RESUMEN
The role of phospholipids in normal assembly and organization of the membrane proteins has been well documented. Cardiolipin, a unique tetra-acyl phospholipid localized in the inner mitochondrial membrane, is implicated in the stability of many inner-membrane protein complexes. Loss of cardiolipin content, alterations in its acyl chain composition and/or cardiolipin peroxidation have been associated with dysfunction in multiple tissues in a variety of pathological conditions. The aim of this study was to analyze the phospholipid composition of the mitochondrial membrane in the four most frequent mutations in the ATP6 gene: L156R, L217R, L156P and L217P but, more importantly, to investigate the possible changes in the cardiolipin profile. Mitochondrial membranes from fibroblasts with mutations at codon 217 of the ATP6 gene, showed a different cardiolipin content compared to controls. Conversely, results similar to controls were obtained for mutations at codon 156. These findings may be attributed to differences in the biosynthesis and remodeling of cardiolipin at the level of the inner mitochondrial transmembrane related to some mutations of the ATP6 gene.
Asunto(s)
Cardiolipinas/metabolismo , Fibroblastos/metabolismo , Mitocondrias/metabolismo , ATPasas de Translocación de Protón Mitocondriales/metabolismo , Mutación Missense , Piel/metabolismo , Sustitución de Aminoácidos , Cardiolipinas/genética , Células Cultivadas , Niño , Preescolar , Femenino , Humanos , Peroxidación de Lípido/genética , Masculino , Mitocondrias/genética , Membranas Mitocondriales/metabolismo , ATPasas de Translocación de Protón Mitocondriales/genéticaRESUMEN
The smallest rotary motor of living cells, F0F1-ATP synthase, couples proton flow-generated by the OXPHOS system-from the intermembrane space back to the matrix with the conversion of ADP to ATP. While all mutations affecting the multisubunit complexes of the OXPHOS system probably impact on the cell's output of ATP, only mutations in complex V can be considered to affect this output directly. So far, most of the F0F1-ATP synthase variations have been detected in the mitochondrial ATPase6 gene. In this study, the four most frequent mutations in the ATPase6 gene, namely L156R, L217R, L156P, and L217P, are studied for the first time together, both in primary cells and in cybrid clones. Arginine ("R") mutations were associated with a much more severe phenotype than Proline ("P") mutations, in terms of both biochemical activity and growth capacity. Also, a threshold effect in both "R" mutations appeared at 50% mutation load. Different mechanisms seemed to emerge for the two "R" mutations: the F1 seemed loosely bound to the membrane in the L156R mutant, whereas the L217R mutant induced low activity of complex V, possibly the result of a reduced rate of proton flow through the A6 channel.