title: Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S) to sequester their translocation during staurosporine-induced apoptosis.
abstract: AlphaA- and alphaB-crystallins are distinct antiapoptotic regulators. Regarding the antiapoptotic mechanisms, we have recently demonstrated that alphaB-crystallin interacts with the procaspase-3 and partially processed procaspase-3 to repress caspase-3 activation. Here, we demonstrate that human alphaA- and alphaB-crystallins prevent staurosporine-induced apoptosis through interactions with members of the Bcl-2 family. Using GST pulldown assays and coimmunoprecipitations, we demonstrated that alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo. Human alphaA- and alphaB-crystallins display similar affinity to both proapoptotic regulators, and so are true with their antiapoptotic ability tested in human lens epithelial cells, human retina pigment epithelial cells (ARPE-19) and rat embryonic myocardium cells (H9c2) under treatment of staurosporine, etoposide or sorbitol. Two prominent mutants, R116C in alphaA-crystallin and R120G, in alphaB-crystallin display much weaker affinity to Bax and Bcl-X(S). Through the interaction, alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis. As a result, alpha-crystallins preserve the integrity of mitochondria, restrict release of cytochrome c, repress activation of caspase-3 and block degradation of PARP. Thus, our results demonstrate a novel antiapoptotic mechanism for alpha-crystallins.
authors.affiliation: Department of Molecular Biology, University of Medicine and Dentistry of New Jersey, Stratford, NJ, USA.
authors.forename: Y-W
authors.initials: YW
authors.lastname: Mao
authors.forename: J-P
authors.initials: JP
authors.lastname: Liu
authors.forename: H
authors.initials: H
authors.lastname: Xiang
authors.forename: D W-C
authors.initials: DW
authors.lastname: Li
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005047:Etoposide / Q000633:toxicity; D019254:Genes, bcl-2 / Q000502:physiology; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D032383:Myocytes, Cardiac / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051381:Rats; D013012:Sorbitol / Q000633:toxicity; D019311:Staurosporine / Q000633:toxicity; D038202:alpha-Crystallin A Chain / Q000378:metabolism*; D038203:alpha-Crystallin B Chain / Q000378:metabolism*; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: C494826:BAX protein, human; C494811:BCL2L1 protein, human; C494828:Bax protein, rat; C494813:Bcl2l1 protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D038202:alpha-Crystallin A Chain; D038203:alpha-Crystallin B Chain; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D013012:Sorbitol; D005047:Etoposide; D045304:Cytochromes c; D020169:Caspases; D019311:Staurosporine