of a large number of genes whose expression is altered in obesity, including a reduction in the expression of the insulin-sensitizing adipokine, adiponectin. The phosphorylation of PPARγ by cdk5 is blocked by anti-diabetic PPARγ ligands, such as rosiglitazone and MRL24. This inhibition works both in vivo and in vitro, and surprisingly, is completely independent of classical receptor transcriptional agonism. Similarly, inhibition of PPARγ phosphorylation in obese patients by rosiglitazone is very tightly associated with the anti-diabetic effects of this drug. These data strongly suggest that cdk5-mediated phosphorylation of PPARγ may be involved in the pathogenesis of insulin-resistance, and present an opportunity for development of an improved generation of anti-diabetic drugs through PPARγ.
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Affiliation(s)
- Jang Hyun Choi
- Department of Cancer Biology and Division of Metabolism and Chronic Disease, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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Inhibition of the PtdIns(5) kinase PIKfyve disrupts intracellular replication of Salmonella. EMBO J 2010; 29:1331-47. [PMID: 20300065 DOI: 10.1038/emboj.2010.28] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Accepted: 02/10/2010] [Indexed: 01/15/2023] Open
Abstract
3-phosphorylated phosphoinositides (3-PtdIns) orchestrate endocytic trafficking pathways exploited by intracellular pathogens such as Salmonella to gain entry into the cell. To infect the host, Salmonellae subvert its normal macropinocytic activity, manipulating the process to generate an intracellular replicative niche. Disruption of the PtdIns(5) kinase, PIKfyve, be it by interfering mutant, siRNA-mediated knockdown or pharmacological means, inhibits the intracellular replication of Salmonella enterica serovar typhimurium in epithelial cells. Monitoring the dynamics of macropinocytosis by time-lapse 3D (4D) videomicroscopy revealed a new and essential role for PI(3,5)P(2) in macropinosome-late endosome/lysosome fusion, which is distinct from that of the small GTPase Rab7. This PI(3,5)P(2)-dependent step is required for the proper maturation of the Salmonella-containing vacuole (SCV) through the formation of Salmonella-induced filaments (SIFs) and for the engagement of the Salmonella pathogenicity island 2-encoded type 3 secretion system (SPI2-T3SS). Finally, although inhibition of PIKfyve in macrophages did inhibit Salmonella replication, it also appears to disrupt the macrophage's bactericidal response.
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Characterization of PXK as a protein involved in epidermal growth factor receptor trafficking. Mol Cell Biol 2010; 30:1689-702. [PMID: 20086096 DOI: 10.1128/mcb.01105-09] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The phox homology (PX) domain is a phosphoinositide-binding module that typically binds phosphatidylinositol 3-phosphate. Out of 47 mammalian proteins containing PX domains, more than 30 are denoted sorting nexins and several of these have been implicated in internalization of cell surface proteins to the endosome, where phosphatidylinositol-3-phosphate is concentrated. Here we investigated a multimodular protein termed PXK, composed of a PX domain, a protein kinase-like domain, and a WASP homology 2 domain. We show that the PX domain of PXK localizes this protein to the endosomal membrane via binding to phosphatidylinositol 3-phosphate. PXK expression in COS7 cells accelerated the ligand-induced internalization and degradation of epidermal growth factor receptors by a mechanism requiring phosphatidylinositol 3-phosphate binding but not involving the WASP homology 2 domain. Conversely, depletion of PXK using RNA interference decreased the rate of epidermal growth factor receptor internalization and degradation. Ubiquitination of epidermal growth factor receptor by the ligand stimulation was enhanced in PXK-expressing cells. These results indicate that PXK plays a critical role in epidermal growth factor receptor trafficking through modulating ligand-induced ubiquitination of the receptor.
