Egr-1 is a downstream effector of GnRH and synergizes by direct interaction with Ptx1 and SF-1 to enhance luteinizing hormone beta gene transcription.
Pituitary gonadotropins are critical regulators of gonadal development and function. Expression and secretion of the mature hormones are regulated by gonadotropin-releasing hormone (GnRH), which is itself secreted from the hypothalamus. GnRH stimulation of gonadotropin expression and secretion occurs through the G-protein-linked phospholipase C/inositol triphosphate intracellular signaling pathway, which ultimately leads to protein kinase C (PKC) activation and increased intracellular calcium levels. Transcription factors mediating the effects of GnRH-induced signals on transcription of gonadotropin genes have not yet been identified. Recent studies have identified key factors involved in luteinizing hormone beta (LHbeta) gonadotropin gene transcription: the nuclear receptor SF-1, the bicoid-related homeoprotein Ptx1 ( Pitx1), and the immediate-early Egr-1 gene. We now show that GnRH is a potent stimulator of Egr-1, but not Ptx1 or SF-1, expression. Further, Egr-1 activation of the LHbeta promoter is specifically enhanced by PKC, in agreement with a role for Egr-1 in mediating a GnRH effect on transcription. Egr-1 interacts directly with Ptx1 and with SF-1, leading to an enhancement of Ptx1- and SF-1- induced LHbeta transcription. Thus, Egr-1 is a likely transcriptional mediator of GnRH- induced signals for activation of the LHbeta gene.[1]References
- Egr-1 is a downstream effector of GnRH and synergizes by direct interaction with Ptx1 and SF-1 to enhance luteinizing hormone beta gene transcription. Tremblay, J.J., Drouin, J. Mol. Cell. Biol. (1999) [Pubmed]
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