Estradiol stimulates tyrosine phosphorylation of the insulin-like growth factor-1 receptor and insulin receptor substrate-1 in the uterus.
The signaling pathways associated with estrogen-induced proliferation of epithelial cells in the reproductive tract have not been defined. To identify receptor tyrosine kinases that are activated in vivo by 17 beta-estradiol (E2), uteri from ovariectomized mice were examined for enhanced tyrosine phosphorylation of various receptors and a receptor substrate following treatment with this hormone. Within 4 hr after hormone exposure, extracts showed increased phosphotyrosine (P-Tyr) immunoreactivity at several bands, including 170- and 180-kDa; these bands were still apparent at 24 hr after E2. Analysis of immunoprecipitates from uterine extracts revealed that E2 enhanced tyrosine phosphorylation of the insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor substrate-1 (IRS-1) by 6 hr. Comparison of supernatants from IRS-1 and control rabbit IgG immunoprecipitates indicated that the 170-kDa P-Tyr band in extracts was equivalent to IRS-1. The receptors for epidermal growth factor, platelet-derived growth factor, and basic fibroblast growth factor did not exhibit an E2-induced increase in P-Tyr content. The nonestrogenic steroid hormones examined did not stimulate the P-Tyr content of IGF-1R or IRS-1. Immunolocalization of P-Tyr and IRS-1 revealed strong reactivity in the epithelial layer of the uterus from E2-treated mice, suggesting that the majority of P-Tyr bands observed in immunoblots originate in the epithelium. Since hormonal activation of IRS-1 is epithelial, estrogen-specific, and initiated before maximal DNA synthesis occurs following treatment with hormone, this protein, as part of the IGF-1R pathway, may be important in mediating estrogen-stimulated proliferation in the uterus.
Richards
R G
RG
Hormones and Cancer Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
DiAugustine
R P
RP
Petrusz
P
P
Clark
G C
GC
Sebastian
J
J
D000818:Animals; D015153:Blotting, Western; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007150:Immunohistochemistry; D055504:Insulin Receptor Substrate Proteins; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D010052:Ovariectomy; D010750:Phosphoproteins / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis / Q000378:metabolism; D011817:Rabbits; D017526:Receptor, IGF Type 1 / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D014599:Uterus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D010750:Phosphoproteins; D019000:Phosphotyrosine; D004958:Estradiol; D017526:Receptor, IGF Type 1