RESUMEN
Mutations of mitochondrial (mt)DNA cause a variety of human diseases and are implicated in premature aging syndromes. Here we investigated a single nucleotide exchange (leucine to methionine) at position nt4738 in the mitochondrial NADH dehydrogenase subunit 2 (Nd2) gene of the respiratory chain. Primary fibroblasts derived from the conplastic mouse strain C57BL/6J-mtALR/LTJ with mutant enzyme, possessed high enzyme activity and ATP production and low ROS production. Furthermore, Nd2-mutant fibroblasts expressed lower senescence markers. Transcriptome analysis revealed that the members of the p38MAPK pathway were significantly downregulated in Nd2-mutant mice. In agreement, inhibition of p38MAPK with SB203580 enhanced proliferation and reduced cytokine secretion in fibroblasts. In Nd2-mutant mouse skin, the amount of Ki67-positive cells was significantly higher than in control skin. The higher amount of Ki67-positive cells and the thicker epidermis in Nd2-mutant mice strongly supported the in vitro data. In conclusion, Nd2 is a mitochondrial gene, involved in age-related signaling pathways.
Asunto(s)
Senescencia Celular/genética , Epidermis/ultraestructura , Fibroblastos/enzimología , Sistema de Señalización de MAP Quinasas/genética , Mutación Missense , NADH Deshidrogenasa/genética , Mutación Puntual , Sustitución de Aminoácidos , Animales , División Celular , Células Cultivadas , ADN Mitocondrial/genética , Regulación hacia Abajo , Doxorrubicina/farmacología , Transporte de Electrón/genética , Femenino , Fibroblastos/citología , Fibroblastos/metabolismo , Imidazoles/farmacología , Antígeno Ki-67/análisis , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BL , Mitocondrias/fisiología , NADH Deshidrogenasa/fisiología , Fosforilación Oxidativa , Estrés Oxidativo/genética , Inhibidores de Proteínas Quinasas/farmacología , Piridinas/farmacología , TranscriptomaRESUMEN
The present study identified miR-638 as one of the most significantly overexpressed miRNAs in metastatic lesions of melanomas compared with primary melanomas. miR-638 enhanced the tumorigenic properties of melanoma cells in vitro and lung colonization in vivo. mRNA expression profiling identified new candidate genes including TP53INP2 as miR-638 targets, the majority of which are involved in p53 signalling. Overexpression of TP53INP2 severely attenuated proliferative and invasive capacity of melanoma cells which was reversed by miR-638. Depletion of miR-638 stimulated expression of p53 and p53 downstream target genes and induced apoptosis and autophagy. miR-638 promoter analysis identified the miR-638 target transcription factor associated protein 2α (TFAP2A/AP-2α) as a direct negative regulator of miR-638, suggestive for a double-negative regulatory feedback loop. Taken together, miR-638 supports melanoma progression and suppresses p53-mediated apoptosis pathways, autophagy and expression of the transcriptional repressor TFAP2A/AP-2α.