WNK1 (WNK lysine deficient protein kinase 1), also known as KDP (kinase deficient protein), PSK, erythrocyte 65 kDa protein (p65), HSN2, HSAN2 or PRKWNK1, is a 2,382 amino acid cytoplasmic protein that participates in cell signaling, proliferation and survival, and regulates electrolyte homeostasis. WNK1 belongs to the Ser/Thr protein kinase family of the protein kinase superfamily, and contains one protein kinase domain. Existing as five alternatively spliced isoforms, WNK1 is widely expressed but is found at highest levels in skeletal muscke, heart, testis and kidney. The gene that encodes WNK1 maps to human chromosome 12p13.33, and when defective, is the cause of an an autosomal dominant disease known as pseudohypoaldosteronism type II (PHAII), as well as a hereditary sensory and autonomic neuropathy designated hereditary sensory and autonomic neuropathy type 2A (HSAN2A).