title: Mitochondrial chaperone Trap1 and the calcium binding protein Sorcin interact and protect cells against apoptosis induced by antiblastic agents.
abstract: TRAP1, a mitochondrial chaperone (Hsp75) with antioxidant and antiapoptotic functions, is involved in multidrug resistance in human colorectal carcinoma cells. Through a proteomic analysis of TRAP1 coimmunoprecipitation complexes, the Ca(2+)-binding protein Sorcin was identified as a new TRAP1 interactor. This result prompted us to investigate the presence and role of Sorcin in mitochondria from human colon carcinoma cells. Using fluorescence microscopy and Western blot analysis of purified mitochondria and submitochondrial fractions, we showed the mitochondrial localization of an isoform of Sorcin with an electrophoretic motility lower than 20 kDa that specifically interacts with TRAP1. Furthermore, the effects of overexpressing or downregulating Sorcin and/or TRAP1 allowed us to demonstrate a reciprocal regulation between these two proteins and to show that their interaction is required for Sorcin mitochondrial localization and TRAP1 stability. Indeed, the depletion of TRAP1 by short hairpin RNA in colorectal carcinoma cells lowered Sorcin levels in mitochondria, whereas the depletion of Sorcin by small interfering RNA increased TRAP1 degradation. We also report several lines of evidence suggesting that intramitochondrial Sorcin plays a role in TRAP1 cytoprotection. Finally, preliminary evidence that TRAP1 and Sorcin are both implicated in multidrug resistance and are coupregulated in human colorectal carcinomas is provided. These novel findings highlight a new role for Sorcin, suggesting that some of its previously reported cytoprotective functions may be explained by involvement in mitochondrial metabolism through the TRAP1 pathway.
authors.affiliation: Clinical Oncology Unit, Department of Medical Sciences, University of Foggia, Foggia, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Landriscina
authors.forename: Gabriella
authors.initials: G
authors.lastname: Laudiero
authors.forename: Francesca
authors.initials: F
authors.lastname: Maddalena
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Amoroso
authors.forename: Annamaria
authors.initials: A
authors.lastname: Piscazzi
authors.forename: Flora
authors.initials: F
authors.lastname: Cozzolino
authors.forename: Maria
authors.initials: M
authors.lastname: Monti
authors.forename: Corrado
authors.initials: C
authors.lastname: Garbi
authors.forename: Alberto
authors.initials: A
authors.lastname: Fersini
authors.forename: Piero
authors.initials: P
authors.lastname: Pucci
authors.forename: Franca
authors.initials: F
authors.lastname: Esposito
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001859:Bone Neoplasms / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D045325:HCT116 Cells; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
chemical_list: D002135:Calcium-Binding Proteins; D018841:HSP90 Heat-Shock Proteins; C503113:SRI protein, human; C092306:TRAP1 protein, human; D002118:Calcium