Prolactin Receptor/STAT5b-Mediated Increases in Cytokine-Inducible SH2-Containing Protein and Suppressor of Cytokine Signaling 3 Promoter Activities are Repressed by Progesterone Receptors

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 112-141-Hypothalamus-Pituitary Development & Biology
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-141
Philip J Jensik* and Lydia A Arbogast
Southern Illinois University School of Medicine, Carbondale, IL
Prolactin (PRL) activates the PRL receptor (PRLR)/signal transducers and activators of transcription 5b (STAT5b) signaling pathway and upregulates cytokine-inducible SH2-containing protein (CISH) and suppressors of cytokine signaling 3 (SOCS3) expression in hypothalamic neuroendocrine dopaminergic neurons.  CISH and SOCS3 act as negative feedback to PRLR signaling.  Progesterone (P4) signaling represses STAT5b-mediated increases in CISH and SOCS3 expression through unknown mechanisms.  The aims of this study were to: 1) determine the influence of progesterone receptors (PR-A and PR-B) on PRLR/STAT5b-mediated activation of CISH and SOCS3 promoters and 2) examine the ability of PR to sustain PRLR/STAT5b signaling.  Mouse neuronal CAD cells were transiently transfected with 1) PRLR and STAT5b, 2) PR-A or PR-B, 3) CMV-Renilla luciferase (transfection efficiency control) and 4) CISH (-0.5 or -1.5 kb) or SOCS3 (-0.5 or -1.5 kb) luciferase promoter constructs.  Transfected cells were treated for 24 hours with vehicle, ovine PRL (1000 ng/mL), P4 (200 nM), or both PRL and P4 and then CISH and SOCS3 promoter activities were assessed.  As expected, PRL treatment alone increased CISH and SOCS3 promoter activities 5-7 fold.  P4 treatment alone did not alter CISH or SOCS3 promoter activities above basal (vehicle) levels.  However, in PR-A co-transfected cells treated with PRL and P4 there was a 52 and 60% decrease in CISH -0.5 kb and -1.5 kb and a 45 and 60% decrease in SOCS3 -0.5 kb and -1.5 kb promoter activities, respectively compared to PRL treatment alone.  In PR-B co-transfected cells treated with both PRL and P4 there was a 57 and 73% decrease in CISH -0.5 kb and -1.5 kb promoter activity, respectively.  Interestingly, there was no significant decrease in SOCS3 promoter activities in PR-B co-transfected cells treated with PRL and P4. The ability of PR to sustain PRLR/STAT5b signaling was then analyzed in vitro using CAD cells transfected with PRLR, STAT5b, PR-A and SOCS3 minigene (SOCS3 promoter fused to SOCS3 coding sequence) constructs and treated with PRL or both PRL and P4 for 6 hours.  Expression of SOCS3 through the minigene is induced by PRLR/STAT5b signaling.  PRLR/STAT5b signaling activity (measured by phospho STAT5b levels) was elevated in the cells treated with both PRL and P4 compared to PRL treatment alone.  These data indicate that PR can inhibit PRLR/STAT5b-induced expression of CISH and SOCS3 and thus can sustain PRLR/STAT5b signaling.

Nothing to Disclose: PJJ, LAA

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: NIH Grant HD045805  NIH Grant HD048925
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