PKD1 and autosomal dominant polycystic kidney disease: These studies are in contrast with Parnell et al. (1998) who showed that PC1 contains a motif that activates guanine nucleotide exchange, and that a PC1 ADPKD patient mutation that disrupts G protein-dependent signaling in cellular assays results in severe cystic disease when introduced into a mouse model (Parnell et al., 2018).