Catalytic domain of the Serine/Threonine Kinase, Nemo-Like Kinase
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. NLK is an atypical mitogen-activated protein kinase (MAPK) that is not regulated by a MAPK kinase. It functions downstream of the MAPK kinase kinase Tak1, which also plays a role in activating the JNK and p38 MAPKs. The Tak1/NLK pathways are regulated by Wnts, a family of secreted proteins that is critical in the control of asymmetric division and cell polarity. NLK can phosphorylate transcription factors from the TCF/LEF family, inhibiting their ability to activate the transcription of target genes. In prostate cancer cells, NLK is involved in regulating androgen receptor-mediated transcription and its expression is altered during cancer progression. MAPKs are important mediators of cellular responses to extracellular signals. The NLK subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.