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Kan A, Ikeda T, Saito T, Yano F, Fukai A, Hojo H, Ogasawara T, Ogata N, Nakamura K, Chung UI, Kawaguchi H. Screening of chondrogenic factors with a real-time fluorescence-monitoring cell line ATDC5-C2ER: identification of sorting nexin 19 as a novel factor. ACTA ACUST UNITED AC 2010; 60:3314-23. [PMID: 19877062 DOI: 10.1002/art.24878] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To establish a cell culture system for noninvasive and real-time monitoring of chondrogenic differentiation in order to screen for chondrogenic factors. METHODS The optimum reporter construct transfected into chondrogenic ATDC5 cells was selected by a luciferase reporter assay and fluorescence analysis during cultures with insulin. The established cell line was validated according to its fluorescence following stimulation with SOX proteins, bone morphogenetic protein 2 (BMP-2), or transforming growth factor beta (TGFbeta) and was compared with the level of messenger RNA for COL2A1 as well as with the degree of Alcian blue staining. Screening of chondrogenic factors was performed by expression cloning using a retroviral expression library prepared from human tracheal cartilage. The expression pattern of the identified molecule was examined by in situ hybridization and immunohistochemistry. Functional analysis was performed by transfection of the identified gene, the small interfering RNA, and the mutated gene. RESULTS We established an ATDC5 cell line with 4 repeats of a highly conserved enhancer ligated to a COL2A1 basal promoter and the DsRed2 reporter (ATDC5-C2ER). Fluorescence was induced under the stimulations with SOX proteins, BMP-2, or TGFbeta, showing good correspondence to the chondrogenic markers. Screening using the ATDC5-C2ER system identified several chondrogenic factors, including sorting nexin 19 (SNX19). SNX19 was expressed in the limb cartilage of mouse embryos and in the degraded cartilage of adult mouse knee joints during osteoarthritis progression. The gain-of-function and loss-of-function analyses revealed a potent chondrogenic activity of SNX19. CONCLUSION We established the ATDC5-C2ER system for efficient monitoring of chondrogenic differentiation by fluorescence analysis, and we identified a novel chondrogenic factor (SNX19) using this system. This system will be useful for elucidating the molecular network of chondrogenic differentiation.
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Affiliation(s)
- Akinori Kan
- Faculty of Medicine, University of Tokyo, Tokyo, Japan
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Koharudin LMI, Furey W, Liu H, Liu YJ, Gronenborn AM. The phox domain of sorting nexin 5 lacks phosphatidylinositol 3-phosphate (PtdIns(3)P) specificity and preferentially binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). J Biol Chem 2009; 284:23697-707. [PMID: 19553671 PMCID: PMC2749144 DOI: 10.1074/jbc.m109.008995] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 06/08/2009] [Indexed: 11/06/2022] Open
Abstract
Subcellular retrograde transport of cargo receptors from endosomes to the trans-Golgi network is critically involved in a broad range of physiological and pathological processes and highly regulated by a genetically conserved heteropentameric complex, termed retromer. Among the retromer components identified in mammals, sorting nexin 5 and 1 (SNX5; SNX1) have recently been found to interact, possibly controlling the membrane binding specificity of the complex. To elucidate how the unique sequence features of the SNX5 phox domain (SNX5-PX) influence retrograde transport, we have determined the SNX5-PX structure by NMR and x-ray crystallography at 1.5 A resolution. Although the core fold of SNX5-PX resembles that of other known PX domains, we found novel structural features exclusive to SNX5-PX. It is most noteworthy that in SNX5-PX, a long helical hairpin is added to the core formed by a new alpha2'-helix and a much longer alpha3-helix. This results in a significantly altered overall shape of the protein. In addition, the unique double PXXP motif is tightly packed against the rest of the protein, rendering this part of the structure compact, occluding parts of the putative phosphatidylinositol (PtdIns) binding pocket. The PtdIns binding and specificity of SNX5-PX was evaluated by NMR titrations with eight different PtdIns and revealed that SNX5-PX preferentially and specifically binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)). The distinct structural and PtdIns binding characteristics of SNX5-PX impart specific properties on SNX5, influencing retromer-mediated regulation of retrograde trafficking of transmembrane cargo receptors.
