RESUMO
Members of the inhibitor of apoptosis protein (IAP) family have demonstrated functions in cell death, cell signalling, cell migration and mitosis. Several of them are E3 enzymes in the ubiquitination of proteins that leads to their degradation by the proteosomal machinery. We previously reported that one of them, cellular inhibitor of apoptosis protein-1 (c-IAP1), migrated from the nucleus to the surface of the Golgi apparatus in cells undergoing differentiation. Here, we show that c-IAP1 is a client protein of the stress protein HSP90 beta. In three distinct cellular models, the two proteins interact and migrate from the nucleus to the cytoplasm along the differentiation process through a leptomycin B-sensitive pathway. Inhibition of HSP90 proteins by small chemical molecules and specific depletion of HSP90 beta isoform by siRNA both lead to auto-ubiquitination of c-IAP1 and its degradation by the proteasome machinery. This chaperone function of HSP90 towards c-IAP1 is specific of its beta isoform as specific depletion of HSP90alpha does not affect c-IAP1 content. Chemical inhibition of HSP90 or siRNA-mediated depletion of HSP90 beta both inhibit cell differentiation, which can be reproduced by siRNA-mediated depletion of c-IAP1. Altogether, these results suggest that HSP90 beta prevents auto-ubiquitination and degradation of its client protein c-IAP1, whose depletion would be sufficient to inhibit cell differentiation.
Assuntos
Diferenciação Celular/fisiologia , Proteínas de Choque Térmico HSP90/metabolismo , Proteínas Inibidoras de Apoptose/metabolismo , Isoformas de Proteínas/metabolismo , Animais , Linhagem Celular Tumoral , Núcleo Celular/metabolismo , Células Epiteliais/citologia , Células Epiteliais/fisiologia , Proteínas de Choque Térmico HSP90/genética , Humanos , Proteínas Inibidoras de Apoptose/genética , Macrófagos/citologia , Macrófagos/fisiologia , Isoformas de Proteínas/genética , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismoAssuntos
Caspases/metabolismo , Precursores Enzimáticos/metabolismo , Proteínas de Neoplasias/metabolismo , Transporte Proteico/efeitos dos fármacos , Frações Subcelulares/enzimologia , Acetato de Tetradecanoilforbol/farmacologia , Células U937/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Núcleo Celular/enzimologia , Citosol/enzimologia , Humanos , Microssomos/enzimologia , Mitocôndrias/enzimologia , Células U937/citologia , Células U937/enzimologiaRESUMO
Members of the inhibitor of apoptosis protein (IAP) family have demonstrated functions in cell death, cell signalling, cell migration and mitosis. Several of them are E3 enzymes in the ubiquitination of proteins that leads to their degradation by the proteosomal machinery. We previously reported that one of them, cellular inhibitor of apoptosis protein-1 (c-IAP1), migrated from the nucleus to the surface of the Golgi apparatus in cells undergoing differentiation. Here, we show that c-IAP1 is a client protein of the stress protein HSP90ß. In three distinct cellular models, the two proteins interact and migrate from the nucleus to the cytoplasm along the differentiation process through a leptomycin B-sensitive pathway. Inhibition of HSP90 proteins by small chemical molecules and specific depletion of HSP90ß isoform by siRNA both lead to auto-ubiquitination of c-IAP1 and its degradation by the proteasome machinery. This chaperone function of HSP90 towards c-IAP1 is specific of its ß isoform as specific depletion of HSP90α does not affect c-IAP1 content. Chemical inhibition of HSP90 or siRNA-mediated depletion of HSP90ß both inhibit cell differentiation, which can be reproduced by siRNA-mediated depletion of c-IAP1. Altogether, these results suggest that HSP90ß prevents auto-ubiquitination and degradation of its client protein c-IAP1, whose depletion would be sufficient to inhibit cell differentiation.Cell Death and Differentiation advance online publication, 1 February 2008; doi:10.1038/sj.cdd.4402320.