Figure 5.

Functional differentiation of actin networks by tropomyosins. (a) Example of the specific localization of tropomyosin 4 (in red) in MTLn3 cells. Tropomyosin localizes with actin (in green) in stress fibres and in lamellar structures (arrowheads), while it is absent from the branched actin structures at the leading edge (arrows) (adapted from [128]). (b) Example of the differential localization of tropomyosin isoforms (in green) in U2OS cells. While Tpm2 shows a strong colocalization with the focal adhesion-specific protein vinculin (in red), Tpm3 localizes proximally to focal adhesions (adapted from [131]). (c) In vitro single-filament scale imaging reveals that while some tropomyosin isoforms (top images: Tpm2.1 in green and Tpm3.2 in red) can copolymerize with actin filaments, others cannot (bottom images: Tpm3.1 in green and Tpm1.6 in red) (adapted from [134], scale bar, 5 µm).