αA- and αB-Crystallins Interact with Caspase-3 and Bax to Guard Mouse Lens Development

The small heat shock protein, alpha-crystallin, exists in two isoforms, alpha A and alpha B, and displays strong ability against stress-induced apoptosis. Regarding their functional mechanisms, we and others have demonstrated that they are able to regulate members in both caspase and Bcl-2 families. In addition, we have also shown that alpha A and alpha B may display differential anti-apoptotic mechanisms under certain stress conditions. While alpha A-crystallin regulates activation of the AKT signaling pathway, alpha B negatively regulates the MAPK pathway to suppress apoptosis induced by UV and oxidative stress. Although previous studies revealed that alpha A and alpha B could regulate members in both caspase and Bcl-2 families, the molecular mechanism, especially the in vivo regulation still waits to be elucidated. In the present communication, we present both in vitro and in vivo evidence to further demonstrate the regulation of caspase-3 and Bax by alpha A and alpha B. First, Surface Plasmon Resonance (SPR) and yeast two-hybrid selection analysis demonstrate that alpha A and alpha B directly bind to caspase-3 and Bax with differential affinities. Second, immunohistochemistry reveals that alpha A and alpha B regulate caspase-3 and Bax at different developmental stages of mouse embryo. Third, co-immunoprecipitation shows that alpha A and alpha B form in vivo interacting complexes with caspase-3 and Bax. Together, our results further confirm that alpha A and alpha B regulate caspase-3 and Bax in vitro and in vivo to regulate lens differentiation.