Several mammalian kinases have been identified with sequence similarity to the Saccharomyces cerevisiae serine/threonine kinase STE20. STE20 is involved in relaying signals from G-protein coupled receptors to cytosolic MAP kinase cascades, and it lies upstream of a MAP kinase kinase kinase. Mammalian STE20-like kinases include KHS, GLK, NIK, YSK1, HPK1, Krs-1, Krs-2 and GC kinase. KHS (for kinase homologous to SPS1/STE20) is a protein that is most closely related to GC kinase. The KHS kinase has been shown to activate a variety of substrates, including JNK, suggesting a role in stress response.