RESUMEN
Two major tenascin-C (TN-C) isoforms are generated by the alternative splicing of the pre-mRNA. The large isoform contains seven extra type three repeats that, by contrast, are omitted in the small TN-C isoform. The large TN-C isoform is mainly expressed at the onset of cellular processes that entail active cell migration, proliferation, or tissue remodeling such as occur in neoplasia, wound healing, and during development. Thus, the large TN-C isoform seems to be a specific component of the provisional extracellular matrix. Here we have studied the degradation of the large and small TN-C isoforms by matrix metalloproteinases (MMPs) 2, 3, 7, and 9. Among these proteolytic enzymes only MMP-7 can degrade the small TN-C isoform removing the NH2-terminal knob. The large TN-C isoform shows the same MMP-7-sensitive site adjacent to the NH2-terminal sequence, but is further degraded in the splicing area where three fibronectin-like type III repeats are completely digested. Moreover, the large TN-C isoform is degraded by MMP-2 and MMP-3 which completely digest a single type III repeat inside the splicing area. By contrast, the large TN-C isoform is resistant to MMP-9 digestion. The results show that the presence of the spliced sequence introduces new protease-sensitive sites in the large TN-C isoform.
Asunto(s)
Moléculas de Adhesión Celular Neuronal/metabolismo , Proteínas de la Matriz Extracelular/metabolismo , Matriz Extracelular/enzimología , Metaloendopeptidasas/metabolismo , Animales , Línea Celular , Cricetinae , Humanos , Hidrólisis , Isomerismo , TenascinaRESUMEN
We have obtained and characterized 11 monoclonal antibodies (mAbs) specific for different domains of human tenascin (TN). Five of these mAbs reacted with epitopes contained in the TN area that undergoes alternative splicing and are thus able to recognize specific TN isoforms. These mAbs are a useful tool to study the expression and distribution of TN and its different isoforms in normal and pathological tissues.
Asunto(s)
Anticuerpos Monoclonales/biosíntesis , Especificidad de Anticuerpos , Moléculas de Adhesión Celular Neuronal/inmunología , Epítopos/inmunología , Proteínas de la Matriz Extracelular/inmunología , Anticuerpos Monoclonales/inmunología , Moléculas de Adhesión Celular Neuronal/metabolismo , Línea Celular , ADN Complementario , Matriz Extracelular/metabolismo , Proteínas de la Matriz Extracelular/metabolismo , Fibroblastos/inmunología , Fibroblastos/metabolismo , Humanos , Inmunohistoquímica , Melanoma/inmunología , Melanoma/metabolismo , Tenascina , Células Tumorales CultivadasRESUMEN
Previous studies indicate that single stranded DNA vectors could be used in different organisms to study mutagenesis induced by DNA damaging agents. We applied this approach to study mutagenesis induced by 4NQO lesions. The use of ssDNA, on which the ultimate metabolite of 4NQO (Ac-4HAQO) induces mainly C8-guanine adducts, allowed us to find a correlation between G-transversions and the dGuo-C8-AQO adduct. This correlation was established in two independent assay-systems, based on prokaryotic and eukaryotic cells.
Asunto(s)
4-Nitroquinolina-1-Óxido/toxicidad , Daño del ADN , ADN de Cadena Simple/genética , Células Eucariotas/efectos de los fármacos , Vectores Genéticos , Células Procariotas/efectos de los fármacos , Animales , Línea Celular , Chlorocebus aethiops , Escherichia coli , MutagénesisRESUMEN
Ten children affected by HBV chronic hepatitis, not responding to a previous treatment with interferon (IFN), have been treated with a reiterated IFN therapy. The response obtained is not encouraging and only one patient became negative for HBeAg and HBV-DNA.
Asunto(s)
Hepatitis B/terapia , Hepatitis Crónica/terapia , Interferón-alfa/uso terapéutico , Niño , Preescolar , ADN Viral/sangre , Femenino , Humanos , Lactante , Masculino , Transaminasas/sangreRESUMEN
In this preliminary study, children with chronic HBV hepatitis, as was also previously shown for adults, respond to interferon therapy in an HLA class I antigen dependent manner. If this can be confirmed on a large scale, HLA typing may serve as a useful indication of interferon-therapy responders.