Glycoprotein hormone receptors: Link between receptor homodimerization and negative cooperativity

Eneko Urizar, Lucia Montanelli, Tiffany Loy, Marco Bonomi, Stéphane Swillens, Céline Gales, Michel Bouvier, Guillaume Smits, Gilbert Vassart, Sabine Costagliola

Research output: Contribution to journalArticle

Abstract

The monomeric model of rhodopsin-like G protein-coupled receptors (GPCRs) has progressively yielded the floor to the concept of GPCRs being oligo(di)mers, but the functional correlates of dimerization remain unclear. In this report, dimers of glycoprotein hormone receptors were demonstrated in living cells, with a combination of biophysical (bioluminescence resonance energy transfer and homogenous time resolved fluorescence/fluorescence resonance energy transfer), functional and biochemical approaches. Thyrotropin (TSHr) and lutropin (LH/CGr) receptors form homo- and heterodimers, via interactions involving primarily their heptahelical domains. The large hormone-binding ectodomains were dispensable for dimerization but modulated protomer interaction. Dimerization was not affected by agonist binding. Observed functional complementation indicates that TSHr dimers may function as a single functional unit. Finally, heterologous binding-competition studies, performed with heterodimers between TSHr and LH/CG-TSHr chimeras, demonstrated the unsuspected existence of strong negative cooperativity of hormone binding. Tracer desorption experiments indicated an allosteric behavior in TSHr and, to a lesser extent, in LH/CGr and FSHr homodimers. This study is the first report of homodimerization associated with negative cooperativity in rhodopsin-like GPCRs. As such, it may warrant revisitation of allosterism in the whole GPCR family.

Original languageEnglish
Pages (from-to)1954-1964
Number of pages11
JournalEMBO Journal
Volume24
Issue number11
DOIs
Publication statusPublished - Jun 1 2005

Keywords

  • Allosterism
  • BRET
  • Glycoprotein hormone receptors
  • GPCR
  • Oligomerization

ASJC Scopus subject areas

  • Genetics
  • Cell Biology

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    Urizar, E., Montanelli, L., Loy, T., Bonomi, M., Swillens, S., Gales, C., Bouvier, M., Smits, G., Vassart, G., & Costagliola, S. (2005). Glycoprotein hormone receptors: Link between receptor homodimerization and negative cooperativity. EMBO Journal, 24(11), 1954-1964. https://doi.org/10.1038/sj.emboj.7600686