title: Glucose and sucrose act as agonist and mannose as antagonist ligands of the G protein-coupled receptor Gpr1 in the yeast Saccharomyces cerevisiae.
abstract: Several examples of G protein-coupled receptors have recently been suggested to respond to common sugars in millimolar concentrations. This low affinity has made it difficult to demonstrate direct receptor-ligand interaction. In the yeast Saccharomyces cerevisiae, rapid activation of the cAMP pathway by glucose and sucrose requires the GPCR Gpr1. Our results obtained by cysteine scanning mutagenesis and SCAM (substituted cysteine accessibility method) of residues in TMD VI provide strong evidence that glucose and sucrose directly interact as ligands with Gpr1. The affinity for sucrose is much higher. Structurally similar sugars such as galactose, mannose, and fructose do not act as agonists, but mannose acts as an antagonist for both sucrose and glucose. These results support the idea that Gpr1 directly senses sugars and that sugars can effectively bind GPCRs with a low affinity in a binding pocket formed by the transmembrane domains. The ligand repertoire of GPCRs can thus be extended to common sugars in millimolar concentrations.
authors.affiliation: Laboratorium voor Moleculaire Celbiologie, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, B-3001 Leuven-Heverlee, Flanders, Belgium.
authors.forename: Katleen
authors.initials: K
authors.lastname: Lemaire
authors.forename: Sam
authors.initials: S
authors.lastname: Van de Velde
authors.forename: Patrick
authors.initials: P
authors.lastname: Van Dijck
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D008024:Ligands; D008358:Mannose / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D013395:Sucrose / Q000378:metabolism*; D013997:Time Factors
chemical_list: C109334:GPR1 protein, S cerevisiae; D008024:Ligands; D043562:Receptors, G-Protein-Coupled; D029701:Saccharomyces cerevisiae Proteins; D013395:Sucrose; D000242:Cyclic AMP; D005947:Glucose; D003545:Cysteine; D008358:Mannose