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Lee V, Hinton BT, Hirashima T. Collective cell dynamics and luminal fluid flow in the epididymis: A mechanobiological perspective. Andrology 2024; 12:939-948. [PMID: 37415418 DOI: 10.1111/andr.13490] [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: 04/22/2023] [Revised: 06/08/2023] [Accepted: 07/04/2023] [Indexed: 07/08/2023]
Abstract
BACKGROUND The mammalian epididymis is a specialized duct system that serves a critical role in sperm maturation and storage. Its distinctive, highly coiled tissue morphology provides a unique opportunity to investigate the link between form and function in reproductive biology. Although recent genetic studies have identified key genes and signaling pathways involved in the development and physiological functions of the epididymis, there has been limited discussion about the underlying dynamic and mechanical processes that govern these phenomena. AIMS In this review, we aim to address this gap by examining two key aspects of the epididymis across its developmental and physiological phases. RESULTS AND DISCUSSION First, we discuss how the complex morphology of the Wolffian/epididymal duct emerges through collective cell dynamics, including duct elongation, cell proliferation, and arrangement during embryonic development. Second, we highlight dynamic aspects of luminal fluid flow in the epididymis, essential for regulating the microenvironment for sperm maturation and motility, and discuss how this phenomenon emerges and interplays with epididymal epithelial cells. CONCLUSION This review not only aims to summarize current knowledge but also to provide a starting point for further exploration of mechanobiological aspects related to the cellular and extracellular fluid dynamics in the epididymis.
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Affiliation(s)
- Veronica Lee
- Mechanobiology, Institute, National University of Singapore, Singapore, Singapore
| | - Barry T Hinton
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Tsuyoshi Hirashima
- Mechanobiology, Institute, National University of Singapore, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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Weisser I, Eckberg K, D'Amico S, Buttram D, Aboudehen K. Ablation of Long Noncoding RNA Hoxb3os Exacerbates Cystogenesis in Mouse Polycystic Kidney Disease. J Am Soc Nephrol 2024; 35:41-55. [PMID: 37953472 PMCID: PMC10786614 DOI: 10.1681/asn.0000000000000265] [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: 07/21/2023] [Accepted: 10/20/2023] [Indexed: 11/14/2023] Open
Abstract
SIGNIFICANCE STATEMENT Long noncoding RNAs (lncRNAs) are a class of nonprotein coding RNAs with pivotal functions in development and disease. They have emerged as an exciting new drug target category for many common conditions. However, the role of lncRNAs in autosomal dominant polycystic kidney disease (ADPKD) has been understudied. This study provides evidence implicating a lncRNA in the pathogenesis of ADPKD. We report that Hoxb3os is downregulated in ADPKD and regulates mammalian target of rapamycin (mTOR)/Akt pathway in the in vivo mouse kidney. Ablating the expression of Hoxb3os in mouse polycystic kidney disease (PKD) activated mTOR complex 2 (mTORC2) signaling and exacerbated the cystic phenotype. The results from our study provide genetic proof of concept for future studies that focus on targeting lncRNAs as a treatment option in PKD. BACKGROUND ADPKD is a monogenic disorder characterized by the formation of kidney cysts and is primarily caused by mutations in two genes, PKD1 and PKD2 . METHODS In this study, we investigated the role of lncRNA Hoxb3os in ADPKD by ablating its expression in the mouse. RESULTS Hoxb3os -null mice were viable and had grossly normal kidney morphology but displayed activation of mTOR/Akt signaling and subsequent increase in kidney cell proliferation. To determine the role of Hoxb3os in cystogenesis, we crossed the Hoxb3os -null mouse to two orthologous Pkd1 mouse models: Pkhd1/Cre; Pkd1F/F (rapid cyst progression) and Pkd1RC/RC (slow cyst progression). Ablation of Hoxb3os exacerbated cyst growth in both models. To gain insight into the mechanism whereby Hoxb3os inhibition promotes cystogenesis, we performed western blot analysis of mTOR/Akt pathway between Pkd1 single-knockout and Pkd1 - Hoxb3os double-knockout (DKO) mice. Compared with single-knockout, DKO mice presented with enhanced levels of total and phosphorylated Rictor. This was accompanied by increased phosphorylation of Akt at Ser 473 , a known mTORC2 effector site. Physiologically, kidneys from DKO mice displayed between 50% and 60% increase in cell proliferation and cyst number. CONCLUSIONS The results from this study indicate that ablation of Hoxb3os in mouse PKD exacerbates cystogenesis and dysregulates mTORC2.
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Affiliation(s)
- Ivan Weisser
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Kara Eckberg
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Stephen D'Amico
- Department of Medicine, Stony Brook University, Stony Brook, New York
| | - Daniel Buttram
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Karam Aboudehen
- Department of Medicine, Stony Brook University, Stony Brook, New York
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Pan F, Bu L, Wu K, Wang A, Xu X. PKD2/polycystin-2 inhibits LPS-induced acute lung injury in vitro and in vivo by activating autophagy. BMC Pulm Med 2023; 23:171. [PMID: 37198573 DOI: 10.1186/s12890-023-02449-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 04/21/2023] [Indexed: 05/19/2023] Open
Abstract
Polycystin-2 (PC2), which is a transmembrane protein encoded by the PKD2 gene, plays an important role in kidney disease, but its role in lipopolysaccharide (LPS)-induced acute lung injury (ALI) is unclear. We overexpressed PKD2 in lung epithelial cells in vitro and in vivo and examined the role of PKD2 in the inflammatory response induced by LPS in vitro and in vivo. Overexpression of PKD2 significantly decreased production of the inflammatory factors TNF-α, IL-1β, and IL-6 in LPS-treated lung epithelial cells. Moreover, pretreatment with 3-methyladenine (3-MA), an autophagy inhibitor, reversed the inhibitory effect of PKD2 overexpression on the secretion of inflammatory factors in LPS-treated lung epithelial cells. We further demonstrated that overexpression of PKD2 could inhibit LPS-induced downregulation of the LC3BII protein levels and upregulation of SQSTM1/P62 protein levels in lung epithelial cells. Moreover, we found that LPS-induced changes in the lung wet/dry (W/D) weight ratio and levels of the inflammatory cytokines TNF-α, IL-6 and IL-1β in the lung tissue were significantly decreased in mice whose alveolar epithelial cells overexpressed PKD2. However, the protective effects of PKD2 overexpression against LPS-induced ALI were reversed by 3-MA pretreatment. Our study suggests that overexpression of PKD2 in the epithelium may alleviate LPS-induced ALI by activating autophagy.
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Affiliation(s)
- Fan Pan
- Department of Anesthesiology, Affiliated Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, 200233, China
| | - Lina Bu
- Department of Anesthesiology, Affiliated Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, 200233, China
| | - Kaixuan Wu
- Department of Anesthesiology, Affiliated Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, 200233, China
| | - Aizhong Wang
- Department of Anesthesiology, Affiliated Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, 200233, China.
| | - Xiaotao Xu
- Department of Anesthesiology, Affiliated Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, 200233, China.
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Assimakopoulou M, Christopoulou ME, Karamani V, Aletras AJ, Gatzounis G. Polycystin-2 Associates With Malignancy in Meningiomas. Appl Immunohistochem Mol Morphol 2023; 31:239-244. [PMID: 36877184 PMCID: PMC10072210 DOI: 10.1097/pai.0000000000001113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 09/28/2022] [Indexed: 03/07/2023]
Abstract
The involvement of polycystin-2 (PC2) in cell survival pathways raises questions about its role in carcinogenesis. Aberrant expression of PC2 has been associated with malignancy in various tumors. No evidence exists referring to PC2 expression in meningiomas. The aim of this study was to investigate the expression levels of PC2 in meningiomas and compare them with normal brain samples including leptomeninges. PC2 immunohistochemical expression was quantitatively analyzed in archival tissue from 60 patients with benign (WHO grade 1) and 22 patients with high-grade (21: WHO grade 2 and 1: grade 3) meningiomas. Specifically, the labeling index [the percentage of positive (labeled) cells out of the total number of tumor cells counted] was determined. PC2 mRNA levels were evaluated by quantitative real-time polymerase chain reaction. PC2 immunostaining was not detected in the leptomeninges. Gene expression analysis revealed increased levels of PC2 in WHO grade 1 ( P = 0.008) and WHO grade 2 ( P = 0.0007) meningiomas compared with that of normal brains. PC2 expression was significantly associated with an ascending grade of malignancy by both immunohistochemistry and quantitative real-time polymerase chain reaction ( P < 0.05). Recurrent meningiomas displayed higher levels of PC2 compared with primary meningiomas ( P = 0.008). Although no significant association of PC2 with the overall survival of the patients was found ( P > 0.05), it was noticed that the patients with WHO grade 2 meningiomas with low expression of PC2 survived longer compared with the patients with WHO grade 1 meningioma with high expression of PC2 (mean survival 49.5 and 28 months, respectively). The above results indicate a possible association of PC2 with malignancy in meningiomas. However, the mechanisms underlying PC2 implication in meningioma pathogenesis should be further elucidated.
