Gelsolin controls HIV-1 Env-gp120-induced cortical actin reorganization and capping, and the changes in pseudopodia morphology. (A) HIV-1 Env-gp120-induced cortical F-actin redistribution and cell morphologies of siRNA(1 + 2)-GSN-silenced lymphocytes, illustrated in the cartoons shown on the left (from a 1 to a 4). a 1, a series of confocal images showing the distribution of endogenous gelsolin and F-actin in the absence of any Env-gp120 stimulus (control, no capping) and in endogenous gelsolin-silenced cells suppressed using a combination of fluorescent siRNA(1 + 2)-GSN oligos. Scrambled fluorescent oligos were used to control for RNA interference. Cells lacking gelsolin accumulated more cortical actin than control cells. a 2, a series of confocal images shows HIV-1 Env-gp120-induced distribution of endogenous gelsolin and F-actin in control cells. An F-actin capping region was observed in 11% of the 200 cells counted, with a pseudopodium evident in some cases. a 3, a series of confocal images shows HIV-1 Env-gp120-induced formation of a pseudopodium containing the F-actin capping region, associated with gelsolin, in cells transfected with fluorescent scrambled siRNA. An F-actin capping region is visible within the prominent pseudopodium (25% of the 200 cells counted). a 4, a series of confocal images shows aberrant HIV-1 Env-gp120-induced pseudopodium formation and the absence of an F-actin capping region in siRNA(1 + 2)-GSN-silenced lymphocytes. An F-actin belt (asterisk) is visible at the base of the aberrant large pseudopodium, which contains no F-actin in its inner region (27% of the 200 siRNA(1 + 2)-GSN-silenced cells counted, where endogenous gelsolin levels were reduced together with an increase of cortical F-actin levels). This profile was not observed in control cells transfected with scrambled siRNA in any experimental condition. In all panels, scale bar = 5 μm and one representative experiment of three with merged images are shown. Scale bar = 5 μm.