Cleavage of N-terminus of polycystin-1 increases calcium permeability of polycystin-1/2 receptor channel complexes
Runping Wang, Danish Idrees, Mohammad Amir, Biswajit Padhy, Jian Xie, Chou-Long Huang
Runping Wang, Danish Idrees, Mohammad Amir, Biswajit Padhy, Jian Xie, Chou-Long Huang
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Research Article Cell biology Nephrology

Cleavage of N-terminus of polycystin-1 increases calcium permeability of polycystin-1/2 receptor channel complexes

Abstract

Mutations on genes encoding polycystin-1 (PC1) and PC2 cause autosomal-dominant polycystic kidney disease. How these 2 proteins work together to exert anticystogenesis remains elusive. PC1 resembles adhesion G-protein coupled receptors and undergoes autocleavage in the extracellular N-terminus to expose a hidden “stalk” region, which is hypothesized to act as a “tethered agonist.” Here, we show that WT PC1 and PC2 formed functional heteromeric channel complexes in Xenopus oocytes with different biophysical properties from PC2 homomeric channels. Deletion of PC1 N-terminus, which exposed the stalk, increased calcium permeability in PC1/PC2 heteromers that required the presence of stalk. Extracellular application of synthetic stalk peptide increased calcium permeation in stalkless PC1/PC2. Application of Wnt9B protein increased calcium permeability in PC1/PC2 but not in heteromers containing cleavage-resistant mutant PC1. Wnt9B interacted with N-terminal leucine-rich repeat (LRR) of PC1. Pretreatment with LRR blunted the increase in calcium permeability by Wnt9B. Thus, PC1 and PC2 form receptor-channel complexes that is activated by exposure of the stalk region following ligand binding to the PC1 N-terminus. The stalk peptide acts as a tethered agonist to activate PC1/PC2 by affecting ion selectivity of the complexes.

Authors

Runping Wang, Danish Idrees, Mohammad Amir, Biswajit Padhy, Jian Xie, Chou-Long Huang

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Figure 5

External application of stalk peptide increases Ca2+ permeability of heteromeric channel formed by PC2 and stalkless sCTF.

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External application of stalk peptide increases Ca2+ permeability of het...
(A) Top: oocytes expressing sCTF.Δstalk/PC2 were incubated with synthetic stalk peptide at 0, 30, 100, or 300 nM for 4 hours. The 21–amino acid peptide corresponds to residues 3049-TAFGASLFVPPSHVRFVFPEP-3069 of human PC1. Bottom left: PCa/PNa was calculated based on reversal potential shift between 100 mM CaCl2 and 100 mM NaCl. Data are shown as mean ± SEM. P < 0.0001 by 1-way ANOVA.; n = 7, 5, 3, and 12 for 0, 30, 100, and 300 nM, respectively, of stalk. Bottom right: time course of stalk peptide (300 nM) on increases in PCa/PNa. (B and C) No effect of stalk peptide (300 nM) on PC2 alone (n = 5 and 8 for 0 and 300 nM peptide) (B) or sCTF.Δstalk.ΔCTT/PC2 (n = 5 and 6 for 0 and 300 nM peptide) (C). Two-tailed unpaired Student’s t test for B and C. In all panels, experimental number (n) is number of oocytes as shown by scatter plots. All experiments were repeated 2 or more times with similar results.