Myosin 1 controls membrane shape by coupling F-Actin to membrane

Abstract

Cellular functions are intimately associated with rapid changes in membrane shape. Different mechanisms interfering with the lipid bilayer, such as the insertion of proteins with amphipatic helices or the association of a protein scaffold, trigger membrane bending. By exerting force on membranes, molecular motors can also contribute to membrane remodeling. Previous studies have shown that actin and myosin 1 participate in the invagination of the plasma membrane during endocytosis while kinesins and dynein with microtubules provide the force to elongate membrane buds at recycling endosomes and at the trans-Golgi network (TGN). Using live cell imaging we have recently shown that a myosin 1 (myosin 1b) regulates the actin dependent post-Golgi traffic of cargo and generates force that controls the assembly of F-actin foci and promotes with the actin cytoskeleton the formation of tubules at the TGN. Our data provide evidence that actin and myosin 1 can regulate membrane remodeling of organelles as well as having an unexpected role in the spatial organization of the actin cytoskeleton. Here, we discuss our results together with the role of actin and other myosins that have been implicated in the traffic of cargo.

Figure 1. Formation of carrier vesicles. Model for the sequential events that induce membrane deformation at the plasma membrane or at the TGN. (A) By interacting with NPF, F- BAR protein or ETNH proteins control the side of actin polymerization for membrane invagination at the plasma membrane and at the TGN. (B) Kinesin and microtubules then elongate the membrane of the TGN.

Figure 2. Model for the role of Myo1b in membrane remodeling. Myo1b moves toward the plus end of F-actin. If Myo1b is immobilized because of its interaction with the membrane then the Myo1b motor activity will move F-actin backward thereby facilitating addition of new G actin next to the plasma membrane. (A) Shows the orientation of Myo1b movement (see blue arrows) and (B) the consequence of this movement on actin dynamics (see gray arrows and new addition of G-actin).