A- and B-Crystallins Interact with Caspase-3 and Bax to Guard Mouse Lens Development

The small heat shock protein, -crystallin, exists in two isoforms, A and 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 A and B may display differential anti-apoptotic mechanisms under certain stress conditions. While A-crystallin regulates activation of the AKT signaling pathway, B negatively regulates the MAPK pathway to suppress apoptosis induced by UV and oxidative stress. Although previous studies revealed that A and 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 A and B. First, Surface Plasmon Resonance (SPR) and yeast two-hybrid selection analysis demonstrate that A and B directly bind to caspase-3 and Bax with differential affinities. Second, immunohistochemistry reveals that A and B regulate caspase-3 and Bax at different developmental stages of mouse embryo. Third, coimmunoprecipitation shows that A and B form in vivo interacting complexes with caspase-3 and Bax. Together, our results further confirm that A and B regulate caspase-3 and Bax in vitro and in vivo to regulate lens differentiation.