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Wang Z, Chen M, Su Q, Morais TDC, Wang Y, Nazginov E, Pillai AR, Qian F, Shi Y, Yu Y. Molecular and structural basis of the dual regulation of the polycystin-2 ion channel by small-molecule ligands. Proc Natl Acad Sci U S A 2024; 121:e2316230121. [PMID: 38483987 PMCID: PMC10962963 DOI: 10.1073/pnas.2316230121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 02/12/2024] [Indexed: 03/19/2024] Open
Abstract
Mutations in the PKD2 gene, which encodes the polycystin-2 (PC2, also called TRPP2) protein, lead to autosomal dominant polycystic kidney disease (ADPKD). As a member of the transient receptor potential (TRP) channel superfamily, PC2 functions as a non-selective cation channel. The activation and regulation of the PC2 channel are largely unknown, and direct binding of small-molecule ligands to this channel has not been reported. In this work, we found that most known small-molecule agonists of the mucolipin TRP (TRPML) channels inhibit the activity of the PC2_F604P, a gain-of-function mutant of the PC2 channel. However, two of them, ML-SA1 and SF-51, have dual regulatory effects, with low concentration further activating PC2_F604P, and high concentration leading to inactivation of the channel. With two cryo-electron microscopy (cryo-EM) structures, a molecular docking model, and mutagenesis results, we identified two distinct binding sites of ML-SA1 in PC2_F604P that are responsible for activation and inactivation, respectively. These results provide structural and functional insights into how ligands regulate PC2 channel function through unusual mechanisms and may help design compounds that are more efficient and specific in regulating the PC2 channel and potentially also for ADPKD treatment.
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Affiliation(s)
- Zhifei Wang
- Department of Biological Sciences, St. John’s University, Queens, NY11375
| | - Mengying Chen
- Research Center for Industries of the Future, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang province310024, China
- Westlake Laboratory of Life Sciences and Biomedicine, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang province310024, China
- Beijing Frontier Research Center for Biological Structures, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing100084, China
| | - Qiang Su
- Research Center for Industries of the Future, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang province310024, China
- Westlake Laboratory of Life Sciences and Biomedicine, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang province310024, China
| | - Tiago D. C. Morais
- Department of Biological Sciences, St. John’s University, Queens, NY11375
| | - Yan Wang
- Department of Biological Sciences, St. John’s University, Queens, NY11375
| | - Elianna Nazginov
- Department of Biological Sciences, St. John’s University, Queens, NY11375
| | - Akhilraj R. Pillai
- Department of Biological Sciences, St. John’s University, Queens, NY11375
| | - Feng Qian
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD21201
| | - Yigong Shi
- Research Center for Industries of the Future, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang province310024, China
- Westlake Laboratory of Life Sciences and Biomedicine, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang province310024, China
- Beijing Frontier Research Center for Biological Structures, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing100084, China
| | - Yong Yu
- Department of Biological Sciences, St. John’s University, Queens, NY11375
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2
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Huang J, Korsunsky A, Yazdani M, Chen J. Targeting TRP channels: recent advances in structure, ligand binding, and molecular mechanisms. Front Mol Neurosci 2024; 16:1334370. [PMID: 38273937 PMCID: PMC10808746 DOI: 10.3389/fnmol.2023.1334370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/26/2023] [Indexed: 01/27/2024] Open
Abstract
Transient receptor potential (TRP) channels are a large and diverse family of transmembrane ion channels that are widely expressed, have important physiological roles, and are associated with many human diseases. These proteins are actively pursued as promising drug targets, benefitting greatly from advances in structural and mechanistic studies of TRP channels. At the same time, the complex, polymodal activation and regulation of TRP channels have presented formidable challenges. In this short review, we summarize recent progresses toward understanding the structural basis of TRP channel function, as well as potential ligand binding sites that could be targeted for therapeutics. A particular focus is on the current understanding of the molecular mechanisms of TRP channel activation and regulation, where many fundamental questions remain unanswered. We believe that a deeper understanding of the functional mechanisms of TRP channels will be critical and likely transformative toward developing successful therapeutic strategies targeting these exciting proteins. This endeavor will require concerted efforts from computation, structural biology, medicinal chemistry, electrophysiology, pharmacology, drug safety and clinical studies.
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Affiliation(s)
- Jian Huang
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| | - Aron Korsunsky
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| | - Mahdieh Yazdani
- Modeling and Informatics, Merck & Co., Inc., West Point, PA, United States
| | - Jianhan Chen
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
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3
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Das P, Mekonnen B, Alkhofash R, Ingle AV, Workman EB, Feather A, Zhang G, Chasen N, Liu P, Lechtreck KF. The Small Interactor of PKD2 protein promotes the assembly and ciliary entry of the Chlamydomonas PKD2-mastigoneme complexes. J Cell Sci 2024; 137:jcs261497. [PMID: 38063216 PMCID: PMC10846610 DOI: 10.1242/jcs.261497] [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: 07/20/2023] [Accepted: 12/04/2023] [Indexed: 01/13/2024] Open
Abstract
In Chlamydomonas, the channel polycystin 2 (PKD2) is primarily present in the distal region of cilia, where it is attached to the axoneme and mastigonemes, extracellular polymers of MST1. In a smaller proximal ciliary region that lacks mastigonemes, PKD2 is more mobile. We show that the PKD2 regions are established early during ciliogenesis and increase proportionally in length as cilia elongate. In chimeric zygotes, tagged PKD2 rapidly entered the proximal region of PKD2-deficient cilia, whereas the assembly of the distal region was hindered, suggesting that axonemal binding of PKD2 requires de novo assembly of cilia. We identified the protein Small Interactor of PKD2 (SIP), a PKD2-related, single-pass transmembrane protein, as part of the PKD2-mastigoneme complex. In sip mutants, stability and proteolytic processing of PKD2 in the cell body were reduced and PKD2-mastigoneme complexes were absent from the cilia. Like the pkd2 and mst1 mutants, sip mutant cells swam with reduced velocity. Cilia of the pkd2 mutant beat with an increased frequency but were less efficient in moving the cells, suggesting a structural role for the PKD2-SIP-mastigoneme complex in increasing the effective surface of Chlamydomonas cilia.
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Affiliation(s)
- Poulomi Das
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Betlehem Mekonnen
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Rama Alkhofash
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Abha V. Ingle
- Department of Computer Science, University of Georgia, Athens, GA 30602, USA
| | - E. Blair Workman
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Alec Feather
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Gui Zhang
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Nathan Chasen
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Peiwei Liu
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Karl F. Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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4
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Ghosh Roy S, Li Z, Guo Z, Long KT, Rehrl S, Tian X, Dong K, Besse W. Dnajb11-Kidney Disease Develops from Reduced Polycystin-1 Dosage but not Unfolded Protein Response in Mice. J Am Soc Nephrol 2023; 34:1521-1534. [PMID: 37332102 PMCID: PMC10482070 DOI: 10.1681/asn.0000000000000164] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 05/18/2023] [Indexed: 06/20/2023] Open
Abstract
SIGNIFICANCE STATEMENT Heterozygous DNAJB11 mutation carriers manifest with small cystic kidneys and renal failure in adulthood. Recessive cases with prenatal cystic kidney dysplasia were recently described. Our in vitro and mouse model studies investigate the proposed disease mechanism as an overlap of autosomal-dominant polycystic kidney disease and autosomal-dominant tubulointerstitial kidney disease pathogenesis. We find that DNAJB11 loss impairs cleavage and maturation of the autosomal-dominant polycystic kidney disease protein polycystin-1 (PC1) and results in dosage-dependent cyst formation in mice. We find that Dnajb11 loss does not activate the unfolded protein response, drawing a fundamental contrast with the pathogenesis of autosomal-dominant tubulointerstitial kidney disease. We instead propose that fibrosis in DNAJB11 -kidney disease may represent an exaggerated response to polycystin-dependent cysts. BACKGROUND Patients with heterozygous inactivating mutations in DNAJB11 manifest with cystic but not enlarged kidneys and renal failure in adulthood. Pathogenesis is proposed to resemble an overlap of autosomal-dominant polycystic kidney disease (ADPKD) and autosomal-dominant tubulointerstitial kidney disease (ADTKD), but this phenotype has never been modeled in vivo . DNAJB11 encodes an Hsp40 cochaperone in the endoplasmic reticulum: the site of maturation of the ADPKD polycystin-1 (PC1) protein and of unfolded protein response (UPR) activation in ADTKD. We hypothesized that investigation of DNAJB11 would shed light on mechanisms for both diseases. METHODS We used germline and conditional alleles to model Dnajb11 -kidney disease in mice. In complementary experiments, we generated two novel Dnajb11-/- cell lines that allow assessment of PC1 C-terminal fragment and its ratio to the immature full-length protein. RESULTS Dnajb11 loss results in a profound defect in PC1 cleavage but with no effect on other cystoproteins assayed. Dnajb11-/- mice are live-born at below the expected Mendelian ratio and die at a weaning age with cystic kidneys. Conditional loss of Dnajb11 in renal tubular epithelium results in PC1 dosage-dependent kidney cysts, thus defining a shared mechanism with ADPKD. Dnajb11 mouse models show no evidence of UPR activation or cyst-independent fibrosis, which is a fundamental distinction from typical ADTKD pathogenesis. CONCLUSIONS DNAJB11 -kidney disease is on the spectrum of ADPKD phenotypes with a PC1-dependent pathomechanism. The absence of UPR across multiple models suggests that alternative mechanisms, which may be cyst-dependent, explain the renal failure in the absence of kidney enlargement.