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Affiliation(s)
| | | | | | - Alexios J. Aletras
- Laboratory of Biochemistry, Department of Chemistry, University of Patras
| | - George Gatzounis
- Department of Neurosurgery, University Hospital of Patras, Patras, Greece
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Scarinci N, Perez PL, Cantiello HF, Cantero MDR. Polycystin-2 (TRPP2) regulates primary cilium length in LLC-PK1 renal epithelial cells. Front Physiol 2022; 13:995473. [PMID: 36267587 PMCID: PMC9577394 DOI: 10.3389/fphys.2022.995473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/14/2022] [Indexed: 11/21/2022] Open
Abstract
Polycystin-2 (PC2, TRPP2) is a Ca2+ permeable nonselective cation channel whose dysfunction generates autosomal dominant polycystic kidney disease (ADPKD). PC2 is present in different cell locations, including the primary cilium of renal epithelial cells. However, little is known as to whether PC2 contributes to the primary cilium structure. Here, we explored the effect(s) of external Ca2+, PC2 channel blockers, and PKD2 gene silencing on the length of primary cilia in wild-type LLC-PK1 renal epithelial cells. Confluent cell monolayers were fixed and immuno-labeled with an anti-acetylated α-tubulin antibody to identify primary cilia and measure their length. Although primary cilia length measurements did not follow a Normal distribution, the data were normalized by Box-Cox transformation rendering statistical differences under all experimental conditions. Cells exposed to high external Ca2+ (6.2 mM) decreased a 13.5% (p < 0.001) primary cilia length as compared to controls (1.2 mM Ca2+). In contrast, the PC2 inhibitors amiloride (200 μM) and LiCl (10 mM), both increased primary ciliary length by 33.2% (p < 0.001), and 17.4% (p < 0.001), respectively. PKD2 gene silencing by siRNA elicited a statistically significant, 10.3% (p < 0.001) increase in primary cilia length compared to their respective scrambled RNA transfected cells. The data indicate that conditions that regulate PC2 function or gene expression modify the length of primary cilia in renal epithelial cells. Blocking of PC2 mitigates the effects of elevated external Ca2+ concentration on primary cilia length. Proper regulation of PC2 function in the primary cilium may be essential in the onset of mechanisms that trigger cyst formation in ADPKD.
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Role of the AMPK/ACC Signaling Pathway in TRPP2-Mediated Head and Neck Cancer Cell Proliferation. BIOMED RESEARCH INTERNATIONAL 2020; 2020:4375075. [PMID: 33274210 PMCID: PMC7683127 DOI: 10.1155/2020/4375075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 09/21/2020] [Accepted: 11/02/2020] [Indexed: 12/24/2022]
Abstract
Transient receptor potential polycystic 2 (TRPP2) exerts vital roles in various types of cancer; however, its underlying mechanisms remain largely unknown. This study is aimed at investigating whether knockdown of TRPP2 affected the AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) signaling pathway and the proliferation of HN-4, cell line originating from human oral and hypopharyngeal squamous cell carcinoma. In addition, the interactions among AMPK/ACC, AMPK/protein kinase RNA-like endoplasmic reticulum kinase (PERK)/eukaryotic initiation factor 2α (eIF2α) and TRPP2/PERK/eIF2α signaling pathways, and their association with cell proliferation were also explored. The results showed that the relative expression levels of phosphorylated (p)-ACC, p-PERK, and p-eIF2α in HN-4 cells were significantly increased following treatment with 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) and significantly decreased in cells treated with compound C. Therefore, consistent with previous studies, the AMPK/ACC and AMPK/PERK/eIF2α signaling pathways were upregulated and downregulated following treatment with an AMPK agonist and inhibitor, respectively. Furthermore, TRPP2 knockdown decreased p-PERK and p-eIF2α expression levels and increased those of p-AMPK and p-ACC. Additionally, knockdown of TRPP2 increased HN-4 cell proliferation, while treatment with an AMPK inhibitor or agonist increased or inhibited TRPP2-specific siRNA-mediated cell proliferation, respectively. In conclusion, silencing of TRPP2 expression increased HN-4 cell proliferation via inhibiting the PERK/eIF2α signaling pathway, while the AMPK/ACC signaling pathway was possibly activated by a feedback mechanism to reduce enhanced cell proliferation.
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Affiliation(s)
- Hiroyuki Morita
- Department of Cardiovascular Medicine, Graduate School of Medicine, The University of Tokyo
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Primary cardiac manifestation of autosomal dominant polycystic kidney disease revealed by patient induced pluripotent stem cell-derived cardiomyocytes. EBioMedicine 2019; 40:675-684. [PMID: 30639418 PMCID: PMC6413318 DOI: 10.1016/j.ebiom.2019.01.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 12/28/2018] [Accepted: 01/07/2019] [Indexed: 02/08/2023] Open
Abstract
Background Mutations in PKD1 or PKD2 gene lead to autosomal dominant polycystic kidney disease (ADPKD). The mechanism of ADPKD progression and its link to increased cardiovascular mortality is still elusive. Methods We differentiated ADPKD patient induced pluripotent stem cells (iPSCs) to cardiomyocytes (CMs). The electrophysiological properties at the cellular level were analyzed by calcium imaging and whole cell patch clamping. Findings The ADPKD patient iPSC-CMs had decreased sarcoplasmic reticulum calcium content compared with Control-CMs. Spontaneous action potential of the PKD2 mutation line-derived CMs demonstrated slower beating rate and longer action potential duration. The PKD1 mutation line-derived CMs showed a comparable dose-dependent shortening of phase II repolarization with the Control-CMs, but a significant increase in beating frequency in response to L-type calcium channel blocker. The PKD1-mutant iPSC-CMs also showed a relatively unstable baseline as a greater percentage of cells exhibited delayed afterdepolarizations (DADs). Both the ADPKD patient iPSC-CMs showed more β-adrenergic agonist-elicited DADs compared with Control-CMs. Interpretation Characterization of ADPKD patient iPSC-CMs provides new insights into the increased clinical risk of arrhythmias, and the results enable disease modeling and drug screening for cardiac manifestations of ADPKD. Fund Ministry of Science and Technology, National Health Research Institutes, Academia Sinica Program for Technology Supporting Platform Axis Scheme, Thematic Research Program and Summit Research Program, and Kaohsiung Medical University Hospital, Taiwan.
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Lu Z, Cui Y, Wei X, Gao P, Zhang H, Wei X, Li Q, Sun F, Yan Z, Zheng H, Yang G, Liu D, Zhu Z. Deficiency of PKD2L1 (TRPP3) Exacerbates Pathological Cardiac Hypertrophy by Augmenting NCX1-Mediated Mitochondrial Calcium Overload. Cell Rep 2018; 24:1639-1652. [DOI: 10.1016/j.celrep.2018.07.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 04/19/2018] [Accepted: 07/06/2018] [Indexed: 10/28/2022] Open
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Vervliet T. Ryanodine Receptors in Autophagy: Implications for Neurodegenerative Diseases? Front Cell Neurosci 2018; 12:89. [PMID: 29636667 PMCID: PMC5880912 DOI: 10.3389/fncel.2018.00089] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 03/13/2018] [Indexed: 12/18/2022] Open
Abstract
Intracellular Ca2+ signaling is important in the regulation of several cellular processes including autophagy. The endoplasmic reticulum (ER) is the main and largest intracellular Ca2+ store. At the ER two protein families of Ca2+ release channels, inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs), are expressed. Several studies have reported roles in the regulation of autophagy for the ubiquitously expressed IP3R. For instance, IP3R-mediated Ca2+ release supresses basal autophagic flux by promoting mitochondrial metabolism, while also promoting the rapid initial increase in autophagic flux in response to nutrient starvation. Insights into the contribution of RyRs in autophagy have been lagging significantly compared to the advances made for IP3Rs. This is rather surprising considering that RyRs are predominantly expressed in long-lived cells with specialized metabolic needs, such as neurons and muscle cells, in which autophagy plays important roles. In this review article, recent studies revealing roles for RyRs in the regulation of autophagy will be discussed. Several RyR-interacting proteins that have been established to modulate both RyR function and autophagy will also be highlighted. Finally, the involvement of RyRs in neurodegenerative diseases will be addressed. Inhibition of RyR channels has not only been shown to be beneficial for treating several of these diseases but also regulates autophagy.
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Affiliation(s)
- Tim Vervliet
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
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11
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Ren JG, Xia HF, Yang JG, Zhu JY, Zhang W, Chen G, Zhao JH, Sun YF, Zhao YF. Down-regulation of polycystin in lymphatic malformations: possible role in the proliferation of lymphatic endothelial cells. Hum Pathol 2017; 65:231-238. [DOI: 10.1016/j.humpath.2017.05.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Revised: 04/27/2017] [Accepted: 05/10/2017] [Indexed: 02/04/2023]
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Reddy BV, Chapman AB. The spectrum of autosomal dominant polycystic kidney disease in children and adolescents. Pediatr Nephrol 2017; 32:31-42. [PMID: 27034070 DOI: 10.1007/s00467-016-3364-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 02/02/2016] [Accepted: 03/02/2016] [Indexed: 12/19/2022]
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disorder. It is characterized by the development of renal cysts and kidney enlargement and ultimately leads to renal failure typically in the sixth decade of life. Although most patients are asymptomatic until well into adulthood, renal cysts develop much earlier, often in utero. Significant renal anatomic and cystic expansion typically occurs before clinical manifestations in children and young adults with AKPKD. The cyst burden detected by imaging represents the minority of cyst burden, and renal and cardiovascular abnormalities are the most common manifestations in children with ADPKD. Here we review the molecular pathogenesis of ADPKD, discuss the screening, diagnosis and clinical manifestations of this renal disorder in childhood and adolescents and review treatment options and potential therapies currently being tested.
