MT depolymerization is not required for GEF-H1 relocalization in response to shear stress. (A) HL-60s were incubated for 30 min with 10 µM Taxol and plated on ICAM-coated surfaces. Cells were allowed to settle for 5 min and left in shear-free conditions or exposed to 2 dynes of shear stress. Samples were fixed after 20 s and stained with the indicated antibodies. Arrow indicates direction of shear. Bar, 5 µm. (B) Localization of GEF-H1 in uropods was determined based on colocalization with flotillin-2. 30 random spread cells were scored per experiment. The means ± SEM of the percentage of cells with uropod associated GEF-H1 were determined from at least three independent experiments.