H‐Ras and PI3K are required for the formation of circular dorsal ruffles induced by low‐power laser irradiation

The formation of circular dorsal ruffles upon growth factor stimulation facilitates the static cells for subsequent motility. Low‐power laser irradiation (LPLI) has been shown to exert some promotive effects on migration and proliferation in various cell types. It is unclear whether LPLI could induce the formation of circular ruffles. In this study, using confocal fluorescence microscope, we for the first time demonstrated that LPLI could induce the production of circular ruffle structures in COS‐7 cells. These structures were proved to be actin‐based and originated from membrane microdomains enriched in cholesterol. Ras was shown to be activated by LPLI and expression of YFP‐H‐Ras (N17), a dominant negative H‐Ras, blocked the generation of circular ruffles induced by LPLI. Wortmannin, PI3K inhibitor, potently suppressed the formation of LPLI‐induced circular ruffles in a dose‐dependent manner. However, blocking the activation of PKC, which was activated during LPLI‐induced cell proliferation in our previous study, had no effect on the formation of circular ruffles. Thus, both H‐Ras and PI3K were required for the formation of circular ruffles induced by LPLI and the generation of circular ruffles provides new information for the mechanisms of biological effects of LPLI. J. Cell. Physiol. 219: 535–543, 2009. © 2009 Wiley‐Liss, Inc.