Figure 2.
The role of the actin cytoskeleton in spherical IAV assembly in host cells. (A) Contrasting roles for the actin cytoskeleton in spherical IAV assembly in different cell types. In IAV-permissive cells, such as epithelial cell lines and a macrophage-like cell line, the actin cytoskeleton either promotes or has no effects on IAV particle production. In contrast, the actin cytoskeleton restricts HA-M2 association and spherical IAV assembly in primary human macrophages. (B) Proposed mechanisms by which actin restricts spherical IAV assembly in primary human macrophages. Microdomain segregation: F-actin partitions HA- and M2-enriched plasma membrane microdomains. Suppression of membrane curvature: F-actin restricts HA-mediated curvature induction at the plasma membrane, which is required for M2 recruitment to the assembling particle. Blocking of cytoplasmic components: F-actin restricts trafficking and incorporation of other curvature-inducing structural components, that is, M1 and vRNP, to virus assembly sites.