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Affiliation(s)
- Sounak Ghosh Roy
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
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5
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Wang Y, Wang Z, Pavel MA, Ng C, Kashyap P, Li B, Morais TDC, Ulloa GA, Yu Y. The diverse effects of pathogenic point mutations on ion channel activity of a gain-of-function polycystin-2. J Biol Chem 2023; 299:104674. [PMID: 37028763 PMCID: PMC10192930 DOI: 10.1016/j.jbc.2023.104674] [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: 06/14/2022] [Revised: 02/27/2023] [Accepted: 03/06/2023] [Indexed: 04/08/2023] Open
Abstract
Autosomal dominant polycystic kidney disease is caused by mutations in PKD1 or PKD2 genes. The latter encodes polycystin-2 (PC2, also known as TRPP2), a member of the transient receptor potential ion channel family. Despite most pathogenic mutations in PKD2 being truncation variants, there are also many point mutations, which cause small changes in protein sequences but dramatic changes in the in vivo function of PC2. How these mutations affect PC2 ion channel function is largely unknown. In this study, we systematically tested the effects of 31 point mutations on the ion channel activity of a gain-of-function PC2 mutant, PC2_F604P, expressed in Xenopus oocytes. The results show that all mutations in the transmembrane domains and channel pore region, and most mutations in the extracellular tetragonal opening for polycystins domain, are critical for PC2_F604P channel function. In contrast, the other mutations in the tetragonal opening for polycystins domain and most mutations in the C-terminal tail cause mild or no effects on channel function as assessed in Xenopus oocytes. To understand the mechanism of these effects, we have discussed possible conformational consequences of these mutations based on the cryo-EM structures of PC2. The results help gain insight into the structure and function of the PC2 ion channel and the molecular mechanism of pathogenesis caused by these mutations.
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Affiliation(s)
- Yan Wang
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Zhifei Wang
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Mahmud Arif Pavel
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Courtney Ng
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Parul Kashyap
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Bin Li
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Tiago D C Morais
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Gabriella A Ulloa
- Department of Biological Sciences, St. John's University, Queens, New York, USA
| | - Yong Yu
- Department of Biological Sciences, St. John's University, Queens, New York, USA.
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6
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Zhao S, Rohacs T. The newest TRP channelopathy: Gain of function TRPM3 mutations cause epilepsy and intellectual disability. Channels (Austin) 2021; 15:386-397. [PMID: 33853504 PMCID: PMC8057083 DOI: 10.1080/19336950.2021.1908781] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 02/25/2021] [Accepted: 02/25/2021] [Indexed: 12/13/2022] Open
Abstract
Transient Receptor Potential Melastatin 3 (TRPM3) is a Ca2+ permeable nonselective cation channel, activated by heat and chemical agonists, such as the endogenous neuro-steroid Pregnenolone Sulfate (PregS) and the chemical compound CIM0216. TRPM3 is expressed in peripheral sensory neurons of the dorsal root ganglia (DRG), and its role in noxious heat sensation in mice is well established. TRPM3 is also expressed in a number of other tissues, including the brain, but its role there has been largely unexplored. Recent reports showed that two mutations in TRPM3 are associated with a developmental and epileptic encephalopathy, pointing to an important role of TRPM3 in the human brain. Subsequent reports found that the two disease-associated mutations increased basal channel activity, and sensitivity of the channel to activation by heat and chemical agonists. This review will discuss these mutations in the context of human diseases caused by mutations in other TRP channels, and in the context of the biophysical properties and physiological functions of TRPM3.
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Affiliation(s)
- Siyuan Zhao
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, Newark, NJ, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, Newark, NJ, USA
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7
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Cardiac Involvement in Autosomal Dominant Polycystic Kidney Disease. CARDIOGENETICS 2021. [DOI: 10.3390/cardiogenetics11020006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Cardiovascular disorders are the main complication in autosomal dominant polycystic kidney disease (ADPKD). contributing to both morbidity and mortality. This review considers clinical studies unveiling cardiovascular features in patients with ADPKD. Additionally, it focuses on basic science studies addressing the dysfunction of the polycystin proteins located in the cardiovascular system as a contributing factor to cardiovascular abnormalities. In particular, the effects of polycystin proteins’ deficiency on the cardiomyocyte function have been considered.
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8
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Liu P, Lou X, Wingfield JL, Lin J, Nicastro D, Lechtreck K. Chlamydomonas PKD2 organizes mastigonemes, hair-like glycoprotein polymers on cilia. J Cell Biol 2021; 219:151720. [PMID: 32348466 PMCID: PMC7265326 DOI: 10.1083/jcb.202001122] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/10/2020] [Accepted: 03/16/2020] [Indexed: 12/20/2022] Open
Abstract
Mutations in the channel protein PKD2 cause autosomal dominant polycystic kidney disease, but the function of PKD2 in cilia remains unclear. Here, we show that PKD2 targets and anchors mastigonemes, filamentous polymers of the glycoprotein MST1, to the extracellular surface of Chlamydomonas cilia. PKD2–mastigoneme complexes physically connect to the axonemal doublets 4 and 8, positioning them perpendicular to the plane of ciliary beating. pkd2 mutant cilia lack mastigonemes, and mutant cells swim with reduced velocity, indicating a motility-related function of the PKD2–mastigoneme complex. Association with both the axoneme and extracellular structures supports a mechanosensory role of Chlamydomonas PKD2. We propose that PKD2–mastigoneme arrays, on opposing sides of the cilium, could perceive forces during ciliary beating and transfer these signals to locally regulate the response of the axoneme.
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Affiliation(s)
- Peiwei Liu
- Department of Cellular Biology, University of Georgia, Athens, GA
| | - Xiaochu Lou
- Departments of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | | | - Jianfeng Lin
- Departments of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Daniela Nicastro
- Departments of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Karl Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA
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9
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Hosszu A, Kaucsar T, Seeliger E, Fekete A. Animal Models of Renal Pathophysiology and Disease. Methods Mol Biol 2021; 2216:27-44. [PMID: 33475992 DOI: 10.1007/978-1-0716-0978-1_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Renal diseases remain devastating illnesses with unacceptably high rates of mortality and morbidity worldwide. Animal models are essential tools to better understand the pathomechanisms of kidney-related illnesses and to develop new, successful therapeutic strategies. Magnetic resonance imaging (MRI) has been actively explored in the last decades for assessing renal function, perfusion, tissue oxygenation as well as the degree of fibrosis and inflammation. This chapter aims to provide a comprehensive overview of animal models of acute and chronic kidney diseases, highlighting MRI-specific considerations, advantages, and pitfalls, and thus assisting the researcher in experiment planning.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.
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Affiliation(s)
- Adam Hosszu
- 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Tamas Kaucsar
- 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Erdmann Seeliger
- Working Group Integrative Kidney Physiology, Institute of Physiology, Charité-University Medicine Berlin, Berlin, Germany
| | - Andrea Fekete
- 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary.
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10
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Tokhmafshan F, Dickinson K, Akpa MM, Brasell E, Huertas P, Goodyer PR. A no-nonsense approach to hereditary kidney disease. Pediatr Nephrol 2020; 35:2031-2042. [PMID: 31807928 DOI: 10.1007/s00467-019-04394-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 07/05/2019] [Accepted: 10/07/2019] [Indexed: 01/12/2023]
Abstract
The advent of a new class of aminoglycosides with increased translational readthrough of nonsense mutations and reduced toxicity offers a new therapeutic strategy for a subset of patients with hereditary kidney disease. The renal uptake and retention of aminoglycosides at a high intracellular concentration makes the kidney an ideal target for this approach. In this review, we explore the potential of aminoglycoside readthrough therapy in a number of hereditary kidney diseases and discuss the therapeutic window of opportunity for subclasses of each disease, when caused by nonsense mutations.
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Affiliation(s)
- Fatima Tokhmafshan
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada
| | - Kyle Dickinson
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada.,Department of Experimental Medicine, McGill University, Montreal, Canada
| | - Murielle M Akpa
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada
| | - Emma Brasell
- Department of Human Genetics, McGill University, Montreal, Canada
| | | | - Paul R Goodyer
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada. .,Department of Experimental Medicine, McGill University, Montreal, Canada. .,Department of Human Genetics, McGill University, Montreal, Canada. .,Department of Pediatrics, McGill University, Montreal, Canada.
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11
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Ta CM, Vien TN, Ng LCT, DeCaen PG. Structure and function of polycystin channels in primary cilia. Cell Signal 2020; 72:109626. [PMID: 32251715 DOI: 10.1016/j.cellsig.2020.109626] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 03/30/2020] [Accepted: 03/31/2020] [Indexed: 12/12/2022]
Abstract
Variants in genes which encode for polycystin-1 and polycystin-2 cause most forms of autosomal dominant polycystic disease (ADPKD). Despite our strong understanding of the genetic determinants of ADPKD, we do not understand the structural features which govern the function of polycystins at the molecular level, nor do we understand the impact of most disease-causing variants on the conformational state of these proteins. These questions have remained elusive because polycystins localize to several organelle membranes, including the primary cilia. Primary cilia are microtubule based organelles which function as cellular antennae. Polycystin-2 and related polycystin-2 L1 are members of the transient receptor potential (TRP) ion channel family, and form distinct ion channels in the primary cilia of disparate cell types which can be directly measured. Polycystin-1 has both ion channel and adhesion G-protein coupled receptor (GPCR) features-but its role in forming a channel complex or as a channel subunit chaperone is undetermined. Nonetheless, recent polycystin structural determination by cryo-EM has provided a molecular template to understand their biophysical regulation and the impact of disease-causing variants. We will review these advances and discuss hypotheses regarding the regulation of polycystin channel opening by their structural domains within the context of the primary cilia.
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Affiliation(s)
- Chau My Ta
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, 320 E Superior, Chicago, IL 60611, USA
| | - Thuy N Vien
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, 320 E Superior, Chicago, IL 60611, USA
| | - Leo C T Ng
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, 320 E Superior, Chicago, IL 60611, USA
| | - Paul G DeCaen
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, 320 E Superior, Chicago, IL 60611, USA.
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12
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Nowak KL, Edelstein CL. Apoptosis and autophagy in polycystic kidney disease (PKD). Cell Signal 2019; 68:109518. [PMID: 31881325 DOI: 10.1016/j.cellsig.2019.109518] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 12/20/2019] [Accepted: 12/21/2019] [Indexed: 02/08/2023]
Abstract
Apoptosis in the cystic epithelium is observed in most rodent models of polycystic kidney disease (PKD) and in human autosomal dominant PKD (ADPKD). Apoptosis inhibition decreases cyst growth, whereas induction of apoptosis in the kidney of Bcl-2 deficient mice increases proliferation of the tubular epithelium and subsequent cyst formation. However, alternative evidence indicates that both induction of apoptosis as well as increased overall rates of apoptosis are associated with decreased cyst growth. Autophagic flux is suppressed in cell, zebra fish and mouse models of PKD and suppressed autophagy is known to be associated with increased apoptosis. There may be a link between apoptosis and autophagy in PKD. The mammalian target of rapamycin (mTOR), B-cell lymphoma 2 (Bcl-2) and caspase pathways that are known to be dysregulated in PKD, are also known to regulate both autophagy and apoptosis. Induction of autophagy in cell and zebrafish models of PKD results in suppression of apoptosis and reduced cyst growth supporting the hypothesis autophagy induction may have a therapeutic role in decreasing cyst growth, perhaps by decreasing apoptosis and proliferation in PKD. Future research is needed to evaluate the effects of direct autophagy inducers on apoptosis in rodent PKD models, as well as the cause and effect relationship between autophagy, apoptosis and cyst growth in PKD.
