Abstract
UVB irradiation is well-known to induce apoptotic cell death. However, we have found that low dose of UVB irradiation prevented apoptosis induced by both serum-depletion and detachement from the extracellular matrix. In this study, we examined the participation of PI3-kinase/Akt pathway in UVB-induced antiapoptosis. Treatment with PI3/kinase inhibitors, wortmannin and LY294002 partly eliminated the UVB-mediated inhibition of apoptosis. Furthermore, phosphorylation of Akt was observed 15min after UVB irradiation. These results suggested that UVB irradiation transduced a survival signal via PI3-kinase activation and phosphorylation of Akt. Three major isoforms of Akt, termed Akt1, Akt2 and Akt3, have been found in mammalian cells, which share a high degree of structural similarity. Experiments with isoform-specific short interference RNA (siRNA) revealed that Akt1, and Akt2 knockdown eliminated the UVB-mediated inhibition of apoptosis. At present, we are trying to confirm the participation of Akt3 in UVB-induced antiapoptosis using siRNA for Akt 3. Among the three Akt isoforms, Akt1 is the predominantly expressed isoform in most tissues. We consider that further analysis of mechanism of antiapoptosis induced by UVB using siRNA for Akt1.
