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Keywords:

  • actin;
  • axon;
  • cytoskeleton;
  • myosin;
  • patches

Abstract

Thumbnail image of graphical abstract

This review focuses on recent advances in the understanding of the organization and roles of actin filaments, and associated myosin motor proteins, in regulating the structure and function of the axon shaft. ‘Patches’ of actin filaments have emerged as a major type of actin filament organization in axons. In the distal axon, patches function as precursors to the formation of filopodia and branches. At the axon initial segment, patches locally capture membranous organelles and contribute to polarized trafficking. The trapping function of patches at the initial segment can be ascribed to interactions with myosin motors, and likely also applies to patches in the more distal axon. Finally, submembranous rings of actin filaments were recently described in axons, which form an actin-spectrin cytoskeleton, likely contributing to the maintenance of axon integrity. Continued investigation into the roles of axonal actin filaments and myosins will shed light on fundamental aspects of the development, adult function and the repair of axons in the nervous system.

This review focuses on recent advances in the understanding of the organization and roles of actin filaments, and associated myosin motor proteins, in regulating the structure and function of the axon shaft. Actin filament patches at the initial segment capture vesicles incorrectly being transported anterogradely into the axon (see schematic). When the vesicle is released from the patch, it undergoes retrograde transport back to the soma. Along the distal axon, actin patches serve as precursors to the emergence of filopodia, the first step in axon branching.