Cells lay their own tracks: optogenetic Cdc42 activation stimulates fibronectin deposition supporting directed migration.
Abstract:
Rho GTPase family members are known regulators of directed migration and therefore play key roles in processes including development, immune response and cancer metastasis. However, their individual contributions to these processes are complex. Here, we regulate the activity of two family members, Rac and Cdc42, by optogenetically recruiting specific GEF DH/PH domains to defined regions on the cell membrane. We find that the localized activation of both GTPases produce lamellipodia in cells plated on a fibronectin substrate. Using a novel optotaxis assay, we show that biased activation can drive directional migration. Interestingly, in the absence of exogenous fibronectin, Rac activation is insufficient to produce stable lamellipodia or directional migration while Cdc42 activation is sufficient. We find that a remarkably small amount of fibronectin (<10 puncta per protrusion) is necessary to support stable GTPase-driven lamellipodia. Cdc42 bypasses the need for exogenous fibronectin by stimulating cellular fibronectin deposition under the newly formed lamellipodia.
