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Description

Serpin B9 (UniProt: P50453, also known as Cytoplasmic antiproteinase 3, CAP-3, CAP3, Peptidase inhibitor 9, PI-9) is encoded by the SERPINB9 (also known as PI9) gene (Gene ID: 5272) in human. Serpins serve as intracellular or extracellular regulators of a wide range of physiological processes such as complement activation, blood coagulation and apoptosis. Within the vertebrate immune system, they control proteases of the classical and innate complement systems, and are also potent inhibitors of many leukocyte granule proteases. Serpin B9 has a broad tissue distribution, being present at high and relatively stable levels natural killer cells and CD8+ T cells, antigen-presenting cells, in many endothelial and mesothelial cells and at sites of immune privilege such as testis and placenta. Serpin B9 serves as a regulator granzyme B activity by acting as an inhibitor of its activity. Overexpression of Serpin B9 may prevent cytotoxic T-lymphocytes from eliminating certain tumor cells. Certain tumors may upregulate Serpin B9 levels as a mechanism of immune evasion. (Ref.: Kaiserman, D., and Bird, PI (2010). Cell Death Differen. 17(4), 586-595).