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Affiliation(s)
- Bharathi V Reddy
- University of Chicago, 5841, S. Maryland Avenue Suite S-511, MC 5100, Chicago, IL, 60637, USA.
| | - Arlene B Chapman
- University of Chicago, 5841, S. Maryland Avenue Suite S-511, MC 5100, Chicago, IL, 60637, USA
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Kleene SJ, Kleene NK. The native TRPP2-dependent channel of murine renal primary cilia. Am J Physiol Renal Physiol 2016; 312:F96-F108. [PMID: 27760766 DOI: 10.1152/ajprenal.00272.2016] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 09/22/2016] [Accepted: 10/13/2016] [Indexed: 12/19/2022] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is the most common life-threatening monogenic renal disease. ADPKD results from mutations in either of two proteins: polycystin-1 (also known as PC1 or PKD1) or transient receptor potential cation channel, subfamily P, member 2 (TRPP2, also known as polycystin-2, PC2, or PKD2). Each of these proteins is expressed in the primary cilium that extends from many renal epithelial cells. Existing evidence suggests that the cilium can promote renal cystogenesis, while PC1 and TRPP2 counter this cystogenic effect. To better understand the function of TRPP2, we investigated its electrophysiological properties in the native ciliary membrane. We recorded directly from the cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin. In one-third of cilia examined, a large-conductance channel was observed. The channel was not permeable to Cl¯ but conducted cations with permeability ratios PK:PCa:PNa of 1:0.55:0.14. The single-channel conductance ranged from 97 pS in typical physiological solutions to 189 pS in symmetrical 145 mM KCl. Open probability of the channel was very sensitive to membrane depolarization or increasing cytoplasmic free Ca2+ in the low micromolar range, with the open probability increasing in either case. Knocking out TRPP2 by CRISPR/Cas9 genome editing eliminated the channel current, establishing it as TRPP2 dependent. Possible mechanisms for activating the TRPP2-dependent channel in the renal primary cilium are discussed.
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Affiliation(s)
- Steven J Kleene
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
| | - Nancy K Kleene
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
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Function and regulation of TRPP2 ion channel revealed by a gain-of-function mutant. Proc Natl Acad Sci U S A 2016; 113:E2363-72. [PMID: 27071085 DOI: 10.1073/pnas.1517066113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mutations in polycystin-1 and transient receptor potential polycystin 2 (TRPP2) account for almost all clinically identified cases of autosomal dominant polycystic kidney disease (ADPKD), one of the most common human genetic diseases. TRPP2 functions as a cation channel in its homomeric complex and in the TRPP2/polycystin-1 receptor/ion channel complex. The activation mechanism of TRPP2 is unknown, which significantly limits the study of its function and regulation. Here, we generated a constitutively active gain-of-function (GOF) mutant of TRPP2 by applying a mutagenesis scan on the S4-S5 linker and the S5 transmembrane domain, and studied functional properties of the GOF TRPP2 channel. We found that extracellular divalent ions, including Ca(2+), inhibit the permeation of monovalent ions by directly blocking the TRPP2 channel pore. We also found that D643, a negatively charged amino acid in the pore, is crucial for channel permeability. By introducing single-point ADPKD pathogenic mutations into the GOF TRPP2, we showed that different mutations could have completely different effects on channel activity. The in vivo function of the GOF TRPP2 was investigated in zebrafish embryos. The results indicate that, compared with wild type (WT), GOF TRPP2 more efficiently rescued morphological abnormalities, including curly tail and cyst formation in the pronephric kidney, caused by down-regulation of endogenous TRPP2 expression. Thus, we established a GOF TRPP2 channel that can serve as a powerful tool for studying the function and regulation of TRPP2. The GOF channel may also have potential application for developing new therapeutic strategies for ADPKD.
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Wu M, Yu S. New Insights into the Molecular Mechanisms Targeting Tubular Channels/Transporters in PKD Development. KIDNEY DISEASES 2016; 2:128-135. [PMID: 27921040 DOI: 10.1159/000444839] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 02/18/2016] [Indexed: 12/15/2022]
Abstract
BACKGROUND Autosomal dominant polycystic kidney disease (PKD) or autosomal recessive PKD is caused by a mutation in the PKD1, PKD2 or PKHD1 gene, which encodes polycystin-1, polycystin-2 or fibrocystin, respectively. Embryonic and postnatal mutation studies show that transport or channel function is dysregulated before the initiation of cystogenesis, suggesting that the abnormality of transport or channel function plays a critical role in the pathology of PKD. SUMMARY Polycystin-2 by itself is a calcium-permeable cation channel, and its channel function can be regulated by polycystin-1 or fibrocystin. In this paper, we reviewed the current knowledge about calcium transports and cyclic adenosine monophosphate (cAMP)-driven chloride transports in PKD. In addition, the function and the underlining mechanism of glucose transporters, phosphate transporters and water channels in PKD are also discussed. KEY MESSAGES Abnormalities in calcium handling and exuberant cAMP-dependent cystic fibrosis transmembrane conductance regulator-mediated fluid secretion in the collecting duct are the most important issues in the pathogenesis of PKD.
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Affiliation(s)
- Ming Wu
- Kidney Institute of PLA, Division of Nephrology, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, PR China
| | - Shengqiang Yu
- Kidney Institute of PLA, Division of Nephrology, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, PR China
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16
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Oliveira AG, Guimarães ES, Andrade LM, Menezes GB, Fatima Leite M. Decoding calcium signaling across the nucleus. Physiology (Bethesda) 2015; 29:361-8. [PMID: 25180265 DOI: 10.1152/physiol.00056.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Calcium (Ca(2+)) is an important multifaceted second messenger that regulates a wide range of cellular events. A Ca(2+)-signaling toolkit has been shown to exist in the nucleus and to be capable of generating and modulating nucleoplasmic Ca(2+) transients. Within the nucleus, Ca(2+) controls cellular events that are different from those modulated by cytosolic Ca(2+). This review focuses on nuclear Ca(2+) signals and their role in regulating physiological and pathological processes.
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Affiliation(s)
- André G Oliveira
- Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Erika S Guimarães
- Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Brazil; Molecular Medicine, School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil; and
| | - Lídia M Andrade
- Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Gustavo B Menezes
- Department of Morphology, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - M Fatima Leite
- Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Brazil;
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Yue Z, Xie J, Yu AS, Stock J, Du J, Yue L. Role of TRP channels in the cardiovascular system. Am J Physiol Heart Circ Physiol 2015; 308:H157-82. [PMID: 25416190 PMCID: PMC4312948 DOI: 10.1152/ajpheart.00457.2014] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 11/14/2014] [Indexed: 12/12/2022]
Abstract
The transient receptor potential (TRP) superfamily consists of a large number of nonselective cation channels with variable degree of Ca(2+)-permeability. The 28 mammalian TRP channel proteins can be grouped into six subfamilies: canonical, vanilloid, melastatin, ankyrin, polycystic, and mucolipin TRPs. The majority of these TRP channels are expressed in different cell types including both excitable and nonexcitable cells of the cardiovascular system. Unlike voltage-gated ion channels, TRP channels do not have a typical voltage sensor, but instead can sense a variety of other stimuli including pressure, shear stress, mechanical stretch, oxidative stress, lipid environment alterations, hypertrophic signals, and inflammation products. By integrating multiple stimuli and transducing their activity to downstream cellular signal pathways via Ca(2+) entry and/or membrane depolarization, TRP channels play an essential role in regulating fundamental cell functions such as contraction, relaxation, proliferation, differentiation, and cell death. With the use of targeted deletion and transgenic mouse models, recent studies have revealed that TRP channels are involved in numerous cellular functions and play an important role in the pathophysiology of many diseases in the cardiovascular system. Moreover, several TRP channels are involved in inherited diseases of the cardiovascular system. This review presents an overview of current knowledge concerning the physiological functions of TRP channels in the cardiovascular system and their contributions to cardiovascular diseases. Ultimately, TRP channels may become potential therapeutic targets for cardiovascular diseases.
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Affiliation(s)
- Zhichao Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Jia Xie
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Albert S Yu
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Jonathan Stock
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Jianyang Du
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Lixia Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
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18
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Nie X, Arend LJ. Novel roles of Pkd2 in male reproductive system development. Differentiation 2014; 87:161-71. [PMID: 24951251 DOI: 10.1016/j.diff.2014.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 04/28/2014] [Accepted: 04/30/2014] [Indexed: 01/26/2023]
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited genetic diseases, caused by mutations in PKD1 and/ or PKD2. Infertility and reproductive tract abnormalities in male ADPKD patients are very common and have higher incidence than in the general population. In this work, we reveal novel roles of Pkd2 for male reproductive system development. Disruption of Pkd2 caused dilation of mesonephric tubules/efferent ducts, failure of epididymal coiling, and defective testicular development. Deletion of Pkd2 in the epithelia alone was sufficient to cause reproductive tract defects seen in Pkd2(-/-) mice, suggesting that epithelial Pkd2 plays a pivotal role for development and maintenance of the male reproductive tract. In the testis, Pkd2 also plays a role in interstitial tissue and testicular cord development. In-depth analysis of epithelial-specific knockout mice revealed that Pkd2 is critical to maintain cellular phenotype and developmental signaling in the male reproductive system. Taken together, our data for the first time reveal novel roles for Pkd2 in male reproductive system development and provide new insights in male reproductive system abnormality and infertility in ADPKD patients.
