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Cell surface (cortical) actin remodeling is a cyclic (9-step) process where each step is directly responsive to a cell signaling mechanism. Over the course of the cycle, actin begins as a monomer, elongates into a polymer with the help of attached actin-binding-proteins, and disassembles back into a monomer so the remodeling cycle may commence again.
Many actin-related molecules create a free barbed end for polymerization by uncapping or severing pre-existing filaments and using these as actin nucleation cores. However, the Arp2/3 complex stimulates actin polymerization by creating a new nucleation core. Actin nucleation is an initial step in the formation of an actin filament.
The distinction between "step-growth polymerization" and "chain-growth polymerization" was introduced by Paul Flory in 1953, and refers to the reaction mechanisms, respectively: [4] by functional groups (step-growth polymerization) by free-radical or ion (chain-growth polymerization)
Actin plays a role in the formation of new spines as well as stabilizing spine volume increase. [1] The changes that actin brings about lead to the formation of new synapses as well as increased cell communication. Actin remodeling consists of the dynamic changes in actin polymerization that underlie the morphological changes at the neural synapse.
The oligomerization is the rate-determining step, considering actin filament formation as a whole. The so-called lag phase of actin polymerization originates from this step. It takes quite a while until polymerization starts, but once it has, the process is autocatalytic until the physiological maximum of the polymerization rate is reached.
Association of G-actin into F-actin is regulated by the critical concentration outlined below. Actin polymerization can further be regulated by profilin and cofilin. [6] Cofilin functions by binding to ADP-actin on the negative end of the filament, destabilizing it, and inducing depolymerization.
Akt phosphorylates many proteins involved in polymerisation and stabilisation of the actin cytoskeleton. In normal cells, this can either increase the stability of cytoskeleton components or promote migration via remodelling. Examples are listed below: Actin filaments - Akt phosphorylates actin directly [36]
Cytoskeletal drugs are small molecules that interact with actin or tubulin.These drugs can act on the cytoskeletal components within a cell in three main ways. Some cytoskeletal drugs stabilize a component of the cytoskeleton, such as taxol, which stabilizes microtubules, or Phalloidin, which stabilizes actin filaments.