| Mitogen-activated protein kinases (MAPKs) are activated by various extracellular signals and play crucial roles in regulating cell proliferation, differentiation, survival, and apoptosis. MAPK-interacting kinases (Mnks or MKNKs) are direct downstream substrates of MAPK and were first discovered independently by the work of Fukunaga and Hunter and Waskiewicz and Cooper. There are 2 Mnks in human, termed Mnk1 and Mnk2. Both Mnks possess a MAPK-binding domain that allows them to bind to and then to be phosphorylated by Erk and p38. The phosphorylation in the T-loop of Mnks stimulates their in vitro kinase activity toward a substrate, eukaryotic initiation factor-4E (eIF4E). eIF4E is a key component of the translational machinery mediating the initiation of translation, but how phosphorylation of eIF4E regulates translation initiation is still under investigation. |
