RESUMO
Prelamin A accumulation and persistent DNA damage response (DDR) are hallmarks of vascular smooth muscle cell (VSMC) ageing and dysfunction. Although prelamin A is proposed to interfere with DNA repair, our understanding of the crosstalk between prelamin A and the repair process remains limited. The extracellular signal-regulated kinases 1 and 2 (ERK1/2) have emerged as key players in the DDR and are known to enhance ataxia telangiectasia-mutated protein (ATM) activity at DNA lesions, and in this study, we identified a novel relationship between prelamin A accumulation and ERK1/2 nuclear compartmentalisation during VSMC ageing. We show both prelamin A accumulation and increased DNA damage occur concomitantly, before VSMC replicative senescence, and induce the localisation of ERK1/2 to promyelocytic leukaemia protein nuclear bodies (PML NBs) at the sites of DNA damage via nesprin-2 and lamin A interactions. Importantly, VSMCs treated with DNA damaging agents also displayed prelamin A accumulation and ERK compartmentalisation at PML NBs, suggesting that prelamin A and nesprin-2 are novel components of the DDR. In support of this, disruption of ERK compartmentalisation at PML NBs, by either depletion of nesprin-2 or lamins A/C, resulted in the loss of ATM from DNA lesions. However, ATM signalling and DNA repair remained intact after lamins A/C depletion, whereas nesprin-2 disruption ablated downstream Chk2 activation and induced genomic instability. We conclude that lamins A/C and PML act as scaffolds to organise DNA-repair foci and compartmentalise nesprin-2/ERK signalling. However, nesprin-2/ERK signalling fidelity, but not their compartmentalisation at PML NBs, is essential for efficient DDR in VSMCs.
Assuntos
Dano ao DNA , Proteínas dos Microfilamentos/metabolismo , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Músculo Liso Vascular/citologia , Músculo Liso Vascular/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Adulto , Ciclo Celular/fisiologia , Senescência Celular/fisiologia , Reparo do DNA , Feminino , Humanos , Corpos de Inclusão Intranuclear/genética , Corpos de Inclusão Intranuclear/metabolismo , Lamina Tipo A/metabolismo , Masculino , Proteínas dos Microfilamentos/genética , Pessoa de Meia-Idade , Proteína Quinase 1 Ativada por Mitógeno/genética , Proteína Quinase 3 Ativada por Mitógeno/genética , Músculo Liso Vascular/enzimologia , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares/genética , Transfecção , Adulto JovemRESUMO
This report describes sensitive and specific methods for the quantitation of alprazolam and triazolam in hemolysed whole blood and liver tissue. Samples of blood and enzyme-digested liver are extracted without pH adjustment with n-butyl chloride, after addition of deuterated internal standards and urea. The evaporated extracts are reconstituted in acetonitrile for analysis by gas chromatography/mass spectrometry/negative ion chemical ionization (GC/MS/NICI). Fatty extracts may be cleaned up by partitioning between pentane and acetonitrile. Two ion pairs are monitored for each drug. Within-day coefficients of variation in the range 10-50 micrograms/L for blood are approximately 5%. Between-day coefficients of variation are less than 10%. The limit of quantitation (based on analysis of 0.2-mL blood samples) is 0.5 microgram/L for triazolam and 4 micrograms/L for alprazolam.
