Actin

Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. Actin exists in three major isoforms, including α-, β-, and γ-actin. α-Actin isoform is predominantly expressed in muscle cells (e.g., α-skeletal, α-cardiac, α-vascular smooth), while β- and γ-actin are primarily found in nonmuscle cells (e.g., β-cytoplasmic, γ-cytoplasmic, γ-enteric smooth). In physiological conditions, actin can reversibly polymerize between its monomeric (G-actin) and filamentous (F-actin) forms. The ability of actin to reversibly assemble into filaments (F-actin) provides the foundation upon which many essential cellular functions rely, such as cell movement, cytokinesis, and maintenance of the cytoskeletal structure, which is closely associated with cancer metastasis.