Actindepolymerizing

Actindepolymerizing refers to the disassembly of filamentous actin (F-actin) into actin monomers (G-actin) and the dynamic processes that promote turnover of the actin cytoskeleton. It encompasses the action of several actin-binding proteins and regulatory pathways that increase the rate at which actin filaments depolymerize or are severed.

The primary drivers are actin-depolymerizing factor (ADF)/cofilin proteins, which preferentially bind ADP-actin in aged portions of filaments. Binding induces conformational changes that destabilize the filament and promote severing, generating new ends that can rapidly depolymerize. Other proteins, such as gelsolin, can sever filaments and cap the newly created ends, further shifting the balance toward disassembly. The process is coordinated with proteins that regulate assembly, including profilin and capping factors, which influence whether actin monomers are added or removed at filament ends. Severing by cofilin and related factors often accelerates disassembly by increasing the number of ends from which depolymerization can occur.

Regulation of actindepolymerizing activity is responsive to cellular signals. The activity of the cofilin/ADF family is controlled by phosphorylation: LIM kinases suppresses activity, while slingshot phosphatases restore it. Rho family GTPases transduce external cues to these regulators, linking actin turnover to processes such as cell migration, cytokinesis, and endocytosis.

Physiological significance includes dynamic remodeling of the cytoskeleton during movement and shape changes. Dysregulation of actin depolymerization is associated with developmental abnormalities and diseases, including cancer metastasis and certain neurodegenerative conditions.

See also actin cytoskeleton, cofilin, ADF, gelsolin, actin dynamics.