Thymosin β4 and Actin: Binding Modes, Biological Functions and Clinical Applications

Thymosin β4 (Tβ4) is the β-thymosin (Tβs) with the highest expression level in human cells; it makes up roughly 70-80% of all Tβs in the human body. Combining the mechanism and activity studies of Tβ4 in recent years, we provide an overview of the subtle molecular mechanism, pharmacological action, and clinical applications of Tβ4. As a G-actin isolator, Tβ4 inhibits the polymerization of G-actin by binding to the matching site of G-actin in a 1:1 ratio through conformational and spatial effects. Tβ4 can control the threshold concentration of G-actin in the cytoplasm, influence the balance of depolymerization and polymerization of F-actin (also called Tread Milling of F-actin), and subsequently affect cell's various physiological activities, especially motility, development and differentiation. Based on this, Tβ4 is known to have a wide range of effects, including regulation of inflammation and tumor metastasis, promotion of angiogenesis, wound healing, regeneration of hair follicles, promotion of the development of the nervous system, and improving bone formation and tooth growth. Tβ4 therefore has extensive medicinal applications in many fields, and serves to preserve the kidney, liver, heart, brain, intestine, and other organs, as well as hair loss, skin trauma, cornea repairing, and other conditions. In this review, we focus on the mechanism of action and clinical application of Tβ4 for its main biological functions.