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Affiliation(s)
- Kristen L Nowak
- Division of Renal Diseases and Hypertension, Univ. of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Charles L Edelstein
- Division of Renal Diseases and Hypertension, Univ. of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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13
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Wang Z, Ng C, Liu X, Wang Y, Li B, Kashyap P, Chaudhry HA, Castro A, Kalontar EM, Ilyayev L, Walker R, Alexander RT, Qian F, Chen X, Yu Y. The ion channel function of polycystin-1 in the polycystin-1/polycystin-2 complex. EMBO Rep 2019; 20:e48336. [PMID: 31441214 PMCID: PMC6832002 DOI: 10.15252/embr.201948336] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/30/2019] [Accepted: 08/01/2019] [Indexed: 12/15/2022] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 or PKD2 gene, encoding the polycystic kidney disease protein polycystin-1 and the transient receptor potential channel polycystin-2 (also known as TRPP2), respectively. Polycystin-1 and polycystin-2 form a receptor-ion channel complex located in primary cilia. The function of this complex, especially the role of polycystin-1, is largely unknown due to the lack of a reliable functional assay. In this study, we dissect the role of polycystin-1 by directly recording currents mediated by a gain-of-function (GOF) polycystin-1/polycystin-2 channel. Our data show that this channel has distinct properties from that of the homomeric polycystin-2 channel. The polycystin-1 subunit directly contributes to the channel pore, and its eleven transmembrane domains are sufficient for its channel function. We also show that the cleavage of polycystin-1 at the N-terminal G protein-coupled receptor proteolysis site is not required for the activity of the GOF polycystin-1/polycystin-2 channel. These results demonstrate the ion channel function of polycystin-1 in the polycystin-1/polycystin-2 complex, enriching our understanding of this channel and its role in ADPKD.
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Affiliation(s)
- Zhifei Wang
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Courtney Ng
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Xiong Liu
- Department of Physiology, Membrane Protein Disease Research GroupFaculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanada
| | - Yan Wang
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Bin Li
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Parul Kashyap
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | | | - Alexis Castro
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | | | - Leah Ilyayev
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Rebecca Walker
- Division of NephrologyDepartment of MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - R Todd Alexander
- Departments of Pediatrics and PhysiologyUniversity of AlbertaEdmontonABCanada
| | - Feng Qian
- Division of NephrologyDepartment of MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Xing‐Zhen Chen
- Department of Physiology, Membrane Protein Disease Research GroupFaculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanada
| | - Yong Yu
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
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14
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Pablo JL, Greka A. Charting a TRP to Novel Therapeutic Destinations for Kidney Diseases. Trends Pharmacol Sci 2019; 40:911-918. [PMID: 31704171 DOI: 10.1016/j.tips.2019.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 09/24/2019] [Accepted: 10/07/2019] [Indexed: 12/29/2022]
Abstract
Ion channels are critical to kidney function, and their dysregulation leads to several distinct kidney diseases. Of the diversity of ion channels in kidney cells, the transient receptor potential (TRP) superfamily of proteins plays important and varied roles in both maintaining homeostasis as well as in causing disease. Recent work showed that TRPC5 blockers could successfully protect critical components of the kidney filter both in vitro and in vivo, thus revealing TRPC5 as a tractable therapeutic target for focal and segmental glomerulosclerosis (FSGS), a common cause of kidney failure. Human genetics point to three additional TRP channels as plausible therapeutic targets: TRPC6 in FSGS, PKD2 in polycystic kidney disease, and TRPM6 in familial hypomagnesemia with secondary hypocalcemia (HSH). We conclude that targeting TRP channels could pave the way for much needed therapies for kidney diseases.
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Affiliation(s)
- Juan Lorenzo Pablo
- Broad Institute of MIT and Harvard, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Anna Greka
- Broad Institute of MIT and Harvard, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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15
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Kim JH, Park EY, Chitayat D, Stachura DL, Schaper J, Lindstrom K, Jewett T, Wieczorek D, Draaisma JM, Sinnema M, Hoeberigs C, Hempel M, Bachman KK, Seeley AH, Stone JK, Kong HK, Vukadin L, Richard A, Shinde DN, McWalter K, Si YC, Douglas G, Lim ST, Vissers LELM, Lemaire M, Ahn EYE. SON haploinsufficiency causes impaired pre-mRNA splicing of CAKUT genes and heterogeneous renal phenotypes. Kidney Int 2019; 95:1494-1504. [PMID: 31005274 DOI: 10.1016/j.kint.2019.01.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 12/10/2018] [Accepted: 01/04/2019] [Indexed: 10/27/2022]
Abstract
Although genetic testing is increasingly used in clinical nephrology, a large number of patients with congenital abnormalities of the kidney and urinary tract (CAKUT) remain undiagnosed with current gene panels. Therefore, careful curation of novel genetic findings is key to improving diagnostic yields. We recently described a novel intellectual disability syndrome caused by de novo heterozygous loss-of-function mutations in the gene encoding the splicing factor SON. Here, we show that many of these patients, including two previously unreported, exhibit a wide array of kidney abnormalities. Detailed phenotyping of 14 patients with SON haploinsufficiency identified kidney anomalies in 8 patients, including horseshoe kidney, unilateral renal hypoplasia, and renal cysts. Recurrent urinary tract infections, electrolyte disturbances, and hypertension were also observed in some patients. SON knockdown in kidney cell lines leads to abnormal pre-mRNA splicing, resulting in decreased expression of several established CAKUT genes. Furthermore, these molecular events were observed in patient-derived cells with SON haploinsufficiency. Taken together, our data suggest that the wide spectrum of phenotypes in patients with a pathogenic SON mutation is a consequence of impaired pre-mRNA splicing of several CAKUT genes. We propose that genetic testing panels designed to diagnose children with a kidney phenotype should include the SON gene.
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Affiliation(s)
- Jung-Hyun Kim
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA
| | - Eun Young Park
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA
| | - David Chitayat
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada; The Prenatal Diagnosis and Medical Genetics Program, Department of Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - David L Stachura
- Department of Biological Sciences, California State University Chico, Chico, California, USA
| | - Jörg Schaper
- Institute of Diagnostic and Interventional Radiology, University of Düsseldorf, Düsseldorf, Germany
| | - Kristin Lindstrom
- Division of Genetics and Metabolism, Phoenix Children's Hospital, Phoenix, Arizona, USA
| | - Tamison Jewett
- Department of Pediatrics, Section on Medical Genetics, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Dagmar Wieczorek
- Institute of Human Genetics, University Clinic Düsseldorf, Heinrich-Heine-University, Düsseldorf, Germany; Institute of Human Genetics, University Clinic Essen, University Duisburg-Essen, Essen, Germany
| | - Jos M Draaisma
- Department of Pediatrics, Radboudumc Amalia Children's Hospital, Nijmegen, The Netherlands
| | - Margje Sinnema
- Department of Clinical Genetics and School for Oncology & Developmental Biology (GROW), Maastricht University Medical Center, Maastricht, The Netherlands
| | - Christianne Hoeberigs
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Maja Hempel
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | | | - Joshua K Stone
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA
| | - Hyun Kyung Kong
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA
| | - Lana Vukadin
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA
| | - Alexander Richard
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA
| | | | | | | | | | - Ssang-Taek Lim
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, Alabama, USA
| | - Lisenka E L M Vissers
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mathieu Lemaire
- Division of Nephrology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada; Cell Biology Program, SickKids Research Institute, University of Toronto, Toronto, Ontario, Canada.
| | - Eun-Young Erin Ahn
- Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA; Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, Alabama, USA.
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16
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Abdelwahed M, Hilbert P, Ahmed A, Mahfoudh H, Bouomrani S, Dey M, Hachicha J, Kamoun H, Keskes-Ammar L, Belguith N. Mutational analysis in patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD): Identification of five mutations in the PKD1 gene. Gene 2018; 671:28-35. [DOI: 10.1016/j.gene.2018.05.112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 05/24/2018] [Accepted: 05/30/2018] [Indexed: 01/01/2023]
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17
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Liu X, Vien T, Duan J, Sheu SH, DeCaen PG, Clapham DE. Polycystin-2 is an essential ion channel subunit in the primary cilium of the renal collecting duct epithelium. eLife 2018; 7:33183. [PMID: 29443690 PMCID: PMC5812715 DOI: 10.7554/elife.33183] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Accepted: 02/01/2018] [Indexed: 01/08/2023] Open
Abstract
Mutations in the polycystin genes, PKD1 or PKD2, results in Autosomal Dominant Polycystic Kidney Disease (ADPKD). Although a genetic basis of ADPKD is established, we lack a clear understanding of polycystin proteins’ functions as ion channels. This question remains unsolved largely because polycystins localize to the primary cilium – a tiny, antenna-like organelle. Using a new ADPKD mouse model, we observe primary cilia that are abnormally long in cells associated with cysts after conditional ablation of Pkd1 or Pkd2. Using primary cultures of collecting duct cells, we show that polycystin-2, but not polycystin-1, is a required subunit for the ion channel in the primary cilium. The polycystin-2 channel preferentially conducts K+ and Na+; intraciliary Ca2+, enhances its open probability. We introduce a novel method for measuring heterologous polycystin-2 channels in cilia, which will have utility in characterizing PKD2 variants that cause ADPKD.
