Synonyms: Activin beta A beta B heterodimer
Activins are homodimers or heterodimers of the various Beta subunit isoforms, belonging to the TGF-beta family. Mature Activin AB has two chains of 116 and 123 amino acids residues (betaA-betaB). Activin exhibits a wide range of biological activities, including mesoderm induction, neural cell differentiation, bone remodelling, haematopoiesis, and reproductive physiology. Activins plays a key role in the production and regulation of hormones such as FSH, LH, GnRH and ACTH. Inhibins /Activins are proteins that are formed by the dimerization of two subunits, i. e. an alpha with either betaA -inhibin A- or betaB - inhibin B. The subunits betaA and betaB can also form homodimers or heterodimers calleds activins: Activin A (betaAbetaA), Activin B (betaBbetaB) and Activin AB (betaAbetaB). The activin gene family comprises the additional, but poorly characterized members activin betaC, betaD, and betaE. - As with other members of the super-family, Activins interact with two types of cell surface trans-membrane receptors (Types I and II) which have intrinsic serine/threonine kinase activities in their cytoplasmic domains, Activin type 1 receptors, ACVR1, ACVR1B, ACVR1C and Activin type 2 receptors, ACVR2A, ACVR2B. - The development of assays distinguishing between different forms of activins and inhibins, along with knock-in and knock-out models, have provided evidence that the betaA- and betaB-subunits have independent and separate roles physiologically. Additionally, evaluation of ligand-receptor interactions indicates significant differences in receptor affinity between activin isoforms, as well as between inhibin isoforms.