Activin A was initially identified in ovarian fluid as a stimulator of FSH secretion from anterior pituitary cells. Activin A is a member of the TGFb1 family which includes TGFs, activins, Nodal, growth and differentiation factors (GDF), and bone morphogenetic proteins (BMPs). Activin A is a dimer of the beta A subunits of human inhibin; the beta A subunit binds the beta B subunit of inhibin to form Activin AB. The beta B subunit also exists as a heterodimer to form Activin B. Activin A binds two type I and two type II serine/threonine kinase receptors at the same time. The type II receptor kinase is constitutively active and phosphorylates the type I receptor after the formation of the ligand-receptor complex. Five type II receptors have been identified: ActRIIA, ActRIIB, BMPRII, TGFβRII, and MISRII. ActRIIB binds to Activin A, BMP-2, BMP-7, GDF-8, and GDF-11. The type I receptors are named activin receptor-like kinases 1 to 7 (ALK1~7), and Activins bind to ALK4 and ALK7. Follistatin (FS) is a natural Activin A antagonist; FS neutralizes its biologic activities by preventing Activin A interaction with its receptors. Activin A has pleiotropic functions. It is a morphogen during embryonal development, regulating chondrogenic and osteogenic differentiation of mesenchymal progenitor cells (MPC). Activin A has been associated with neuroprotection, apoptosis, and fibrosis. Also, high levels of Activin A have been found in synovial fluid from patients with rheumatoid arthritis, inflammatory bowel disease, and gout. In addition, it has been speculated that Activin A, in collaboration with TGFb1 and IL-25, promotes TH9 generation and the development of allergic pathology.
Size
500 μg
Concentration
n/a
Applications
BA
Other Names
Inhibin BA (INHBA), Inhibin B-1, Follicule stimulating hormone-releasing protein (FRP), FSH releasing protein, FSH releasing factor, Erythroid differentiation factor (EDF)