Structural architecture of a dimeric class C GPCR based on co-trafficking of sweet taste receptor subunits

Jihye Park, Balaji Selvam, Keisuke Sanematsu, Noriatsu Shigemura, Diwakar Shukla, Erik Procko

Research output: Contribution to journalArticle

Abstract

Class C G protein– coupled receptors (GPCRs) are obligatory dimers that are particularly important for neuronal responses to endogenous and environmental stimuli. Ligand recognition through large extracellular domains leads to the reorganization of transmembrane regions to activate G protein signaling. Although structures of individual domains are known, the complete architecture of a class C GPCR and the mechanism of interdomain coupling during receptor activation are unclear. By screening a mutagenesis library of the human class C sweet taste receptor subunit T1R2, we enhanced surface expression and identified a dibasic intracellular retention motif that modulates surface expression and co-trafficking with its heterodimeric partner T1R3. Using a highly expressed T1R2 variant, dimerization sites along the entire subunit within all the structural domains were identified by a comprehensive mutational scan for co-trafficking with T1R3 in human cells. The data further reveal that the C terminus of the extracellular cysteine-rich domain needs to be properly folded for T1R3 dimerization and co-trafficking, but not for surface expression of T1R2 alone. These results guided the modeling of the T1R2–T1R3 dimer in living cells, which predicts a twisted arrangement of domains around the central axis, and a continuous folded structure between transmembrane domain loops and the cysteine-rich domains. These insights have implications for how conformational changes between domains are coupled within class C GPCRs.

Original languageEnglish (US)
Pages (from-to)4759-4774
Number of pages16
JournalJournal of Biological Chemistry
Volume294
Issue number13
DOIs
StatePublished - Mar 29 2019

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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