Maturation kinetics of phagosomes depends on their transport switching from actin to microtubule tracks

Phagosomes, where internalized pathogens are ingested, mature into a degradative unit through a sequence of dynamical and biochemical changes. The maturation process requires the active transport of phagosomes on actin and microtubules, but how phagosome maturation is kinetically dependent on their actin- and microtubule-mediated transport is poorly characterized. Here, we focused on the early-to-late phagosome maturation and investigated how the kinetic rate of this early maturation process depends on the timing of phagosome transition from actin to microtubules. We performed single-phagosome tracking of their sequential maturation activities, including recruitment of phagosome markers and acidification. Simultaneously, we measured their transport dynamics. We showed that the timing of phagosome transport from actin cortex to microtubules controls the kinetics of early phagosome assembly and transition to late phagosomes. This ultimately determines the fate of phagosome maturation. Our results reveal distinct mechanisms by which the actin- and microtubule-based transport of phagosomes temporally controls the maturation progression of phagosomes during their degradative function.