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Affiliation(s)
- Xiaowen Liu
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Thuy Vien
- Department of Pharmacology, Northwestern University, Feinberg School of Medicine, Chicago, United States
| | - Jingjing Duan
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Shu-Hsien Sheu
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States.,Department of Pathology, Boston Children's Hospital, Boston, United States
| | - Paul G DeCaen
- Department of Pharmacology, Northwestern University, Feinberg School of Medicine, Chicago, United States
| | - David E Clapham
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
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18
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England SJ, Campbell PC, Banerjee S, Swanson AJ, Lewis KE. Identification and Expression Analysis of the Complete Family of Zebrafish pkd Genes. Front Cell Dev Biol 2017; 5:5. [PMID: 28271061 PMCID: PMC5318412 DOI: 10.3389/fcell.2017.00005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 01/19/2017] [Indexed: 01/01/2023] Open
Abstract
Polycystic kidney disease (PKD) proteins are trans-membrane proteins that have crucial roles in many aspects of vertebrate development and physiology, including the development of many organs as well as left–right patterning and taste. They can be divided into structurally-distinct PKD1-like and PKD2-like proteins and usually one PKD1-like protein forms a heteromeric polycystin complex with a PKD2-like protein. For example, PKD1 forms a complex with PKD2 and mutations in either of these proteins cause Autosomal Dominant Polycystic Kidney Disease (ADPKD), which is the most frequent potentially-lethal single-gene disorder in humans. Here, we identify the complete family of pkd genes in zebrafish and other teleosts. We describe the genomic locations and sequences of all seven genes: pkd1, pkd1b, pkd1l1, pkd1l2a, pkd1l2b, pkd2, and pkd2l1. pkd1l2a/pkd1l2b are likely to be ohnologs of pkd1l2, preserved from the whole genome duplication that occurred at the base of the teleosts. However, in contrast to mammals and cartilaginous and holostei fish, teleosts lack pkd2l2, and pkdrej genes, suggesting that these have been lost in the teleost lineage. In addition, teleost, and holostei fish have only a partial pkd1l3 sequence, suggesting that this gene may be in the process of being lost in the ray-finned fish lineage. We also provide the first comprehensive description of the expression of zebrafish pkd genes during development. In most structures we detect expression of one pkd1-like gene and one pkd2-like gene, consistent with these genes encoding a heteromeric protein complex. For example, we found that pkd2 and pkd1l1 are expressed in Kupffer's vesicle and pkd1 and pkd2 are expressed in the developing pronephros. In the spinal cord, we show that pkd1l2a and pkd2l1 are co-expressed in KA cells. We also identify potential co-expression of pkd1b and pkd2 in the floor-plate. Interestingly, and in contrast to mouse, we observe expression of all seven pkd genes in regions that may correspond to taste receptors. Taken together, these results provide a crucial catalog of pkd genes in an important model system for elucidating cell and developmental processes and modeling human diseases and the most comprehensive analysis of embryonic pkd gene expression in any vertebrate.
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Affiliation(s)
| | - Paul C Campbell
- Department of Biology, Syracuse University Syracuse, NY, USA
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19
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Salehi-Najafabadi Z, Li B, Valentino V, Ng C, Martin H, Yu Y, Wang Z, Kashyap P, Yu Y. Extracellular Loops Are Essential for the Assembly and Function of Polycystin Receptor-Ion Channel Complexes. J Biol Chem 2017; 292:4210-4221. [PMID: 28154010 DOI: 10.1074/jbc.m116.767897] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/31/2017] [Indexed: 12/15/2022] Open
Abstract
Polycystin complexes, or TRPP-PKD complexes, made of transient receptor potential channel polycystin (TRPP) and polycystic kidney disease (PKD) proteins, play key roles in coupling extracellular stimuli with intracellular Ca2+ signals. For example, the TRPP2-PKD1 complex has a crucial function in renal physiology, with mutations in either protein causing autosomal dominant polycystic kidney disease. In contrast, the TRPP3-PKD1L3 complex responds to low pH and was proposed to be a sour taste receptor candidate. It has been shown previously that the protein partners interact via association of the C-terminal or transmembrane segments, with consequences for the assembly, surface expression, and function of the polycystin complexes. However, the roles of extracellular components, especially the loops that connect the transmembrane segments, in the assembly and function of the polycystin complex are largely unknown. Here, with an immunoprecipitation method, we found that extracellular loops between the first and second transmembrane segments of TRPP2 and TRPP3 associate with the extracellular loops between the sixth and seventh transmembrane segments of PKD1 and PKD1L3, respectively. Immunofluorescence and electrophysiology data further confirm that the associations between these loops are essential for the trafficking and function of the complexes. Interestingly, most of the extracellular loops are also found to be involved in homomeric assembly. Furthermore, autosomal dominant polycystic kidney disease-associated TRPP2 mutant T448K significantly weakened TRPP2 homomeric assembly but had no obvious effect on TRPP2-PKD1 heteromeric assembly. Our results demonstrate a crucial role of these functionally underexplored extracellular loops in the assembly and function of the polycystin complexes.
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Affiliation(s)
| | - Bin Li
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Victoria Valentino
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Courtney Ng
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Hannah Martin
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Yang Yu
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Zhifei Wang
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Parul Kashyap
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
| | - Yong Yu
- From the Department of Biological Sciences, St. John's University, Queens, New York 11439
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20
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Pablo JL, DeCaen PG, Clapham DE. Progress in ciliary ion channel physiology. J Gen Physiol 2016; 149:37-47. [PMID: 27999145 PMCID: PMC5217089 DOI: 10.1085/jgp.201611696] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 12/06/2016] [Indexed: 11/20/2022] Open
Abstract
Mammalian cilia are ubiquitous appendages found on the apical surface of cells. Primary and motile cilia are distinct in both morphology and function. Most cells have a solitary primary cilium (9+0), which lacks the central microtubule doublet characteristic of motile cilia (9+2). The immotile primary cilia house unique signaling components and sequester several important transcription factors. In contrast, motile cilia commonly extend into the lumen of respiratory airways, fallopian tubes, and brain ventricles to move their contents and/or produce gradients. In this review, we focus on the composition of putative ion channels found in both types of cilia and in the periciliary membrane and discuss their proposed functions. Our discussion does not cover specialized cilia in photoreceptor or olfactory cells, which express many more ion channels.
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Affiliation(s)
- Juan Lorenzo Pablo
- Howard Hughes Medical Institute, Boston Children's Hospital, Boston, MA 02115.,Department of Cardiology, Boston Children's Hospital, Boston, MA 02115.,Department of Neurobiology, Harvard Medical School, Boston, MA 02115
| | - Paul G DeCaen
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - David E Clapham
- Howard Hughes Medical Institute, Boston Children's Hospital, Boston, MA 02115 .,Department of Cardiology, Boston Children's Hospital, Boston, MA 02115.,Department of Neurobiology, Harvard Medical School, Boston, MA 02115
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21
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DeCaen PG, Liu X, Abiria S, Clapham DE. Atypical calcium regulation of the PKD2-L1 polycystin ion channel. eLife 2016; 5. [PMID: 27348301 PMCID: PMC4922860 DOI: 10.7554/elife.13413] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 05/12/2016] [Indexed: 11/13/2022] Open
Abstract
Native PKD2-L1 channel subunits are present in primary cilia and other restricted cellular spaces. Here we investigate the mechanism for the channel's unusual regulation by external calcium, and rationalize this behavior to its specialized function. We report that the human PKD2-L1 selectivity filter is partially selective to calcium ions (Ca(2+)) moving into the cell, but blocked by high internal Ca(2+)concentrations, a unique feature of this transient receptor potential (TRP) channel family member. Surprisingly, we find that the C-terminal EF-hands and coiled-coil domains do not contribute to PKD2-L1 Ca(2+)-induced potentiation and inactivation. We propose a model in which prolonged channel activity results in calcium accumulation, triggering outward-moving Ca(2+) ions to block PKD2-L1 in a high-affinity interaction with the innermost acidic residue (D523) of the selectivity filter and subsequent long-term channel inactivation. This response rectifies Ca(2+) flow, enabling Ca(2+) to enter but not leave small compartments such as the cilium.
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Affiliation(s)
- Paul G DeCaen
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Xiaowen Liu
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Sunday Abiria
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - David E Clapham
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
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22
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Kim S, Nie H, Nesin V, Tran U, Outeda P, Bai CX, Keeling J, Maskey D, Watnick T, Wessely O, Tsiokas L. The polycystin complex mediates Wnt/Ca(2+) signalling. Nat Cell Biol 2016; 18:752-764. [PMID: 27214281 PMCID: PMC4925210 DOI: 10.1038/ncb3363] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/22/2016] [Indexed: 01/22/2023]
Abstract
WNT ligands induce Ca2+ signaling on target cells. PKD1 (Polycystin 1) is considered an orphan, atypical G protein coupled receptor complexed with TRPP2 (Polycystin 2 or PKD2), a Ca2+-permeable ion channel. Inactivating mutations in their genes cause autosomal dominant polycystic kidney disease (ADPKD), one of the most common genetic diseases. Here, we show that WNTs bind to the extracellular domain of PKD1 and induce whole cell currents and Ca2+ influx dependent on TRPP2. Pathogenic PKD1 or PKD2 mutations that abrogate complex formation, compromise cell surface expression of PKD1, or reduce TRPP2 channel activity suppress activation by WNTs. Pkd2−/− fibroblasts lack WNT-induced Ca2+ currents and are unable to polarize during directed cell migration. In Xenopus embryos, PKD1, Dishevelled 2 (DVL2), and WNT9A act within the same pathway to preserve normal tubulogenesis. These data define PKD1 as a WNT (co)receptor and implicate defective WNT/Ca2+ signaling as one of the causes of ADPKD.
