WNK4

Serine/threonine-protein kinase component of the WNK4-SPAK/OSR1 kinase cascade, which acts as a key regulator of ion transport in the distal nephron and blood pressure (By similarity). The WNK4-SPAK/OSR1 kinase cascade is composed of WNK4, which mediates phosphorylation and activation of downstream kinases OXSR1/OSR1 and STK39/SPAK. Following activation, OXSR1/OSR1 and STK39/SPAK catalyze phosphorylation of ion cotransporters, such as SLC12A1/NKCC2, SLC12A2/NKCC1, SLC12A3/NCC, SLC12A5/KCC2 or SLC12A6/KCC3, regulating their activity. Acts as a molecular switch that regulates the balance between renal salt reabsorption and K(+) secretion by modulating the activities of renal transporters and channels, including the Na-Cl cotransporter SLC12A3/NCC and the K(+) channel, KCNJ1/ROMK (By similarity). Regulates NaCl reabsorption in the distal nephron by activating the thiazide-sensitive Na-Cl cotransporter SLC12A3/NCC in distal convoluted tubule cells of kidney: activates SLC12A3/NCC in a OXSR1/OSR1- and STK39/SPAK-dependent process (By similarity). Also acts as a scaffold protein independently of its protein kinase activity: negatively regulates cell membrane localization of various transporters and channels (CFTR, KCNJ1/ROMK, SLC4A4, SLC26A9 and TRPV4) by clathrin-dependent endocytosis (By similarity). Also inhibits the activity of the epithelial Na(+) channel (ENaC) SCNN1A, SCNN1B, SCNN1D in a inase-independent mechanism (By similarity). May also phosphorylate NEDD4L..

Function from UniProtKB (Q96J92), read 2026-09-23. CC BY 4.0.