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Affiliation(s)
| | - William Furey
- Pharmacology and Chemical Biology
- the Biocrystallography Laboratory, Veterans Affairs Medical Center, Pittsburgh, Pennsylvania 15240
| | | | - Yong-Jian Liu
- Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
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Abstract
As obligatory intracellular parasites, viruses rely on host-cell functions for most aspects of their replication cycle. This is born out during entry, when most viruses that infect vertebrate and insect cells exploit the endocytic activities of the host cell to move into the cytoplasm. Viruses belonging to vaccinia, adeno, picorna and other virus families have been reported to take advantage of macropinocytosis, an endocytic mechanism normally involved in fluid uptake. The virus particles first activate signalling pathways that trigger actin-mediated membrane ruffling and blebbing. Usually, this is followed by the formation of large vacuoles (macropinosomes) at the plasma membrane, internalization of virus particles and penetration by the viruses or their capsids into the cytosol through the limiting membrane of the macropinosomes. We review the molecular machinery involved in macropinocytosis and describe what is known about its role in virus entry.
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Aboghe DH, Yoshioka M, Phaneuf D, St-Amand J. Regulation of gene expression by estrogen in mammary gland of wild type and estrogen receptor alpha knockout mice. J Steroid Biochem Mol Biol 2009; 113:116-26. [PMID: 19126430 DOI: 10.1016/j.jsbmb.2008.12.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 12/02/2008] [Accepted: 12/08/2008] [Indexed: 01/20/2023]
Abstract
Using serial analysis of gene expression, we examined the effects of estrogen (E2) replacement in gonadectomized wild type (WT) and E2 receptor alpha knockout (ERalphaKO) mice on global gene expression in mammary gland. In WT mice, a total of 429,302 tags were sequenced, representing the expression level of 99,854 tag species. A total of ten transcripts were found to be modulated by E2, such as sorting nexin 5 and two no match tags. In the ERalphaKO mice, a total of 459,439 tags were sequenced, representing the expression level of 120,149 tag species. Interestingly, the same three transcripts were inversely regulated by E2 in ERalphaKO mice. In total, 78 transcripts were upregulated by E2, while 29 transcripts were downregulated. In contrast to WT mice, the majority of transcripts related to immunity were repressed in ERalphaKO mice. Moreover, induction of transcripts involved in cell differentiation, Ca2+ response, cytoskeleton, protein biosynthesis and secretion, glycolysis, and oxidative phosphorylation were seen only in ERalphaKO mice. The current study will provide useful information to understand the cellular mechanisms of E(2)-mediated gene regulation in tissues in vivo for the development of novel drugs targeting specific ER action in pathological conditions.
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Affiliation(s)
- David Hyacinthe Aboghe
- Functional Genomics Laboratory, Molecular Endocrinology and Oncology Research Center, Laval University Medical Center, Department of Anatomy and Physiology, Laval University, Québec, Canada
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Affiliation(s)
- Brett M Collins
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
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Phan NQ, Kim SJ, Bassham DC. Overexpression of Arabidopsis sorting nexin AtSNX2b inhibits endocytic trafficking to the vacuole. MOLECULAR PLANT 2008; 1:961-976. [PMID: 19825596 DOI: 10.1093/mp/ssn057] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Sorting nexins are conserved proteins that function in vesicular trafficking and contain a characteristic phox homology (PX) domain. Here, we characterize the ubiquitously expressed Arabidopsis thaliana sorting nexin AtSNX2b. Sub-cellular fractionation studies indicate that AtSNX2b is peripherally associated with membranes. The AtSNX2b PX domain binds to phosphatidylinositol 3-phosphate in vitro and this association is required for the localization of GFP-AtSNX2b to punctate structures in vivo, identified as the trans-Golgi network, prevacuolar compartment and endosomes. Overexpression of GFP-tagged AtSNX2b produces enlarged GFP-labeled compartments that can also be labeled by the endocytic tracer FM4-64. Endocytic trafficking of FM4-64 to the vacuole is arrested in these GFP-AtSNX2b compartments, and similar FM4-64-accumulating compartments are seen upon overexpression of untagged AtSNX2b. This suggests that exit of membrane components from these enlarged or aggregated endosomes is inhibited. Vacuolar proteins containing an N-terminal propeptide, but not those with a C-terminal propeptide, are also present in these enlarged compartments. We hypothesize that AtSNX2b is involved in vesicular trafficking from endosomes to the vacuole.
