| Bcl-2 is a pro-survival protein which regulates the intrinsic mitochondrial pathway of apoptosis. Disruption of Bcl-2 function has profound consequences on the mitochondria and the cell, triggering activation of mitochondrial-associated cell death pathways (intrinsic apoptosis). Here, we investigate the effect of Bcl-2 loss-of-function on neuronal survival. When Bcl-2 is inactivated via antisensemediated downregulation or BH3 domain binding in the hydrophobic groove (BH3 groove), its antioxidant-like function is disrupted and neurons succumb to apoptosis. Addition of cell permeable antioxidants completely block this oxidative stress-dependent death. We report here that Bcl-2 loss of antioxidant function induced by addition of small molecule BH3 domain mimetics is likely due to disruption of a critical and previously unknown glutathione binding property of Bcl-2 mediated by the BH3 groove. In addition, this novel interaction regulates the uptake of GSH into the mitochondria which is essential to protect the organelle from incurring oxidative damage. Alternatively, when Bcl-2 function is inhibited by phosphorylation, as occurs when specific cellular kinases are activated in reovirus infection, the addition of antioxidants has no effect on neuronal survival. In an effort to determine whether phosphorylation of Bcl-2 inhibits its anti-apoptotic function, we analyzed the protective capacity of a panel of Bcl-2 phosphorylation mutants. Overexpression of a phosphorylation-mimic Bcl-2 mutant confirms that although its antioxidant-like function appears to remain intact, its capacity to protect against reovirus-induced apoptosis is abolished. This phosphorylation mimic Bcl-2 mutant exhibits decreased binding of pro-apoptotic Bax, suggesting a potential mechanism through which reovirus inhibits Bcl-2 and initiates apoptosis. Bcl-2 anti-apoptotic function mediates neuronal survival and understanding how its activity is disrupted in apoptosis could potentially facilitate neurodegenerative disease research. The form and content of this abstract are approved. |
