Abstract: 482

DIRECT VISUALIZATION OF MEMBRANE-MEDIATED UPTAKE AND TRANSLOCATION OF ESTROGEN-BSA: COLLOIDAL GOLD BY HEP G2 CELLS.

Robert Moats^{1 *}, Victor Ramirez^{1 *}
Department of Molecular and Integrative Physiology, University of Illinois, Urbana, IL ¹

Recent evidence suggests that estradiol can modify mitochondrial ion permeability and inhibit a key enzyme in the mitochondrial electron transport chain. Current experiments have visualized the membrane-mediated uptake and translocation of estradiol-17-17 hemisuccinate: BSA colloidal gold conjugate (E17BSA: Au) in Hep G2 cells in culture. Isolated plasmalemmal/microsomal fractions (P3 fractions) from Hep G2 cells display stereospecific, high-affinity binding of E17[¹²⁵I]BSA (K_d = 1.26 nM, B_max = 68.5 pmol/mg protein). These cells also rapidly transport E17[¹²⁵ I]BSA from the P3 fraction to the mitochondrial/lysosomal fraction (P2 fraction; maximum uptake 138 ± 13 fmol/mg protein). [¹²⁵ I]BSA is not removed from the culture medium (maximum uptake 2.98 ± 0.3 fmol/mg protein). Electron micrography using E17BSA: Au in Hep G2 cells has shown uptake of this ligand by clathrin coated pits, indicating a receptor-mediated endocytosis. Furthermore, the ligand could also be found in multivesicular bodies, suggesting involvement of the CURL. As soon as 1 hr post-exposure, the colloidal gold ligand could be seen in large, membrane-delimned organelles, many with vesiculated interiors resembling rounded, vesiculated mitochondria. These results are the first to visually demonstrate the membrane binding and uptake of an estrogen-containing ligand while allowing the subcellular structures responsible to be seen.

    This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.