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Affiliation(s)
- Xuguang Nie
- Department of Pathology, Johns Hopkins University, Ross 632 E, 720 Rutland Ave, Baltimore, MD 21205, USA.
| | - Lois J Arend
- Department of Pathology, Johns Hopkins University, Ross 632 E, 720 Rutland Ave, Baltimore, MD 21205, USA.
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19
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Abstract
The TRPC1 ion channel was the first mammalian TRP channel to be cloned. In humans, it is encoded by the TRPC1 gene located in chromosome 3. The protein is predicted to consist of six transmembrane segments with the N- and C-termini located in the cytoplasm. The extracellular loop connecting transmembrane segments 5 and 6 participates in the formation of the ionic pore region. Inside the cell, TRPC1 is present in the endoplasmic reticulum, plasma membrane, intracellular vesicles, and primary cilium, an antenna-like sensory organelle functioning as a signaling platform. In human and rodent tissues, it shows an almost ubiquitous expression. TRPC1 interacts with a diverse group of proteins including ion channel subunits, receptors, and cytosolic proteins to mediate its effect on Ca(2+) signaling. It primarily functions as a cation nonselective channel within pathways controlling Ca(2+) entry in response to cell surface receptor activation. Through these pathways, it affects basic cell functions, such as proliferation and survival, differentiation, secretion, and cell migration, as well as cell type-specific functions such as chemotropic turning of neuronal growth cones and myoblast fusion. The biological role of TRPC1 has been studied in genetically engineered mice where the Trpc1 gene has been experimentally ablated. Although these mice live to adulthood, they show defects in several organs and tissues, such as the cardiovascular, central nervous, skeletal and muscular, and immune systems. Genetic and functional studies have implicated TRPC1 in diabetic nephropathy, Parkinson's disease, Huntington's disease, Duchenne muscular dystrophy, cancer, seizures, and Darier-White skin disease.
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Affiliation(s)
- Vasyl Nesin
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK, 73104, USA
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20
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Muzika F, Schreiberová L, Schreiber I. Chemical computing based on Turing patterns in two coupled cells with equal transport coefficients. RSC Adv 2014. [DOI: 10.1039/c4ra08859j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Two diffusively coupled reaction cells with a nonlinear reaction are used to perform chemical computing based on targeted perturbations switching between two Turing patterns defining two states of a logical device.
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21
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Muzika F, Schreiber I. Control of Turing patterns and their usage as sensors, memory arrays, and logic gates. J Chem Phys 2013; 139:164108. [PMID: 24182005 DOI: 10.1063/1.4825379] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We study a model system of three diffusively coupled reaction cells arranged in a linear array that display Turing patterns with special focus on the case of equal coupling strength for all components. As a suitable model reaction we consider a two-variable core model of glycolysis. Using numerical continuation and bifurcation techniques we analyze the dependence of the system's steady states on varying rate coefficient of the recycling step while the coupling coefficients of the inhibitor and activator are fixed and set at the ratios 100:1, 1:1, and 4:5. We show that stable Turing patterns occur at all three ratios but, as expected, spontaneous transition from the spatially uniform steady state to the spatially nonuniform Turing patterns occurs only in the first case. The other two cases possess multiple Turing patterns, which are stabilized by secondary bifurcations and coexist with stable uniform periodic oscillations. For the 1:1 ratio we examine modular spatiotemporal perturbations, which allow for controllable switching between the uniform oscillations and various Turing patterns. Such modular perturbations are then used to construct chemical computing devices utilizing the multiple Turing patterns. By classifying various responses we propose: (a) a single-input resettable sensor capable of reading certain value of concentration, (b) two-input and three-input memory arrays capable of storing logic information, (c) three-input, three-output logic gates performing combinations of logical functions OR, XOR, AND, and NAND.
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Affiliation(s)
- František Muzika
- Department of Chemical Engineering, Institute of Chemical Technology, Prague, 16628 Prague 6, Czech Republic
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22
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Wang S, Dong Z. Primary cilia and kidney injury: current research status and future perspectives. Am J Physiol Renal Physiol 2013; 305:F1085-98. [PMID: 23904226 DOI: 10.1152/ajprenal.00399.2013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cilia, membrane-enclosed organelles protruding from the apical side of cells, can be divided into two classes: motile and primary cilia. During the past decades, motile cilia have been intensively studied. However, it was not until the 1990s that people began to realize the importance of primary cilia as cellular-specific sensors, particularly in kidney tubular epithelial cells. Furthermore, accumulating evidence indicates that primary cilia may be involved in the regulation of cell proliferation, differentiation, apoptosis, and planar cell polarity. Many signaling pathways, such as Wnt, Notch, Hedgehog, and mammalian target of rapamycin, have been located to the primary cilia. Thus primary cilia have been regarded as a hub that integrates signals from the extracellular environment. More importantly, dysfunction of this organelle may contribute to the pathogenesis of a large spectrum of human genetic diseases, named ciliopathies. The significance of primary cilia in acquired human diseases such as hypertension and diabetes has gradually drawn attention. Interestingly, recent reports disclosed that cilia length varies during kidney injury, and shortening of cilia enhances the sensitivity of epithelial cells to injury cues. This review briefly summarizes the current status of cilia research and explores the potential mechanisms of cilia-length changes during kidney injury as well as provides some thoughts to allure more insightful ideas and promotes the further study of primary cilia in the context of kidney injury.
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Affiliation(s)
- Shixuan Wang
- Dept. of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912.
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23
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Kim S, Dynlacht BD. Assembling a primary cilium. Curr Opin Cell Biol 2013; 25:506-11. [PMID: 23747070 DOI: 10.1016/j.ceb.2013.04.011] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 04/24/2013] [Indexed: 12/28/2022]
Abstract
Cilia are evolutionarily conserved, membrane-bound, microtubular projections emanating from the cell surface. They are assembled on virtually all cell types in the human body, with very few exceptions, and several recent reviews have covered the topic in great detail. The cilium is assembled from mature (mother) centrioles or basal bodies, which serve to nucleate growth of axonemes that give rise to two structurally distinct variants, motile and nonmotile cilia. Whereas motile cilia are typically found in large bundles and beat synchronously to generate fluid flow, primary cilia (with the exception of those found at the embryonic node) are generally immotile and are found as solitary organelles. Remarkably, until recently, the primary cilium was considered a vestigial organelle without apparent biological function. However, research over the past decade has established that the primary cilium is capable of transducing essential signaling information from the extracellular milieu. Defects in the cilium, and the structure from which it arises, the basal body, have been shown to cause a spectrum of diseases, ranging from developmental defects to obesity, diabetes, and cancer. Many of these diseases, or ciliopathies, are manifested as genetic syndromes, such as Joubert syndrome, Bardet-Biedel (BBS), Meckel-Gruber (MKS), and Nephronophthisis (NPHP), illustrating the importance of understanding cilium structure and function and the mechanisms required for its assembly. This review focuses primarily on recent advances in our understanding of the regulatory controls governing the assembly and maintenance of the primary cilium.
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Affiliation(s)
- Sehyun Kim
- Department of Pathology and Cancer Institute, Smilow Research Center, New York University School of Medicine, New York, NY 10016, USA
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24
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Paavola J, Schliffke S, Rossetti S, Kuo IYT, Yuan S, Sun Z, Harris PC, Torres VE, Ehrlich BE. Polycystin-2 mutations lead to impaired calcium cycling in the heart and predispose to dilated cardiomyopathy. J Mol Cell Cardiol 2013; 58:199-208. [PMID: 23376035 PMCID: PMC3636149 DOI: 10.1016/j.yjmcc.2013.01.015] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 01/04/2013] [Accepted: 01/17/2013] [Indexed: 12/31/2022]
Abstract
Mutations in PKD1 and PKD2, the genes encoding the proteins polycystin-1 (PC1) and polycystin-2 (PC2), cause autosomal dominant polycystic kidney disease (ADPKD). Although the leading cause of mortality in ADPKD is cardiovascular disease, the relationship between these conditions remains poorly understood. PC2 is an intracellular calcium channel expressed in renal epithelial cells and in cardiomyocytes, and is thus hypothesized to modulate intracellular calcium signaling and affect cardiac function. Our first aim was to study cardiac function in a zebrafish model lacking PC2 (pkd2 mutants). Next, we aimed to explore the relevance of this zebrafish model to human ADPKD by examining the Mayo Clinic's ADPKD database for an association between ADPKD and idiopathic dilated cardiomyopathy (IDCM). Pkd2 mutant zebrafish showed low cardiac output and atrioventricular block. Isolated pkd2 mutant hearts displayed impaired intracellular calcium cycling and calcium alternans. These results indicate heart failure in the pkd2 mutants. In human ADPKD patients, we found IDCM to coexist frequently with ADPKD. This association was strongest in patients with PKD2 mutations. Our results demonstrate that PC2 modulates intracellular calcium cycling, contributing to the development of heart failure. In human subjects we found an association between ADPKD and IDCM and suggest that PKD mutations contribute to the development of heart failure.
