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. Author manuscript; available in PMC: 2020 Dec 18.
Published in final edited form as: Annu Rev Condens Matter Phys. 2019 Dec 6;11(1):421–439. doi: 10.1146/annurev-conmatphys-031218-013231

Figure 3.

Figure 3

Active growth of F-actin networks. (a) In cells, dendritic actin networks generated by the branching agent Arp2/3 are used to create pushing forces on the objects that nucleate them, for example, on the plasma membrane during migration, on endocytosing vesicles that have to be pushed inside the cell during cytoplasmic streaming and when pathogens push themselves through the cytoplasm. (b) When membrane tension and thus mechanical load on the lamellipodium is first increased and then decreased by micropipette aspiration of migrating keratocytes, filament density first increases and then decreases. At the same time, the orientation distribution changes from two symmetric peaks at ±35° to one peak at 0°. Panel adapted from Reference 75 with permission. (c) These results agree well with the theoretical predictions that the classical ±35° structure (slingshot) competes with a +70/0/−70° structure (trident) depending on the growth kinetics determined by external load. Panel adapted from Reference 77.