INHBB
Encyclopedia
Inhibin, beta B, also known as INHBB, is a protein
which in humans is encoded by the INHBB gene
. INHBB is a subunit of both activin and inhibin
, two closely related glycoproteins with opposing biological effects.
s 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. 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.
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.
s. In adult animals, binding of 125I inhibin was localized primarily to the interstitial compartment of the testis. Also, Jin et al., (2001) reported that Leydig cells showed strong positive staining for the inhibin βA subunit in pigs testis.
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. 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
.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
which in humans is encoded by the INHBB gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. INHBB is a subunit of both activin and inhibin
Activin and inhibin
Activin and inhibin are two closely related protein complexes that have almost directly opposite biological effects. Activin enhances FSH biosynthesis and secretion, and participates in the regulation of the menstrual cycle...
, two closely related glycoproteins with opposing biological effects.
Inhibin
Inhibins are heterodimeric glycoproteinGlycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
s composed of an α subunit (INHA
INHA
Inhibin, alpha, also known as INHA, is a protein which in humans is encoded by the INHA gene.- Function :The inhibin alpha subunit joins either the beta A or beta B subunit to form a pituitary FSH secretion inhibitor. Inhibin has been shown to regulate gonadal stromal cell proliferation...
) and one of two homologous, but distinct, β subunits (βA
INHBA
Inhibin, beta A, also known as INHBA, is a protein which in humans is encoded by the INHBA gene. INHBA is a subunit of both activin and inhibin, two closely related glycoproteins with opposing biological effects.- Function :...
or βB, this protein). mRNA for the two subunits has been demonstrated in the testes of adult rats. Inhibin can bind specifically to testicular interstitial cells throughout development and may be an important regulator of Leydig cell
Leydig cell
Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone...
testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
production or interstitial cell function.
The inhibin beta B subunit joins the α subunit to form a pituitary FSH
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...
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.Tissue distribution
Sections of testicular tissue from rat revealed positive immunoreactivity against anti-inhibin intensely appeared in Leydig cellLeydig cell
Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone...
s. In adult animals, binding of 125I inhibin was localized primarily to the interstitial compartment of the testis. Also, Jin et al., (2001) reported that Leydig cells showed strong positive staining for the inhibin βA subunit in pigs testis.
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. Recently, additional inhibin specific binding proteins were identified in inhibin target tissues, including pituitary and Leydig cells. From these receptors β-glycan (the TGFß type IIITGF beta 3
Transforming growth factor beta 3 is a type of protein, known as a cytokine, which is involved in cell differentiation, embryogenesis and development...
receptor) and InhBP
IGSF1
Immunoglobulin superfamily member 1 is a protein that in humans is encoded by the IGSF1 gene.-Further reading:...
/p120 (a membrane-tethered proteoglycan
Proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan chain. The point of attachment is a Ser residue to which the glycosaminoglycan is joined through a tetrasaccharide bridge...
) 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
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
in rats treated with anise
Anise
Anise , Pimpinella anisum, also called aniseed, is a flowering plant in the family Apiaceae native to the eastern Mediterranean region and Southwest Asia. Its flavor resembles that of liquorice, fennel, and tarragon.- Biology :...
oil. 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
Safrole
Safrole, also known as shikimol, is a phenylpropene. It is a colorless or slightly yellow oily liquid. It is typically extracted from the root-bark or the fruit of sassafras plants in the form of sassafras oil , or synthesized from other related methylenedioxy...
.