ESTROGEN-SPECIFIC TARGET SITE IDENTIFIED BY E-11-ALPHA-HEMISUCCINATE-(2-[I-125]-IODOHISTAMINE) IN MOUSE-BRAIN MEMBRANES

Using photoaffinity labeling with the progesterone analogue, progester one-11 alpha-hemisuccinate-(2-[I-125]-iodohistamine) ([I-125]-his-PG), we identified and characterized a protein band of MW 29 kDa (p29) in mouse cerebellar membranes whose labeling is markedly inhibited by est rogens. Inhibition of the labeling was specific with respect to steroi d structure. Labeling was strongly inhibited by estradiol-17 beta, est radiol-17 alpha, and the anti-estrogen tamoxifen and the synthetic est rogen diethylstilbestrol. Other estrogens (estriol, estrone) were less effective and the steroids, dihydroandrosterone, androsterone and ald osterone were ineffective. Preincubation with estradiol-17 alpha or es tradiol-17 beta inhibited the labeling in a dose-dependent manner with IC50 values of 0.3 and 2.0 mu M, respectively. The extent of labeling was three times as high in cerebellar membranes from males as from fe males. In males, labeling of cerebellar membranes was greater than tha t of cortex or limbic region. The labeling pattern of p29 was also dif ferent in membranes prepared from cerebellum, heart and liver. Moreove r, PG enhanced the labeling of p29 in Liver demonstrating a tissue-spe cific mode of interaction. The present results characterize p29 as a m embrane-bound estrogen target site. Copyright (C) 1996 Elsevier Scienc e Ltd.