MST4: Proteins and Enzymes

Novel human Ste20-related kinase Mst4 is highly expressed in placenta, thymus, and peripheral blood leukocytes. Mst4 is biologically active in the activation of MEK/ERK pathway and in mediating cell growth and transformation (1). Wild type and C-terminally truncated forms of Mst4 can both induce apoptosis upon overexpression in mammalian cells that is abrogated by CrmA, suggesting involvement of Mst4 in the apoptotic machinery in mammalian cells (2). Mst4 was found to be expressed in prostate carcinoma tumor samples and cell lines. In addition, expression levels appeared to correlate with tumorigenicity and androgen receptor status of the cells. Mst4 kinase activity was stimulated significantly by epidermal growth factor receptor ligands, which are known to promote growth of prostate cancer cells (3).