Requirement of estrogen receptor-alpha in insulin-like growth factor-1 (IGF-1)-induced uterine responses and in vivo evidence for IGF-1/estrogen receptor cross-talk.
In the uterus insulin-like growth factor-1 (IGF-1) signaling can be initiated by estradiol acting through its nuclear receptor (estrogen receptor (ER)) to stimulate the local synthesis of IGF-1. Conversely, in vitro studies have demonstrated that estradiol-independent ER transcriptional activity can be induced by IGF-1 signaling, providing evidence for a cross-talk mechanism between IGF-1 and ER. To investigate whether ER alpha is required for uterine responses to IGF-1 in vivo, both wild-type (WT) and ER alpha knockout (alpha ERKO) mice were administered IGF-1, and various uterine responses to IGF-1 were compared. In both WT and alpha ERKO mice, IGF-1 treatment resulted in phosphorylation of uterine IGF-1 receptor (IGF-1R) and formation of an IGF-1R/insulin receptor substrate-1/ phosphatidylinositol 3-kinase signaling complex. In addition, IGF-1 stimulated phosphorylation of uterine Akt and MAPK in both WT and alpha ERKO mice. However, IGF-1 treatment stimulated BrdUrd incorporation and proliferating cell nuclear antigen expression in WT uteri only. To determine whether ER alpha can be activated in vivo by IGF-1 signaling, transgenic mice carrying a luciferase gene driven by two estrogen response elements (ERE-luciferase mice) were utilized. Treatment of ovariectomized ERE-luciferase mice with IGF-1 resulted in an increase in uterine luciferase activity that was attenuated in the presence of the ER antagonist ICI 182,780. Together these data demonstrate that 1) functional signaling proximal to IGF-1R is maintained in the alpha ERKO mouse uterus, 2) ER alpha is necessary for IGF-1 induction of uterine nuclear proliferative responses, and 3) cross-talk between IGF-1R and ER signaling pathways exists in vivo.
Klotz
Diane M
DM
Laboratory of Molecular Carcinogenesis, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
Hewitt
Sylvia Curtis
SC
Ciana
Paolo
P
Raviscioni
Michele
M
Lindzey
Jonathan K
JK
Foley
Julie
J
Maggi
Adriana
A
DiAugustine
Richard P
RP
Korach
Kenneth S
KS
D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D004789:Enzyme Activation; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D005260:Female; D000077267:Fulvestrant; D015151:Immunoblotting; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011960:Receptors, Estrogen / Q000378:metabolism / Q000502:physiology*; D020218:Response Elements; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic; D014599:Uterus / Q000201:enzymology / Q000378:metabolism*
D001973:Bromodeoxyuridine; D004958:Estradiol; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D000077267:Fulvestrant; D007334:Insulin-Like Growth Factor I; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011960:Receptors, Estrogen