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Affiliation(s)
- Jere Paavola
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
- Department of Anatomy II: Experimental Morphology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
| | - Simon Schliffke
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
- Department of Anatomy II: Experimental Morphology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
| | - Sandro Rossetti
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Ivana Y.-T. Kuo
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Shiaulou Yuan
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290, Helsinki, Finland
| | - Zhaoxia Sun
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290, Helsinki, Finland
| | - Peter C. Harris
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Vicente E. Torres
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Barbara E. Ehrlich
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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25
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Abstract
BACKGROUND Most cells in the body possess a single primary cilium. These cilia are key transducers of sensory stimuli, and defects in cilia have been linked to several diseases. Evidence suggests that some transduction of sensory stimuli by the primary cilium depends on ion-conducting channels. However, the tiny size of the cilium has been a critical barrier to understanding its electrical properties. We report a novel method that allows sensitive, repeatable electrical recordings from primary cilia. Adherent cells were grown on small, spherical beads that could be easily moved within the recording chamber. In this configuration, an entire cilium could be pulled into a recording microelectrode. RESULTS In 47% of attempts, suction resulted in a seal with high input resistance. Single channels could be recorded while the cilium remained attached to the cell. When the pipette was raised into the air, the cell body was pulled off at the air-bath interface. The pipette retained the cilium and could then be immersed in various solutions that bathed the cytoplasmic face of the membrane. In excised cilia, ionic currents through ciliary channels were modulated by cytoplasmic Ca(2+) and transmembrane voltage. CONCLUSIONS Ciliary recording is a direct way to learn the effects of second messengers and voltage changes on ciliary transduction channels.
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26
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G-protein signaling modulator 1 deficiency accelerates cystic disease in an orthologous mouse model of autosomal dominant polycystic kidney disease. Proc Natl Acad Sci U S A 2012; 109:21462-7. [PMID: 23236168 DOI: 10.1073/pnas.1216830110] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Polycystic kidney diseases are the most common genetic diseases that affect the kidney. There remains a paucity of information regarding mechanisms by which G proteins are regulated in the context of polycystic kidney disease to promote abnormal epithelial cell expansion and cystogenesis. In this study, we describe a functional role for the accessory protein, G-protein signaling modulator 1 (GPSM1), also known as activator of G-protein signaling 3, to act as a modulator of cyst progression in an orthologous mouse model of autosomal dominant polycystic kidney disease (ADPKD). A complete loss of Gpsm1 in the Pkd1(V/V) mouse model of ADPKD, which displays a hypomorphic phenotype of polycystin-1, demonstrated increased cyst progression and reduced renal function compared with age-matched cystic Gpsm1(+/+) and Gpsm1(+/-) mice. Electrophysiological studies identified a role by which GPSM1 increased heteromeric polycystin-1/polycystin-2 ion channel activity via Gβγ subunits. In summary, the present study demonstrates an important role for GPSM1 in controlling the dynamics of cyst progression in an orthologous mouse model of ADPKD and presents a therapeutic target for drug development in the treatment of this costly disease.
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27
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Mekahli D, Parys JB, Bultynck G, Missiaen L, De Smedt H. Polycystins and cellular Ca2+ signaling. Cell Mol Life Sci 2012; 70:2697-712. [PMID: 23076254 PMCID: PMC3708286 DOI: 10.1007/s00018-012-1188-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 10/01/2012] [Accepted: 10/02/2012] [Indexed: 12/19/2022]
Abstract
The cystic phenotype in autosomal dominant polycystic kidney disease is characterized by a profound dysfunction of many cellular signaling patterns, ultimately leading to an increase in both cell proliferation and apoptotic cell death. Disturbance of normal cellular Ca2+ signaling seems to be a primary event and is clearly involved in many pathways that may lead to both types of cellular responses. In this review, we summarize the current knowledge about the molecular and functional interactions between polycystins and multiple components of the cellular Ca2+-signaling machinery. In addition, we discuss the relevant downstream responses of the changed Ca2+ signaling that ultimately lead to increased proliferation and increased apoptosis as observed in many cystic cell types.
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Affiliation(s)
- D. Mekahli
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-I, B-802, Herestraat 49, 3000 Leuven, Belgium
| | - Jan B. Parys
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-I, B-802, Herestraat 49, 3000 Leuven, Belgium
| | - G. Bultynck
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-I, B-802, Herestraat 49, 3000 Leuven, Belgium
| | - L. Missiaen
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-I, B-802, Herestraat 49, 3000 Leuven, Belgium
| | - H. De Smedt
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-I, B-802, Herestraat 49, 3000 Leuven, Belgium
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28
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Orts-Del'immagine A, Wanaverbecq N, Tardivel C, Tillement V, Dallaporta M, Trouslard J. Properties of subependymal cerebrospinal fluid contacting neurones in the dorsal vagal complex of the mouse brainstem. J Physiol 2012; 590:3719-41. [PMID: 22570378 DOI: 10.1113/jphysiol.2012.227959] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cerebrospinal fluid (CSF) contacting neurones have been observed in various brain regions such as the hypothalamus, the dorsal nucleus of the raphe and around the central canal (cc) of the spinal cord but their functional role remains unclear. At the level of the spinal cord, subependymal cerebrospinal fluid contacting neurones (S-CSF-cNs) present a peculiar morphology with a soma close to the ependymal layer, a process projecting towards the cc and ending with a bud and a cilium. These neurones were recently shown to express polycystin kidney disease 2-like 1 (PKD2L1 or TRPP3) channels that are members of the polycystin subtype of the transient receptor potential (TRP) channel superfamily and that have been proposed as either chemo- or mechanoreceptors in several tissues. Using immunohistological techniques and whole-cell electrophysiological recordings in brain slices obtained from PKD2L1:EGFP transgenic adult mice, we looked for and determined the functional properties of S-CSF-cNs in the dorsal vagal complex (DVC), a hindbrain structure controlling autonomic functions such as blood pressure, energy balance and food intake. Here, we demonstrate that S-CSF-cNs received GABAergic and/or glycinergic synaptic entries and were also characterised by the presence of non-selective cationic channels of large conductance that could be detected even under whole-cell configuration. The channel activity was not affected by Psalmopoeus cambridgei toxin 1, a blocker of acid sensing ion channels (ASICs), but was blocked by amiloride and by a strong extracellular acidification. In contrast, extracellular alkalinisation and hypo-osmotic shocks increased channel activity. Based on these properties, we suggest that the single-channel activity recorded in medullar S-CSF-cNs is carried by PKD2L1 channels. Our study therefore reinforces the idea that PKD2L1 is a marker of S-CSF-cNs and points toward a role for S-CSF-cNs in the detection of circulating signals and of modifications in the extracellular environment.
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Affiliation(s)
- Adeline Orts-Del'immagine
- Laboratoire de Physiologie et Physiopathologie du Système Nerveux Somato-moteur et Neurovégétatif (PPSN) EA 4674 Aix-Marseille Université (AMU), Faculté des Sciences et Techniques St. Jérôme, BP 352, Avenue Escadrille Normandie Niemen, F-13397 Marseille cedex 20, France
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29
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Grimm C, Hassan S, Wahl-Schott C, Biel M. Role of TRPML and two-pore channels in endolysosomal cation homeostasis. J Pharmacol Exp Ther 2012; 342:236-44. [PMID: 22518024 DOI: 10.1124/jpet.112.192880] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The transient receptor potential (TRP) channels TRPML1, TRPML2, and TRPML3 (also called mucolipins 1-3 or MCOLN1-3) are nonselective cation channels. Mutations in the Trpml1 gene cause mucolipidosis type IV in humans with clinical features including psychomotor retardation, corneal clouding, and retinal degeneration, whereas mutations in the Trpml3 gene cause deafness, circling behavior, and coat color dilution in mice. No disease-causing mutations are reported for the Trpml2 gene. Like TRPML channels, which are expressed in the endolysosomal pathway, two-pore channels (TPCs), namely TPC1, TPC2, and TPC3, are found in intracellular organelles, in particular in endosomes and lysosomes. Both TRPML channels and TPCs may function as calcium/cation release channels in endosomes, lysosomes, and lysosome-related organelles with TRPMLs being activated by phosphatidylinositol 3,5-bisphosphate and regulated by pH and TPCs being activated by nicotinic acid adenine dinucleotide phosphate in a calcium- and pH-dependent manner. They may also be involved in endolysosomal transport and fusion processes, e.g., as intracellular calcium sources. Currently, however, the exact physiological roles of TRPML channels and TPCs remain quite elusive, and whether TRPML channels are purely endolysosomal ion channels or whether they may also be functionally active at the plasma membrane in vivo remains to be determined.
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Affiliation(s)
- Christian Grimm
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, 81377 Germany.
