Caspase-3 is a cytoplasmic cysteine protease involved in the activation cascade of caspases responsible for execution of apoptosis. At the onset of apoptosis caspase-3 cleaves and activates caspase-6, -7 and -9. It also cleaves poly (ADP-ribose) polymerase (PARP). Caspase-3 cleaves and activates sterol regulatory element binding proteins (SREBPs). Caspase-3 is involved in the cleavage of huntingtin. Caspase-3 is expressed in an inactive pro-form (pro caspase-3). In apoptosis, the pro caspase-3 is activated by proteolytic cleavages at Asp28-Ser29 and Asp175-Ser176 bonds catalyzed by granzyme B, caspase-6, caspase-8, caspase-9 and caspase-10, generating two subunits p17 and p12 that are assembled into heterotetrameric active enzyme. Additional processing of the propeptides is likely due to the autocatalytic activity of the activated protease. The pro-form and the active form are useful biomarkers of apoptosis.
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