Activin A is a protein involved in regulating various biological processes throughout the human body, from early development to specialized functions in mature tissues. This protein’s instructions are encoded by a specific gene, and its activity is crucial for healthy bodily functions.
Understanding Activin A and Its Gene
Activin A is a protein derived from the inhibin subunit beta A (INHBA). The INHBA gene, located on chromosome 7p14.1, encodes this protein. As a member of the transforming growth factor-beta (TGF-beta) superfamily, Activin A shares structural similarities with other proteins that regulate cell growth and differentiation.
The Activin A protein forms as a homodimer, consisting of two identical beta-A subunits linked by disulfide bonds. This dimeric structure enables it to bind to specific cell surface receptors and initiate cellular responses. The INHBA gene is highly conserved across many species, including chimpanzees, mice, and fruit flies, highlighting its fundamental biological importance.
Diverse Roles of Activin A in the Body
Activin A performs many functions in the body. In reproduction, it enhances secretion of follicle-stimulating hormone (FSH) from the pituitary gland, which is involved in the menstrual cycle. It also supports ovarian function by increasing FSH binding and aromatization, and in males, it promotes spermatogenesis.
Beyond reproduction, Activin A is significant in embryonic development, contributing to processes like mesoderm induction and neural cell differentiation. It is also involved in inflammatory and immune responses, produced by activated macrophages and influencing cytokine production. Activin A’s presence is often elevated in both acute and chronic inflammation.
Activin A also contributes to tissue repair, notably in wound healing and bone formation. It is strongly expressed in wounded skin, and its overexpression can improve wound healing and enhance scar formation by stimulating keratinocytes and stromal cells. In bone fracture healing, Activin A becomes abundant and promotes the differentiation of progenitor cells into cartilage and bone cells, supporting the repair process. It directly stimulates myofibroblastic differentiation, chondrogenesis, and osteogenesis in periosteal mesenchymal progenitor cultures.
Activin A’s Influence on Health and Disease
Disruptions in Activin A regulation can significantly impact health and contribute to various diseases. In cancer, Activin A can have a dual role; it may promote tumor progression, as seen in gastric and cervical cancers where elevated INHBA expression correlates with worse outcomes. Other studies suggest it can also promote cell migration and invasion in certain cancers, such as oral squamous cell carcinoma.
Activin A is also implicated in reproductive disorders, with its involvement in regulating FSH secretion linked to infertility issues when its balance is disturbed. In fibrotic diseases, such as liver and lung fibrosis, Activin A levels can increase. Inhibiting its action has shown potential to reduce fibrosis in disease models. For instance, Activin A contributes to collagen production in systemic sclerosis fibroblasts.
Activin A is linked to inflammatory conditions. Antagonists like follistatin, which bind to Activin A, are being explored as potential therapies for conditions such as sepsis and asthma. Understanding Activin A’s complex roles in these health and disease states opens avenues for developing targeted therapeutic strategies.