INHBB
Lua error in Module:Infobox_gene at line 33: attempt to index field 'wikibase' (a nil value). Inhibin, beta B, also known as INHBB, is a protein which in humans is encoded by the INHBB gene.[1][2] INHBB is a subunit of both activin and inhibin, two closely related glycoproteins with opposing biological effects.
Contents
Function
Inhibin
Inhibins are heterodimeric glycoproteins composed of an α subunit (INHA) and one of two homologous, but distinct, β subunits (βA or βB, this protein). mRNA for the two subunits has been demonstrated in the testes of adult rats.[3] Inhibin can bind specifically to testicular interstitial cells throughout development and may be an important regulator of Leydig cell testosterone production or interstitial cell function.[4]
The inhibin beta B subunit joins the α subunit to form a pituitary FSH secretion inhibitor. Inhibin has been shown to regulate gonadal stromal cell proliferation negatively and to have tumour-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.
Activin
Furthermore, the beta B subunit forms a homodimer, activin B, and also joins with the beta A subunit to form a heterodimer, activin AB, both of which stimulate FSH secretion.[2]
Tissue distribution
Sections of testicular tissue from rat revealed positive immunoreactivity against anti-inhibin intensely appeared in Leydig cells.[5] In adult animals, binding of 125I inhibin was localized primarily to the interstitial compartment of the testis.[4] Also, Jin et al., (2001) reported that Leydig cells showed strong positive staining for the inhibin βA subunit in pigs testis.[6]
Receptors
In situ ligand binding studies have shown that 125I inhibin βA binds specifically to Leydig cells throughout rat testis development. These results suggest that inhibin has been considered as a regulator of Leydig cell differentiated function.[7][8] Recently, additional inhibin specific binding proteins were identified in inhibin target tissues, including pituitary and Leydig cells.[9][10] From these receptors β-glycan (the TGFß type III receptor) and InhBP/p120 (a membrane-tethered proteoglycan) were identified as putative inhibin receptors and they are all present in Leydig cells. However, a faint positive reaction was detected in Leydig cell cytoplasm in rats treated with anise oil.[5] This may be related to the damaged Leydig cells, as a result of the decreasing of inhibin expression. This may be related to its content of safrole.
References
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Further reading
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This article incorporates text from the United States National Library of Medicine, which is in the public domain.