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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 5.

Figure 5

Feedback control systems in the actin cytoskeleton. (a) Rho-GTPases are localized to the cell membrane and cycle between an active GTP-bound state and an inactive GDP-bound state. The switching rates are determined by a large range of regulators (GEFs for activation and GAPs for inactivation). (b) A simplified diagram of the cross talks and feedback loops in the actin cytoskeleton controlled by the small GTPases of the Rho family. (c) Negative feedback control of protrusive activity in the lamellipodium controlled by the Rac pathway. (d) Positive feedback control of stress fiber assembly and contraction, downstream of the Rho pathway. (e) The actin cortex exhibits a mixture of contractile and protrusive activities downstream of the Rho and Rac pathways. Abbreviations: GAP, GTPase-activating protein; GDP, guanosine diphosphate; GEF, guanine nucleotide exchange factor; GTP, guanosine triphosphate.