Myosin 1b promotes the formation of post-Golgi carriers by regulating actin assembly and membrane remodelling at the trans-Golgi network.

The function of organelles is intimately associated with rapid changes in membrane shape. By exerting force on membranes, the cytoskeleton and its associated motors have an important role in membrane remodelling. Actin and myosin 1 have been implicated in the invagination of the plasma membrane during endocytosis. However, whether myosin 1 and actin contribute to the membrane deformation that gives rise to the formation of post-Golgi carriers is unknown. Here we report that myosin 1b regulates the actin-dependent post-Golgi traffic of cargo, generates force that controls the assembly of F-actin foci and, together with the actin cytoskeleton, promotes the formation of tubules at the TGN. Our results provide evidence that actin and myosin 1 regulate organelle shape and uncover an important function for myosin 1b in the initiation of post-Golgi carrier formation by regulating actin assembly and remodelling TGN membranes.