Alpha-smooth muscle actin (α-SMA)

Molecular Classification

Structural protein, Actin isoform, Cytoskeletal protein

Other Names

ACTA2, actin alpha 2, alpha-actin-2, aortic smooth muscle actin, SMactin, alpha-SM-actin, ASMA

Disease Roles

Fibrosis (e.g., liver, lung, heart)Vascular diseases (e.g., thoracic aortic disease, coronary artery disease, stroke, Moyamoya disease, multisystemic smooth muscle dysfunction)Cancer (stromal reaction, wound repair, fibrotic tumor microenvironment)

Alpha-smooth muscle actin Overview

Alpha-smooth muscle actin (α-SMA) is a specialized actin isoform predominantly expressed in vascular and visceral smooth muscle cells, encoded by the ACTA2 gene. It is a globular structural protein that polymerizes to form filaments (microfilaments), forming a key component of the cytoskeleton and contractile apparatus in muscle cells. In non-muscle cells, notably myofibroblasts, α-SMA expression correlates with increased contractile activity important for wound healing, matrix remodeling, and fibrogenesis. α-SMA is a hallmark marker of myofibroblast activation and is used extensively in research and pathology as a biomarker for fibrosis and tissue repair processes. Mutations in ACTA2 underpin a range of vascular and fibrotic diseases. Although it plays crucial roles in cellular contractility and mechanotransduction, it is not a classical drug target such as a receptor, transporter, or enzyme, but rather serves as a structural marker and effector in disease-related cellular phenotypes.

Mechanism of Action

Biological Functions

Muscle contraction

Cell-generated mechanical tension

Matrix remodeling

Mechanotransduction

Fibrogenesis

Cell migration modulation

Disease Associations

Fibrosis (e.g., liver, lung, heart)

Vascular diseases (e.g., thoracic aortic disease, coronary artery disease, stroke, Moyamoya disease, multisystemic smooth muscle dysfunction)

Cancer (stromal reaction, wound repair, fibrotic tumor microenvironment)

Safety Considerations

Targeting alpha-smooth muscle actin may disrupt essential contractile functions of vascular and visceral smooth muscle
Challenges in targeting due to high homology with other actin isoforms

Associated Biomarkers

Biomarker
Marker for myofibroblast formation and activation
Indicator for fibrotic activity