LOSK, or STE20 like kinase, is a human gene encoded by SLK. It may also be known as: STE20-like serine/threonine-protein kinase; hSLK; CTCL tumor antigen se20-9; STE20-related serine/threonine-protein kinase; STE20-related kinase; STE20-like kinase; STK2; bA16H23.1; se20-9. The encoded protein is an enzyme with an amino acid length of 1235 and a mass of 142.7 kDa. Other isoforms may exist. LOSK is a member of the Protein kinase superfamily, STE Ser/Thr protein kinase family, STE20 subfamily. Homologs of this gene exist in other organisms, including: Fly, Mouse, Rat, Chicken.