?Non-classical localization of 17beta-estradiol binding proteins in C2C12 muscle cell line.?

MILANESI, LORENA; RUSSO DE BOLAND, ANA; BOLAND, RICARDO

Pinamar, argentina

Congreso; XLI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB), XX Reunión Anual de la SAN y X Congreso de la PABMB; 2005

SAIB

NON-CLASSICAL LOCALIZATION OF ESTROGEN BINDING PROTEINS IN C2C12 MUSCLE CELL LINE. Milanesi Lorena, Russo de Boland Ana and  Boland Ricardo. Laboratorio de Química Biológica. Universidad Nacional del Sur.8000  Bahía Blanca.  milanesi @criba.edu.ar       The classical isoform of the estrogen receptor (ERa) has been reported to localize almost exclusively in the nucleus. However, studies on non-genomic steroid effects have also suggested the existence of receptors residing at the cell surface. In this work we present biochemical and immunological data supporting extra-nuclear ERa localization in C2C12 murine muscle cell line. Immunocytological studies revealed that estrogen binding proteins have mitochondrial and perinuclear localization. The immunoreactivity was estrogen-responsive since the hormone impeded the binding of a specific antibody against the steroid ligand domain of the ERa. These results were confirmed by the detection of estrogen binding sites using fluorescent estrogen-BSA conjugates and binding assays, in which tritiated estradiol could be partially displaced by different estrogen agonists and antagonists. Western blot detection and protein purification of ERa in subcellular fractions using estrogen-BSA and specific antibodies confirmed that ERa-like proteins could be expressed at the mitochondrial-microsomal level. The non-classical distribution of native pools of ERa-related immunoreactivity suggests an alternative mode of ERa localization/function in muscle cells.