title: The anti-apoptotic function of human αA-crystallin is directly related to its chaperone activity.
abstract: αA-crystallin is a molecular chaperone and an antiapoptotic protein. This study investigated the mechanism of inhibition of apoptosis by human αA-crystallin and determined if the chaperone activity of αA-crystallin is required for the antiapoptotic function. αA-crystallin inhibited chemical-induced apoptosis in Chinese hamster ovary (CHO) cells and HeLa cells by inhibiting activation of caspase-3 and -9. In CHO cells, it inhibited apoptosis induced by the overexpression of human proapoptotic proteins, Bim and Bax. αA-crystallin inhibited doxorubicin-mediated activation of human procaspase-3 in CHO cells and it activated the PI3K/Akt cell survival pathway by promoting the phosphorylation of PDK1, Akt and phosphatase tensin homologue in HeLa cells. The phosphoinositide 3 kinase (PI3K) activity was increased by αA-crystallin overexpression but the protein content was unaltered. Downregulation of PI3K by the expression of a dominant-negative mutant or inhibition by LY294002 abrogated the ability of αA-crystallin to phosphorylate Akt. These antiapoptotic functions of αA-crystallin were enhanced in a mutant protein (R21A) that shows increased chaperone activity than the wild-type (Wt) protein. Interestingly, a mutant protein (R49A) that shows decreased chaperone activity was far weaker than the Wt protein in its antiapoptotic functions. Together, our study results show that αA-crystallin inhibits apoptosis by enhancing PI3K activity and inactivating phosphatase tensin homologue and that the antiapoptotic function is directly related to its chaperone activity.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: N
authors.initials: N
authors.lastname: Pasupuleti
authors.forename: S
authors.initials: S
authors.lastname: Matsuyama
authors.forename: O
authors.initials: O
authors.lastname: Voss
authors.forename: A I
authors.initials: AI
authors.lastname: Doseff
authors.forename: K
authors.initials: K
authors.lastname: Song
authors.forename: D
authors.initials: D
authors.lastname: Danielpour
authors.forename: R H
authors.initials: RH
authors.lastname: Nagaraj
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D016466:CHO Cells; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D061945:Caspase Inhibitors; D006224:Cricetinae; D003412:Cricetulus; D003459:Crystallins / Q000235:genetics / Q000502:physiology*; D045304:Cytochromes c / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D004789:Enzyme Activation / Q000235:genetics; D004791:Enzyme Inhibitors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C511246:CRYAA protein, human; D061945:Caspase Inhibitors; D003459:Crystallins; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; C000631429:PDK1 protein, human; D011518:Proto-Oncogene Proteins; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051028:bcl-2-Associated X Protein; D004317:Doxorubicin; D045304:Cytochromes c; D058539:Phosphatidylinositol 3-Kinase; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D053148:Caspase 3; D053453:Caspase 9