| First Author | Li Y | Year | 2018 |
| Journal | Endocrinology | Volume | 159 |
| Issue | 12 | Pages | 4077-4091 |
| PubMed ID | 30364975 | Mgi Jnum | J:266352 |
| Mgi Id | MGI:6227841 | Doi | 10.1210/en.2018-00770 |
| Citation | Li Y, et al. (2018) Betaglycan (TGFBR3) functions as an inhibin A, but not inhibin B, co-receptor in pituitary gonadotrope cells in mice. Endocrinology |
| abstractText | Inhibins are gonadal hormones that act on pituitary gonadotrope cells to suppress follicle-stimulating hormone (FSH) synthesis and secretion. Inhibin A and B are heterodimers of the inhibin subunit disulfide-linked to one of two inhibin beta subunits. Homo- or heterodimers of the inhibin beta subunits form the activins, which stimulate FSH production. Activins signal through complexes of type I and II receptor serine/threonine kinases to increase transcription of the FSHbeta subunit gene. According to in vitro observations, inhibins impair FSH synthesis by competitively binding to activin type II receptors, particularly in the presence of the TGFbeta type III receptor (TGFBR3 or betaglycan). TGFBR3's role in inhibin action in vivo has not been determined. Here, we ablated Tgfbr3 specifically in murine gonadotropes. Conditional knockout females were supra-fertile, exhibiting enhanced folliculogenesis, numbers of ovulated eggs per cycle, and litter sizes relative to control mice. Despite these phenotypes, FSH levels appeared to be unaltered in knockout mice and the mechanisms underlying their enhanced fertility remain unexplained. Inhibin B is the predominant form of the hormone in males and in females during most stages of the estrous cycle. Remarkably, inhibin A, but not inhibin B, suppression of FSH synthesis was impaired in cultured pituitaries of knockout mice, which may explain the absence of discernible changes in FSH levels in vivo. Collectively, these data challenge current dogma by demonstrating that TGFBR3 (betaglycan) functions as an inhibin A, but not inhibin B, co-receptor in gonadotrope cells in vivo. Mechanisms of inhibin B action merit further investigation. |
