Activation of nucleus-independent signals triggered by N-methyl-N'-nitro-N- nitrosoguanidine

Abstract

To study the effect of MNNG on inducement of non-targeted mutation and activation of several cellular signal transduction pathways, and to determine whether the activation of these signaling pathways was dependent on the DNA-damage. Vero cells were enucleated by discontinuous density centrifugation. The PKA activities were measured by enzyme-linked immunosorbent assay. The status of cell membrane receptors was studied with immunofluorescent staining and confocal microscopy. In enucleated cytoplasts, MNNG-treatment increased PKA activity for about 2.3-fold in accordance with the 2.7-fold up-regulation of PKA activity in whole vero cells exposed to MNNG. The clustering of cell surface receptors of epidermal growth factor and tumor necrosis factor alpha was also observed in cells exposed to MNNG; this phenomenon was also found in enucleated cells. The results indicate that the initiation of signal cascades induced by low concentration of MNNG might be associated with its interaction with cell surface receptors and/or direct activation of related signal proteins but not its DNA damage.