Component of a heteromeric calcium-permeable ion channel formed by PKD1 and PKD2 that is activated by interaction between PKD1 and a Wnt family member, such as WNT3A and WNT9B (PubMed:27214281). Can also form a functional, homotetrameric ion channel (PubMed:29899465). Functions as a cation channel involved in fluid-flow mechanosensation by the primary cilium in renal epithelium (PubMed:18695040). Functions as outward-rectifying K(+) channel, but is also permeable to Ca(2+), and to a much lesser degree also to Na(+) (PubMed:11854751, PubMed:15692563, PubMed:27071085, PubMed:27991905). May contribute to the release of Ca(2+) stores from the endoplasmic reticulum (PubMed:11854751, PubMed:20881056). Together with TRPV4, forms mechano- and thermosensitive channels in cilium (PubMed:18695040). PKD1 and PKD2 may function through a common signaling pathway that is necessary to maintain the normal, differentiated state of renal tubule cells. Acts as a regulator of cilium length, together with PKD1. The dynamic control of cilium length is essential in the regulation of mechanotransductive signaling. The cilium length response creates a negative feedback loop whereby fluid shear-mediated deflection of the primary cilium, which decreases intracellular cAMP, leads to cilium shortening and thus decreases flow-induced signaling. Also involved in left-right axis specification via its role in sensing nodal flow; forms a complex with PKD1L1 in cilia to facilitate flow detection in left-right patterning. Detection of asymmetric nodal flow gives rise to a Ca(2+) signal that is required for normal, asymmetric expression of genes involved in the specification of body left-right laterality (By similarity). Channel activity is regulated by phosphorylation (PubMed:16551655, PubMed:20881056, PubMed:26269590). Channel activity is regulated by intracellular Ca(2+) (PubMed:11854751). Homotetramer (PubMed:20881056, PubMed:27768895, PubMed:27991905, PubMed:28092368, PubMed:29899465). Heterotetramer with PKD1, giving rise to a complex formed by one PKD1 chain and three PKD2 chains (PubMed:20881056, PubMed:19556541, PubMed:27214281, PubMed:30093605). Interaction with PKD1 is required for ciliary localization (By similarity) Isoform 1 interacts with PKD1 while isoform 3 does not (By similarity). Interacts with PKD1L1. Interacts with CD2AP (PubMed:10913159). Interacts with HAX1 (PubMed:10760273). Interacts with NEK8 (By similarity). Part of a complex containing AKAP5, ADCY5, ADCY6 and PDE4C (By similarity). Interacts (via C-terminus) with TRPV4 (via C-terminus) (PubMed:18695040). Interacts (via C-terminal acidic region) with PACS1 and PACS2; these interactions retain the protein in the endoplasmic reticulum and prevent trafficking to the cell membrane (PubMed:15692563). Interacts with TMEM33 (By similarity). PKD2 localization to the plasma and ciliary membranes requires PKD1. PKD1:PKD2 interaction is required to reach the Golgi apparatus form endoplasmic reticulum and then traffic to the cilia (By similarity). Retained in the endoplasmic reticulum by interaction with PACS1 and PACS2 (PubMed:15692563). Detected on kidney tubule basolateral membranes and basal cytoplasmic vesicles (PubMed:10770959). Cell surface and cilium localization requires GANAB (PubMed:27259053). Detected in fetal and adult kidney (PubMed:10770959). Detected at the thick ascending limb of the loop of Henle, at distal tubules, including the distal convoluted tubule and cortical collecting tubules, with weak staining of the collecting duct (PubMed:10770959). Detected on placenta syncytiotrophoblasts (at protein level) (PubMed:26269590). Strongly expressed in ovary, fetal and adult kidney, testis, and small intestine. Not detected in peripheral leukocytes. The C-terminal coiled-coil domain is involved in oligomerization and the interaction with PKD1 (PubMed:18694932, PubMed:19556541). The isolated coiled-coil domain forms a homotrimer in vitro; the homotrimer interacts with a single PKD1 chain (PubMed:19556541). The coiled-coil domain binds calcium and undergoes a calcium-induced conformation change (in vitro) (PubMed:18694932). Phosphorylated. Phosphorylation is important for protein function; a mutant that lacks the N-terminal phosphorylation sites cannot complement a zebrafish pkd2-deficient mutant (PubMed:16551655). PKD-mediated phosphorylation at the C-terminus regulates its function in the release of Ca(2+) stores from the endoplasmic reticulum (PubMed:20881056). PKA-mediated phosphorylation at a C-terminal site strongly increases the open probability of the channel, but does not increase single channel conductance (PubMed:26269590). N-glycosylated. The four subunits in a tetramer probably differ in the extent of glycosylation; simultaneous glycosylation of all experimentally validated sites would probably create steric hindrance. Thus, glycosylation at Asn-305 is not compatible with glycosylation at Asn-328; only one of these two residues is glycosylated at a given time. The disease is caused by variants affecting the gene represented in this entry. The mechanisms that govern channel opening are complex and still under debate; heterologous expression of PKD2 by itself or together with PKD1 gives rise to very low or undetectable spontaneous ion channel activity, in spite of its presence at the cell membrane. Minor isoform. Belongs to the polycystin family. Polycystin 2 - Not a C-type lectin