Actin alpha skeletal muscle (ACTA1) and Actin alpha smooth muscle (ACTA2) (ACTA1/ACTA2)

Actin alpha isoforms ACTA1 and ACTA2 are highly conserved proteins that serve as essential components of the contractile apparatus in skeletal and smooth muscle, respectively (UniProt P68133, P62736). ACTA1 (alpha-skeletal muscle actin) is the predominant actin in adult skeletal muscle thin filaments, where it interacts with myosin to drive muscle contraction (MedlinePlus, 2016). Mutations in ACTA1 are a leading cause of congenital myopathies, such as nemaline myopathy, characterized by severe muscle weakness and the presence of protein aggregates called nemaline bodies (Nowak et al., 2012). ACTA2 (alpha-smooth muscle actin) is primarily expressed in vascular smooth muscle cells and is critical for maintaining vascular tone and blood pressure (Guo et al., 2007). Mutations in ACTA2 are associated with a spectrum of vascular diseases, including familial thoracic aortic aneurysms and dissections (TAAD) and multisystemic smooth muscle dysfunction syndrome (MSMDS) (Milewicz et al., 2010). Beyond its role in contraction, ACTA2 is a hallmark marker of activated myofibroblasts in fibrosis and the tumor microenvironment, making it a target of interest for anti-fibrotic and oncology therapies (Wikipedia, 2024). While direct targeting of actin is challenging due to its ubiquity and structural conservation, therapeutic strategies include small-molecule modulators of the contractile complex like Tirasemtiv, which sensitizes the thin filament to calcium, and novel approaches such as base editing to correct pathogenic mutations (Squire et al., 2011; Kleinstiver et al., 2025). Additionally, research compounds like Cytochalasins and Latrunculins are widely used to study actin dynamics, though their clinical utility is limited by systemic toxicity (SCBT, 2024).

Other names

Alpha-skeletal actinAlpha-smooth muscle actinalpha-SMAASMAAAT6ACTSAMYMY5NEM3CFTDActin alpha 1Actin alpha 2

Troponin activation to sensitize the actin-containing thin filament to calcium, thereby increasing contractile force; stabilization of mutant actin filaments to restore structural integrity; sequestration of actin monomers or capping of filament ends to disrupt polymerization dynamics; modulation of gene expression through nuclear translocation and SRF/MRTF-A signaling.