Specifically, XIAP possesses two different caspase-inhibitory activities, which can be attributed to distinct domains within XIAP. The BIR3 of XIAP is a specific inhibitor of cas-pase-9, whereas BIR2 plus the linker region of BIR1 and BIR2 is specific for caspase-3 and caspase-7. The IAPs suppress Fas ligand- and TNFa-induced apoptosis by directly inhibiting caspase-3 and caspase-7 activation and activity, but they are ineffective in the activation of caspase-1, caspase-6, or caspase-10. generic female Viagra
In addition, XIAP modulates the cytochrome c/caspase-9-dependent mitochondrial death pathway. The mammalian HIAP-1, HIAP-2, and XIAP interfere with the function of caspase-9 by binding to inactive procaspase-9, thereby preventing its processing and activation. However, whether XIAP functions in this manner in the ovary remains to be determined. Interestingly, recent studies have shown that overexpression of XIAP increases phospho-Akt content in cultured rat granulosa cells and human ovarian cancer cells. This raises the possibility that XIAP may exert its antiapoptotic action via up-regulation of the PI3K/Akt pathway through a caspase-independent mechanism.