Serine/threonine kinase which plays an important role in the regulation of electrolyte homeostasis, cell signaling, survival, and proliferation. Acts as an activator and inhibitor of sodium-coupled chloride cotransporters and potassium-coupled chloride cotransporters respectively. Activates SLC12A2, SCNN1A, SCNN1B, SCNN1D and SGK1 and inhibits SLC12A5. Negatively regulates the EGF-induced activation of the ERK/MAPK-pathway and the downstream cell cycle progression. Affects MAPK3/MAPK1 activity by modulating the activity of MAP2K1 and this modulation depends on phosphorylation of MAP2K1 by PAK1. WNK2 acts by interfering with the activity of PAK1 by controlling the balance of the activity of upstream regulators of PAK1 activity, RHOA and RAC1, which display reciprocal activity. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activation requires autophosphorylation of Ser-356. Phosphorylation of Ser-352 also promotes increased activity (By similarity). Forms a complex with the phosphorylated form of STK39 in the brain. Brain and heart. Autophosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. WNK subfamily. Was named WNK/'with no lysine(K)' because key residues for catalysis, including the lysine involved in ATP binding, are either not conserved or differ compared to the residues described in other kinase family proteins. Extended N-terminus. Truncated N-terminus. Truncated N-terminus.