Polycystin 1
Polycystin 1 is a protein that in humans is encoded by the PKD1 gene. Mutations of PKD1 are associated with most cases of autosomal dominant polycystic kidney disease, a severe hereditary disorder of the kidneys characterised by the development of renal cysts and severe kidney dysfunction.
Protein structure and function
PC1 is a membrane-bound protein 4303 amino acids in length expressed largely upon the primary cilium, as well as apical membranes, adherens junctions, and desmosomes. It has 11 transmembrane domains, a large extracellular N-terminal domain, and a short cytoplasmic C-terminal domain. This intracellular domain contains a coiled-coil domain through which PC1 interacts with polycystin 2, a membrane-bound Ca2+-permeable ion channel.PC1 has been proposed to act as a G protein–coupled receptor. The C-terminal domain may be cleaved in a number of different ways. In one instance, a ~35 kDa portion of the tail has been found to accumulate in the cell nucleus in response to decreased fluid flow in the mouse kidney. In another instance, a 15 kDa fragment may be yielded, interacting with transcriptional activator and co-activator STAT6 and p100, or components of the canonical Wnt signaling pathway in an inhibitory manner.
The structure of the human PKD1-PKD2 complex has been solved by cryo-electron microscopy, which showed a 1:3 ratio of PKD1 and PKD2 in the structure. PKD1 consists of a voltage-gated ion channel fold that interacts with PKD2.
PC1 mediates mechanosensation of fluid flow by the primary cilium in the renal epithelium and of mechanical deformation of articular cartilage.