Dynamic activation of H-Ras induced by low power laser irradiation in living cells

Low-power laser irradiation (LPLI) has been shown to promote cell proliferation in various cell types, yet the mechanism of which has not been fully clarified. Studying the signaling pathways involved in the laser irradiation is important for understanding these processes. The Ras/Raf/MEK/ERK (extracellular-signal-regulated kinase) signaling pathway is a network that governs proliferation, differentiation and cell survival. Recent studies suggest that Ras/Raf signaling pathway is involved in the LPLI-induced cell proliferation, but the dynamic activation of Ras in living cells induced by LPLI has not been reported. In present study, to monitor the dynamic activation of H-Ras after LPLI treatment in living cells in real time, Raichu-Ras reporter was utilized, which was constructed based on fluorescence resonance energy transfer (FRET) technique. Our results show that the dynamic activation of H-Ras at the cell edges of the plasma membrane is monitored during cell proliferation induced by LPLI (0.8 J/cm2) in serum-starved COS-7 cells expressing Raichu-Ras reporter using FRET imaging on laser scanning confocal microscope, and that LPLI causes the redistribution of H-Ras from the cytoplasm to plasma membrane. The same results are observed in EGF treated COS-7 cells. Taken together, LPLI induces the COS-7 cells proliferation by activated Ras.