Biswajit Padhy1, Jian Xie1, Runping Wang1, Fang Lin2, Chou-Long Huang3. 1. Division of Nephrology, Department of Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa. 2. Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, Iowa. 3. Division of Nephrology, Department of Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa chou-long-huang@uiowa.edu.
Abstract
BACKGROUND: Mutations of PKD2, which encodes polycystin-2, cause autosomal dominant polycystic kidney disease (ADPKD). The prevailing view is that defects in polycystin-2-mediated calcium ion influx in the primary cilia play a central role in the pathogenesis of cyst growth. However, polycystin-2 is predominantly expressed in the endoplasmic reticulum (ER) and more permeable to potassium ions than to calcium ions. METHODS: The trimeric intracellular cation (TRIC) channel TRIC-B is an ER-resident potassium channel that mediates potassium-calcium counterion exchange for inositol trisphosphate-mediated calcium ion release. Using TRIC-B as a tool, we examined the function of ER-localized polycystin-2 and its role in ADPKD pathogenesis in cultured cells, zebrafish, and mouse models. RESULTS: Agonist-induced ER calcium ion release was defective in cells lacking polycystin-2 and reversed by exogenous expression of TRIC-B. Vice versa, exogenous polycystin-2 reversed an ER calcium-release defect in cells lacking TRIC-B. In a zebrafish model, expression of wild-type but not nonfunctional TRIC-B suppressed polycystin-2-deficient phenotypes. Similarly, these phenotypes were suppressed by targeting the ROMK potassium channel (normally expressed on the cell surface) to the ER. In cultured cells and polycystin-2-deficient zebrafish phenotypes, polycystin-2 remained capable of reversing the ER calcium release defect even when it was not present in the cilia. Transgenic expression of Tric-b ameliorated cystogenesis in the kidneys of conditional Pkd2-inactivated mice, whereas Tric-b deletion enhanced cystogenesis in Pkd2-heterozygous kidneys. CONCLUSIONS: Polycystin-2 in the ER appears to be critical for anticystogenesis and likely functions as a potassium ion channel to facilitate potassium-calcium counterion exchange for inositol trisphosphate-mediated calcium release. The results advance the understanding of ADPKD pathogenesis and provides proof of principle for pharmacotherapy by TRIC-B activators.
BACKGROUND: Mutations of PKD2, which encodes polycystin-2, cause autosomal dominant polycystic kidney disease (ADPKD). The prevailing view is that defects in polycystin-2-mediated calcium ion influx in the primary cilia play a central role in the pathogenesis of cyst growth. However, polycystin-2 is predominantly expressed in the endoplasmic reticulum (ER) and more permeable to potassium ions than to calcium ions. METHODS: The trimeric intracellular cation (TRIC) channel TRIC-B is an ER-resident potassium channel that mediates potassium-calcium counterion exchange for inositol trisphosphate-mediated calcium ion release. Using TRIC-B as a tool, we examined the function of ER-localized polycystin-2 and its role in ADPKD pathogenesis in cultured cells, zebrafish, and mouse models. RESULTS: Agonist-induced ER calcium ion release was defective in cells lacking polycystin-2 and reversed by exogenous expression of TRIC-B. Vice versa, exogenous polycystin-2 reversed an ER calcium-release defect in cells lacking TRIC-B. In a zebrafish model, expression of wild-type but not nonfunctional TRIC-B suppressed polycystin-2-deficient phenotypes. Similarly, these phenotypes were suppressed by targeting the ROMK potassium channel (normally expressed on the cell surface) to the ER. In cultured cells and polycystin-2-deficient zebrafish phenotypes, polycystin-2 remained capable of reversing the ER calcium release defect even when it was not present in the cilia. Transgenic expression of Tric-b ameliorated cystogenesis in the kidneys of conditional Pkd2-inactivated mice, whereas Tric-b deletion enhanced cystogenesis in Pkd2-heterozygous kidneys. CONCLUSIONS: Polycystin-2 in the ER appears to be critical for anticystogenesis and likely functions as a potassium ion channel to facilitate potassium-calcium counterion exchange for inositol trisphosphate-mediated calcium release. The results advance the understanding of ADPKD pathogenesis and provides proof of principle for pharmacotherapy by TRIC-B activators.
Authors: G Wu; G S Markowitz; L Li; V D D'Agati; S M Factor; L Geng; S Tibara; J Tuchman; Y Cai; J H Park; J van Adelsberg; H Hou; R Kucherlapati; W Edelmann; S Somlo Journal: Nat Genet Date: 2000-01 Impact factor: 38.330
Authors: F Ann Ran; Patrick D Hsu; Jason Wright; Vineeta Agarwala; David A Scott; Feng Zhang Journal: Nat Protoc Date: 2013-10-24 Impact factor: 13.491
Authors: Tamio Yamaguchi; Darren P Wallace; Brenda S Magenheimer; Scott J Hempson; Jared J Grantham; James P Calvet Journal: J Biol Chem Date: 2004-07-19 Impact factor: 5.157
Authors: Mariana Grieben; Ashley C W Pike; Chitra A Shintre; Elisa Venturi; Sam El-Ajouz; Annamaria Tessitore; Leela Shrestha; Shubhashish Mukhopadhyay; Pravin Mahajan; Rod Chalk; Nicola A Burgess-Brown; Rebecca Sitsapesan; Juha T Huiskonen; Elisabeth P Carpenter Journal: Nat Struct Mol Biol Date: 2016-12-19 Impact factor: 15.369
Authors: Edmund C Lee; Tania Valencia; Charles Allerson; Annelie Schairer; Andrea Flaten; Matanel Yheskel; Kara Kersjes; Jian Li; Sole Gatto; Mandeep Takhar; Steven Lockton; Adam Pavlicek; Michael Kim; Tiffany Chu; Randy Soriano; Scott Davis; John R Androsavich; Salma Sarwary; Tate Owen; Julia Kaplan; Kai Liu; Graham Jang; Steven Neben; Philip Bentley; Timothy Wright; Vishal Patel Journal: Nat Commun Date: 2019-09-12 Impact factor: 14.919