RhoG controls F-actin through modulation of Rac1 activity. (A) Graphs comparing F-actin intensity (phalloidin staining) in WT and RhoG-deficient NK-92 (left) and patient-derived T cells (right). (B) Histogram showing activation of Rac1, RhoA, and Cdc42 in WT and RHOG KO NK-92 cells upon stimulation. Activation of GTPases was measured using G-LISA assay (Cytoskeleton, Inc). (C) Histogram comparing activation of Rac1, RhoA, and Cdc42 in WT and RHOG KO NK-92 cells upon treatment with MLN4924. (D) Scheme demonstrating the mechanism of action for the top hit MLN4924 identified in pharmacological screening experiment. (E) Graph showing F-actin intensity in WT and RhoG-deficient NK-92 cells without, and after 16 hours of treatment with MLN4924. (F) Histogram demonstrating the effect of Rac1, RhoA, and Cdc42 inhibitors on degranulation in MLN4924-treated RHOG KO NK-92 cells. ICAM, human recombinant ICAM-1 Fc chimera; PLL, poly-L lysine. Data shown as mean ± SEM. P values were calculated using a multiple Student t test. **P < .01; *****P < .0001.