Abstract
Radioadaptive response is a biological defense mechanism that is induced by low-dose ionizing irradiation for cellular resistance to the genotoxic effects of subsequent irradiation. We also showed that the pre-treatment with low concentration of TPA or hydrogen peroxide mimics the pre-irradiation with low dose of X-rays. We have suggested that the radioadaptive response is mediated through the pathways involving protein kinase C (PKC) and p38 mitogen-activated protein kinase. Especially, we found that one isoform of PKC, PKC alpha, is activated by irradiation with 2 cGy X-rays, suggesting that PKC alpha is playing an important role in the induction of radioadaptive response. However, the molecular role of PKC is still largely elusive. Here, we examined the involvement of PKC alpha in radioadaptive response by the use of RNAi for PKC alpha. We introduced three kinds of siRNA into m5S cells, each of which targets defferent site of the mouse PKC alpha gene, Prkca. One of them greatly reduced the amount of Prkca mRNA, indicating that RNAi is effective for suppressing the expression of the Prkca gene. We examined the radioadaptive response in the m5S cells in which the Prkca mRNA was reduced. The radioadaptive response was suppressed in the cells with low amount of the Prkca mRNA. This results indicate that PKC alpha is one of the critical factor in the signal transduction pathway of the radioadaptive response.