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Affiliation(s)
- Seokho Kim
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA
| | - Hongguang Nie
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA.,Institute of Metabolic Disease Research and Drug Development, China Medical University, Liaoning Shenyang, 110001 China (H.N)
| | - Vasyl Nesin
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA
| | - Uyen Tran
- Department of Cellular and Molecular Medicine, Cleveland Clinic, 9500 Euclid Avenue/NC10, Cleveland, OH 44195, USA
| | - Patricia Outeda
- Division of Nephrology, Baltimore PKD Research and Clinical Core Center, University of Maryland School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201, USA
| | - Chang-Xi Bai
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA.,Department of Advanced Research on Mongolian Medicine, Research Institute for Mongolian Medicine, Inner Mongolia Medical University, Hohhot 010110, Inner Mongolia, China (CB)
| | - Jacob Keeling
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA
| | - Dipak Maskey
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA
| | - Terry Watnick
- Division of Nephrology, Baltimore PKD Research and Clinical Core Center, University of Maryland School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201, USA
| | - Oliver Wessely
- Department of Cellular and Molecular Medicine, Cleveland Clinic, 9500 Euclid Avenue/NC10, Cleveland, OH 44195, USA
| | - Leonidas Tsiokas
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, USA
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23
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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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24
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Singh V, Singla SK, Jha V, Puri V, Puri S. Hepatocyte nuclear factor-1β: A regulator of kidney development and cystogenesis. Indian J Nephrol 2015; 25:70-6. [PMID: 25838642 PMCID: PMC4379628 DOI: 10.4103/0971-4065.139492] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The understanding of the genomics of the renal tissue has gathered a considerable interest and is making rapid progress. The molecular mechanisms as well as the precise function of the associated molecular components toward renal pathophysiology have recently been realized. For the cystic kidney disease, the regulation of gene expression affecting epithelial cells proliferation, apoptosis as well as process of differentiation/de-differentiation represent key molecular targets. For the cystic disorders, molecular targets have been identified, which besides lending heterogeneity to cysts may also provide tools to unravel their functional importance to understand the renal tissue homeostasis. This review focuses on providing comprehensive information about the transcriptional regulatory role of hepatocyte nuclear factor-1β, a homeoprotein, as well as its interacting partners in renal tissue development and pathophysiology.
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Affiliation(s)
- V Singh
- Department of Biochemistry, Panjab University, Chandigarh, India
| | - S K Singla
- Department of Biochemistry, Panjab University, Chandigarh, India
| | - V Jha
- Department of Nephrology, PGIMER, Chandigarh, India
| | - V Puri
- Centre for Systems Biology and Bioinformatics, Under University Institute of Emerging Areas in Science and Technology, Panjab University, Chandigarh, India
| | - S Puri
- Biotechnology Branch, University Institute of Engineering and Technology, Chandigarh, India ; Centre for Stem Cell and Issue Engineering, University Institute of Emerging Areas in Science and Technology, Panjab University, Chandigarh, India
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25
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Yuan X, Serra RA, Yang S. Function and regulation of primary cilia and intraflagellar transport proteins in the skeleton. Ann N Y Acad Sci 2015; 1335:78-99. [PMID: 24961486 PMCID: PMC4334369 DOI: 10.1111/nyas.12463] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Primary cilia are microtubule-based organelles that project from the cell surface to enable transduction of various developmental signaling pathways. The process of intraflagellar transport (IFT) is crucial for the building and maintenance of primary cilia. Ciliary dysfunction has been found in a range of disorders called ciliopathies, some of which display severe skeletal dysplasias. In recent years, interest has grown in uncovering the function of primary cilia/IFT proteins in bone development, mechanotransduction, and cellular regulation. We summarize recent advances in understanding the function of cilia and IFT proteins in the regulation of cell differentiation in osteoblasts, osteocytes, chondrocytes, and mesenchymal stem cells (MSCs). We also discuss the mechanosensory function of cilia and IFT proteins in bone cells, cilia orientation, and other functions of cilia in chondrocytes.
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Affiliation(s)
- Xue Yuan
- Department of Oral Biology, School of Dental Medicine, University at Buffalo, The State University of New York, Buffalo, NY
| | - Rosa A. Serra
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Shuying Yang
- Department of Oral Biology, School of Dental Medicine, University at Buffalo, The State University of New York, Buffalo, NY
- Developmental Genomics Group, New York State Center of Excellence in Bioinformatics and Life Sciences, University at Buffalo, The State University of New York, Buffalo, NY
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Keeler C, Poon G, Kuo IY, Ehrlich BE, Hodsdon ME. An explicit formulation approach for the analysis of calcium binding to EF-hand proteins using isothermal titration calorimetry. Biophys J 2014; 105:2843-53. [PMID: 24359756 DOI: 10.1016/j.bpj.2013.11.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/08/2013] [Accepted: 11/12/2013] [Indexed: 11/28/2022] Open
Abstract
We present an improved and extended version of a recently proposed mathematical approach for modeling isotherms of ligand-to-macromolecule binding from isothermal titration calorimetry. Our approach uses ordinary differential equations, solved implicitly and numerically as initial value problems, to provide a quantitative description of the fraction bound of each competing member of a complex mixture of macromolecules from the basis of general binding polynomials. This approach greatly simplifies the formulation of complex binding models. In addition to our generalized, model-free approach, we have introduced a mathematical treatment for the case where ligand is present before the onset of the titration, essential for data analysis when complete removal of the binding partner may disrupt the structural and functional characteristics of the macromolecule. Demonstration programs playable on a freely available software platform are provided. Our method is experimentally validated with classic calcium (Ca(2+)) ion-selective potentiometry and isotherms of Ca(2+) binding to a mixture of chelators with and without residual ligand present in the reaction vessel. Finally, we simulate and compare experimental data fits for the binding isotherms of Ca(2+) binding to its canonical binding site (EF-hand domain) of polycystin 2, a Ca(2+)-dependent channel with relevance to polycystic kidney disease.
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Affiliation(s)
- Camille Keeler
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Gregory Poon
- Department of Pharmaceutical Sciences, Washington State University, Pullman, Washington
| | - Ivana Y Kuo
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut
| | - Barbara E Ehrlich
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut
| | - Michael E Hodsdon
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut.
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diIorio P, Rittenhouse AR, Bortell R, Jurczyk A. Role of cilia in normal pancreas function and in diseased states. ACTA ACUST UNITED AC 2014; 102:126-38. [PMID: 24861006 DOI: 10.1002/bdrc.21064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2014] [Indexed: 12/25/2022]
Abstract
Primary cilia play an essential role in modulating signaling cascades that shape cellular responses to environmental cues to maintain proper tissue development. Mutations in primary cilium proteins have been linked to several rare developmental disorders, collectively known as ciliopathies. Together with other disorders associated with dysfunctional cilia/centrosomes, affected individuals have increased risk of developing metabolic syndrome, neurologic disorders, and diabetes. In pancreatic tissues, cilia are found exclusively in islet and ductal cells where they play an essential role in pancreatic tissue organization. Their absence or disorganization leads to pancreatic duct abnormalities, acinar cell loss, polarity defects, and dysregulated insulin secretion. Cilia in pancreatic tissues are hubs for cellular signaling. Many signaling components, such as Hh, Notch, and Wnt, localize to pancreatic primary cilia and are necessary for proper development of pancreatic epithelium and β-cell morphogenesis. Receptors for neuroendocrine hormones, such as Somatostatin Receptor 3, also localize to the cilium and may play a more direct role in controlling insulin secretion due to somatostatin's inhibitory function. Finally, unique calcium signaling, which is at the heart of β-cell function, also occurs in primary cilia. Whereas voltage-gated calcium channels trigger insulin secretion and serve a variety of homeostatic functions in β-cells, transient receptor potential channels regulate calcium levels within the cilium that may serve as a feedback mechanism, regulating insulin secretion. This review article summarizes our current understanding of the role of primary cilia in normal pancreas function and in the diseased state.
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Affiliation(s)
- Philip diIorio
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts
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Abstract
Polycystic kidney disease (PKD) is a common hereditary disorder which is characterized by fluid-filled cysts in the kidney. Mutation in either PKD1, encoding polycystin-1 (PC1), or PKD2, encoding polycystin-2 (PC2), are causative genes of PKD. Recent studies indicate that renal cilia, known as mechanosensors, detecting flow stimulation through renal tubules, have a critical function in maintaining homeostasis of renal epithelial cells. Because most proteins related to PKD are localized to renal cilia or have a function in ciliogenesis. PC1/PC2 heterodimer is localized to the cilia, playing a role in calcium channels. Also, disruptions of ciliary proteins, except for PC1 and PC2, could be involved in the induction of polycystic kidney disease. Based on these findings, various PKD mice models were produced to understand the roles of primary cilia defects in renal cyst formation. In this review, we will describe the general role of cilia in renal epithelial cells, and the relationship between ciliary defects and PKD. We also discuss mouse models of PKD related to ciliary defects based on recent studies. [BMB Reports 2013; 46(2): 73-79]
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Affiliation(s)
- Je Yeong Ko
- Department of Biological Science, Sookmyung Women's University, Seoul 140-742, Korea
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Ćelić AS, Petri ET, Benbow J, Hodsdon ME, Ehrlich BE, Boggon TJ. Calcium-induced conformational changes in C-terminal tail of polycystin-2 are necessary for channel gating. J Biol Chem 2012; 287:17232-17240. [PMID: 22474326 DOI: 10.1074/jbc.m112.354613] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycystin-2 (PC2) is a Ca(2+)-permeable transient receptor potential channel activated and regulated by changes in cytoplasmic Ca(2+). PC2 mutations are responsible for ∼15% of autosomal dominant polycystic kidney disease. Although the C-terminal cytoplasmic tail of PC2 has been shown to contain a Ca(2+)-binding EF-hand domain, the molecular basis of PC2 channel gating by Ca(2+) remains unknown. We propose that the PC2 EF-hand is a Ca(2+) sensor required for channel gating. Consistent with this, Ca(2+) binding causes a dramatic decrease in the radius of gyration (R(g)) of the PC2 EF-hand by small angle x-ray scattering and significant conformational changes by NMR. Furthermore, increasing Ca(2+) concentrations cause the C-terminal cytoplasmic tail to transition from a mixture of extended oligomers to a single compact dimer by analytical ultracentrifugation, coupled with a >30 Å decrease in maximum interatomic distance (D(max)) by small angle x-ray scattering. Mutant PC2 channels unable to bind Ca(2+) via the EF-hand are inactive in single-channel planar lipid bilayers and inhibit Ca(2+) release from ER stores upon overexpression in cells, suggesting dominant negative properties. Our results support a model where PC2 channels are gated by discrete conformational changes in the C-terminal cytoplasmic tail in response to changes in cytoplasmic Ca(2+) levels. These properties of PC2 are lost in autosomal dominant polycystic kidney disease, emphasizing the importance of PC2 to kidney cell function. We speculate that PC2 and the Ca(2+)-dependent transient receptor potential channels in general are regulated by similar conformational changes in their cytoplasmic domains that are propagated to the channel pore.
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Affiliation(s)
- Andjelka S Ćelić
- Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Departments of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Edward T Petri
- Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Jennifer Benbow
- Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Departments of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Michael E Hodsdon
- Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Barbara E Ehrlich
- Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Departments of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Titus J Boggon
- Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520.
