A new approach to analyze cell surface protein complexes reveals specific heterodimeric metabotropic glutamate receptors.
G-protein-coupled receptors (GPCRs) can form heteromeric complexes. Herein, we describe a new approach to test the heteromerization of 2 receptors, or 2 receptor subunits, and to study the stoichiometry of the resulting complexes. As a proof-of-concept study, we investigated whether metabotropic glutamate receptors (mGluRs), in addition to being well-known homodimers, can form heteromers. To that aim, we combine the benefits of time-resolved fluorescence resonance energy transfer (trFRET) with the specific, cell-surface labeling of SNAP- and CLIP-tagged rat mGluR subunits, expressed in a mammalian cell line. First, we show that mGlu2 and mGlu4 subunits (but not mGlu2 and mGlu1) can heteromerize. Moreover, our trFRET data are consistent with mGluR subunits forming strict homodimeric receptors on single expression, and a combination of strict heterodimeric and strict homodimeric receptors on coexpression. Second, a comprehensive analysis reveals that from the 21 possible pairs of 2 mGluR subunits out of 7 subtypes (mGlu1 to 8, but not 6), only 11 are able to form heterodimers. These findings were further validated by biochemical and functional complementation studies. In addition to describing a new method to analyze cell-surface receptor complexes, our data reveal a new level of complexity within the mGluR family.
Doumazane
Etienne
E
Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, Montpellier, France.
Scholler
Pauline
P
Zwier
Jurriaan M
JM
Trinquet
Eric
E
Rondard
Philippe
P
Pin
Jean-Philippe
JP
D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002522:Chlorocebus aethiops; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D011485:Protein Binding; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D008565:Membrane Proteins; D021122:Protein Subunits; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; C108823:metabotropic glutamate receptor 4