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Affiliation(s)
- Nguyen Q Phan
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
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Lim JP, Wang JTH, Kerr MC, Teasdale RD, Gleeson PA. A role for SNX5 in the regulation of macropinocytosis. BMC Cell Biol 2008; 9:58. [PMID: 18854019 PMCID: PMC2576169 DOI: 10.1186/1471-2121-9-58] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 10/14/2008] [Indexed: 11/10/2022] Open
Abstract
Background The mechanisms and components that regulate macropinocytosis are poorly understood. Here we have investigated the role of sorting nexin 5 (SNX5) in the regulation of macropinocytic activity. Results SNX5 is abundantly expressed in macrophages, cells very active in macropinocytosis, and is recruited onto newly-formed macropinosomes. LPS treatment of bone marrow-derived macrophages resulted in a 2.5 fold decrease in macropinosome formation that correlates with a reduction in the levels of SNX5. To investigate the relationship between SNX5 levels and macropinocytic activity we examined the formation of macropinosomes in HEK-FlpIn cells stably expressing GFP-SNX5. Constitutive macropinocytosis was increased ~2 fold in HEK-GFP-SNX5 cells compared with parental HEK-FlpIn cells. Furthermore, EGF stimulation resulted in a significant increase in macropinocytosis and there was also a 2.0 fold increase in the generation of macropinosomes in HEK-GFP-SNX5 cells compared with parental HEK-FlpIn cells. SNX5, which interacts specifically with PtdIns(3)P and PtdIns(3,4)P2 through its PX domain, was recruited to regions on the plasma membrane containing EGF receptor or positive for PtdIns(3,4)P2 as detected with the PH domain of TAPP1. Treatment with AG1478, an EGF receptor specific tyrosine kinase inhibitor, prevented the recruitment of SNX5 to the cytosolic face of the plasma membrane and inhibited the formation of macropinosomes in response to EGF treatment. Conclusion Based on these data, we propose that SNX5 requires the generation of phosphoinositides for recruitment to the plasma membrane and, moreover, influences the level of macropinocytic activity.
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Affiliation(s)
- Jet Phey Lim
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia.
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McLaughlin NJD, Banerjee A, Khan SY, Lieber JL, Kelher MR, Gamboni-Robertson F, Sheppard FR, Moore EE, Mierau GW, Elzi DJ, Silliman CC. Platelet-activating factor-mediated endosome formation causes membrane translocation of p67phox and p40phox that requires recruitment and activation of p38 MAPK, Rab5a, and phosphatidylinositol 3-kinase in human neutrophils. THE JOURNAL OF IMMUNOLOGY 2008; 180:8192-203. [PMID: 18523285 DOI: 10.4049/jimmunol.180.12.8192] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Neutrophils (polymorphonuclear leukocytes, PMNs) are vital to innate immunity and receive proinflammatory signals that activate G protein-coupled receptors (GPCRs). Because GPCRs transduce signals through clathrin-mediated endocytosis (CME), we hypothesized that platelet-activating factor (PAF), an effective chemoattractant that primes the PMN oxidase, would signal through CME, specifically via dynamin-2 activation and endosomal formation resulting in membrane translocation of cytosolic phagocyte oxidase (phox) proteins. PMNs were incubated with buffer or 2 muM PAF for 1-3 min, and in some cases activated with PMA, and O(2)(-) was measured, whole-cell lysates and subcellular fractions were prepared, or the PMNs were fixed onto slides for digital or electron microscopy. PAF caused activation of dynamin-2, resulting in endosomal formation that required PI3K and contained early endosomal Ag-1 (EEA-1) and Rab5a. The apoptosis signal-regulating kinase-1/MAPK kinase-3/p38 MAPK signalosome assembled on Rab5a and phosphorylated EEA-1 and Rab GDP dissociation inhibitor, with the latter causing Rab5a activation. Electron microscopy demonstrated that PAF caused two distinct sites for activation of p38 MAPK. EEA-1 provided a scaffold for recruitment of the p40(phox)-p67(phox) complex and PI3K-dependent Akt1 phosphorylation of these two phox proteins. PAF induced membrane translocation of p40(phox)-p67(phox) localizing to gp91(phox), which was PI3K-, but not p47(phox)-, dependent. In conclusion, PAF transduces signals through CME, and such GPCR signaling may allow for pharmacological manipulation of these cells to decrease PMN-mediated acute organ injury.
