RESUMEN
Deleterious consequences of heterozygous OPA1 mutations responsible for autosomal dominant optic atrophy remain a matter of debate. Primary skin fibroblasts derived from patients have shown diverse mitochondrial alterations that were however difficult to resolve in a unifying scheme. To address the potential use of these cells as disease model, we undertook parallel and quantitative analyses of the diverse reported alterations in four fibroblast lines harboring different OPA1 mutations, nonsense or missense, in the guanosine triphosphatase or the C-terminal coiled-coil domains. We tackled several factors potentially underlying discordant reports and showed that fibroblasts with heterozygous OPA1 mutations present with several mitochondrial alterations. These included defective mitochondrial fusion during pharmacological challenge with the protonophore carbonyl cyanide m-chlorophenyl hydrazone, significant mitochondrial elongation with decreased OPA1 and DRP1 proteins, and abnormal mitochondrial fragmentation during glycolysis shortage or exogenous oxidative stress. Respiratory complex IV activity and subunits steady-state were decreased without alteration of the mitochondrial deoxyribonucleic acid size, amount or transcription. Physical link between OPA1 protein and oxidative phosphorylation was shown by reciprocal immunoprecipitation. Altered cristae structure coexisted with normal response to pro-apoptotic stimuli and expression of Bax or Bcl2 proteins. Skin fibroblasts with heterozygous OPA1 mutations thus share significant mitochondrial remodeling, and may therefore be useful for analyzing disease pathophysiology. Identifying whether the observed alterations are also present in ganglion retinal cells, and which of them underlies their degeneration process remains however an essential goal for therapeutic strategy.
Asunto(s)
Respiración de la Célula/genética , GTP Fosfohidrolasas/genética , Fusión de Membrana/genética , Proteínas Asociadas a Microtúbulos/genética , Mitocondrias/genética , Proteínas Mitocondriales/genética , Fenómenos Fisiológicos de la Piel/genética , Apoptosis/efectos de los fármacos , Apoptosis/genética , Carbonil Cianuro m-Clorofenil Hidrazona/farmacología , Respiración de la Célula/efectos de los fármacos , Respiración de la Célula/fisiología , Células Cultivadas , ADN Mitocondrial/genética , Dinaminas , Complejo IV de Transporte de Electrones/genética , Complejo IV de Transporte de Electrones/metabolismo , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , GTP Fosfohidrolasas/metabolismo , Glucólisis/efectos de los fármacos , Glucólisis/genética , Heterocigoto , Humanos , Fusión de Membrana/efectos de los fármacos , Fusión de Membrana/fisiología , Proteínas Asociadas a Microtúbulos/metabolismo , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , Atrofia Óptica Autosómica Dominante/genética , Atrofia Óptica Autosómica Dominante/metabolismo , Fosforilación Oxidativa/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/genética , Estructura Terciaria de Proteína/efectos de los fármacos , Estructura Terciaria de Proteína/genética , Piel/citología , Piel/efectos de los fármacos , Piel/metabolismo , Fenómenos Fisiológicos de la Piel/efectos de los fármacos , Proteína X Asociada a bcl-2/genética , Proteína X Asociada a bcl-2/metabolismo , Proteína Letal Asociada a bcl/genética , Proteína Letal Asociada a bcl/metabolismoRESUMEN
To facilitate the study of the structure-function relationship of human hemoglobin (Hb A), we have developed a new hemoglobin expression vector, pGEX6P-alpha-[SD]-beta. This vector allows the co-expression of alpha-Hb as a fusion protein with Glutathione S-Transferase (GST-alpha-Hb) and beta-Hb with an additional methionine at the N-terminal extremity (rbeta-Hb). These proteins were solubilized as GST-alpha-Hb/rbeta-Hb complex form and purified in one step by affinity chromatography on immobilized glutathione. The CO binding kinetic studies show that the GST-alpha-Hb/rbeta-Hb complex and recombinant Hb A exhibit the same allosteric behavior as for native Hb A. The GST moiety, which does not modify the function of the complex, can be easily eliminated by cleavage by the PreScission Protease. After cleavage during the rapid purification procedure, over 20mg of recombinant Hb per liter of culture were obtained, more than double the yield of previous co-expression systems. This polycistronic vector system, which offers the additional advantage of a very rapid purification, is especially well suited for the study of abnormal, unstable globins in order to better understand the associated pathology.
Asunto(s)
Clonación Molecular/métodos , Vectores Genéticos , Hemoglobina A/genética , Hemoglobina A/aislamiento & purificación , Monóxido de Carbono/metabolismo , Expresión Génica , Glutatión Transferasa/genética , Glutatión Transferasa/aislamiento & purificación , Glutatión Transferasa/metabolismo , Hemoglobina A/metabolismo , Humanos , Cinética , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/aislamiento & purificación , Proteínas Recombinantes de Fusión/metabolismo , Globinas alfa/genética , Globinas beta/genéticaRESUMEN
DNA repair mechanisms are key components for the maintenance of the essential mitochondrial genome. Among them, base excision repair (BER) processes, dedicated in part to oxidative DNA damage, are individually well known in mitochondria. However, no large view of these systems in differential physiological conditions is available yet. Combining the use of pure mitochondrial fractions and a multiplexed oligonucleotide cleavage assay on a microarray, we demonstrated that a large range of glycosylase activities were present in Drosophila mitochondria. Most of them were quantitatively different from their nuclear counterpart. Moreover, these activities were modified during aging.