title: Altered trafficking and stability of polycystins underlie polycystic kidney disease.
abstract: The most severe form of autosomal dominant polycystic kidney disease occurs in patients with mutations in the gene (PKD1) encoding polycystin-1 (PC1). PC1 is a complex polytopic membrane protein expressed in cilia that undergoes autoproteolytic cleavage at a G protein-coupled receptor proteolytic site (GPS). A quarter of PKD1 mutations are missense variants, though it is not clear how these mutations promote disease. Here, we established a cell-based system to evaluate these mutations and determined that GPS cleavage is required for PC1 trafficking to cilia. A common feature among a subset of pathogenic missense mutations is a resulting failure of PC1 to traffic to cilia regardless of GPS cleavage. The application of our system also identified a missense mutation in the gene encoding polycystin-2 (PC2) that prevented this protein from properly trafficking to cilia. Using a Pkd1-BAC recombineering approach, we developed murine models to study the effects of these mutations and confirmed that only the cleaved form of PC1 exits the ER and can rescue the embryonically lethal Pkd1-null mutation. Additionally, steady-state expression levels of the intramembranous COOH-terminal fragment of cleaved PC1 required an intact interaction with PC2. The results of this study demonstrate that PC1 trafficking and expression require GPS cleavage and PC2 interaction, respectively, and provide a framework for functional assays to categorize the effects of missense mutations in polycystins.
authors.forename: Yiqiang
authors.initials: Y
authors.lastname: Cai
authors.forename: Sorin V
authors.initials: SV
authors.lastname: Fedeles
authors.forename: Ke
authors.initials: K
authors.lastname: Dong
authors.forename: Georgia
authors.initials: G
authors.lastname: Anyatonwu
authors.forename: Tamehito
authors.initials: T
authors.lastname: Onoe
authors.forename: Michihiro
authors.initials: M
authors.lastname: Mitobe
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Gao
authors.forename: Dayne
authors.initials: D
authors.lastname: Okuhara
authors.forename: Xin
authors.initials: X
authors.lastname: Tian
authors.forename: Anna-Rachel
authors.initials: AR
authors.lastname: Gallagher
authors.forename: Zhangui
authors.initials: Z
authors.lastname: Tang
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Xie
authors.forename: Maria D
authors.initials: MD
authors.lastname: Lalioti
authors.forename: Ann-Hwee
authors.initials: AH
authors.lastname: Lee
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Ehrlich
authors.forename: Stefan
authors.initials: S
authors.lastname: Somlo
mesh_terms: D000818:Animals; D002460:Cell Line; D002923:Cilia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D020125:Mutation, Missense; D007690:Polycystic Kidney Diseases / Q000235:genetics / Q000378:metabolism* / Q000517:prevention & control; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000235:genetics; D050396:TRPP Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D050396:TRPP Cation Channels