Endosomes make tracks

Early endosomes may help to create their own short-range tracks, according to a report from Stéphane Gasman, Yannis Kalaidzidis, and Marino Zerial (Max Planck Institute, Dresden, Germany). The results also suggest parallels between membrane trafficking, signaling, and regulation of the cytoskeleton.

Trafficking of early endosomes requires the small GTPase RhoD. Zerial's group identified the first known downstream effector for RhoD, hDia2C, a relative of the actin-polymerizing protein formin. In vivo, RhoD recruited hDia2C onto endosomes, where the two proteins probably stabilize the association of endosomes with the actin network, as their overexpression caused the vesicles to align along actin filaments. In the overexpressing cells, endosomal motility was also slowed and long-range trafficking was inhibited, probably because the endosomes were unable to jump from actin to microtubules, where Rab5 stimulates long-range movements.

The results...