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Structural model of the TRPP2/PKD1 C-terminal coiled-coil complex produced by a combined computational and experimental approach. Proc Natl Acad Sci U S A 2011; 108:10133-8. [PMID: 21642537 DOI: 10.1073/pnas.1017669108] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in TRPP2 and PKD1, which form an ion channel/receptor complex containing three TRPP2 and one PKD1. A TRPP2 C-terminal coiled-coil trimer, critical for the assembly of this complex, associates with a single PKD1 C-terminal coiled-coil. Many ADPKD pathogenic mutations result in the abolishment of the TRPP2/PKD1 coiled-coil complex. To gain molecular and functional insights into this heterotetrameric complex, we computationally constructed a structural model by using a two-step docking strategy, based on a known crystal structure of the TRPP2 coiled-coil trimer. The model shows that this tetrameric complex has a novel di-trimer configuration: An upstream trimer made of three TRPP2 helices and a downstream trimer made of two TRPP2 helices and one PKD1 helix. Mutagenesis and biochemical analysis identified critical TRPP2/PKD1 interface contacts essential for the heteromeric coiled-coil complex. Mutation of these interface positions in the full-length proteins showed that these interactions were critical for the assembly of the full-length complex in cells. Our results provide a means to specifically weaken the TRPP2 and PKD1 association, thus facilitating future in vitro and in vivo studies on the functional importance of this association.
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Transient Receptor Potential Genes and Human Inherited Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:1011-32. [DOI: 10.1007/978-94-007-0265-3_52] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Miller RM, Portman DS. A latent capacity of the C. elegans polycystins to disrupt sensory transduction is repressed by the single-pass ciliary membrane protein CWP-5. Dis Model Mech 2010; 3:441-50. [PMID: 20223935 PMCID: PMC2898535 DOI: 10.1242/dmm.002816] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Accepted: 10/29/2009] [Indexed: 01/26/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) results from loss-of-function mutations in PKD1 or PKD2. The products of these genes, the polycystins PC-1 and PC-2, form a transmembrane channel that is necessary for flow sensing by renal cilia. In C. elegans, the polycystin orthologs LOV-1 and PKD-2 function in sensory neurons that mediate male mating behavior. Here, we report that the novel single-pass membrane protein CWP-5 is necessary for polycystin signaling during the response step of mating behavior. As with the polycystins, CWP-5 localizes to neuronal cilia; this localization requires LOV-1. The response defect of cwp-5 mutants does not appear to result from disruption of ciliogenesis or polycystin localization. Instead, genetic and behavioral analyses indicate that CWP-5 represses a previously undescribed antagonistic effect of the polycystins on sensory function. Although cwp-5 does not have a primary-sequence ortholog in vertebrates, it has intriguing parallels with the autosomal recessive PKD gene FPC (also known as PKHD1). Together, this study identifies a new component of C. elegans polycystin signaling, demonstrates that the polycystins have a latent capacity to hinder sensory transduction, and suggests that aberrant functions of the polycystins could contribute to the pathogenesis of PKD.
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Affiliation(s)
| | - Douglas S. Portman
- Center for Neural Development and Disease
- Department of Biomedical Genetics and
- Department of Biology, University of Rochester, Rochester, NY 14642, USA
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Torrice A, Cardinale V, Gatto M, Semeraro R, Napoli C, Onori P, Alpini G, Gaudio E, Alvaro D. Polycystins play a key role in the modulation of cholangiocyte proliferation. Dig Liver Dis 2010; 42:377-85. [PMID: 19897428 DOI: 10.1016/j.dld.2009.09.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 09/13/2009] [Accepted: 09/20/2009] [Indexed: 12/11/2022]
Abstract
BACKGROUND Polycystin-1 and -2 (PC-1 and PC-2) are critical components of primary cilia, which act as mechanosensors and drive cell response to injury. PC-1 activation involves the cleavage/processing of PC-1 cytoplasmic tail, driven by regulated intramembrane proteolysis or ubiquitine/proteasome, translocation in the nucleus and activation of transcription factors. Mutations of PC-1 or PC-2 occur in polycystic liver where cholangiocyte proliferation is enhanced. AIM We evaluated the involvement of PC-1 and PC-2 in modulating cholangiocyte proliferation. METHODS We investigated rat cholangiocytes induced to proliferate by 17beta-oestradiol. Proliferation was evaluated by PCNA immunoblotting or [(3)H]-thymidine incorporation into DNA. PC-1 silencing was performed by siRNA, while inhibition of regulated intramembrane proteolysis or proteasome by gamma-secretase inhibitor, leupeptin or MG115. RESULTS Cholangiocyte proliferation was associated with decreased PC-1 and PC-2 expression, which was inversely correlated with enhanced PCNA. The selective silencing of PC-1 induced activation of cholangiocyte proliferation in association with decreased PC-1 expression. Two different regulated intramembrane proteolysis inhibitors, gamma-secretase-inhibitor and leupeptin, and the proteasome inhibitor, MG115, abolished the 17beta-oestradiol proliferative effect. CONCLUSIONS PC-1 and PC-2 play a major role as modulators of cholangiocyte proliferation suggesting that primary cilia may act as sensors of cell injury driving, when activated, a proliferative cholangiocyte response to trigger the reparative processes.
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Affiliation(s)
- Alessia Torrice
- Division of Gastroenterology, University of Rome, Sapienza, Rome, Italy
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Lennerz JK, Spence DC, Iskandar SS, Dehner LP, Liapis H. Glomerulocystic kidney: one hundred-year perspective. Arch Pathol Lab Med 2010; 134:583-605. [PMID: 20367310 DOI: 10.5858/134.4.583] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
CONTEXT Glomerular cysts, defined as Bowman space dilatation greater than 2 to 3 times normal size, are found in disorders of diverse etiology and with a spectrum of clinical manifestations. The term glomerulocystic kidney (GCK) refers to a kidney with greater than 5% cystic glomeruli. Although usually a disease of the young, GCK also occurs in adults. OBJECTIVE To assess the recent molecular genetics of GCK, review our files, revisit the literature, and perform in silico experiments. DATA SOURCES We retrieved 20 cases from our files and identified more than 230 cases published in the literature under several designations. CONCLUSIONS Although GCK is at least in part a variant of autosomal dominant or recessive polycystic kidney disease (PKD), linkage analysis has excluded PKD-associated gene mutations in many cases of GCK. A subtype of familial GCK, presenting with cystic kidneys, hyperuricemia, and isosthenuria is due to uromodullin mutations. In addition, the familial hypoplastic variant of GCK that is associated with diabetes is caused by mutations in TCF2, the gene encoding hepatocyte nuclear factor-1beta. The term GCK disease (GCKD) should be reserved for the latter molecularly recognized/inherited subtypes of GCK (not to include PKD). Review of our cases, the literature, and our in silico analysis of the overlapping genetic entities integrates established molecular-genetic functions into a proposed model of glomerulocystogenesis; a classification scheme emerged that (1) emphasizes the clinical significance of glomerular cysts, (2) provides a pertinent differential diagnosis, and (3) suggests screening for probable mutations.
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Affiliation(s)
- Jochen K Lennerz
- Department of Pathology and Immunology, Washington University, St Louis, Missouri 63110, USA
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Abstract
Many ion channels and transporters are involved in the filtration, secretion, and resorption of electrolytes by the kidney. In recent years, the superfamily of transient receptor potential (TRP) ion channels have received deserved attention because mutated TRP channels are linked to human kidney diseases. This review focuses on two TRP members--TRPC6 and TRPM6--and their functions in the kidney. Gain-of-function mutations in TRPC6 are the cause for progressive kidney failure with urinary protein loss such as FSGS. Thus, TRPC6 is an essential signaling component in a functional slit diaphragm formed by podocytes around the glomerular capillaries. Loss-of-function mutations in TRPM6 are a molecular cause of hypomagnesemia with secondary hypocalcemia, suggesting that TRPM6 is critically involved in transcellular Mg2+ transport in the kidney. Here, we highlight how recent studies analyzing function and expression of these channels in the kidney improve our mechanistic understanding of TRP channel function in general and pave the way to new, promising therapeutic strategies to target kidney diseases such as FSGS and hypomagnesemia with secondary hypocalcemia.
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Affiliation(s)
- Alexander Dietrich
- Institute of Pharmacology and Toxicology, School of Medicine, University of Marburg, Marburg, Germany
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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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Giamarchi A, Feng S, Rodat-Despoix L, Xu Y, Bubenshchikova E, Newby LJ, Hao J, Gaudioso C, Crest M, Lupas AN, Honoré E, Williamson MP, Obara T, Ong ACM, Delmas P. A polycystin-2 (TRPP2) dimerization domain essential for the function of heteromeric polycystin complexes. EMBO J 2010; 29:1176-91. [PMID: 20168298 PMCID: PMC2857461 DOI: 10.1038/emboj.2010.18] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 01/25/2010] [Indexed: 01/26/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in two genes, PKD1 and PKD2, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. Earlier work has shown that PC1 and PC2 assemble into a polycystin complex implicated in kidney morphogenesis. PC2 also assembles into homomers of uncertain functional significance. However, little is known about the molecular mechanisms that direct polycystin complex assembly and specify its functions. We have identified a coiled coil in the C-terminus of PC2 that functions as a homodimerization domain essential for PC1 binding but not for its self-oligomerization. Dimerization-defective PC2 mutants were unable to reconstitute PC1/PC2 complexes either at the plasma membrane (PM) or at PM-endoplasmic reticulum (ER) junctions but could still function as ER Ca(2+)-release channels. Expression of dimerization-defective PC2 mutants in zebrafish resulted in a cystic phenotype but had lesser effects on organ laterality. We conclude that C-terminal dimerization of PC2 specifies the formation of polycystin complexes but not formation of ER-localized PC2 channels. Mutations that affect PC2 C-terminal homo- and heteromerization are the likely molecular basis of cyst formation in ADPKD.
