MAP4K

MAP4Ks (Mitogen-activated protein kinase kinase kinase kinases) belong to the mammalian Ste20-like family of serine/threonine kinases. MAP4K family members, including Hematopoietic progenitor kinase 1 (HPK1/MAP4K1), Germinal centre kinase (GCK/MAP4K2), Germinal centre kinase-like kinase (GLK/MAP4K3), HPK/GCK-like kinase (HGK/MAP4K4), Misshapen-like kinase 1 (MINK1/MAP4K6) and TRAF2 and NCK interacting kinase (TNIK/MAP4K7), as potent LATS1/2-activating kinases.

Overexpression or deletion of MAP4Ks affects the phosphorylation and activity of Large tumor suppressor 1/2 (LATS1/2, homologues of Wts) and Yes-associated protein (YAP) /transcriptional co-activator with PDZ-binding motif (TAZ). By acting in a LATS-dependent, but Mammalian Ste20-like kinases 1/2 (MST1/2, homologues of Hpo)-independent manner, MAP4Ks restrict the activity of YAP/TAZ by promoting their phosphorylation and inhibiting target gene expression. MAP4Ks are components of the Hippo pathway by directly phosphorylating and activating the LATS1/2 kinases.MAP4K2/4/6 and MST1/2 both belong to the STE20-like kinase family, and their kinase domains are highly homologous to one another. MAP4K4 acts through LATS to inhibit YAP and cell proliferation.