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Complement modulates the function of the ubiquitin-proteasome system and endoplasmic reticulum-associated degradation in glomerular epithelial cells.
Kitzler, Thomas M; Papillon, Joan; Guillemette, Julie; Wing, Simon S; Cybulsky, Andrey V.
Afiliação
  • Kitzler TM; Department of Medicine, McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
Biochim Biophys Acta ; 1823(5): 1007-16, 2012 May.
Article em En | MEDLINE | ID: mdl-22426620
In experimental membranous nephropathy, complement C5b-9 induces sublethal glomerular epithelial cell (GEC) injury and proteinuria. C5b-9 also activates mechanisms that restrict injury or facilitate recovery. The ubiquitin-proteasome system (UPS) selectively degrades damaged or abnormal proteins, while misfolded proteins in the endoplasmic reticulum (ER) undergo ER-associated degradation (ERAD). In this study, we investigated the effect of complement on the UPS and ERAD. We monitored UPS function by transfection of rat GECs with a UPS reporter, GFP(u) (CL1 degron fused with green fluorescent protein). By analogy, CD3δ-yellow fluorescent protein (YFP) was employed as a reporter of ERAD. We demonstrated decreased GFP(u) levels in GECs after incubation with antibody and complement, compared with control. Using C8-deficient serum with or without purified C8, cycloheximide (an inhibitor of protein synthesis), and the proteasome inhibitor, MG132, we confirmed that the decrease of GFP(u) was mediated by C5b-9, and subsequent proteasomal degradation of the reporter. Inhibition of the c-Jun N-terminal kinase attenuated the effect of complement on GFP(u) degradation. Complement, however, increased the level of CD3δ-YFP in GECs, implying an impairment of ERAD, likely due to an overabundance of misfolded proteins in the ER. The overall ubiquitination of proteins was enhanced in complement-treated GECs and in glomeruli of rats with experimental membranous nephropathy, although ubiquitin mRNA was unchanged in GECs. Proteasome inhibition with MG132 increased the cytotoxic effect of complement in GECs. Complement-stimulated UPS function, by accelerating removal of damaged proteins, may be a novel mechanism to limit complement-induced injury.
Assuntos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Proteínas do Sistema Complemento / Ubiquitina / Complexo de Endopeptidases do Proteassoma / Células Epiteliais / Degradação Associada com o Retículo Endoplasmático / Glomérulos Renais Tipo de estudo: Risk_factors_studies Limite: Animals Idioma: En Revista: Biochim Biophys Acta Ano de publicação: 2012 Tipo de documento: Article País de afiliação: Canadá

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Proteínas do Sistema Complemento / Ubiquitina / Complexo de Endopeptidases do Proteassoma / Células Epiteliais / Degradação Associada com o Retículo Endoplasmático / Glomérulos Renais Tipo de estudo: Risk_factors_studies Limite: Animals Idioma: En Revista: Biochim Biophys Acta Ano de publicação: 2012 Tipo de documento: Article País de afiliação: Canadá