Anti-Livin (KIAP)

This antibody recognizes Livin, both isoform alpha and isoform beta. Human Livin isoform alpha is a 298 amino acid protein. Livin (BIRC7/KIAP) is a member of the family of inhibitor of apoptosis proteins (IAP) and contains a single copy of a baculovirus IAP repeat (BIR) as well as a RING-type zinc finger domain. Some IAP members, like Liven, also have a RING-type finger motif at their carboxyl-terminal which may enhance anti-apoptotic activity. Many RING finger-containing IAPs possess E3 ubiquitin ligase activity, and it has been shown that Liven acts an E3 ubiquitin ligase for targeting the degradation of Smac/DIABLO. Thus degradation of Smac/DIABLO is thought to be a mechanism to enhance Livin anti-apoptotic activity, thereby promoting cell survival. Two splicing variants of Livin, alpha and beta, have been identified. The two isoforms are thought to have different anti-apoptotic properties, however, there are conflicting reports are to whether they actually differ in their biological activities. Liven is expressed at low levels in adult tissues, and relatively higher levels in developmental tissues and in many cancer cells. Certain cancers patients develop autoantibodies against liven and in a number of cancers, Liven is detected only in the tumors but not, or to substantially lower levels, in the corresponding normal adjacent tissue. Protein function: Apoptotic regulator capable of exerting proapoptotic and anti-apoptotic activities and plays crucial roles in apoptosis, cell proliferation, and cell cycle control. Its anti-apoptotic activity is mediated through the inhibition of CASP3, CASP7 and CASP9, as well as by its E3 ubiquitin-protein ligase activity. As it is a weak caspase inhibitor, its anti-apoptotic activity is thought to be due to its ability to ubiquitinate DIABLO/SMAC targeting it for degradation thereby promoting cell survival. May contribute to caspase inhibition, by blocking the ability of DIABLO/SMAC to disrupt XIAP/BIRC4-caspase interactions. Protects against apoptosis induced by TNF or by chemical agents such as adriamycin, etoposide or staurosporine. Suppression of apoptosis is mediated by activation of MAPK8/JNK1, and possibly also of MAPK9/JNK2. This activation depends on TAB1 and NR2C2/TAK1. In vitro, inhibits CASP3 and proteolytic activation of pro-CASP9. Isoform 1 blocks staurosporine-induced apoptosis. Isoform 2 blocks etoposide-induced apoptosis. Isoform 2 protects against natural killer (NK) cell killing whereas isoform 1 augments killing. [The UniProt Consortium]