MST3: Proteins and Enzymes

The growth of axons is fundamental to the development and repair of brain circuitry. It has been shown that Mst3, a neuron-specific homolog of the yeast kinase Ste20, is critical for axon outgrowth. Mst3 is activated in response to trophic factors, and suppressing its expression or its function blocks axon outgrowth (1). Mst3 has been recently demonstrated to undergo a caspase-mediated cleavage during apoptosis. The proteolytic cleavage of the C-terminus of Mst3 caused nuclear translocation of its kinase domain. Mst3 contains both nuclear localization sequence (NLS) and NES signals, which may cooperate to control the subcellular distribution of Mst3 (2). In situ hybridization of rat brain sections indicated that MST3b is widely expressed in different brain regions, with especially high expression in hippocampus and cerebral cortex. When expressed in human embryonic kidney 293 (HEK293) cells, MST3b effectively phosphorylated myelin basic protein, as well as undergoing autophosphorylation (3)