MST3 (F9X8B) Rabbit Monoclonal Antibody #68334

Mammalian sterile-20-like (MST) kinases are upstream regulators of mitogen-activated protein kinase (MAPK) signaling pathways that regulate multiple biological processes, including apoptosis, morphogenesis, cell migration, and cytoskeletal rearrangements (1). This group of serine/threonine kinases includes a pair of closely related proteins (MST1, MST2) that are functionally distinct from the more distantly related MST3 and MST4 kinases. All four MST kinases share a conserved amino-terminal kinase domain and carboxy-terminal regulatory and interaction domains (1-3). At least three of these kinases (MST1-3) promote apoptosis and are activated by caspase cleavage, followed by nuclear translocation of the active kinase. MST1/2 kinases play a key role in the Hippo signaling pathway, an evolutionarily conserved program that controls organ size by regulating cell proliferation, apoptosis, and stem cell self-renewal (4). Mammalian Sterile 20-like kinase 3 (MST3, STK24) is ubiquitously expressed as a longer MST3b isoform and a shorter MST3a protein lacking a portion of the amino-terminal region (5). MST3a protein regulates neuronal migration during CNS development, cell motility, and apoptosis (6,7). MST3 phosphorylates and activates the NDR protein kinases that regulate cell cycle progression and cell morphology (8). Autophosphorylation of MST3 at Thr178 is required for in vitro kinase activity, and alteration of this residue inhibits MST3 regulation of cell migration in vivo (7). The brain-specific MST3b protein is activated by nerve growth factor or inosine and localizes to neurons where it helps regulate axon growth and regeneration (9).