Caspase 3 (also known as cpp32, Apopain, Yama, and PARP cleavage protease) is a member of the peptidase family C14. This cytoplasmic caspase functions as a heterotetramer and has two isoforms (one acts as a dominant negative inhibitor). The pro-form of this caspase is approximately 32 kD. Caspase 3 is involved in the caspase activation cascade responsible for apoptosis execution. This caspase cleaves/activates SREBPs, Caspase 6, Caspase 7, and Caspase 9. Caspase 3 is inhibited by c-IAP1, c-IAP2, XIAP, survivin, and Livin and activated by Caspase 6, -8 , and -10, granzyme B, Apaf-1 by cleavage into large p17 and small p12 subunits. Active heterodimers form between the large p17 subunit and small p11 subunit of Caspase 7 and vice versa. Caspase 3 has been shown to cleave PARP, huntingtin, androgen receptor, atrophin-1, DNA- PKcs, D4-GDI, hnRNPs C1/C2, U1snRNP, PKC delta, ATM, fodrin, gelsolin, ICAD, RIP, X-IAP, STAT1, topoisomerase I, vimentin, Rb, lamin B, mdm2, and beta-catenin. The 4-1-18 monoclonal antibody has been shown to be useful for Western blotting of human caspase 3 (32 kD pro-caspase and 17 kD cleaved caspase).