Acute inhibition of Dyn2 reversibly disrupts autophagic lysosomal reformation (ALR) and lysosomal tubule scission. (A–D) Still frames from time-lapse movies of Hep3B cells expressing LAMP1-mCherry. Cells were starved for 2 h in HBSS and subsequently treated for 30 min with either DMSO (A and B) or 40 µM Dynasore (C and D), which induced extensive tubulation of LAMP1-positive compartments. Bars (A–D): 20 µM; (A′–B′) 2 µM; (C′–D′) 10 µM. (E–G) To demonstrate the reversibility of this tubulation, Dynasore-treated cells were washed extensively with drug-free media containing 10% FBS and monitored by time-lapse microscopy for 45 min. Frequently, after drug washout, LAMP1-positive tubules exhibited noticeable varicosities (E and F, arrows; bars, 10 µM) along their length. These sites are suggestive of areas of scission and resumed budding of nascent protolysosomes from the reformation tubules (G; bars, 10 µM). (H) Tubules from cells undergoing drug washout were quantified by tracing their lengths at the beginning and end of these movies. Still frames from a representative movie show tubule content at t = 10 and 45 min after drug washout. Bars, 20 µM. (I) Analysis of five independent movies showed an average decrease in total tubulation of ∼50% after drug washout. Data represent the average relative change in total tubule length between the first and last frames of the time-lapse movies. Error bars represent SE; *, P < 0.05.