PLAT/LH2 domain of polycystin-1 like proteins. Polycystins are a large family of membrane proteins composed of multiple domains, present in fish, invertebrates, mammals, and humans that are widely expressed in various cell types and whose biological functions remain poorly defined. In human, mutations in polycystin-1 (PKD1) and polycystin-2 (PKD2) have been shown to be the cause for autosomal dominant polycystic kidney disease (ADPKD). The generally proposed function of PLAT/LH2 domains is to mediate interaction with lipids or membrane bound proteins.