PKD2

PKD2 encodes polycystin-2/TRPP2, a six-transmembrane, non-selective cation channel that localizes to the primary cilium, plasma membrane, and endoplasmic reticulum[1][2]. Mechanistically, PKD2 supports ciliary ion-channel activity in renal collecting duct epithelium, where the native channel conducts K+ and Na+ and is sensitized by high intraciliary Ca2+[1]. Through interaction with PKD1, PKD2 contributes to a receptor-ion-channel complex that links extracellular cues to Ca2+-dependent signaling, including WNT/Ca2+ responses[3]. In disease models, loss of PKD2 or exclusion of channel-functional polycystin-2 from cilia promotes renal cystogenesis, supporting a cilia-centered mechanism in autosomal dominant polycystic kidney disease[1][4]. Compared with PKD1, PKD2 provides the required ciliary channel subunit, while PKD1 can confer distinct channel properties within the PKD1-PKD2 complex[1][5]. Compared with PKD2L1, PKD2 shows different ciliary ion selectivity, because PKD2L1-containing channels preferentially conduct Ca2+[1][6]. For experimental applications, direct ciliary electrophysiology and heterologous ciliary expression provide practical systems for evaluating PKD2 variants and channel behavior[1]. Pharmacological work should distinguish PKD2 from associated subunits, because pregnenolone sulfate and isosakuranetin modulate a TRPM3-dependent TRPP2 ciliary channel rather than proving PKD2-specific agonism or inhibition[7].