Intracellular transport is accelerated in early apoptotic cells*

Apoptosis is a process of programmed cell death with dramatic changes in cell morphology and organization, during which signaling molecules are transported within the cells between different organelles. However, how the intracellular transport changes in cells undergoing apoptosis remains unknown. Here, we study the dynamics of intracellular transport by using single-particle tracking method, and find that both the directed motion and diffusive motion of endocytic vesicles are accelerated in early apoptotic cells. With careful elimination of the other factors involving in the intracellular transport, the reason for the acceleration is attributed to be the elevation of ATP concentration. More importantly, we show that the accelerated intracellular transport is critical for apoptosis. Apoptosis is delayed when the dynamics of intracellular transport is regulated back to the normal level. Our results demonstrate the important role of transport dynamics in apoptosis and shed light on the apoptosis mechanism from a physical perspective.