FUNCTIONAL AND STRUCTURAL ANALYSIS OF GLUCOCORTICOID AND PROGESTERONE RECEPTOR CROSSTALK

ALVES, N. R. CARINA; DANSEY, M. VIRGINIA; PECCI, ADALI; ALVAREZ, LAUTARO D.

Mar del Plata

Congreso; REUNIÓN CONJUNTA SAIC SAI&FAIC SAFIS 2022; 2022

Steroid Receptors (SR; Estrogen, Androgen, Progesterone, Glucocorticoid, and Mineralocorticoid Receptors) are ligand-activated transcription factors involved in cell signaling, survival, and proliferation. SRs share conserved sequences and structures arranged in an N-terminal domain, a highly conserved DNA-binding domain (DBD), and a conserved ligand-binding domain (LBD). Activated SRs dimerize and bind to hormone response elements (HRE). Since SRs are coexpressed and coactivated in many cell types, their integral study requires including their crosstalk mechanisms. Specifically, our group focused on PR/GR crosstalk and found an antagonisticeffect of activated GR on PR-dependent features, showing GR-PR complexes formation and co-recruitment to shared sites; on that basis, we aimed to assess a potential GR/PR direct interaction. In reporter gene assays with different HREs in various cell lines in the presence of selective GR agonist dexamethasone, selective PR agonist R5020, or both, we obtained marked interferences within their activity with combined treatment. In particular, using a single-HRE (AGAACAgttTGTTCT) reporter, we observed that one SR activation inhibits the other’s transcriptional activity. Picturing a possible heterodimerization scenario and based on GR/MR reports, we performed GR-DBD and PR-DBD structural analysis and molecular dynamics (MD) simulations of GR/PR homo and heterodimers bound to such HRE. MD analysis showed different dynamic behavior of thedimerization interface (D-loop) and adjacent residues (lever-arm) between homo and heterodimers. We identified unique interactions within each SR involved in D-loop stabilization; in particular, theorientation of a His in the lever-arm appears critical for GR proper dimer binding. Indeed, shifts in its orientation led to conformational D-loop rearrangements that destabilize heterodimers. In line withour experimental results, these observations could aid explain the interference we found in vitro.