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Catalytic domain of the Serine/Threonine protein kinase, With No Lysine (WNK) 1 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. WNK1 is widely expressed and is most abundant in the testis. In hyperosmotic or hypotonic low-chloride stress conditions, WNK1 is activated and it phosphorylates its substrates including SPAK and OSR1 kinases, which regulate the activity of cation-chloride cotransporters through direct interaction and phosphorylation. Mutations in WNK1 cause PseudoHypoAldosteronism type II (PHAII), characterized by hypertension and hyperkalemia. WNK1 negates WNK4-mediated inhibition of the sodium-chloride cotransporter NCC and activates the epithelial sodium channel ENaC by activating SGK1. WNK1 also decreases the surface expression of renal outer medullary potassium channel (ROMK) by stimulating their endocytosis. Hypertension and hyperkalemia in PHAII patients with WNK1 mutations may be due partly to increased activity of NCC and ENaC, and impaired renal potassium secretion by ROMK, respectively. In addition, WNK1 interacts with MEKK2/3 and acts as an activator of extracellular signal-regulated kinase (ERK) 5. It also negatively regulates TGFbeta signaling. WNKs comprise a subfamily of STKs with an unusual placement of the catalytic lysine relative to all other protein kinases. The WNK1 subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",