title: O-GlcNAcylation of αB-crystallin regulates its stress-induced translocation and cytoprotection.
abstract: Under normal conditions, the ubiquitously expressed αB-crystallin functions as a chaperone. αB-crystallin has been implicated in a variety of pathologies, consistent with a build-up of protein aggregates, such as neuromuscular disorders, myofibrillar myopathies, and cardiomyopathies. αB-crystallins' cardioprotection is partially attributed to its translocation and binding to cytoskeletal elements in response to stress. The triggers for this translocation are not clearly understood. In the heart, αB-crystallin undergoes at least three significant post-translational modifications: phosphorylation at ser-45 and 59 and O-GlcNAcylation (O-linked attachment of the monosaccharide β-N-acetyl-glucosamine) at thr-170. Whether phosphorylation status drives translocation remains controversial. Therefore, we evaluated the role of αB-crystallins' O-GlcNAcylation in its stress-induced translocation and cytoprotection in cardiomyocytes under stress. Immunoblotting and precipitation experiments with anti-O-GlcNAc antibody (CTD110.6) and glycoprotein staining (Pro-Q Emerald) both demonstrate robust stress-induced O-GlcNAcylation of αB-crystallin. A non-O-GlcNAcylatable αB-crystallin mutant (αB-T170A) showed diminished translocation in response to heat shock and robust phosphorylation at both ser-45 and ser-59. Cell survival assays show a loss of overexpression-associated cytoprotection with the non-glycosylatable mutant to multiple stresses. While ectopic expression of wild-type αB-crystallin strongly stabilized ZsProSensor, a fusion protein rapidly degraded by the proteasome, the non-O-GlcNAcylatable version did not. Therefore, we believe the O-GlcNAcylation of αB-crystallin is a dynamic and important regulator of both its localization and function.
authors.affiliation: Health Sciences Division, Department of Medicine, The Cardiovascular Institute, Loyola University Chicago, Maywood, IL 60153, USA.
authors.forename: Vigneshwaran
authors.initials: V
authors.lastname: Krishnamoorthy
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Donofrio
authors.forename: Jody L
authors.initials: JL
authors.lastname: Martin
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D002470:Cell Survival; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003459:Crystallins / Q000235:genetics / Q000378:metabolism*; D019610:Cytoprotection; D006031:Glycosylation; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism; D018869:Heat-Shock Response; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D032383:Myocytes, Cardiac / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D051381:Rats; D013912:Threonine / Q000235:genetics
chemical_list: D003459:Crystallins; D055551:HSP27 Heat-Shock Proteins; C486114:Hspb1 protein, rat; D008869:Microtubule-Associated Proteins; C530883:cryaB protein, rat; D013912:Threonine; D000117:Acetylglucosamine
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