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Affiliation(s)
- Nathan J D McLaughlin
- Bonfils Blood Center, University of Colorado Denver School of Medicine, Children's Hospital, Denver, CO 80230, USA
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Hara S, Kiyokawa E, Iemura SI, Natsume T, Wassmer T, Cullen PJ, Hiai H, Matsuda M. The DHR1 domain of DOCK180 binds to SNX5 and regulates cation-independent mannose 6-phosphate receptor transport. Mol Biol Cell 2008; 19:3823-35. [PMID: 18596235 DOI: 10.1091/mbc.e08-03-0314] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
DOCK180 is the archetype of the DOCK180-family guanine nucleotide exchange factor for small GTPases Rac1 and Cdc42. DOCK180-family proteins share two conserved domains, called DOCK homology region (DHR)-1 and -2. Although the function of DHR2 is to activate Rac1, DHR1 is required for binding to phosphoinositides. To better understand the function of DHR1, we searched for its binding partners by direct nanoflow liquid chromatography/tandem mass spectrometry, and we identified sorting nexins (SNX) 1, 2, 5, and 6, which make up a multimeric protein complex mediating endosome-to-trans-Golgi-network (TGN) retrograde transport of the cation-independent mannose 6-phosphate receptor (CI-MPR). Among these SNX proteins, SNX5 was coimmunoprecipitated with DOCK180 most efficiently. In agreement with this observation, DOCK180 colocalized with SNX5 at endosomes. The RNA interference-mediated knockdowns of SNX5 and DOCK180, but not Rac1, resulted in the redistribution of CI-MPR from TGN to endosomes. Furthermore, expression of the DOCK180 DHR1 domain was sufficient to restore the perturbed CI-MPR distribution in DOCK180 knockdown cells. These data suggest that DOCK180 regulates CI-MPR trafficking via SNX5 and that this function is independent of its guanine nucleotide exchange factor activity toward Rac1.
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Affiliation(s)
- Shigeo Hara
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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Bujny MV, Ewels PA, Humphrey S, Attar N, Jepson MA, Cullen PJ. Sorting nexin-1 defines an early phase of Salmonella-containing vacuole-remodeling during Salmonella infection. J Cell Sci 2008; 121:2027-36. [PMID: 18505799 DOI: 10.1242/jcs.018432] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Salmonella enterica serovar Typhimurium replicate within host cells in a specialized membrane-bound compartment, the Salmonella-containing vacuole (SCV). Interaction of SCVs with the host endocytic network is modulated by bacterial effectors, some of which, such as SigD/SopB, manipulate the level of endosomal phosphoinositides. Here, we establish that at early stages of Salmonella infection, sorting nexin-1 (SNX1) - a host phosphoinositide-binding protein that normally associates with early endosomes and regulates transport to the trans-Golgi network (TGN) - undergoes a rapid and transient translocation to bacterial entry sites, an event promoted by SigD/SopB. Recruitment of SNX1 to SCVs results in the formation of extensive, long-range tubules that we have termed ;spacious vacuole-associated tubules'. Formation of these tubules is coupled with size reduction of vacuoles and the removal of TGN-resident cargo. SNX1 suppression perturbs intracellular progress of bacteria, resulting in a delayed replication. We propose that SNX1 is important in tubular-based re-modeling of nascent SCVs and, in doing so, regulates intracellular bacterial progression and replication.
