FAST (Fas-activated serine/threonine) is a novel serine/threonine kinase that is activated as a result of Fas ligation. FAST resides in the cytoplasm as a highly phosphorylated protein and is quickly dephosphorylated and activated in response to stimulated Fas. FAST shows kinase specificity towards both TIA-1 and TIAR，both of which are thought to function as mediators of apoptotic cell death.
