N-terminal Catalytic domain of the Serine/Threonine Kinases, Mitogen-Activated Protein Kinase Kinase Kinase Kinase 4 and 6
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Members of this subfamily contain an N-terminal catalytic domain and a C-terminal citron homology (CNH) regulatory domain. MAP4K4 is also called Nck Interacting kinase (NIK). It facilitates the activation of the MAPKs, extracellular signal-regulated kinase (ERK) 1, ERK2, and c-Jun N-terminal kinase (JNK), by phosphorylating and activating MEKK1. MAP4K4 plays a role in tumor necrosis factor (TNF) alpha-induced insulin resistance. MAP4K4 silencing in skeletal muscle cells from type II diabetic patients restores insulin-mediated glucose uptake. MAP4K4, through JNK, also plays a broad role in cell motility, which impacts inflammation, homeostasis, as well as the invasion and spread of cancer. MAP4K4 is found to be highly expressed in most tumor cell lines relative to normal tissue. MAP4K6 (also called MINK for Misshapen/NIKs-related kinase) is activated after Ras induction and mediates activation of p38 MAPK. MAP4K6 plays a role in cell cycle arrest, cytoskeleton organization, cell adhesion, and cell motility. The MAP4K4/6 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",