Inhibin, beta A, also known as INHBA, is a protein which in humans is encoded by the INHBAgene. INHBA is a subunit of both activin and inhibin, two closely related glycoproteins with opposing biological effects.
The inhibin beta A subunit joins the alpha subunit to form a pituitary FSH secretion inhibitor. Inhibin has been shown to regulate gonadal stromal cell proliferation negatively and to have tumor-suppressor activity. In addition, serum levels of inhibin have been shown to reflect the size of granulosa-cell tumors and can therefore be used as a marker for primary as well as recurrent disease. Because expression in gonadal and various extragonadal tissues may vary severalfold in a tissue-specific fashion, it is proposed that inhibin may be both a growth/differentiation factor and a hormone. Furthermore, the beta A subunit forms a homodimer, activin A, and also joins with a beta B subunit to form a heterodimer, activin AB, both of which stimulate FSH secretion. Finally, it has been shown that the beta A subunit mRNA is identical to the erythroid differentiation factor subunit mRNA and that only one gene for this mRNA exists in the human genome.
^Lewis, K A; Gray P C; Blount A L; MacConell L A; Wiater E; Bilezikjian L M; Vale W (March 2000). "Betaglycan binds inhibin and can mediate functional antagonism of activin signalling". Nature. ENGLAND. 404 (6776): 411–4. doi:10.1038/35006129. ISSN0028-0836. PMID10746731.
^Martens, J W; de Winter J P; Timmerman M A; McLuskey A; van Schaik R H; Themmen A P; de Jong F H (July 1997). "Inhibin interferes with activin signaling at the level of the activin receptor complex in Chinese hamster ovary cells". Endocrinology. UNITED STATES. 138 (7): 2928–36. doi:10.1210/endo.138.7.5250. ISSN0013-7227. PMID9202237.
Welt C, Sidis Y, Keutmann H, Schneyer A (2002). "Activins, inhibins, and follistatins: from endocrinology to signaling. A paradigm for the new millennium.". Exp. Biol. Med. (Maywood). 227 (9): 724–52. PMID12324653.
Barton DE, Yang-Feng TL, Mason AJ, et al. (1989). "Mapping of genes for inhibin subunits alpha, beta A, and beta B on human and mouse chromosomes and studies of jsd mice". Genomics. 5 (1): 91–9. doi:10.1016/0888-7543(89)90091-8. PMID2767687.
Sumitomo S, Inouye S, Liu XJ, et al. (1995). "The heparin binding site of follistatin is involved in its interaction with activin". Biochem. Biophys. Res. Commun. 208 (1): 1–9. doi:10.1006/bbrc.1995.1297. PMID7887917.
Xu J, McKeehan K, Matsuzaki K, McKeehan WL (1995). "Inhibin antagonizes inhibition of liver cell growth by activin by a dominant-negative mechanism". J. Biol. Chem. 270 (11): 6308–13. doi:10.1074/jbc.270.11.6308. PMID7890768.
ten Dijke P, Ichijo H, Franzén P, et al. (1993). "Activin receptor-like kinases: a novel subclass of cell-surface receptors with predicted serine/threonine kinase activity". Oncogene. 8 (10): 2879–87. PMID8397373.
Tanimoto K, Yoshida E, Mita S, et al. (1997). "Human activin betaA gene. Identification of novel 5' exon, functional promoter, and enhancers". J. Biol. Chem. 271 (51): 32760–9. doi:10.1074/jbc.271.51.32760. PMID8955111.