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30
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Mekahli D, Sammels E, Luyten T, Welkenhuyzen K, van den Heuvel LP, Levtchenko EN, Gijsbers R, Bultynck G, Parys JB, De Smedt H, Missiaen L. Polycystin-1 and polycystin-2 are both required to amplify inositol-trisphosphate-induced Ca2+ release. Cell Calcium 2012; 51:452-8. [PMID: 22456092 DOI: 10.1016/j.ceca.2012.03.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 02/27/2012] [Accepted: 03/02/2012] [Indexed: 12/31/2022]
Abstract
Autosomal dominant polycystic kidney disease is caused by loss-of-function mutations in the PKD1 or PKD2 genes encoding respectively polycystin-1 and polycystin-2. Polycystin-2 stimulates the inositol trisphosphate (IP(3)) receptor (IP(3)R), a Ca(2+)-release channel in the endoplasmic reticulum (ER). The effect of ER-located polycystin-1 is less clear. Polycystin-1 has been reported both to stimulate and to inhibit the IP(3)R. We now studied the effect of polycystin-1 and of polycystin-2 on the IP(3)R activity under conditions where the cytosolic Ca(2+) concentration was kept constant and the reuptake of released Ca(2+) was prevented. We also studied the interdependence of the interaction of polycystin-1 and polycystin-2 with the IP(3)R. The experiments were done in conditionally immortalized human proximal-tubule epithelial cells in which one or both polycystins were knocked down using lentiviral vectors containing miRNA-based short hairpins. The Ca(2+) release was induced in plasma membrane-permeabilized cells by various IP(3) concentrations at a fixed Ca(2+) concentration under unidirectional (45)Ca(2+)-efflux conditions. We now report that knock down of polycystin-1 or of polycystin-2 inhibited the IP(3)-induced Ca(2+) release. The simultaneous presence of the two polycystins was required to fully amplify the IP(3)-induced Ca(2+) release, since the presence of polycystin-1 alone or of polycystin-2 alone did not result in an increased Ca(2+) release. These novel findings indicate that ER-located polycystin-1 and polycystin-2 operate as a functional complex. They are compatible with the view that loss-of-function mutations in PKD1 and in PKD2 both cause autosomal dominant polycystic kidney disease.
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Affiliation(s)
- D Mekahli
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven Campus Gasthuisberg O&N I, Belgium
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31
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Simms RJ, Hynes AM, Eley L, Inglis D, Chaudhry B, Dawe HR, Sayer JA. Modelling a ciliopathy: Ahi1 knockdown in model systems reveals an essential role in brain, retinal, and renal development. Cell Mol Life Sci 2012; 69:993-1009. [PMID: 21959375 PMCID: PMC11115044 DOI: 10.1007/s00018-011-0826-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 09/09/2011] [Accepted: 09/12/2011] [Indexed: 02/03/2023]
Abstract
Joubert syndrome and related diseases (JSRD) are cerebello-oculo-renal syndromes with phenotypes including cerebellar hypoplasia, retinal dystrophy, and nephronophthisis (a cystic kidney disease). Mutations in AHI1 are the most common genetic cause of JSRD, with developmental hindbrain anomalies and retinal degeneration being prominent features. We demonstrate that Ahi1, a WD40 domain-containing protein, is highly conserved throughout evolution and its expression associates with ciliated organisms. In zebrafish ahi1 morphants, the phenotypic spectrum of JSRD is modeled, with embryos showing brain, eye, and ear abnormalities, together with renal cysts and cloacal dilatation. Following ahi1 knockdown in zebrafish, we demonstrate loss of cilia at Kupffer's vesicle and subsequently defects in cardiac left-right asymmetry. Finally, using siRNA in renal epithelial cells we demonstrate a role for Ahi1 in both ciliogenesis and cell-cell junction formation. These data support a role for Ahi1 in epithelial cell organization and ciliary formation and explain the ciliopathy phenotype of AHI1 mutations in man.
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Affiliation(s)
- Roslyn J. Simms
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - Ann Marie Hynes
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - Lorraine Eley
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - David Inglis
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE UK
| | - Bill Chaudhry
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - Helen R. Dawe
- Biosciences: College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QD UK
| | - John A. Sayer
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
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Ibraghimov-Beskrovnaya O, Natoli TA. mTOR signaling in polycystic kidney disease. Trends Mol Med 2011; 17:625-33. [PMID: 21775207 DOI: 10.1016/j.molmed.2011.06.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 04/16/2011] [Accepted: 06/07/2011] [Indexed: 12/15/2022]
Abstract
Polycystic kidney diseases (PKDs) comprise a large group of genetic disorders characterized by formation of cysts in the kidneys and other organs, ultimately leading to end-stage renal disease. Although PKDs can be caused by mutations in different genes, they converge on a set of common molecular mechanisms involved in cystogenesis and ciliary dysfunction, and can be qualified as ciliopathies. Recent advances in understanding the mechanisms regulating disease progression have led to the development of new therapies that are being tested in both preclinical and clinical trials. In this article, we briefly review a network of molecular pathways of cystogenesis that are regulated by ciliary functions. We discuss the mTOR pathway in depth, highlighting recent progress in understanding its role in PKD and the current results of clinical trials.
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Lee K, Battini L, Gusella GL. Cilium, centrosome and cell cycle regulation in polycystic kidney disease. Biochim Biophys Acta Mol Basis Dis 2011; 1812:1263-71. [PMID: 21376807 DOI: 10.1016/j.bbadis.2011.02.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 01/10/2011] [Accepted: 02/16/2011] [Indexed: 12/19/2022]
Abstract
Polycystic kidney disease is the defining condition of a group of common life-threatening genetic disorders characterized by the bilateral formation and progressive expansion of renal cysts that lead to end stage kidney disease. Although a large body of information has been acquired in the past years about the cellular functions that characterize the cystic cells, the mechanisms triggering the cystogenic conversion are just starting to emerge. Recent findings link defects in ciliary functions, planar cell polarity pathway, and centrosome integrity in early cystic development. Many of the signals dysregulated during cystogenesis may converge on the centrosome for its central function as a structural support for cilia formation and a coordinator of protein trafficking, polarity, and cell division. Here, we will discuss the contribution of proliferation, cilium and planar cell polarity to the cystic signal and will analyze in particular the possible role that the basal bodies/centrosome may play in the cystogenetic mechanisms. This article is part of a Special Issue entitled: Polycystic Kidney Disease.
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Affiliation(s)
- Kyung Lee
- Department of Medicine, The Mount Sinai School of Medicine, New York, NY, USA
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Abstract
Polycystic kidney disease is a common genetic disorder in which fluid-filled cysts displace normal renal tubules. Here we focus on autosomal dominant polycystic kidney disease, which is attributable to mutations in the PKD1 and PKD2 genes and which is characterized by perturbations of renal epithelial cell growth control, fluid transport, and morphogenesis. The mechanisms that connect the underlying genetic defects to disease pathogenesis are poorly understood, but their exploration is shedding new light on interesting cell biological processes and suggesting novel therapeutic targets.
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Affiliation(s)
- Hannah C Chapin
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA
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Regulation of TRP signalling by ion channel translocation between cell compartments. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:545-72. [PMID: 21290316 DOI: 10.1007/978-94-007-0265-3_30] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The TRP (transient receptor potential) family of ion channels is a heterogeneous family of calcium permeable cation channels that is subdivided into seven subfamilies: TRPC ("Canonical"), TRPV ("Vanilloid"), TRPM ("Melastatin"), TRPA ("Ankyrin"), TRPN ("NOMPC"), TRPP ("Polycystin"), and TRPML ("Mucolipin"). TRP-mediated ion currents across the cell membrane are determined by the single channel conductance, by the fraction of activated channels, and by the total amount of TRP channels present at the plasma membrane. In many cases, the amount of TRP channels at the plasma membrane is altered in response to physiological stimuli by translocation of channels to and from the plasma membrane. Regulated translocation has been described for channels of the TRPC, TRPV, TRPM, and TRPA family and is achieved by vesicular transport of these channels along cellular exocytosis and endocytosis pathways. This review summarizes the stimuli and signalling cascades involved in the translocation of TRP channels and highlights interactions of TRP channels with proteins of the endocytosis and exocytosis machineries.
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36
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Sammels E, Devogelaere B, Mekahli D, Bultynck G, Missiaen L, Parys JB, De Smedt H. Unraveling the role of polycystin-2/inositol 1,4,5-trisphosphate receptor interaction in Ca signaling. Commun Integr Biol 2010; 3:530-2. [PMID: 21331231 DOI: 10.4161/cib.3.6.12751] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Accepted: 06/18/2010] [Indexed: 01/04/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) arises as a consequence of mutations of the genes PKD1 and PKD2, encoding respectively the integral membrane proteins polycystin-1 and polycystin-2 (TRPP2), resulting in a disturbance in intracellular Ca(2+) signaling. Previously we investigated the interaction between TRPP2 and the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R), an intracellular Ca(2+) channel in the endoplasmic reticulum (ER). We identified the molecular determinants of this interaction and observed an enhanced IP(3)-induced Ca(2+) release (IICR). Since we found that TRPP2 strongly bound to a cluster of positively charged amino acids in the N-terminal ligand-binding domain (LBD) of the IP(3)R, we now investigated whether TRPP2 would interfere with the binding of IP(3) to the IP(3)R. In in vitro experiments we observed that TRPP2 partially inhibited the binding of IP(3) to the LBD of the IP(3)R with an IC(50) of ∼350 nM. The suppressor domain, i.e., the N-terminal 225 amino acids of the LBD of the IP(3)R, mediated this inhibitory effect of TRPP2 on IP(3) binding. The observation that the interaction between the IP(3)R and TRPP2 decreased IP(3) binding is in apparent contrast to the increased IICR. The data can be explained however by a subsequent activation of Ca(2+)-induced Ca(2+) release (CICR) via TRPP2. Implications of this mechanism for cellular Ca(2+) signaling are discussed in this addendum.
