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. Author manuscript; available in PMC: 2021 Dec 21.
Published in final edited form as: Dev Cell. 2020 Dec 11;55(6):723–736.e8. doi: 10.1016/j.devcel.2020.11.024

Figure 1. Actin Fluctuations Alone Do Not Initiate Protrusion.

Figure 1.

(A) Schematics of the tethered Brownian ratchet model for actin-driven protrusion, including the addition of ezrin as a canonical actin-membrane linker.

(B) Simulation of the model, including stochastic fluctuations in working actin filaments, resulting in no protrusion initiation events.

(C) Magnification of a portion of the data in (B) showing the relationship between working actin filaments and linked actin filaments.

(D) Phase diagram showing the computationally predicted relationship between working filaments and linked filaments. Circles indicate fixed points bifurcated by a separatrix, with red indicating the non-protrusive region and the green indicating the protrusive region. Light gray streamlines show deterministic model solutions, and the dark purple lines show an example simulation trajectory that never crosses over the separatrix.

(E) Schematic showing how actin-membrane links via ezrin equilibrate with newly polymerized actin filaments to prevent protrusion.