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Affiliation(s)
- Aurélie Giamarchi
- Centre de Recherche en Neurophysiologie et Neurobiologie de Marseille, UMR 6231, CNRS, Université de la Méditerranée, Bd Pierre Dramard, Marseille Cedex 15, France
| | - Shuang Feng
- Kidney Genetics Group, Academic Unit of Nephrology, The Henry Wellcome Laboratories for Medical Research, University of Sheffield Medical School, Sheffield, UK
| | - Lise Rodat-Despoix
- Centre de Recherche en Neurophysiologie et Neurobiologie de Marseille, UMR 6231, CNRS, Université de la Méditerranée, Bd Pierre Dramard, Marseille Cedex 15, France
| | - Yaoxian Xu
- Kidney Genetics Group, Academic Unit of Nephrology, The Henry Wellcome Laboratories for Medical Research, University of Sheffield Medical School, Sheffield, UK
| | - Ekaterina Bubenshchikova
- Department of Medicine, MetroHealth Medical Center, Case Western Reserve University, MetroHealth Drive, Cleveland, OH, USA
| | - Linda J Newby
- Kidney Genetics Group, Academic Unit of Nephrology, The Henry Wellcome Laboratories for Medical Research, University of Sheffield Medical School, Sheffield, UK
| | - Jizhe Hao
- Centre de Recherche en Neurophysiologie et Neurobiologie de Marseille, UMR 6231, CNRS, Université de la Méditerranée, Bd Pierre Dramard, Marseille Cedex 15, France
| | - Christelle Gaudioso
- Centre de Recherche en Neurophysiologie et Neurobiologie de Marseille, UMR 6231, CNRS, Université de la Méditerranée, Bd Pierre Dramard, Marseille Cedex 15, France
| | - Marcel Crest
- Centre de Recherche en Neurophysiologie et Neurobiologie de Marseille, UMR 6231, CNRS, Université de la Méditerranée, Bd Pierre Dramard, Marseille Cedex 15, France
| | - Andrei N Lupas
- Department of Protein Evolution at the Max-Planck-Institute for Developmental Biology, Tuebingen, Germany
| | - Eric Honoré
- IPMC-CNRS UMR 6097, route des Lucioles, Valbonne, France
| | - Michael P Williamson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK
| | - Tomoko Obara
- Department of Medicine, MetroHealth Medical Center, Case Western Reserve University, MetroHealth Drive, Cleveland, OH, USA
- Department of Genetics, Case Western Reserve University, Cleveland, OH, USA
| | - Albert CM Ong
- Kidney Genetics Group, Academic Unit of Nephrology, The Henry Wellcome Laboratories for Medical Research, University of Sheffield Medical School, Sheffield, UK
| | - Patrick Delmas
- Centre de Recherche en Neurophysiologie et Neurobiologie de Marseille, UMR 6231, CNRS, Université de la Méditerranée, Bd Pierre Dramard, Marseille Cedex 15, France
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Kim I, Ding T, Fu Y, Li C, Cui L, Li A, Lian P, Liang D, Wang DW, Guo C, Ma J, Zhao P, Coffey RJ, Zhan Q, Wu G. Conditional mutation of Pkd2 causes cystogenesis and upregulates beta-catenin. J Am Soc Nephrol 2009; 20:2556-69. [PMID: 19939939 DOI: 10.1681/asn.2009030271] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Loss of polycystin-2 (PC2) in mice (Pkd2(-/-)) results in total body edema, focal hemorrhage, structural cardiac defects, abnormal left-right axis, hepatorenal and pancreatic cysts, and embryonic lethality. The molecular mechanisms by which loss of PC2 leads to these phenotypes remain unknown. We generated a model to allow targeted Pkd2 inactivation using the Cre-loxP system. Global inactivation of Pkd2 produced a phenotype identical to Pkd2(-/-) mice with undetectable PC2 protein and perinatal lethality. Using various Cre mouse lines, we found that kidney, pancreas, or time-specific deletion of Pkd2 led to cyst formation. In addition, we developed an immortalized renal collecting duct cell line with inactive Pkd2; these cells had aberrant cell-cell contact, ciliogenesis, and tubulomorphogenesis. They also significantly upregulated beta-catenin, axin2, and cMyc. Our results suggest that loss of PC2 disrupts normal behavior of renal epithelial cells through dysregulation of beta-catenin-dependent signaling, revealing a potential role for this signaling pathway in PC2-associated ADPKD.
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Affiliation(s)
- Ingyu Kim
- Division of Genetic Medicine, Department of Medicine and Cell and Developmental Biology, Vanderbilt University, 2215 Garland Avenue, Nashville, TN 37232, USA
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Ma L, Xu M, Forman JR, Clarke J, Oberhauser AF. Naturally occurring mutations alter the stability of polycystin-1 polycystic kidney disease (PKD) domains. J Biol Chem 2009; 284:32942-9. [PMID: 19759016 PMCID: PMC2781709 DOI: 10.1074/jbc.m109.021832] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mutations in polycystin-1 (PC1) can cause autosomal dominant polycystic kidney disease, which is a leading cause of renal failure. The available evidence suggests that PC1 acts as a mechanosensor, receiving signals from the primary cilia, neighboring cells, and extracellular matrix. PC1 is a large membrane protein that has a long N-terminal extracellular region (about 3000 amino acids) with a multimodular structure including 16 Ig-like polycystic kidney disease (PKD) domains, which are targeted by many naturally occurring missense mutations. Nothing is known about the effects of these mutations on the biophysical properties of PKD domains. Here we investigate the effects of several naturally occurring mutations on the mechanical stability of the first PKD domain of human PC1 (HuPKDd1). We found that several missense mutations alter the mechanical unfolding pathways of HuPKDd1, resulting in distinct mechanical phenotypes. Moreover, we found that these mutations also alter the thermodynamic stability of a structurally homologous archaeal PKD domain. Based on these findings, we hypothesize that missense mutations may cause autosomal dominant polycystic kidney disease by altering the stability of the PC1 ectodomain, thereby perturbing its ability to sense mechanical signals.
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Affiliation(s)
- Liang Ma
- Department of Neuroscience and Cell Biology, MRC Centre for Protein Engineering, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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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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Abstract
The primary cilium is a microtubule-based nonmotile organelle that is found on most cells in the mammalian body. Once regarded as a vestigial organelle, it has been recently shown to play unforeseen roles in mammalian physiology and tissue homeostasis. In kidney epithelial cells, the primary cilium plays a fundamental role in tubule organization and function and it is now considered to serve as a versatile mechanosensor and chemosensor. Diseases related to kidney primary cilia include autosomal polycystic kidney disease, recessive polycystic kidney disease, Bardet-Biedl syndrome, and nephronophthisis. Multiple proteins whose functions are disrupted in cystic kidney diseases have been localized in the primary cilium. This review provides a general introduction to the cell biology and function of renal primary cilia and an overview of cilia-related kidney diseases.
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Pedersen SF, Owsianik G, Nilius B. TRP channels: an overview. Cell Calcium 2008; 38:233-52. [PMID: 16098585 DOI: 10.1016/j.ceca.2005.06.028] [Citation(s) in RCA: 544] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 12/12/2022]
Abstract
The TRP ("transient receptor potential") family of ion channels now comprises more than 30 cation channels, most of which are permeable for Ca2+, and some also for Mg2+. On the basis of sequence homology, the TRP family can be divided in seven main subfamilies: the TRPC ('Canonical') family, the TRPV ('Vanilloid') family, the TRPM ('Melastatin') family, the TRPP ('Polycystin') family, the TRPML ('Mucolipin') family, the TRPA ('Ankyrin') family, and the TRPN ('NOMPC') family. The cloning and characterization of members of this cation channel family has exploded during recent years, leading to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs.
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Affiliation(s)
- Stine Falsig Pedersen
- Department of Biochemistry, Institute for Molecular Biology and Physiology, University of Copenhagen, Denmark
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Purinergic signaling in the lumen of a normal nephron and in remodeled PKD encapsulated cysts. Purinergic Signal 2008; 4:109-24. [PMID: 18438719 DOI: 10.1007/s11302-008-9102-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 04/08/2008] [Indexed: 01/10/2023] Open
Abstract
The nephron is the functional unit of the kidney. Blood and plasma are continually filtered within the glomeruli that begin each nephron. Adenosine 5' triphosphate (ATP) and its metabolites are freely filtered by each glomerulus and enter the lumen of each nephron beginning at the proximal convoluted tubule (PCT). Flow rate, osmolality, and other mechanical or chemical stimuli for ATP secretion are present in each nephron segment. These ATP-release stimuli are also different in each nephron segment due to water or salt permeability or impermeability along different luminal membranes of the cells that line each nephron segment. Each of the above stimuli can trigger additional ATP release into the lumen of a nephron segment. Each nephron-lining epithelial cell is a potential source of secreted ATP. Together with filtered ATP and its metabolites derived from the glomerulus, secreted ATP and adenosine derived from cells along the nephron are likely the principal two of several nucleotide and nucleoside candidates for renal autocrine and paracrine ligands within the tubular fluid of the nephron. This minireview discusses the first principles of purinergic signaling as they relate to the nephron and the urinary bladder. The review discusses how the lumen of a renal tubule presents an ideal purinergic signaling microenvironment. The review also illustrates how remodeled and encapsulated cysts in autosomal dominant polycystic kidney disease (ADPKD) and remodeled pseudocysts in autosomal recessive PKD (ARPKD) of the renal collecting duct likely create an even more ideal microenvironment for purinergic signaling. Once trapped in these closed microenvironments, purinergic signaling becomes chronic and likely plays a significant epigenetic and detrimental role in the secondary progression of PKD, once the remodeling of the renal tissue has begun. In PKD cystic microenvironments, we argue that normal purinergic signaling within the lumen of the nephron provides detrimental acceleration of ADPKD once remodeling is complete.
