RESUMO
Normal anterior pituitary function is essential for fertility. Release from the gland of the reproductive hormones luteinising hormone and follicle-stimulating hormone is regulated primarily by hypothalamically-derived gonadotrophin-releasing hormone (GnRH), although other releasing factors (RF) have been postulated to exist. Using a bioinformatic approach, we have identified a novel peptide, phoenixin, that regulates pituitary gonadotrophin secretion by modulating the expression of the GnRH receptor, an action with physiologically relevant consequences. Compromise of phoenixin in vivo using small interfering RNA resulted in the delayed appearance of oestrus and a reduction in GnRH receptor expression in the pituitary. Phoenixin may represent a new class of hypothalamically-derived pituitary priming factors that sensitise the pituitary to the action of other RFs, rather than directly stimulating the fusion of secretary vesicles to pituitary membranes.
Assuntos
Hormônios Hipotalâmicos/metabolismo , Hormônios Peptídicos/metabolismo , Hormônios Hipofisários/isolamento & purificação , Reprodução/genética , Sequência de Aminoácidos , Animais , Células Cultivadas , Clonagem Molecular , Relação Dose-Resposta a Droga , Feminino , Fármacos para a Fertilidade/química , Fármacos para a Fertilidade/isolamento & purificação , Fármacos para a Fertilidade/metabolismo , Fármacos para a Fertilidade/farmacologia , Hormônio Liberador de Gonadotropina/genética , Hormônio Liberador de Gonadotropina/metabolismo , Hormônios Hipotalâmicos/genética , Hormônios Hipotalâmicos/isolamento & purificação , Hormônios Hipotalâmicos/farmacologia , Hormônio Luteinizante/sangue , Masculino , Dados de Sequência Molecular , Hormônios Peptídicos/genética , Hormônios Peptídicos/isolamento & purificação , Hormônios Peptídicos/farmacologia , Hormônios Hipofisários/genética , Hormônios Hipofisários/metabolismo , Hormônios Hipofisários/farmacologia , Ratos , Ratos Sprague-Dawley , Reprodução/efeitos dos fármacos , Reprodução/fisiologia , Homologia de Sequência de AminoácidosRESUMO
A cDNA clone (C3) with high homology to plant oleosins was isolated from citrus cultured cells. The 827-bp cDNA insert has an open reading frame of 144 amino-acid residues. The central hydrophobic domain of the protein is nearly identical to oleosins from Brassica napus and maize, and the C-terminal hydrophilic region following the hydrophobic domain is also highly conserved. The steady-state level of mRNA hybridizing to C3 was significantly increased upon exposure of citrus cells to 0.2 M NaCl. A lower level of transcript was found in seeds, but none could be detected in any other vegetative tissue (leaves, roots or fruit) even in the presence of salt under the conditions used. The induction of the oleosin homologue in citrus cells by salt does not depend on the developmental stage of the cells.