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Affiliation(s)
- Miriam V Bujny
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
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Retromer. Curr Opin Cell Biol 2008; 20:427-36. [PMID: 18472259 DOI: 10.1016/j.ceb.2008.03.009] [Citation(s) in RCA: 383] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Revised: 03/20/2008] [Accepted: 03/20/2008] [Indexed: 01/17/2023]
Abstract
The retromer is a heteropentameric complex that associates with the cytosolic face of endosomes and mediates retrograde transport of transmembrane cargo from endosomes to the trans-Golgi network. The mammalian retromer complex comprises a sorting nexin dimer composed of a still undefined combination of SNX1, SNX2, SNX5 and SNX6, and a cargo-recognition trimer composed of Vps26, Vps29 and Vps35. The SNX subunits contain PX and BAR domains that allow binding to PI(3)P enriched, highly curved membranes of endosomal vesicles and tubules, while Vps26, Vps29 and Vps35 have arrestin, phosphoesterase and alpha-solenoid folds, respectively. Recent studies have implicated retromer in a broad range of physiological, developmental and pathological processes, underscoring the critical nature of retrograde transport mediated by this complex.
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A combinatorial approach to crystallization of PX-BAR unit of the human Sorting Nexin 9. J Struct Biol 2007; 162:356-60. [PMID: 18065239 DOI: 10.1016/j.jsb.2007.10.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 09/21/2007] [Accepted: 10/24/2007] [Indexed: 11/22/2022]
Abstract
Sorting nexins (SNXs) form a family of proteins known to interact with endosomal vesicles and to regulate various steps of vesicle transport. Sorting Nexin 9 (SNX9) is involved in the interface of endocytic, actin polymerizing, and signal transduction events in the cell. Here we report crystallization of the SNX9 PX-BAR domain protein. Initially we used an ordinary protein construct design, and protein crystallization approaches resulted in obtaining granular crystal-like precipitation. SDS-PAGE and MS analysis of the crystal-like precipitation followed by protein construct optimization and using of macro seeding technique resulted in X-ray quality diffracting crystals. The crystals belonged to P2(1)2(1)2(1) space group (a=65.6 A, b=117.5 A, c=145.8 A) with two protein molecules per asymmetric unit. A complete SAD data set from Se-Methionine derived crystal (3.2 A) has been collected to solve the structure.
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Champine PJ, Michaelson J, Weimer BC, Welch DR, DeWald DB. Microarray analysis reveals potential mechanisms of BRMS1-mediated metastasis suppression. Clin Exp Metastasis 2007; 24:551-65. [PMID: 17896182 PMCID: PMC2214901 DOI: 10.1007/s10585-007-9092-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Accepted: 07/27/2007] [Indexed: 12/14/2022]
Abstract
We used Affymetrix microarrays to compare gene expression profiles of the metastatic parental breast cancer cell line MDA-MB-435 (435) and the non-metastatic daughter cell line created by the stable expression of the BReast cancer Metastasis Suppressor 1 (BRMS1) gene in 435 cells, MDA-MB-435-BRMS1 (435/BRMS1). Analysis of microarray data provided insight into some of the potential mechanisms by which BRMS1 inhibits tumor formation at secondary sites. Furthermore, due to the importance of the microenvironment, we also examined gene expression under different growth conditions (i.e., plus or minus serum). Expression of 565 genes was significantly (adjusted P-value <0.05) altered regardless of in vitro growth conditions. BRMS1 expression significantly increased multiple major histocompatability complex (MHC) genes and significantly decreased expression of several genes associated with protein localization and secretion. The pattern of gene expression associated with BRMS1 expression suggests that metastasis suppression may be mediated by enhanced immune recognition, altered transport, and/or secretion of metastasis-associated proteins.
