Elucidating the mechanism of anti-apoptotic activity of α-crystallin and its therapeutic potential

Abstract

α- Crystallins are the structural proteins of the eye lens which possess anti-apoptotic activity. Both αA- and αB- crystallins are distinct antiapoptotic regulators which can interact with Bax and Bcl-XS, proapoptotic members of the Bcl-2 family in order to sequester their translocation into the mitochondria. Thus they may interfere with the mitochondrial apoptotic pathway which triggers Bax pro-apoptotic activity and the downstream activation of effector caspases such as Caspase-9 and Caspase-3. The differential regulation of α- crystallins has been observed in several ocular diseases such as age-related macular degeneration and many others. Crystallins interact with pro-apoptotic Bax and displayed cytoprotection against Bax-triggered apoptosis. αA-crystallin was found to inhibit chemical-induced apoptosis by inhibiting the activation of caspase-3 and caspase-9. Its antiapoptotic activity was found to be directly related to its chaperone activity. On the other hand, αB- crystallin associated with IKK-β activates its kinase activity which in turn, leads to the activation of NF- ĸB; this activation protects myoblasts from tumor necrosis factor-α (TNF-α) - induced cytotoxicity by enhancing the expression of Bcl-2, an anti-apoptotic protein. The anti- apoptotic mechanisms may be exploited for therapeutic purposes in near future.

Keywords

• α- crystallin
• antiapoptotic mechanism
• pro-apoptotic members
• bax
• bcl-2
• caspase-3
• caspase-9
• retinal degenerations
• ikkβ
• nf- ĸb
• therapeutic purposes