Lock-hTf–endosomes interacting with mitochondria have increased speeds. (A) Percent frequency distribution of overall instantaneous speeds (during kiss and run phases combined) of interacting hTf-endosomes versus lock-hTf–endosomes indicates that lock-hTf–endosomes have higher motility. (B) The mean instantaneous speed of lock-hTf–endosomes was significantly higher than that of hTf-endosomes. (C) Percent frequency distribution of endosomal track speeds (total length of track divided by time taken to form the track) of interacting hTf-endosomes versus lock-hTf–endosomes also indicate higher speeds for the lock-hTf–endosomes. (D) The mean track speed of the lock-hTf–endosomes was significantly higher than that of the hTf-endosomes. (E and F) The percent frequency distribution of track lengths for hTf- and lock-hTf–endosomes was similar (E), and the difference between their mean track lengths (F) was not statistically significant. (G and H) The percent frequency distribution of track displacement lengths (the shortest linear distance between the starting and ending point of a track) for hTf- and lock-hTf–endosomes was also similar (G), and the difference between their mean values (H) was not statistically significant. Error bars: 95% confidence interval; **, P < 0.001, Student’s t test. (I) Interacting hTf-endosomal tracks magnified (ROIs 1 and 2) from a representative time lapse. (J) Interacting lock-hTf–endosomal tracks magnified (ROIs 1 and 2) from a representative time lapse. Bars, 10 µm.