Interaction of the N-terminus of ecdysone receptor isoforms with the ligand binding domain

Ch. Tremmel (1) , M. Schaefer (2) , A. Azoitei (1) , H. Ruff (1) , M. Spindler-Barth (1)

1 Universität Ulm - Ulm University [Ulm, Allemagne]
2 Leipzig University / Universität Leipzig

Ecdysone receptor (EcR) isoforms exert different biological functions, although they vary only in their N-terminal domain. Despite identical C-termini, which mediate hormone-induced activity, the influence of ligand is isoform specific, which indicates an N/C-interaction. The position of helix 12 with and without hormone varies among isoforms and modifies N/C-interaction determined by fluorescence resonance-energy transfer (FRET), which depends on the salt bridge between helices 4 and 12 of the ligand-binding domain (LBD). Disruption of the salt bridge by mutation of K497 (helix 4) had no effect on basal N/C interaction, but prevented the hormone-induced increase, which was partially restored by a salt bridge with reversed polarity. The heterodimerization partner Ultraspiracle (Usp) can compensate for the disruption of the salt bridge. Without ligand the AB-domains of EcR-A and EcR-B1, but not EcR-B2, interact with the LBD via K497 and repress transcriptional activity. This intramolecular cross talk between N- and C-terminus along with the position of helix 12 stabilized by K497 regulates transcriptional activity of EcR isoforms.

Mots clés: nuclear receptor; Corepressor; N/C-interaction; FRET; insect; nuclear receptor.

Ch. Tremmel, M. Schaefer, A. Azoitei, H. Ruff, M. Spindler-Barth. Interaction of the N-terminus of ecdysone receptor isoforms with the ligand binding domain. Molecular and Cellular Endocrinology, 2010, 332 (1-2), pp.293. ⟨10.1016/j.mce.2010.11.013⟩. ⟨hal-00654959⟩