Novel Functional Complexity of Polycystin-1 by GPS Cleavage In Vivo: Role in Polycystic Kidney Disease

Abstract

Polycystin-1 (Pc1) cleavage at the G protein-coupled receptor (GPCR) proteolytic site (GPS) is required for normal kidney morphology in humans and mice. We found a complex pattern of endogenous Pc1 forms by GPS cleavage. GPS cleavage generates not only the heterodimeric cleaved full-length Pc1 (Pc1^cFL) in which the N-terminal fragment (NTF) remains noncovalently associated with the C-terminal fragment (CTF) but also a novel (Pc1) form (Pc1^deN) in which NTF becomes detached from CTF. Uncleaved Pc1 (Pc1^U) resides primarily in the endoplasmic reticulum (ER), whereas both Pc1^cFL and Pc1^deN traffic through the secretory pathway in vivo. GPS cleavage is not a prerequisite, however, for Pc1 trafficking in vivo. Importantly, Pc1^deN is predominantly found at the plasma membrane of renal epithelial cells. By functional genetic complementation with five Pkd1 mouse models, we discovered that CTF plays a crucial role in Pc1^deN trafficking. Our studies support GPS cleavage as a critical regulatory mechanism of Pc1 biogenesis and trafficking for proper kidney development and homeostasis.

ACKNOWLEDGMENTS

We thank J. Calvet, Chiara Gamberi, and Owen Woodward for reading and commenting on the manuscript and B. Magenheimer and M. Chiaravalli for technical assistance.

This work was supported by grants from the Canadian Institutes of Health Research and the Polycystic Kidney Disease Foundation of Canada (to M.T.), by grants from the NIH (R01 DK062199 and P30 DK090868) and National Kidney Foundation of Maryland (to F.Q.), by a Frederick Banting and Charles Best of Canada Graduate Scholarship Award (to A.K.), and by a Korea Research Foundation grant by the Korean Government (KRF-2008-357-E00030, to H.K.).