title: Transglutaminase 2 interaction with small heat shock proteins mediate cell survival upon excitotoxic stress.
abstract: Transglutaminase 2 has been postulated to be involved in the pathogenesis of central nervous system neurodegenerative disorders. However, its role in neuronal cell death remains to be elucidated. Excitotoxicity is a common event underlying neurodegeneration. We aimed to evaluate the protein targets for transglutaminase 2 in cell response to NMDA-induced excitotoxic stress, using SH-SY5Y neuroblastoma cells which express high tranglutaminase 2 levels upon retinoic acid-driven differentiation toward neurons. NMDA-evoked calcium increase led to transglutaminase 2 activation that mediated cell survival, as at first suggested by the exacerbation of NMDA toxicity in the presence of R283, a synthetic competitive inhibitor of transglutaminase active site. Assays of R283-mediated transglutaminase inhibition showed the involvement of enzyme activity in NMDA-induced reduction in protein basal levels of pro-apoptotic caspase-3 and the stress protein Hsp20. However, this occurred in a way different from protein cross-linking, given that macromolecular assemblies were not observed in our experimental conditions for both proteins. Co-immunoprecipitation experiments provided evidence for the interaction, in basal conditions, between transglutaminase 2 and Hsp20, as well as between Hsp20 and Hsp27, a major anti-apoptotic protein promoting caspase-3 inactivation and degradation. NMDA treatment disrupted both these interactions that were restored upon transglutaminase 2 inhibition with R283. These results suggest that transglutaminase 2 might be protective against NMDA-evoked excitotoxic insult in neuronal-like SH-SY5Y cells in a way, independent from transamidation that likely involves its interaction with the complex Hsp20/Hsp27 playing a pro-survival role.
authors.affiliation: Department of Biochemical, Physiological and Nutritional Sciences, University of Messina, Via C. Valeria, Policlinico Universitario, 98125 Messina, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Caccamo
authors.forename: Salvatore
authors.initials: S
authors.lastname: Condello
authors.forename: Nadia
authors.initials: N
authors.lastname: Ferlazzo
authors.forename: Monica
authors.initials: M
authors.lastname: Currò
authors.forename: Martin
authors.initials: M
authors.lastname: Griffin
authors.forename: Riccardo
authors.initials: R
authors.lastname: Ientile
mesh_terms: D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D004789:Enzyme Activation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D019204:GTP-Binding Proteins; D050886:HSP20 Heat-Shock Proteins / Q000378:metabolism*; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins; D006801:Humans; D018832:Molecular Chaperones; D016202:N-Methylaspartate / Q000494:pharmacology* / Q000502:physiology; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D060066:Protein Interaction Maps; D059748:Proteolysis; D013312:Stress, Physiological; D011503:Transglutaminases / Q000378:metabolism* / Q000502:physiology
chemical_list: D018690:Excitatory Amino Acid Agonists; D050886:HSP20 Heat-Shock Proteins; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; C494382:HSPB6 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D016202:N-Methylaspartate; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; C505407:CASP3 protein, human; D053148:Caspase 3; D019204:GTP-Binding Proteins; D002118:Calcium