TMEM16A drives renal cyst growth by augmenting Ca2+ signaling in M1 cells

Ines Cabrita,Karl Kunzelmann,Rainer Schreiber,Björn Buchholz

doi:10.1007/s00109-020-01894-y

Ines Cabrita, Karl Kunzelmann + Show 2 more

Open Access

https://doi.org/10.1007/s00109-020-01894-y

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Abstract

Polycystic kidney disease (PKD) leads to continuous decline of renal function by growth of renal cysts. Enhanced proliferation and transepithelial chloride secretion through cystic fibrosis transmembrane conductance regulator (CFTR) and Ca2+-activated TMEM16A Cl− channels is thought to cause an increase in cyst volume. Recent work shows the pro-proliferative role of the Ca2+ activated Cl− channel TMEM16A (anoctamin 1), and demonstrates the essential contribution of TMEM16A to CFTR-dependent Cl− secretion. The present data demonstrate an increase in intracellular Ca2+ ([Ca2+]i) signals and Cl− secretion by TMEM16A, in renal collecting duct principle cells from dog (MDCK) and mouse (M1) as well as primary tubular epithelial cells from PKD1−/− knockout mice. M1 organoids proliferated, increased expression of TMEM16A, and secreted Cl− upon knockdown of endogenous polycystin 1 or 2 (PKD1,2), by retroviral transfection with shPKD1 and shPKD2, respectively. Knockdown of PKD1 or PKD2 increased basal intracellular Ca2+ levels and enhanced purinergic Ca2+ release from endoplasmic reticulum. In contrast, ryanodine receptors were found not to be expressed in mouse renal epithelial cells and caffeine had no effects on [Ca2+]i. Ca2+ signals, proliferation, and Cl− secretion were largely reduced by knockdown or blockade of TMEM16A. TMEM16A may be therefore important for enhanced Ca2+ release from IP3-sensitive Ca2+ stores in polycystic kidney disease.Key messages• ADPKD leads to continuous decline of renal function by growth of renal cysts.• Knockdown of PKD1 or PKD2 increases TMEM16A expression.• TMEM16A enhanced intracellular Ca2+ signals, Cl− secretion, and proliferation.• TMEM16A contributes to cyst growth in ADPKD.

Highlights

Frequent autosomal dominant polycystic kidney disease (ADPKD) accounts for 5–10% of end-stage renal disease [1]
ADPKD is caused by mutations in PKD1 or PKD2, but the underlying complex molecular events leading to continuous cyst growth are still poorly understood [3]
In normal renal epithelial cells, PKD1 and PKD2 appear to be located in the primary cilium, a single antennalike protrusion of the plasma membrane, where they form a complex of receptor and Ca2+ influx channel [4]

Summary

Introduction

Frequent autosomal dominant polycystic kidney disease (ADPKD) accounts for 5–10% of end-stage renal disease [1]. ADPKD is characterized by continuous cyst enlargement over time, leading to compression of adjacent healthy parenchyma [2]. ADPKD is caused by mutations in PKD1 (polycystin 1) or PKD2 (polycystin 2), but the underlying complex molecular events leading to continuous cyst growth are still poorly understood [3]. In normal renal epithelial cells, PKD1 and PKD2 appear to be located in the primary cilium, a single antennalike protrusion of the plasma membrane, where they form a complex of receptor and Ca2+ influx channel [4]. Ca2+ ions are more concentrated within the primary cilium compared to. Loss of the primary cilium or loss of PKD1/PKD2 function leads to relocation of the polycystins to plasma membrane and endoplasmic reticulum, with the consequence of disturbed intracellular Ca2+ signaling [6]

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