Catalytic domain of the Serine/Threonine Kinase, p38gamma Mitogen-Activated Protein Kinase (also called MAPK12)
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. p38gamma/MAPK12 is predominantly expressed in skeletal muscle. Unlike p38alpha and p38beta, p38gamma is insensitive to pyridinylimidazoles. It displays an antagonizing function compared to p38alpha. p38gamma inhibits, while p38alpha stimulates, c-Jun phosphorylation and AP-1 mediated transcription. p38gamma also plays a role in the signaling between Ras and the estrogen receptor and has been implicated to increase cell invasion and breast cancer progression. In Xenopus, p38gamma is critical in the meiotic maturation of oocytes. p38 kinases are MAPKs, serving as important mediators of cellular responses to extracellular signals. They are activated by the MAPK kinases MKK3 and MKK6, which in turn are activated by upstream MAPK kinase kinases including TAK1, ASK1, and MLK3, in response to cellular stresses or inflammatory cytokines. The p38gamma subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.