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Affiliation(s)
- Patricia J. Champine
- Center for Integrated BioSystems, Utah State University, Logan, Utah 84322-4700, USA
| | - Jacob Michaelson
- Center for Integrated BioSystems, Utah State University, Logan, Utah 84322-4700, USA
| | - Bart C. Weimer
- Center for Integrated BioSystems, Utah State University, Logan, Utah 84322-4700, USA
| | - Danny R. Welch
- Department of Pathology, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA
- National Foundation for Cancer Research, Center for Metastasis Research, Logan, Utah 84322-5305, USA
| | - Daryll B. DeWald
- National Foundation for Cancer Research, Center for Metastasis Research, Logan, Utah 84322-5305, USA
- Department of Biology, Utah State University, Logan, Utah 84322-5305, USA
- Correspondence to: D.B. DeWald, Department of Biology and Center for Integrated BioSystems, Utah State University, Logan, Utah 84322-5305 (435)-797-1909
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Iwasaki SI, Aoyagi H. Expression of keratin 14 in the basal cells of the lingual epithelium of mice during the morphogenesis of filiform papillae: visualization by fluorescent immunostaining and confocal laser-scanning microscopy in the transmission mode. Odontology 2007; 95:61-5. [PMID: 17660983 DOI: 10.1007/s10266-007-0072-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Accepted: 03/14/2007] [Indexed: 11/28/2022]
Abstract
We examined the expression of keratin 14 (K14) on the lingual epithelium by immunofluorescent staining while monitoring morphological changes in the filiform papillae of mice by confocal laser-scanning microscopy in the transmission mode of the same sections to define both the histology and the morphology of cells. It is difficult to visualize histological details of the fetal lingual epithelium of the mouse on semi-ultrathin sections by light microscopy after immunohistochemical staining because the histological structures in such sections cannot be distinguished by standard counterstaining. To solve this problem and to visualize the immunoreactivity specific for K14, we analyzed the results of immunofluorescent staining of semi-ultrathin sections in combination with an examination of the corresponding images by laser-scanning microscopy in the transmission mode after staining of specimens with toluidine blue. No immunoreactivity specific for K14 was detected on the lingual epithelium of fetuses on embryonic day 15 (E15), but immunoreactivity was distinct at all postnatal stages from postnatal day 0 (P0) to P21.
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Affiliation(s)
- Shin-Ichi Iwasaki
- Advanced Research Center, The Nippon Dental University School of Life Dentistry at Niigata, Niigata, Japan.
