Drp1-x01 promotes MT stability. (A and B) HeLa cells expressing GFP (vector), GFP-Drp-111, or GFP-Drp--101 were immunofluorescently labeled for tyrosinated (tyrosin., dynamic, red) and acetylated (acetyl., stable, green) α-tubulin (α-tub.) and imaged by epifluorescence microscopy with constant camera settings. (A) Representative overlays of red and green channels. Drp1-101 increases MT stability quantified as the ratio of acetylated to tyrosinated α-tubulin signals integrated over the entire cell (B; means ± SEM [up]/SD [down] of 170–178 cells). (C and D) HeLa cells transfected, labeled, and imaged as in A and B were subjected to MT morphometry, quantifying MT bundling as an increase in the area/perimeter ratio of the autosegmented MT network. Representative epifluorescence images (C) and bar graph (D; means ± SEM [up]/SD [down] of 150–199 cells) show that Drp1-x01 induces bundling of MTs. (E–G) HeLa cells coexpressing EYFP-α-tubulin and mCherry-Drp1-111, mCherry-Drp1-101, or mCherry (vector) alone were analyzed for recovery of EYFP-α-tubulin after photobleaching; vector-transfected cells were also treated with taxol (10 µM, 3 h). Frames of representative time series are shown in E, whereas recovery curves and 50% recovery time (t_1/2) derived from biexponential fits of the recovery curves are plotted in F and G (means ± SEM [up]/SD [down] of 7–20 cells). Ø, P < 0.01; ⊗, P < 10⁻⁶; *, P < 10⁻⁹.