ABSTRACT
Polycystin-1 (PC1), the principal causative protein of autosomal dominant polycystic kidney disease (ADPKD), plays an essential role in renal tubular morphogenesis. ADPKD is characterized by cyst formation, which may initiate during fetal development and continue through adult life, resulting in kidney failure around the sixth decade. PC1 is a large receptor-like protein with 11 transmembrane domains which undergoes cis-autoproteolytic cleavage at the juxtamembrane G protein-coupled receptor (GPCR) proteolysis site (GPS). This cleavage is a key posttranslational modification of PC1 and is essential for its full biological function. Disruption of PC1 GPS cleavage contributes to cystogenesis in ADPKD. Cleavage of PC1 gives rise to multiple PC1 forms, which localize and function in different compartments of the cell. The additional complexity of the multiple PC1 forms, in combination with its large size and low abundance, make analysis of PC1 particularly demanding. Analysis of the full complement of PC1 products requires a combination of specific antibodies directed to different regions of PC1 under defined experimental conditions that can discriminate these forms. This chapter will describe the biochemical complexity of PC1 due to GPS cleavage and provide detailed protocols for analyzing the full complement of PC1 products and the polycystin complex in vivo.
