Purification and characterization of an FSH releasing protein from porcine ovarian follicular fluid

Abstract

A variety of hypophysiotropic peptides or proteins have been reported to be present in mammalian gonads. Inhibin, a hormone that under most circumstances selectively suppresses the secretion of follicle-stimulating hormone (FSH) but not luteinizing hormone (LH), has been isolated from the gonadal fluids of several species and characterized as a heterodimeric protein consisting of alpha- and beta-polypeptides associated by disulphide bonds. The complete amino-acid sequences of the precursors of porcine and human inhibin alpha-subunits and two distinct porcine inhibin beta-subunits (beta A and beta B) have been deduced from complementary DNA sequences. Gonadotropin releasing peptides have also been found in the gonad and have generally been shown to be active in radioreceptor assays for gonadotropin releasing hormone (GnRH) but to exhibit different chromatographic and immunological characteristics from those of GnRH. During our purification of inhibin from porcine follicular fluid, we noted fractions that could stimulate the secretion of FSH by cultured anterior pituitary cells. We report here the purification of an FSH releasing protein (FRP) and its characterization by SDS-polyacrylamide gel electrophoresis under non-reducing and reducing conditions and by partial sequence analysis. Our results indicate that porcine gonadal FRP is a homodimer consisting of two inhibin beta A-chains linked by disulphide bonds. FRP is highly potent (50% effective concentration (EC50) approximately 25 pM) in stimulating the secretion and biosynthesis of FSH but not of LH or any other pituitary hormone. In contrast to the effects of GnRH and other reported gonadal gonadotropin releasing fractions, the action of FRP is not mediated by GnRH receptors.

Down‐modulation of c‐kit mRNA and protein expression by erythroid differentiation factor/activin A

“…Several cytokines regulate the proliferation and differentiation of hematopoietic stem cells, Erythroid differentiation factor (EDF), which was isolated from conditioned media of phorbol ester-treated THP-1 cells, has a potent differentiation-inducing activity for murine erythroleukemia (MEL) cells [1]. A subsequent study showed that EDF was identical to activin A that was first purified from ovarian fluid as a factor to stimulate the secretion of pituitary follicular-stimulating hormone [2]. Several reports have shown that activin A can modulate the colony formation of erythroid burst-forming units and erythroid colony-forming units [3][4][5].…”

Mcl-1, an early-induction molecule, modulates activin A-induced apoptosis and differentiation of CML cells

“…It was initially recognized as a gonadal protein that stimulates the release of follicular-stimulating hormone (FSH) from the pituitary gland (Vale et al, 1986;Ling et al, 1986). Several studies have shown that activin A carries out a variety of functions including regulation of hematopoiesis (Eto et al, 1987;Yu et al, 1989;Yamashita et al, 1991).…”

“…Activin A is highly homologous with transforming growth factor (TGF)-b and consists of two bA subunits (Vale et al, 1986;Ling et al, 1986). It was initially recognized as a gonadal protein that stimulates the release of follicular-stimulating hormone (FSH) from the pituitary gland (Vale et al, 1986;Ling et al, 1986).…”

Activin A‐induced apoptosis is suppressed by BCL‐2

“…Activin A was originally isolated as a factor stimulating secretion of follicle-stimulating hormone (FSH) from anterior pituitary cells [1]. It possesses various in vitro activities such as enhancement of neuronal survival [2], induction of erythroid differentiation [3] and mesoderm formation during amphibian embryonic development [4,5].…”