There are two wellcharacterized apoptotic pathways, one initiated through the engagement of cell surface death receptors by their specific ligands. Both pathways converge, resulting in activation of caspases that represent the effector arm of the apoptotic process proteins are major regulators of Cyanocobalamin apoptosis due, in part, to their ability to inhibit caspases. Originally identified in baculoviruses, IAP proteins have been discovered in both invertebrates and vertebrates.All IAP proteins contain one to three baculovirus IAP repeat domains that are required for antiapoptotic activity, and most of them also possess a carboxylterminal RING domain. It is unique among IAP proteins because of its ability to directly bind to and inhibit activated caspase, caspase, and caspase. Structurefunction analysis of XIAP showed that it uses different BIR domains for inhibition of distinct classes of caspases; the second BIR domain together with the immediately preceding linker region binds and inhibits caspase and caspase, whereas the third BIR domain specifically inhibits caspase. This IAP protein interaction motif binds to a surface groove on the BIR domains of the IAP proteins. Interactions with the corresponding groove on the surface of XIAPBIR also contribute substantially to inhibition of caspase and caspase. Other human IAP proteins, such as cIAP, cIAP, and MLIAP, are not potent physiologic inhibitors of caspases. The cIAP and cIAP proteins were originally identified through their ability to interact with tumor necrosis factor receptor associated factor. This leads to activation of caspase and subsequent activation of the effector caspase and caspase.IAP proteins represent the ultimate line of defense against cellular suicide as they inhibit caspase, caspase, and caspase. Survivin, the smallest human IAP protein with a single BIR domain, is associated with polymerized microtubules through its coiledcoil domain.Although the mechanistic aspects of its antiapoptotic activity remain somewhat controversial, survivin is essential for cell division. Studies that have examined the prognostic significance of IAP protein expression indicated potential links to poor prognosis. There is also a large body of data demonstrating elevated expression of IAP proteins. Survivin expression has a prominent cancer bias because it is undetectable in most adult tissues but is expressed at high levels in a majority of human tumors. MLIAP also has a tumorexclusive expression pattern with the highest levels detected in melanomas. In addition, cIAP is a target of genetic amplification and cIAP undergoes genetic translocation that fuses its BIR domains with MALT. These genetic modifications seem to be correlated with resistance to antitumor agents and activation of prosurvival and inflammatory pathways. The functional importance of IAP proteins in progression and resistance of various malignancies has been tested through the employment of antisense oligonucleotide or RNA interference technologies. Binding of this molecule to IAP proteins in vitro induces apoptosis, as measured by caspase and caspase activation and cell viability assays, in a subset of cancer cell lines. This, together with demonstrated preclinical Choline chloride efficacy in human tumor xenograft mouse models of breast cancer, colon cancer, and melanoma, suggests that it may be very useful for treatment of cancer. Parallel efforts aimed at disrupting exclusively the XIAPBIR interaction with caspase have also led to the discovery of nonpeptidic smallmolecule inhibitors that show efficacy in vitro and in vivo.

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