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Hamilton N, Kerr MC, Burrage K, Teasdale RD. Analyzing Real‐Time Video Microscopy: The Dynamics and Geometry of Vesicles and Tubules in Endocytosis. ACTA ACUST UNITED AC 2007; Chapter 14:Unit 4.16. [DOI: 10.1002/0471143030.cb0416s35] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Nicholas Hamilton
- ARC Centre in Bioinformatics Institute for Molecular Bioscience The University of Queensland St. Lucia Australia
| | - Markus C. Kerr
- ARC Centre in Bioinformatics Institute for Molecular Bioscience The University of Queensland St. Lucia Australia
| | - Kevin Burrage
- ARC Centre in Bioinformatics Institute for Molecular Bioscience The University of Queensland St. Lucia Australia
| | - Rohan D. Teasdale
- ARC Centre in Bioinformatics Institute for Molecular Bioscience The University of Queensland St. Lucia Australia
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Wassmer T, Attar N, Bujny MV, Oakley J, Traer CJ, Cullen PJ. A loss-of-function screen reveals SNX5 and SNX6 as potential components of the mammalian retromer. J Cell Sci 2006; 120:45-54. [PMID: 17148574 DOI: 10.1242/jcs.03302] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The mammalian retromer is a multimeric protein complex involved in mediating endosome-to-trans-Golgi-network retrograde transport of the cation-independent mannose-6-phosphate receptor. The retromer is composed of two subcomplexes, one containing SNX1 and forming a membrane-bound coat, the other comprising VPS26, VPS29 and VPS35 and being cargo-selective. In yeast, an additional sorting nexin--Vps17p--is a component of the membrane bound coat. It remains unclear whether the mammalian retromer requires a functional equivalent of Vps17p. Here, we have used an RNAi loss-of-function screen to examine whether any of the other 30 mammalian sorting nexins are required for retromer-mediated endosome-to-trans-Golgi-network retrieval of the cation-independent mannose-6-phosphate receptor. Using this screen, we identified two proteins, SNX5 and SNX6, that, when suppressed, induced a phenotype similar to that observed upon suppression of known retromer components. Whereas SNX5 and SNX6 colocalised with SNX1 on early endosomes, in immunoprecipitation experiments only SNX6 appeared to exist in a complex with SNX1. Interestingly, suppression of SNX5 and/or SNX6 resulted in a significant loss of SNX1, an effect that seemed to result from post-translational regulation of the SNX1 level. Such data suggest that SNX1 and SNX6 exist in a stable, endosomally associated complex that is required for retromer-mediated retrieval of the cation-independent mannose-6-phosphate receptor. SNX5 and SNX6 may therefore constitute functional equivalents of Vps17p in mammals.
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Affiliation(s)
- Thomas Wassmer
- The Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK
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Iwasaki SI, Aoyagi H, Yoshizawa H. Immunohistochemical detection of epidermal growth factor and epidermal growth factor receptor in the lingual mucosa of rats during the morphogenesis of filiform papillae. Acta Histochem 2006; 109:37-44. [PMID: 17098278 DOI: 10.1016/j.acthis.2006.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 07/31/2006] [Accepted: 09/01/2006] [Indexed: 12/24/2022]
Abstract
We examined the immunofluorescence labelling epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR), as well as differential interference contrast (DIC) images, during the morphogenesis of filiform papillae and the keratinization of the lingual epithelium of rats on semi-ultrathin sections of epoxy resin-embedded samples using laser-scanning microscopy. We also examined semi-ultrathin sections of epoxy resin-embedded, toluidine blue-stained samples by light microscopy to obtain details of cell histology and morphology. No immunoreactivity specific for EGF and EGFR was detected on the lingual epithelium of fetuses on days 12 and 16 after conception (E12 and E16), during which time the number of layers of cuboidal cells in the lingual epithelium increased from one to several. Immunoreactivity specific for EGF and EGFR was first detected on the lingual epithelium of fetuses at birth or on postnatal day 0 (P0). Immunoreactivity specific both for EGF and EGFR appeared in the connective tissue and the basal cells of the papillary and interpapillary cell columns. The lingual epithelium was composed of stratified squamous cells. The rudiments of filiform papillae were compactly arranged and interpapillary cell columns were very narrow. Immunoreactivity specific for EGF and EGFR was distinct on the cell membrane of basal cells of the papillary cell column and weakly positive on the cell membrane of basal cells of the interpapillary cell column on postnatal day 21 (P21). Thus, the patterns of immunoreactivity of EGF and EGFR differed as the filiform papillae developed. Filiform papillae developed gradually from P0 to P21. The width of interpapillary spaces also increased during this period. These observations indicate a possibility that EGF might affect the expression of keratins in the lingual epithelium via epithelium-mesenchymal interactions.
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Affiliation(s)
- Shin-ichi Iwasaki
- Advanced Research Center, The Nippon Dental University School of Life Dentistry at Niigata, Niigata 951-8580, Japan.
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