CONICET | Buscador de Institutos y Recursos Humanos

, Insights on GR activity modulation through the binding of rigid steroid analogs Presman DM1, Álvarez LD3; Levi V1; Veleiro AS3; Burton G.3 and Pecci A1,2. FILIACIONES: 1Dpto Química Biológica, FCEN-UBA,2IFIBYNE-CONICET,3Dpto Química Orgánica, FCEN-UBA, UMYMFOR-CONICET - RESUMEN In previous works, we used molecular dynamics simulations to investigate the molecular basis of action of the selective antiglucocorticoid 21-Hydroxy-6,19-epoxyprogesterone (21OH-6,19OP) and the partial glucocorticoid receptor (GR) agonist 21-Hemisuccinate-6,19- epoxyprogesterone (21HS-6,19OP). The simulations of GR Ligand Binding Domain (GR-LBD) suggest that the GR-LBD-21OH-6,19OP complex is not able to homodimerize. On the other hand, the presence of the bulky hemisuccinate group induced a significant displacement of the average position of Helix 12 in the GR-LBD-21HS-6,19OP complex, possibly altering cofactors binding ability. In order to confirm or rule out the simulation predictions we performed experiments on living cells. First, we used a GFP-GR chimera to show that the rigid steroid analogs were able to induce GR nuclear translocation. Second, we performed transactivation assays in the presence or absence of the co-activator TIF2. Results suggest that the partial agonist 21HS-6,19OP recruits TIF2 to GR while the transactivation antagonist 21OH-6,19OP does not. Third, we performed transrepression assays to confirm the ability of both steroid analogs to activate GR heterodimerization. Finally, we are currently studying the aggregation state of GR upon steroid binding through N&B analysis, a technique that will allow us to investigate GR dimerization state in vivo. - Keywords: Glucocortioid receptor; receptor dimer; rigid steroid analogs; 21OH-6,19OP; 21HS-6,19OP; TIF2.