Investigating G protein signalling bias at the glucagon-like peptide-1 receptor in yeast.
OBJECTIVE
The glucagon-like peptide 1 (GLP-1) receptor performs an important role in glycaemic control, stimulating the release of insulin. It is an attractive target for treating type 2 diabetes. Recently, several reports of adverse side effects following prolonged use of GLP-1 receptor therapies have emerged: most likely due to an incomplete understanding of signalling complexities.


METHODS
We describe the expression of the GLP-1 receptor in a panel of modified yeast strains that couple receptor activation to cell growth via single Gα/yeast chimeras. This assay enables the study of individual ligand-receptor G protein coupling preferences and the quantification of the effect of GLP-1 receptor ligands on G protein selectivity.


RESULTS
The GLP-1 receptor functionally coupled to the chimeras representing the human Gαs, Gαi and Gαq subunits. Calculation of the dissociation constant for a receptor antagonist, exendin-3 revealed no significant difference between the two systems. We obtained previously unobserved differences in G protein signalling bias for clinically relevant therapeutic agents, liraglutide and exenatide; the latter displaying significant bias for the Gαi pathway. We extended the use of the system to investigate small-molecule allosteric compounds and the closely related glucagon receptor.


CONCLUSIONS
These results provide a better understanding of the molecular events involved in GLP-1 receptor pleiotropic signalling and establish the yeast platform as a robust tool to screen for more selective, efficacious compounds acting at this important class of receptors in the future.
Division of Biomedical Cell Biology, Warwick Medical School, University of Warwick, Coventry, UK.
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C
Weston
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Poyner
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V
Patel
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Dowell
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Ladds
D019204:GTP-Binding Proteins / Q000378:metabolism*; D000067757:Glucagon-Like Peptide-1 Receptor / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000097789:Glucagon-Like Peptide-1 Receptor Agonists
D000067757:Glucagon-Like Peptide-1 Receptor; D019204:GTP-Binding Proteins; D000097789:Glucagon-Like Peptide-1 Receptor Agonists
G proteins; GPCR; diabetes; exenatide; glucagon; glucagon-like peptide-1 (GLP-1); liraglutide; signal bias