“Extra-nuclear localization of alpha and beta estrogen receptors in C2C12 skeletal muscle cells “.

LORENA MILANESI; ANA RUSSO DE BOLAND; RICARDO BOLAND

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

EXTRA-NUCLEAR LOCALIZATION OF a AND b ESTROGEN RECEPTORS IN C2C12 SKELETAL MUSCLE CELLS. Milanesi Lorena, Russo de Boland Ana and  Boland Ricardo. Laboratorio de Química Biológica. Universidad Nacional del Sur. 8000  Bahía Blanca.  milanesi@criba.edu.ar There is evidence for extra- nuclear localization of estrogen receptors (ERs). We present biochemical, immunological and molecular data supporting non-classical localization of a and b ERs in C2C12 murine skeletal muscle cells. We first established binding characteristics in whole cells employing [3H]17b-estradiol and an excess of 17b-estradiol, 17a-estradiol, estradiol impeded ligands, agonists and antagonists. Saturation assays and blocking experiments with specific antibodies, performed in subcellular fractions, showed predominant specific binding activity in mitochondria and microsomes. Protein purification, Western and Ligand blots confirmed these results. Low molecular weight estrogen receptor a-like proteins representing a population of binding and immunoreactive sites were also detected. Immunocytological studies by conventional and confocal microscopy revealed that ERb was localized in mitochondria and ERa exhibited a perinuclear and a granular cytoplasmic distribution (Golgi apparatus, mitochondria and endoplasmic reticulum). The specific binding and the immunoreactivity detected by confocal microscopy and Western blots were reduced when cells were transiently transfected with specific ER a and b siRNAs. The non-classical distribution of native pools of ERs suggests an alternative mode of ER localization whose functions are under study (Vasconsuelo & Boland, SAIB 2006).