Breast Cancer Associated Estrogen Receptors: Catechol Estrogen Receptors in ER-Minus Mice
Abstract
Previous studies suggest the presence of a distinct non-ER-alpha/ER-beta estrogen-signaling pathway in the ER-alpha-KO mouse. To further characterize the receptor mechanism regulating these novel 4OHE2-induced responses, we have synthesized (3H)4OHE2 (4-hydroxy-estradiol) and (3H)4OHEl (4-hydroxyestrone) using a cytochrome P450-mediated enzymatic procedure. Using ER-alpha-KO cellular cytosolic extracts, (3H)4OHE2 specific binding was competed with various unlabeled catechol estrogen compounds but not unlabeled 17-beta-E2 and ICI 182,780. (3H)4OHE2 binding studies indicated significant binding differences among various tissues in WT (wild-type), ER-alpha-KO and ArKO (aromatase knockout) female mice which may indicate regulation by either E2 or ER-square. In WT & ER-alpha-KO mice, the highest concentrations of specific (3H)4OHE2 binding were found in the bladder, lung & skeletal muscle. Interestingly, the highest concentrations of specific (3H)4OHE2 binding among ArKO tissues were found in the mammary, uterus and ovary. Scatchard analysis of (3H)4OHE1 binding in ER-alpha-KO mice identified a single class of high-affinity (Kd ^/= 1.7 nM), saturable binding sites in several tissues not competed by E2. Collectively, our results suggest the interaction of these radiolabeled catechol estrogen compounds with a putative mouse "ER-gamma" protein. Efforts to clone this "ER-gamma" are ongoing.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2000
- Accession Number
- ADA396166
Entities
People
- Dennis B. Lubahn
Organizations
- University of Missouri