Receptor Domains Involved in Signal Transduction of Prolactin and Growth Hormone

Abstract

Prolactin (PRL) and growth hormone (GH) receptors are members of a superfamily that include receptors for a number of cytokines. GH and its receptor form an unusual homodimer consisting of one molecule of GH and two molecules of receptor. A similar homodimer of the PRL receptor is probably required for biological effects to be seen. Using specific assays to measure the functional activity of PRL and GH receptors, a 25 amino acid juxtamembrane region has been identified as essential but not sufficient for normal action. More detailed studies have limited the region to eight amino acids, rich in prolines, that is highly conserved in many members of the receptor superfamily. Finally, GH and PRL have been shown to induce the rapid tyrosine phosphorylation of an associated kinase, Janus kinase 2, and of the receptor itself.

Prolactin and growth hormone affect metaphase-II chromosomes in aging oocytes via cumulus cells using similar signaling pathways

“…Our data have demonstrated that both PRL and GH affect the morphology of M-II chromosomes in CEOs in a biphasic dose-dependent manner, which is typical for actions of these hormones in different cell systems ( Ilondo et al, 1994 ; Hodson et al, 2010 ; Lebedeva et al, 2014b ). A bell-shaped pattern of dose-response curves for PRL and GH is usually attributed to the two-site mechanism of the hormone binding to their receptors involving dimerization of these latter and self-antagonism at high concentrations when monomeric hormone-receptor complexes become predominant ( Kelly et al, 1994 ). However, this theoretical model cannot explain the opposite pattern of effects of low and high hormonal concentrations found in the present study, suggesting an implication of additional factors.…”

“…The revealed similarity in mechanisms of PRL and GH actions on senescent oocytes is obviously due to the close relationship both between the hormones and between their receptors ( Kelly et al, 1994 ). Although JAK2/STAT (Janus kinase 2/Signal transducers and activators of transcription) is the main signal pathway activated in response to PRL and GH, other pathways are also involved in their effects.…”

Stimulatory effect of growth hormone on in vitro maturation of bovine oocytes is exerted through cumulus cells and not mediated by IGF-I

“…The GHR which has been cloned from liver of several species including human, rabbit, rat, mouse, sheep, and cow is considered to be a member of the cytokine hematopoietin receptor superfamily, a family defined by limited homology in the extracellular domain (Bazan, 1989;Kelly et al, 1994). Ligand binding to GHR and a number of other members of this superfamily has been shown to stimulate JAK2 tyrosine kinase activity, which is followed by association of JAK2 with the receptor itself; thus, activation of JAK2 is an early and perhaps first step in intracellular signalling by GHR (Hackett et al, 1995;Postel et al, 1995;Vanderkuur et al, 1994).…”