30GATA augments GnRH-mediated increases in Adcyap1 gene expression in pituitary gonadotrope cells

Pituitary adenylate cyclase-activating polypeptide 1 (PACAP or ADCYAP1) regulates gonadotropin biosynthesis and secretion, both alone and in conjunction with gonadotropin-releasing hormone (GnRH). Initially identified as a hypothalamic-releasing factor, ADCYAP1 subsequently has been identified in pituitary gonadotropes, suggesting it may act as an autocrine-paracrine factor in this tissue. GnRH has been shown to increase pituitary Adcyap1 gene expression though the interaction of CREB and jun/fos with CRE/AP-1 cis-elements in the proximal promoter. For the current studies, we were interested in identifying additional transcription factors and cognate cis-elements which regulate Adcyap1 gene promoter activity and chose to focus on the GATA family of transcription factors known to be critical for both pituitary cell differentiation and gonadotropin subunit expression. By transient transfection and EMSA analysis, we demonstrate that GATA2 and GATA4 stimulate Adcyap1 promoter activity via a GATA cis-element located at position −191 in the rat Adcyap1 gene promoter. Furthermore, we show that addition of GATA2 or GATA4 significantly augments GnRH-mediated stimulation of Adcyap1 gene promoter activity in the gonadotrope LβT2 cell line. Conversely, blunting GATA expression with specific siRNA inhibits the ability of GnRH to stimulate ADCYAP1 mRNA levels in these cells. These data demonstrate a complex interaction between GnRH and GATA on ADCYAP1 expression, providing important new insights into the regulation of gonadotrope function.