Actin is a protein that plays a critical role in a variety of biological processes, including muscle contraction, cell motility, and cell division. In muscle cells, actin filaments interact with myosin filaments to generate force and cause muscle contraction. In non-muscle cells, actin is involved in cell motility, which is essential for many physiological processes such as wound healing and immune responses. Additionally, actin is involved in maintaining the shape and structure of cells and is essential for cell division during mitosis.
There are two main types of actin: alpha-actin and beta-actin. Alpha-actin is primarily found in muscle cells, while beta-actin is found in non-muscle cells. Actin is also classified as either globular (G-actin) or filamentous (F-actin), depending on its state. G-actin is the monomeric form of actin, while F-actin is the polymerized form, consisting of two chains of G-actin twisted together.
Actin dysfunction has been implicated in several human diseases, including muscular dystrophies, cancer, and autoimmune disorders such as systemic lupus erythematosus (SLE) and multiple sclerosis (MS). In these diseases, the regulation of actin dynamics is disrupted, leading to various pathologies.