RhoG regulates synaptic F-actin density and architecture in human lymphocytes. (A) Representative images demonstrating synaptic F-actin network (gray, upper) in WT and RHOG KO NK-92 cells with or without MLN4924 treatment. Lower panel shows corresponding images from upper panel after convolution. (B) Graph showing percentage of surface (area) within the IS covered by F-actin. (C) Comparison of the F-actin density (brightness) in the IS of WT and RHOG KO NK-92 cells with or without MLN4924 treatment. (D) Representative images demonstrating colocalization of synaptic F-actin meshwork (red) and CG (green) in NK-92 cells. White frames show magnified F-actin neighborhood around individual CG. (E) Graph indicating difference (shown as standard deviation [SD]) of F-actin density around individual CGs. (F) Scheme illustrating the effect of RhoG-deficiency and MLN4924 treatment on the of F-actin density in CG neighborhood. Reconstitution of the F-actin density (brightness) (G) and degranulation capacity (H) in WT and RHOG KO NK-92 cells upon supplementation with constitutively active (Q61L) RAC1 and RHOG constructs. Scale bars, 5 μm. Data on the graphs shown as mean ± SEM. P values were calculated using Student t test. ***P < .001; *****P < .0001.