Hydrophobic pore gates regulate ion permeation in polycystic kidney disease 2 and 2L1 channels

Wang Zheng,Veit Flockerzi,Ruiqi Cai,Xiaoyong Yang,David Bulkley,Yong Yu,Zhifei Wang,Jingfeng Tang,Ying Cao,Xiong Liu,Erhu Cao,Xing-Zhen Chen,Ruikun Hu,Laura Hofmann,Qiaolin Hu

doi:10.1038/s41467-018-04586-x

Abstract

PKD2 and PKD1 genes are mutated in human autosomal dominant polycystic kidney disease. PKD2 can form either a homomeric cation channel or a heteromeric complex with the PKD1 receptor, presumed to respond to ligand(s) and/or mechanical stimuli. Here, we identify a two-residue hydrophobic gate in PKD2L1, and a single-residue hydrophobic gate in PKD2. We find that a PKD2 gain-of-function gate mutant effectively rescues PKD2 knockdown-induced phenotypes in embryonic zebrafish. The structure of a PKD2 activating mutant F604P by cryo-electron microscopy reveals a π- to α-helix transition within the pore-lining helix S6 that leads to repositioning of the gate residue and channel activation. Overall the results identify hydrophobic gates and a gating mechanism of PKD2 and PKD2L1.

Highlights

Autosomal dominant polycystic kidney disease (ADPKD) is a prominent human monogenic disease and affects over 12.5 million people worldwide[1]
We replaced each of the hydrophobic residues in the F676-I679 fragment (Fig. 3a) with asparagine and found that only the L677N mutant exhibits substantially increased channel activity, comparable to that of the GOF mutant F604P that we reported recently[5] (Fig. 3a, b)
Agonist capsaicin only induced widening of the activation gate, while resiniferatoxin (RTX) and spider double-knot toxin (DkTx) together induced widening of both the activation gate and selectivity filter[37], suggesting that the hydrophobic I679 may serve as a primary gate and the hydrophilic G463 as a secondary gate involved in activation by only a subset of TRPV1 agonists, e.g., RTX/DkTx

Summary

Introduction

Autosomal dominant polycystic kidney disease (ADPKD) is a prominent human monogenic disease and affects over 12.5 million people worldwide[1] It is characterized by the formation of fluid-filled renal cysts, leading to an increase in the total kidney volume and a decline in the renal function. PKD1 and PKD2 have been shown to form a complex[10,11,12], which is hypothesized to sense fluid flow on the membrane of primary cilia This hypothesis remains debatable[13,14,15,16,17]. We9 and two other groups[7,8] recently resolved PKD2 structures and revealed two constriction points in the distal portion of S6 formed by residues L677 and N681 It remains unclear whether both L677 and N681 or just one of them function as a gate in PKD2. A PKD2 structure in an activated state is needed to provide insights into the PKD2 gating mechanism and associated conformational changes

Methods

Results

Conclusion