Endosomal tubulation in spastin-depleted cells requires intact MTs. (a) HeLa cells depleted of spastin by transfection with an siRNA pool were labeled with antibodies to endogenous SNX1 and α-tubulin (MT). In this and subsequent color images, the color of the lettering in the black and white images indicates the color of that image in the corresponding merged image. Arrowheads in the magnified images of the boxed areas indicate an aligned SNX1 tubule and MT. (b–d) Mock-transfected cells or cells depleted of spastin by transfection with an siRNA pool were treated with vehicle (DMSO) or the MT-depolymerizing agent nocodazole (b), the MT stabilizing agent taxol (c), or the actin-depolymerizing agent latrunculin (d), and then, the number of SNX1 tubules per cell was counted (30 cells per condition), and the mean values of three (or four for latrunculin treatment) independent experiments were plotted. Representative immunofluorescence images from these experiments are shown in Fig. S2. KD, knockdown. Bars, 10 µm. Error bars show SEMs.