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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. Investigating the signaling pathways involved in the laser irradiation is
important for understanding these processes. The small G protein Ras works as a binary switch in many important
intracellular signaling pathways and, therefore, has been one of the focal targets of signal-transduction investigations and
drug development. 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. On the other hand, Protein kinase Cs (PKCs), the Ca2+ activated,
phospholipid-dependent serine/threonine protein kinases, have been recently presumed to be involved in the regulation
of cell proliferation induced by LPLI. In this report, to monitor the direct activations of Ras and PKCs after LPLI
treatment in living cells in real time, Raichu-Ras reporter and C kinase activity reporter (CKAR) were utilized, both of
which were constructed based on fluorescence resonance energy transfer (FRET) technique. The direct activation of Ras
is predominantly initiated from the different microdomains of the plasma membrane. The results are 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. Furthermore, the increasing activation of PKCs is also monitored during
cell proliferation induced by LPLI (0.8 J/cm2) in serum-starved human lung adenocarcinoma cells (ASTC-a-1)
expressing CKAR reporter using the similar way. Taken together, the dynamic increases of H-Ras and PKCs activities
are observed during the processes of cell proliferation induced by LPLI.
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