The Rho family GEF Asef2 regulates adhesion dynamics and therefore cell migration by modulating Rac and Rho activity

Abstract

BIOLOGICAL SCIENCES

THE RHO FAMILY GEF ASEF2 REGULATES ADHESION DYNAMICS AND THEREFORE CELL MIGRATION BY MODULATING RAC AND RHO ACTIVITY

JEANNE MALLOY BRISTOW

Dissertation under the direction of Assistant Professor Donna J. Webb The Rho family of small GTPases, including Rac, Cdc42, and Rho, are key regulators of cell migration and its underlying processes. By modulating the actin cytoskeleton, these GTPases control cell polarization, leading edge protrusion, and cell-matrix adhesion turnover. GTPases act as molecular switches whose activity is tightly regulated by their bound guanine nucleotide state. Guanine nucleotide exchange factors (GEFs) tightly regulate GTPase activity by facilitating the exchange of bound GDP for GTP. Asef2 is a recently identified Rho family GEF that has been shown to activate Rac and Cdc42. However, its function as a regulator of cell migration and adhesion dynamics is poorly understood. Immunofluorescence microscopy revealed that Asef2 localizes with actin and Akt at the leading edge of migrating HT-1080 human fibrosarcoma cells. Our data indicate Asef2 activates Cdc42 and Rac and indirectly inhibits Rho through a Rac-mediated pathway. We have shown that Asef2 promotes migration and rapid adhesion turnover in a Rac-dependent manner. Further, Asef2-mediated random migration and adhesion turnover effects are dependent on a previously unknown mechanism requiring Asef2-mediated Rac, PI3K, and Akt activation leading to Rho inhibition. Together, these data indicate a role for Asef2 as an important regulator of cell migration and adhesion dynamics as it coordinately regulates the activity of Rho family GTPases.