RGS10 Restricts Upregulation by Chemokines of T Cell Adhesion Mediated by α4β1 and αLβ2 Integrins

Chemokines rapidly and transiently upregulate alpha 4 beta 1 and alpha L beta 2 integrin-mediated adhesion during T lymphocyte extravasation by activating G alpha-dependent inside-out signaling. To limit and terminate G alpha-mediated signaling, cells can use several mechanisms, including the action of regulator of G protein signaling (RGS) proteins, which accelerate the GTPase activity of G alpha subunits. Using human T cells silenced for or overexpressing RGS10, we show in this article that RGS10 functions as an inhibitor of G(alpha 1)-dependent, chemokine-upregulated T cell adhesion mediated by alpha 4 beta 1 and alpha L beta 2. Shear stress-dependent detachment and cell spreading analyses revealed that RGS10 action mainly targets the adhesion strengthening and spreading phases of alpha 4 beta 1-mediated cell attachment. Associated with these observations, chemokine-stimulated Vav1-Rac1 activation was longer sustained and of higher intensity in RGS10-silenced T cells, or inhibited in cells overexpressing RGS10. Of importance, expression of constitutively activated Rac1 forms in cells overexpressing RGS10 led to the rescue of CXCL12-stimulated adhesion to VCAM-1 to levels similar to those in control transfectants. Instead, adhesion under flow conditions, soluble binding experiment, flow cytometry, and biochemical analyses revealed that the earlier chemokine-triggered integrin activation step was mostly independent of RGS10 actions. The data strongly suggest that RGS10 opposes activation by chemokines of the Vav1-Rac1 pathway in T cells, leading to repression of adhesion strengthening mediated by alpha 4 beta 1. In addition to control chemokine-upregulated T cell attachment, RGS10 also limited adhesion-independent cell chemotaxis and activation of cdc42. These results identify RGS10 as a key molecule that contributes to the termination of G alpha-dependent signaling during chemokine-activated alpha 4 beta 1- and alpha L beta 2-dependent T cell adhesion. The Journal of Immunology, 2011, 187: 1264-1272.