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Affiliation(s)
- Eva Sammels
- Laboratory of Molecular and Cellular Signaling; Department of Molecular Cell Biology; K.U. Leuven, Leuven Belgium
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37
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Deltas C, Papagregoriou G. Cystic diseases of the kidney: molecular biology and genetics. Arch Pathol Lab Med 2010; 134:569-82. [PMID: 20367309 DOI: 10.5858/134.4.569] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
CONTEXT Cystic diseases of the kidney are a very heterogeneous group of renal inherited conditions, with more than 33 genes involved and encompassing X-linked, autosomal dominant, and autosomal recessive inheritance. Although mostly monogenic with mendelian inheritance, there are clearly examples of oligogenic inheritance, such as 3 mutations in 2 genes, while the existence of genetic modifiers is perhaps the norm, based on the extent of variable expressivity and the broad spectrum of symptoms. OBJECTIVES To present in the form of a mini review the major known cystic diseases of the kidney for which genes have been mapped or cloned and characterized, with some information on their cellular and molecular biology and genetics, and to pay special attention to commenting on the issues of molecular diagnostics, in view of the genetic and allelic heterogeneity. Data Sources.-We used major reviews that make excellent detailed presentation of the various diseases, as well as original publications. CONCLUSIONS There is already extensive genetic heterogeneity in the group of cystic diseases of the kidney; however, there are still many more genes awaiting to be discovered that are implicated or mutated in these diseases. In addition, the synergism and interaction among this repertoire of gene products is largely unknown, while a common unifying aspect is the expression of nearly all of them at the primary cilium or the basal body. A major interplay of functions is anticipated, while mutations in all converge in the unifying phenotype of cyst formation.
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38
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Sammels E, Devogelaere B, Mekahli D, Bultynck G, Missiaen L, Parys JB, Cai Y, Somlo S, De Smedt H. Polycystin-2 activation by inositol 1,4,5-trisphosphate-induced Ca2+ release requires its direct association with the inositol 1,4,5-trisphosphate receptor in a signaling microdomain. J Biol Chem 2010; 285:18794-805. [PMID: 20375013 DOI: 10.1074/jbc.m109.090662] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Autosomal dominant polycystic kidney disease is characterized by the loss-of-function of a signaling complex involving polycystin-1 and polycystin-2 (TRPP2, an ion channel of the TRP superfamily), resulting in a disturbance in intracellular Ca(2+) signaling. Here, we identified the molecular determinants of the interaction between TRPP2 and the inositol 1,4,5-trisphosphate receptor (IP(3)R), an intracellular Ca(2+) channel in the endoplasmic reticulum. Glutathione S-transferase pulldown experiments combined with mutational analysis led to the identification of an acidic cluster in the C-terminal cytoplasmic tail of TRPP2 and a cluster of positively charged residues in the N-terminal ligand-binding domain of the IP(3)R as directly responsible for the interaction. To investigate the functional relevance of TRPP2 in the endoplasmic reticulum, we re-introduced the protein in TRPP2(-/-) mouse renal epithelial cells using an adenoviral expression system. The presence of TRPP2 resulted in an increased agonist-induced intracellular Ca(2+) release in intact cells and IP(3)-induced Ca(2+) release in permeabilized cells. Using pathological mutants of TRPP2, R740X and D509V, and competing peptides, we demonstrated that TRPP2 amplified the Ca(2+) signal by a local Ca(2+)-induced Ca(2+)-release mechanism, which only occurred in the presence of the TRPP2-IP(3)R interaction, and not via altered IP(3)R channel activity. Moreover, our results indicate that this interaction was instrumental in the formation of Ca(2+) microdomains necessary for initiating Ca(2+)-induced Ca(2+) release. The data strongly suggest that defects in this mechanism may account for the altered Ca(2+) signaling associated with pathological TRPP2 mutations and therefore contribute to the development of autosomal dominant polycystic kidney disease.
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Affiliation(s)
- Eva Sammels
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KU Leuven, Campus Gasthuisberg O&N1, Herestraat 49 bus 802, B-3000 Leuven, Belgium
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Intracellular Ca2+ storage in health and disease: a dynamic equilibrium. Cell Calcium 2010; 47:297-314. [PMID: 20189643 DOI: 10.1016/j.ceca.2010.02.001] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 01/31/2010] [Accepted: 02/01/2010] [Indexed: 12/17/2022]
Abstract
Homeostatic control of the endoplasmic reticulum (ER) both as the site for protein handling (synthesis, folding, trafficking, disaggregation and degradation) and as a Ca2+ store is of crucial importance for correct functioning of the cell. Disturbance of the homeostatic control mechanisms leads to a vast array of severe pathologies. The Ca2+ content of the ER is a dynamic equilibrium between active uptake via Ca2+ pumps and Ca2+ release by a number of highly regulated Ca2+-release channels. Regulation of the Ca2+-release channels is very complex and several mechanisms are still poorly understood or controversial. There is increasing evidence that a number of unrelated proteins, either by themselves or in association with other Ca2+ channels, can provide additional Ca2+-leak pathways. The ER is a dynamic organelle and changes in its size and components have been described, either as a result of (de)differentiation processes affecting the secretory capacity of cells, or as a result of adaptation mechanisms to diverse stress conditions such as the unfolded protein response and autophagy. In this review we want to give an overview of the current knowledge of the (short-term) regulatory mechanisms that affect Ca2+-release and Ca2+-leak pathways and of the (long-term) adaptations in ER size and capacity. Understanding of the consequences of these mechanisms for cellular Ca2+ signaling could provide a huge therapeutic potential.
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40
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Cardenas-Rodriguez M, Badano JL. Ciliary biology: Understanding the cellular and genetic basis of human ciliopathies. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2009; 151C:263-80. [PMID: 19876935 DOI: 10.1002/ajmg.c.30227] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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41
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Abstract
The accumulation of unfolded proteins in the endoplasmic reticulum (ER), leading to ER stress, is caused by a wide range of physiologic and pathologic conditions. Cells respond to ER stress by activating a series of integrative stress pathways termed the unfolded protein response (UPR). This either may be adaptive and promote cell survival, or if the ER stress is chronic or excessive, may lead to cell death. The role of ER stress in the pathophysiology of both acute and chronic kidney diseases has been gaining increasing interest. This review highlights the current knowledge of ER stress in renal disease, with emphasis on more recent advances. Potential therapeutic options targeting ER stress are discussed.
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Affiliation(s)
- Jeffrey G Dickhout
- Department of Medicine, Division of Nephrology, McMaster University, St. Joseph's, Hamilton, Ontario, Canada
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42
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Bian GH, Cao G, Lv XY, Li QW, Sun H, Xiao Y, Ai JZ, Yang QT, Duan JJ, Wang YD, Zhang Z, Tan RZ, Liu YH, Yang Y, Wei YQ, Zhou Q. Down-regulation of Pkd2 by siRNAs suppresses cell-cell adhesion in the mouse melanoma cells. Mol Biol Rep 2009; 37:2387-95. [PMID: 19688268 DOI: 10.1007/s11033-009-9746-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 08/05/2009] [Indexed: 02/05/2023]
Abstract
The Pkd2 gene encodes an integral protein (~130 kDa), named polycystin-2 (PC-2). PC-2 is mainly involved in autosomal dominant polycystic kidney disease. Recently, polycystin-1/polycystin-2 complex has been shown to act as an adhesion complex mediating or regulating cell-cell or cell-matrix adhesion, suggesting that PC-2 may play a role in cell-cell/cell-matrix interactions. Here, we knocked down the expression of Pkd2 gene with small interfering RNAs (siRNAs) in the mouse melanoma cells (B16 cells), indicating that the cells transfected with the targeted siRNAs significantly suppressed cell-cell adhesion, but not cell-matrix adhesion, compared to the cells transfected with non-targeted control (NC) siRNA. This study provides the first directly functional evidence that PC-2 mediates cell-cell adhesion. Furthermore, we demonstrated that PC-2 modulated cell-cell adhesion may be, at least partially, associated with E-cadherin. Collectively, these findings for the first time showed that PC-2 may mediate cell-cell adhesion, at least partially, through E-cadherin.
