A mutation affecting polycystin-1 mediated heterotrimeric G-protein signaling causes PKD

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the growth of renal cysts that ultimately destroy kidney function. Mutations in the PKD1 and PKD2 genes cause ADPKD. Their protein products, polycystin-1 (PC1) and polycystin-2 (PC2) have been proposed to form a calcium-permeable receptor-channel complex; however the mechanisms by which they function are almost completely unknown. Most mutations in PKD1 are truncating loss-of-function mutations or affect protein biogenesis, trafficking or stability and reveal very little about the intrinsic biochemical properties or cellular functions of PC1. An ADPKD patient mutation (L4132Δ or ΔL), resulting in a single amino acid deletion in a putative G-protein binding region of the PC1 C-terminal cytosolic tail, was found to significantly decrease PC1-stimulated, G-protein-dependent signaling in transient transfection assays. Pkd1ΔL/ΔL mice were embryo-lethal suggesting that ΔL is a functionally null mutation. Kidney-specific Pkd1ΔL/cond mice were born but developed severe, postnatal cystic disease. PC1ΔL protein expression levels and maturation were comparable to those of wild type PC1, and PC1ΔL protein showed cell surface localization. Expression of PC1ΔL and PC2 complexes in transfected CHO cells failed to support PC2 channel activity, suggesting that the role of PC1 is to activate G-protein signaling to regulate the PC1/PC2 calcium channel.