RESUMEN
The investigational anticancer agent 7-hydroxystaurosporine (UCN-01) abrogates the G2 checkpoint in tumor cells and sensitizes them to the lethal effects of genotoxic anticancer agents. On the basis of the role of the Cdc25C phosphatase in maintenance of this damage-inducible checkpoint, we hypothesized that UCN-01 inhibits a component of the signal transduction pathway that modulates Cdc25C phosphorylation. Of the three kinases known to phosphorylate Cdc25C on Ser216, both checkpoint kinase 1 (hChk1) and Cdc25C-associated protein kinase 1 (cTAK1) were potently inhibited by UCN-01 with IC50s of 11 and 27 nM, respectively. Treatment of K562 erythroblastoid leukemia cells with similar drug concentrations resulted in decreased levels of Ser216 phosphorylation of Cdc25C and complete disruption of the y-radiation-induced G2 checkpoint. In contrast to hChk1, the hChk2 kinase was 100-fold more resistant to inhibition by UCN-01 (IC50, 1040 nM). These results suggest that disruption of the DNA damage-induced G2 checkpoint by UCN-01 is mediated through the inhibition of the Cdc25C kinases, hChk1 and cTAK1, and that hChk2 activity is not sufficient to enforce the G2 checkpoint in cells treated with a pharmacological inhibitor of hChk1.
Asunto(s)
Alcaloides/farmacología , Proteínas de Ciclo Celular/metabolismo , Fase G2/efectos de los fármacos , Inhibidores de Proteínas Quinasas , Fármacos Sensibilizantes a Radiaciones/farmacología , Fosfatasas cdc25/metabolismo , Antineoplásicos/farmacología , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1) , Quinasa de Punto de Control 2 , Daño del ADN/efectos de los fármacos , Daño del ADN/genética , Daño del ADN/efectos de la radiación , Fase G2/efectos de la radiación , Humanos , Concentración 50 Inhibidora , Células K562 , Modelos Biológicos , Fosforilación/efectos de los fármacos , Fosfoserina/metabolismo , Proteínas Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal/efectos de los fármacos , Estaurosporina/análogos & derivadosRESUMEN
Dunnigan-type partial lipodystrophy (familial partial lipodystrophy, Dunnigan variety, FPLD2) can be caused by LMNA mutations. We identified a novel heterozygous LMNA mutation, P485R, in a patient referred to the International Registry of Werner Syndrome because of features consistent with that of progeroid disorder but who was wild type at the WRN locus. The novel mutation is located 2 amino acids away from the canonical FPLD mutations in exon 8 of the LMNA gene. Immunocytochemical analysis revealed abnormal nuclear morphology characteristic of laminopathies within primary fibroblast cultures, but not in a lymphoblastoid cell line, in keeping with previous observations. Our findings indicate that FPLD2 should be considered in the differential diagnosis of the Werner syndrome.