FIGURE 4:

Comparison of GPCR-driven vs. Cdc42-driven migration. Optically stimulated migration of RAW cells through either localized photoactivation of GPCR signaling using blue opsin-mCherry or direct activation of Cdc42 using ITSN-tgRFPt-SspB together with iLID-CaaX. Both are capable of generating directional migration, but cells are more elongated along the direction of migration upon GPCR stimulation relative to Cdc42 activation. We found previously that asymmetric optical activation is best achieved when the optical input is positioned slightly outside of the cell using the laser power reported here (Karunarathne et al., 2013b). Here we found that asymmetric activation of the iLID construct, on the other hand, was optimized by positioning the optical input at the edge of the cell. This difference likely reflects different sensitivities of the chromophores present in opsins and LOV domains. See also Supplemental Movie S2.