Prolactin Signaling Through the Short Isoform of its Receptor Represses Sp1 and Foxo3 Transcription Factors in Both ovaries and Decidua

Y. SANGEETA DEVI, AURORA SHEHU, JULIA HALPERIN, CARLOS STOCCO, JIFANG MAO, JAMIE LE AND GEULA GIBORI.

Monticello, USA

Conferencia; 10º Biennial Allerton Reproductive Biology Conference; 2007

University of Illinois at Urbana-Champaign

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} @font-face {font-family:Gisha; panose-1:2 11 5 2 4 2 4 2 2 3; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-2147481593 1073741890 0 0 33 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin-top:0in; margin-right:0in; margin-bottom:10.0pt; margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-fareast-font-family:Calibri; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-AR;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; mso-ascii-font-family:Calibri; mso-fareast-font-family:Calibri; mso-hansi-font-family:Calibri;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin-top:0in; margin-right:0in; margin-bottom:10.0pt; margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-fareast-font-family:Calibri; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-AR;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; mso-ascii-font-family:Calibri; mso-fareast-font-family:Calibri; mso-hansi-font-family:Calibri;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> Prolactin (PRL) is critical for the maintenance of pregnancy in rodent. This is due, in large part, to repression of genes detrimental to pregnancy in both the corpus luteum and decidua. Prolactin has been shown to bind to two distinct receptors; long (PRL-RL) and short (PRL-RS). PRL signaling through PRL-RL was shown to activate several pathways including JAK/STAT, PI3K/ AKT and MAPK; yet the signaling mechanism through PRL-RS has not been identified. Recently, we have shown that transgenic mice expressing only the PRL-RS developed premature ovarian failure due to massive granulosa and oocyte death.  In this investigation we show that activation of PRL-RS down regulates the activity of two transcription factors, SP1 and Foxo3 independently of PRL-RL. DNA binding activity of Sp1, which is known to prevent cell death in response to oxidative stress, is remarkably inhibited upon PRL treatment in ovary as well as in decidua. These results are confirmed by EMSA analysis using decidual tissue and ovarian cell line expressing PRL-RS only. The inhibition of Sp1 DNA binding activity appears to be regulated at the level of expression not at the level of phosphorylation. CK2, a kinase known to phosphorylate and inhibit DNA binding activity of Sp1 is not upregulated by PRL through PRL-RS whereas immunocytochemical analysis indicates that PRL treatment depletes nuclear expression of Sp1. Interestingly, we also found that Foxo3a, a transcription factor known to regulate follicular development, is profoundly down regulated. Using a cell line expressing only PRL-RS, we show that PRL induces Foxo3 protein degradation through a proteosomal-dependant pathway independent of Jak2 and AKT activation. PRL also suppresses Foxo3 gene expression. We have   isolated Foxo3 promoter and found in the 1578 bp ustream region several putative Sp1 binding sites. Taken together, our results indicate that PRL can signal through PRL-RS in the ovary as well as in the decidua, two of the known targets of PRL. Our results further revealed that PRL signaling through PRL-RS represses Sp1 and Foxo3a transcription factors at mRNA as well as protein levels and we propose that inhibition of Sp1 may be a mechanism of regulating Foxo3 expression.