mHypoA-55 cells are kisspeptin-expressing neuronal cells originating from the arcuate nucleus of the mouse hypothalamus. These cells are called KNDy neurons because they co-express kisspeptin, neurokinin B, and dynorphin A. In addition, they express gonadotropin-releasing hormone (GnRH). Here, we found that kisspeptin 10 (KP10) increased Kiss-1 (encoding kisspeptin) and GnRH gene expression in kisspeptin receptor (Kiss-1R)-overexpressing mHypoA-55 cells. KP10 greatly increased serum response element (SRE) promoter activity, which is a target of extracellular signal-regulated kinase (ERK) (20.0 ± 2.54-fold). KP10 also increased cAMP-response element (CRE) promoter activity in these cells (2.32 ± 0.36-fold). KP10-increased SRE promoter activity was significantly prevented in the presence of PD098095, a MEK kinase (MEKK) inhibitor, and KP10-induced CRE promoter activity was also inhibited by PD098059. Similarly, H89, a protein kinase A (PKA) inhibitor, significantly inhibited the KP10 induction of SRE and CRE promoters. KP10-induced Kiss-1 and GnRH gene expressions were inhibited in the presence of PD098059. Likewise, H89 significantly inhibited the KP10-induced increase in Kiss-1 and GnRH. Transfection of mHypoA-55 cells with constitutively active MEKK (pFC-MEKK) increased SRE and CRE promoter activities by 9.75 ± 1.77- and 1.36 ± 0.12-fold, respectively. Induction of constitutively active PKA (pFC-PKA) also increased SRE and CRE promoter activities by 2.41 ± 0.42- and 40.71 ± 7.77-fold, respectively. Furthermore, pFC-MEKK and -PKA transfection of mHypoA-55 cells increased both Kiss-1 and GnRH gene expression. Our current observations suggest that KP10 increases both the ERK and PKA pathways and that both pathways mutually interact in mHypoA-55 hypothalamic cells. Activation of both ERK and PKA signaling might be necessary to induce Kiss-1 and GnRH gene expressions.
Keywords: GnRH; Hypothalamus; Kisspeptin; Signal transduction.
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