HTScan^® Mst4 Kinase Assay Kit #7639

MST kinases, members of the STE20 family of kinases, are upstream activators of MAPK pathways that regulate processes such as apoptosis, morphogenesis and cytoskeletal rearrangements. The amino-terminal kinase domains of MST kinases are highly similar to the kinase domains of yeast STE20 kinase and other p21-activated kinases (1). The carboxy-terminal regions of MST1 and MST2 contain dimerization and inhibitory domains (1-3). Dimerization and phosphorylation at the activation loop results in translocation of MST1 from the cytosol to the nucleus (3). Growing evidence indicates that MST1, MST2 and MST3 are activated by apoptotic signals as well as other stress conditions (4-6). Complete activation of MST1 requires both phosphorylation and caspase-mediated cleavage (4). Sequence alignment of the activation loop of the GCK family indicates that Thr183 of MST1 and Thr180 of MST2 are the conserved residues and are critical for activation of the kinases. Activated MST kinases may rely on p38 MAPK and JNK pathways to amplify apoptotic signals (5). Phosphorylation at Ser327 of MST1, which is close to the caspase-3 recognition site, inhibits caspase-mediated cleavage (4).