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Affiliation(s)
- Guo-Hui Bian
- Core Facility of Gene Engineered Mice, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Keyuan the Fourth Road, The District of Hi&Tech, 610041 Chengdu, People's Republic of China
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43
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Sheehy PA, Riley LG, Raadsma HW, Williamson P, Wynn PC. A functional genomics approach to evaluate candidate genes located in a QTL interval for milk production traits on BTA6. Anim Genet 2009; 40:492-8. [DOI: 10.1111/j.1365-2052.2009.01862.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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44
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Yu Y, Ulbrich MH, Li MH, Buraei Z, Chen XZ, Ong ACM, Tong L, Isacoff EY, Yang J. Structural and molecular basis of the assembly of the TRPP2/PKD1 complex. Proc Natl Acad Sci U S A 2009; 106:11558-63. [PMID: 19556541 PMCID: PMC2710685 DOI: 10.1073/pnas.0903684106] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Indexed: 01/20/2023] Open
Abstract
Mutations in PKD1 and TRPP2 account for nearly all cases of autosomal dominant polycystic kidney disease (ADPKD). These 2 proteins form a receptor/ion channel complex on the cell surface. Using a combination of biochemistry, crystallography, and a single-molecule method to determine the subunit composition of proteins in the plasma membrane of live cells, we find that this complex contains 3 TRPP2 and 1 PKD1. A newly identified coiled-coil domain in the C terminus of TRPP2 is critical for the formation of this complex. This coiled-coil domain forms a homotrimer, in both solution and crystal structure, and binds to a single coiled-coil domain in the C terminus of PKD1. Mutations that disrupt the TRPP2 coiled-coil domain trimer abolish the assembly of both the full-length TRPP2 trimer and the TRPP2/PKD1 complex and diminish the surface expression of both proteins. These results have significant implications for the assembly, regulation, and function of the TRPP2/PKD1 complex and the pathogenic mechanism of some ADPKD-producing mutations.
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Affiliation(s)
- Yong Yu
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Maximilian H. Ulbrich
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Ming-Hui Li
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Xing-Zhen Chen
- Membrane Protein Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada T6G 2H7; and
| | - Albert C. M. Ong
- Kidney Genetics Group, Academic Unit of Nephrology, Sheffield Kidney Institute, University of Sheffield Medical School, Sheffield S10 2RX, United Kingdom
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Ehud Y. Isacoff
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- Material Science and Physical Bioscience Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY 10027
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45
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Aydar E, Palmer CP. Polycystic kidney disease channel and synaptotagmin homologues play roles in schizosaccharomyces pombe cell wall synthesis/repair and membrane protein trafficking. J Membr Biol 2009; 229:141-52. [PMID: 19543678 DOI: 10.1007/s00232-009-9180-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 06/02/2009] [Indexed: 11/24/2022]
Abstract
Eukaryotic cells can sense a wide variety of environmental stresses, including changes in temperature, pH, osmolarity and nutrient availability. They respond to these changes through a variety of signal-transduction mechanisms, including activation of Ca(2+)-dependent signaling pathways. This research has discovered important implications in the function(s) of polycystic kidney disease (PKD) channels and the mechanisms through which they act in the control of cell growth and cell polarity in Schizosaccharomyces pombe by ion channel-mediated Ca(2+) signaling. Pkd2 was expressed maximally during the exponential growth phase. At the cell surface pkd2 was localized at the cell tip during the G(2) phase of the cell cycle, although following cell wall damage, the cell surface-expressed protein relocalized to the whole plasma membrane. Pkd2 depletion affected Golgi trafficking, resulting in a buildup of vesicles at the cell poles, and strongly affected plasma membrane protein delivery. Surface-localized pkd2 was present in the plasma membrane for a very short time and was rapidly internalized. Internalization was dependent on Ca(2+), enhanced by amphipaths and inhibited by gadolinium. The pkd2 protein was in a complex with a yeast synaptotagmin homologue and myosin V. Depletion of pkd2 severely affected the localization of glucan synthase. A role for pkd2 in a cell polarity and cell wall synthesis signaling complex with a synaptotagmin homologue, myosin V and glucan synthase is proposed.
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Affiliation(s)
- Ebru Aydar
- Institute for Health Research and Policy, London Metropolitan University, 166-220 Holloway Road, London, N7 8DB, UK
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46
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Abstract
Renal cystic diseases are a major clinical concern as they are the most common genetic cause of end-stage renal disease. While many of the genes causing cystic disease have been identified in recent years, knowing the molecular nature of the mutations has not clarified the mechanisms underlying cyst formation. Recent research in model organisms has suggested that cyst formation may be because of defective planar cell polarity (PCP) and/or ciliary defects. In this review, we first outline the clinical features of renal cystic diseases and then discuss current research linking our understanding of cystic kidney disease to PCP and cilia.
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Affiliation(s)
- R L Bacallao
- Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, USA
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47
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Abstract
Cilia are complex structures that have garnered interest because of their roles in vertebrate development and their involvement in human genetic disorders. In contrast to multicellular invertebrates in which cilia are restricted to specific cell types, these organelles are found almost ubiquitously in vertebrate cells, where they serve a diverse set of signaling functions. Here, we highlight properties of vertebrate cilia, with particular emphasis on their relationship with other subcellular structures, and explore the physiological consequences of ciliary dysfunction.
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Affiliation(s)
- Jantje M Gerdes
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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48
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Affiliation(s)
- Jing Zhou
- Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115;
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49
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Xu C, Shmukler BE, Nishimura K, Kaczmarek E, Rossetti S, Harris PC, Wandinger-Ness A, Bacallao RL, Alper SL. Attenuated, flow-induced ATP release contributes to absence of flow-sensitive, purinergic Cai2+ signaling in human ADPKD cyst epithelial cells. Am J Physiol Renal Physiol 2009; 296:F1464-76. [PMID: 19244404 DOI: 10.1152/ajprenal.90542.2008] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Flow-induced cytosolic Ca2+ Ca(i)2+ signaling in renal tubular epithelial cells is mediated in part through P2 receptor (P2R) activation by locally released ATP. The ability of P2R to regulate salt and water reabsorption has suggested a possible contribution of ATP release and paracrine P2R activation to cystogenesis and/or enlargement in autosomal dominant polycystic kidney disease (ADPKD). We and others have demonstrated in human ADPKD cyst cells the absence of flow-induced Ca(i)2+ signaling exhibited by normal renal epithelial cells. We now extend these findings to primary and telomerase-immortalized normal and ADPKD epithelial cells of different genotype and of both proximal and distal origins. Flow-induced elevation of Ca(i)2+ concentration ([Ca2+](i)) was absent from ADPKD cyst cells, but in normal cells was mediated by flow-sensitive ATP release and paracrine P2R activation, modulated by ecto-nucleotidase activity, and abrogated by P2R inhibition or extracellular ATP hydrolysis. In contrast to the elevated ATP release from ADPKD cells in static isotonic conditions or in hypotonic conditions, flow-induced ATP release from cyst cells was lower than from normal cells. Extracellular ATP rapidly reduced thapsigargin-elevated [Ca2+](i) in both ADPKD cyst and normal cells, but cyst cells lacked the subsequent, slow, oxidized ATP-sensitive [Ca2+](i) recovery present in normal cells. Telomerase-immortalized cyst cells also exhibited altered CD39 and P2X7 mRNA levels. Thus the loss of flow-induced, P2R-mediated Ca(i)2+ signaling in human ADPKD cyst epithelial cells was accompanied by reduced flow-sensitive ATP release, altered purinergic regulation of store-operated Ca2+ entry, and altered expression of gene products controlling extracellular nucleotide signaling.
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Affiliation(s)
- Chang Xu
- Molecular and Vascular Medicine and Renal Divs., Beth Israel Deaconess Medical Center, 330 Brookline Ave., E/RW763, Boston, MA 02215, USA
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50
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Tsiokas L. Function and regulation of TRPP2 at the plasma membrane. Am J Physiol Renal Physiol 2009; 297:F1-9. [PMID: 19244406 DOI: 10.1152/ajprenal.90277.2008] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The vast majority (approximately 99%) of all known cases of autosomal dominant polycystic kidney disease (ADPKD) are caused by naturally occurring mutations in two separate, but genetically interacting, loci, pkd1 and pkd2. pkd1 encodes a large multispanning membrane protein (PKD1) of unknown function, while pkd2 encodes a protein (TRPP2, polycystin-2, or PKD2) of the transient receptor potential (TRP) superfamily of ion channels. Biochemical, functional, and genetic studies support a model in which PKD1 physically interacts with TRPP2 to form an ion channel complex that conveys extracellular stimuli to ionic currents. However, the molecular identity of these extracellular stimuli remains elusive. Functional studies in cell culture show that TRPP2 can be activated in response to mechanical cues (fluid shear stress) and/or receptor tyrosine kinase (RTK) and G protein-coupled receptor (GPCR) activation at the cell surface. Recent genetic studies in Chlamydomonas reinhardtii show that CrPKD2 functions in a pathway linking cell-cell adhesion and Ca(2+) signaling. The mode of activation depends on protein-protein interactions with other channel subunits and auxiliary proteins. Therefore, understanding the mechanisms underlying the molecular makeup of TRPP2-containing complexes is critical in delineating the mechanisms of TRPP2 activation and, most importantly, the mechanisms by which naturally occurring mutations in pkd1 or pkd2 lead not only to ADPKD, but also to other defects reported in model organisms lacking functional TRPP2. This review focuses on the molecular assembly, function, and regulation of TRPP2 as a cell surface cation channel and discusses its potential role in Ca(2+) signaling and ADPKD pathophysiology.
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Affiliation(s)
- Leonidas Tsiokas
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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