Activins are members of the transforming growth factor P (TGFp) superfamily of dimeric proteins, which include the TGF(3s, inhibins, activins, Mullerian inhibiting substance, vascular endothelial growth factor, bone morphogenetic protein, and growth and differentiation factors. Activins are composed of two subunits, (ЗА and (3B, that homo- or heterodimerize to generate three different dimeric proteins called activin A, B, and AB. Three new activin members have been discovered recently, activin pC in human liver, activin (3D in Xenopus laevis, and activin (3E in mouse liver. Activins bind to cell surface receptors with serine/threonine kinase activity. The activin receptors are involved in many aspects of development and cell differentiation, including regulation of reproductive cell responses. Follistatin is an activin binding protein that has been implicated in modulating activin-dependent cellular functions in target cells. buy levaquin online
Much of our understanding of activin signaling in the ovary comes from experiments on murine granulosa cells (GC). The genes encoding the activin type II and IIB receptors are expressed in GC during the normal estrous cycle.