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Alvaro D, Onori P, Alpini G, Franchitto A, Jefferson DM, Torrice A, Cardinale V, Stefanelli F, Mancino MG, Strazzabosco M, Angelico M, Attili A, Gaudio E. Morphological and functional features of hepatic cyst epithelium in autosomal dominant polycystic kidney disease. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 172:321-32. [PMID: 18202196 DOI: 10.2353/ajpath.2008.070293] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We evaluated the morphological and functional features of hepatic cyst epithelium in adult autosomal dominant polycystic kidney disease (ADPKD). In six ADPKD patients, we investigated the morphology of cyst epithelium apical surface by scanning electron microscopy and the expression of estrogen receptors (ERs), insulin-like growth factor 1 (IGF1), IGF1 receptors (IGF1-R), growth hormone receptor, the proliferation marker proliferating cell nuclear antigen, and pAKT by immunohistochemistry and immunofluorescence. Proliferation of liver cyst-derived epithelial cells was evaluated by both MTS proliferation assay and [(3)H]thymidine incorporation into DNA. The hepatic cyst epithelium displayed heterogeneous features, being normal in small cysts (<1 cm), characterized by rare or shortened cilia in 1- to 3-cm cysts, and exhibiting the absence of both primary cilia and microvilli in large cysts (>3 cm). Cyst epithelium showed marked immunohistochemical expression of ER, growth hormone receptor, IGF1, IGF1-R, proliferating cell nuclear antigen, and pAKT. IGF1 was 10-fold more enriched in the hepatic cyst fluid than in serum. Serum-deprived liver cyst-derived epithelial cells proliferated when exposed to 17beta-estradiol and IGF1 and when exposed to human cyst fluid. ER or IGF1-R antagonists inhibited the proliferative effect of serum readmission, cyst fluid, 17beta-estradiol, and IGF1. Our findings could explain the role of estrogens in accelerating the progression of ADPKD and may suggest a potential benefit of therapeutic strategies based on estrogen antagonism.
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Affiliation(s)
- Domenico Alvaro
- Department of Clinical Medicine, University of Rome Sapienza, via R. Rossellini 51, 00137 Rome, Italy. domenico.alvaro@uniroma1
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Hovater MB, Olteanu D, Hanson EL, Cheng NL, Siroky B, Fintha A, Komlosi P, Liu W, Satlin LM, Bell PD, Yoder BK, Schwiebert EM. Loss of apical monocilia on collecting duct principal cells impairs ATP secretion across the apical cell surface and ATP-dependent and flow-induced calcium signals. Purinergic Signal 2007; 4:155-70. [PMID: 18368523 PMCID: PMC2377318 DOI: 10.1007/s11302-007-9072-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 09/25/2006] [Accepted: 11/01/2006] [Indexed: 01/11/2023] Open
Abstract
Renal epithelial cells release ATP constitutively under basal conditions and release higher quantities of purine nucleotide in response to stimuli. ATP filtered at the glomerulus, secreted by epithelial cells along the nephron, and released serosally by macula densa cells for feedback signaling to afferent arterioles within the glomerulus has important physiological signaling roles within kidneys. In autosomal recessive polycystic kidney disease (ARPKD) mice and humans, collecting duct epithelial cells lack an apical central cilium or express dysfunctional proteins within that monocilium. Collecting duct principal cells derived from an Oak Ridge polycystic kidney (orpk ( Tg737 ) ) mouse model of ARPKD lack a well-formed apical central cilium, thought to be a sensory organelle. We compared these cells grown as polarized cell monolayers on permeable supports to the same cells where the apical monocilium was genetically rescued with the wild-type Tg737 gene that encodes Polaris, a protein essential to cilia formation. Constitutive ATP release under basal conditions was low and not different in mutant versus rescued monolayers. However, genetically rescued principal cell monolayers released ATP three- to fivefold more robustly in response to ionomycin. Principal cell monolayers with fully formed apical monocilia responded three- to fivefold greater to hypotonicity than mutant monolayers lacking monocilia. In support of the idea that monocilia are sensory organelles, intentionally harsh pipetting of medium directly onto the center of the monolayer induced ATP release in genetically rescued monolayers that possessed apical monocilia. Mechanical stimulation was much less effective, however, on mutant orpk collecting duct principal cell monolayers that lacked apical central monocilia. Our data also show that an increase in cytosolic free Ca(2+) primes the ATP pool that is released in response to mechanical stimuli. It also appears that hypotonic cell swelling and mechanical pipetting stimuli trigger release of a common ATP pool. Cilium-competent monolayers responded to flow with an increase in cell Ca(2+) derived from both extracellular and intracellular stores. This flow-induced Ca(2+) signal was less robust in cilium-deficient monolayers. Flow-induced Ca(2+) signals in both preparations were attenuated by extracellular gadolinium and by extracellular apyrase, an ATPase/ADPase. Taken together, these data suggest that apical monocilia are sensory organelles and that their presence in the apical membrane facilitates the formation of a mature ATP secretion apparatus responsive to chemical, osmotic, and mechanical stimuli. The cilium and autocrine ATP signaling appear to work in concert to control cell Ca(2+). Loss of a cilium-dedicated autocrine purinergic signaling system may be a critical underlying etiology for ARPKD and may lead to disinhibition and/or upregulation of multiple sodium (Na(+)) absorptive mechanisms and a resultant severe hypertensive phenotype in ARPKD and, possibly, other diseases.
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Affiliation(s)
- Michael B Hovater
- Department of Physiology and Biophysics, University of Alabama at Birmingham, 1918 University Blvd., Birmingham, AL, 35294-0005, USA
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Alvaro D, Mancino MG. New insights on the molecular and cell biology of human cholangiopathies. Mol Aspects Med 2007; 29:50-7. [PMID: 18230407 DOI: 10.1016/j.mam.2007.09.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 09/28/2007] [Indexed: 01/20/2023]
Abstract
Cholangiopathies are diseases of high social impact representing the main indication for liver transplantation in the infanthood and the third in adulthood. Despite the heterogeneous etiology and pathogenesis, cholangiopathies share many different common morphological features and, chronically progress toward a ductupenic condition clinically evidenced by the classical features of a cholestatic syndrome. The primary target of damage in the course of cholangiopathies are cholangiocytes, the epithelia cells lining the biliary tree. A bulk of researches performed in the last decade, highlighted the extraordinary biological properties of cholangiocytes involved in a number of important processes such as bile formation, proliferation, injury repair, fibrosis, angiogenesis and regulation of blood flow. Recent advances on the molecular and cell biology of human cholangiopathies are opening new potential therapeutic perspectives for these diseases.
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Affiliation(s)
- Domenico Alvaro
- Division of Gastroenterology, Department of Clinical Medicine, Rome, Italy
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Jeon JO, Yoo KH, Park JH. Expression of the Pkd1 gene is momentously regulated by Sp1. Nephron Clin Pract 2007; 107:e57-64. [PMID: 17890878 DOI: 10.1159/000108643] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Accepted: 03/13/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Autosomal dominant polycystic kidney disease (ADPKD) is a common human genetic disease that is caused by a mutation of a single gene inherited from either parent. Mutations in the Pkd1 gene result in the formation of multiple fluid-filled cysts in kidneys. In previous studies, the functional regulatory sequences of Pkd1 promoter region were detected by the use of comparative genome analysis. METHODS To investigate the transcriptional regulation of the Pkd1 gene, the Pkd1 promoter was isolated. This promoter contains three Sp1-binding sites. Two of the sites which are found in a 300 bp fragment (-127 to +157) were mutated. An electrophoretic mobility shift assay (EMSA) was performed to determine which transcription factors are bound to Pkd1. RESULTS Based on studies using a luciferase assay, the Sp1-A site (the nearest Sp1 to the ATG start codon) is more important for activation of Pkd1. The result of EMSA showed that Sp1 transcription factor binds with Pkd1 promoter regions. CONCLUSIONS Two of the Sp1 sites were found in a proximal promoter region of Pkd1 (-127 to +157). Sp1 sites affect an important role in the activation of the gene. Especially, the Sp1-A site is more important for expression of Pkd1.
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Affiliation(s)
- Jeong Ok Jeon
- Department of Biological Science, Sookmyung Women's University, Seoul, Korea
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Tian Y, Kolb R, Hong JH, Carroll J, Li D, You J, Bronson R, Yaffe MB, Zhou J, Benjamin T. TAZ promotes PC2 degradation through a SCFbeta-Trcp E3 ligase complex. Mol Cell Biol 2007; 27:6383-95. [PMID: 17636028 PMCID: PMC2099608 DOI: 10.1128/mcb.00254-07] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Studies of a TAZ knockout mouse reveal a novel function of the transcriptional regulator TAZ, that is, as a binding partner of the F-box protein beta-Trcp. TAZ-/- mice develop polycystic kidney disease (PKD) and emphysema. The calcium-permeable cation channel protein polycystin 2 (PC2) is overexpressed in kidneys of TAZ-/- mice as a result of decreased degradation via an SCF(beta-Trcp) E3 ubiquitin ligase pathway. Replacements of serines in a phosphodegron motif in TAZ prevent beta-Trcp binding and PC2 degradation. Coexpression of a cytoplasmic fragment of polycystin 1 blocks the PC2-TAZ interaction and prevents TAZ-mediated degradation of PC2. Depletion of TAZ in zebrafish also results in a cystic kidney accompanied by overexpression of PC2. These results establish a common role of TAZ across vertebrate species in a protein degradation pathway regulated by phosphorylation and implicate deficiencies in this pathway in the development of PKD.
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Affiliation(s)
- Yu Tian
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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50
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Anyatonwu GI, Estrada M, Tian X, Somlo S, Ehrlich BE. Regulation of ryanodine receptor-dependent calcium signaling by polycystin-2. Proc Natl Acad Sci U S A 2007; 104:6454-9. [PMID: 17404231 PMCID: PMC1851053 DOI: 10.1073/pnas.0610324104] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Mutations in polycystin-2 (PC2) cause autosomal dominant polycystic kidney disease. A function for PC2 in the heart has not been described. Here, we show that PC2 coimmunoprecipitates with the cardiac ryanodine receptor (RyR2) from mouse heart. Biochemical assays showed that the N terminus of PC2 binds the RyR2, whereas the C terminus only binds to RyR2 in its open state. Lipid bilayer electrophysiological experiments indicated that the C terminus of PC2 functionally inhibited RyR2 channel activity in the presence of calcium (Ca(2+)). Pkd2(-/-) cardiomyocytes had a higher frequency of spontaneous Ca(2+) oscillations, reduced Ca(2+) release from the sarcoplasmic reticulum stores, and reduced Ca(2+) content compared with Pkd2(+/+) cardiomyocytes. In the presence of caffeine, Pkd2(-/-) cardiomyocytes exhibited decreased peak fluorescence, a slower rate of rise, and a longer duration of Ca(2+) transients compared with Pkd2(+/+). These data suggest that PC2 is important for regulation of RyR2 function and that loss of this regulation of RyR2, as occurs when PC2 is mutated, results in altered Ca(2+) signaling in the heart.
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Affiliation(s)
| | | | | | | | - Barbara E. Ehrlich
- Departments of *Pharmacology
- Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8066
- To whom correspondence should be addressed. E-mail:
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