Functional importance of GLP-1 receptor species and expression levels in cell lines

• Published in: Regulatory peptides Vol. 175; no. 1-3; pp. 21 - 29
• Main Authors: Knudsen, Lotte Bjerre, Hastrup, Sven, Underwood, Christina Rye, Wulff, Birgitte Schjellerup, Fleckner, Jan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.04.2012
• Subjects: Adenylyl Cyclases - metabolism; Amino Acid Sequence; Animals; Cell Line; Cell Membrane - metabolism; Cricetinae; Glucagon-Like Peptide 1 - pharmacology; Glucagon-Like Peptide-1 Receptor; GPCR; Humans; Immunoblotting; Incretin; Liraglutide; Lung - cytology; Lung - drug effects; Lung - metabolism; Metabolite; Mice; Molecular Sequence Data; Rabbits; Rats; Receptors, Glucagon - metabolism; Sequence Homology, Amino Acid; Swine; Incretin; GPCR; Metabolite; Liraglutide
• ISSN: 0167-0115; 1873-1686; 1873-1686
• DOI: 10.1016/j.regpep.2011.12.006

Of the mammalian species, only the GLP-1 receptors of rat and human origin have been described and characterized. Here, we report the cloning of the homologous GLP-1 receptors from mouse, rabbit, pig, cynomolgus monkey and chimp. The GLP-1 receptor is highly conserved across species, thus underlining the physiological importance of the peptide hormone and its receptor across a wide range of mammals. We expressed the receptors by stable transfection of BHK cells, both in cell lines with high expression levels of the cloned receptors, as well as in cell lines with lower expression levels, more comparable to endogenous expression of these receptors. High expression levels of cloned GLP-1 receptors markedly increased the potency of GLP-1 and other high affinity ligands, whereas the Kd values were not affected. For a low affinity ligand like the ago-allosteric modulator Compound 2, expression levels of the human GLP-1 receptor were important for maximal efficacy as well as potency. The two natural metabolites of GLP-1, GLP-1(9–37) and GLP-1(9–36)amide were agonists when tested on a cell line with high expression of the recombinant human GLP-1 receptor, whereas they behaved as (low potent) antagonists on a cell line that expressed the receptor endogenously, as well as cells expressing a moderate level of the recombinant human GLP-1 receptor. The amide form was a more potent agonist than the free acid from. In conclusion, receptor expression level is an important parametre for selecting cell lines with cloned GLP-1 receptors for functional characterization of physiological and pharmaceutical ligands. ►Five novel species' GLP-1 receptors are reported cloned and characterized. ►Receptor expression level correlates with the potency for high affinity agonists. ►Over-expression of cloned receptors is physiologically irrelevant. ►Functional receptor data should always be seen in relation to expression levels.