Human glucagon receptor monoclonal antibodies: antagonism of glucagon action and use in receptor characterization.

This paper describes the development and characterization of the first monoclonal antibody specific for the recently cloned human glucagon receptor (hGR), and its use in probing receptor structure and function. We demonstrate specificity of one of the antibodies, CIV395.7A, by immunofluorescence staining and immunoprecipitation analysis. In addition, CIV395.7A specifically competes with glucagon for the hormone binding site on the receptor, indicating that the antibody's specific recognition epitope overlaps with the receptor's hormone binding domain. As a consequence, the mAB antagonizes glucagon-stimulated signal transduction as assayed by in vitro cAMP accumulation. Binding inhibition studies further reveal that the antibody specifically recognizes the human and rat GR, but not mouse. Using hGR/glucagon-like peptide I receptor chimeras, we have localized the recognition epitope of the antibody to the membrane-proximal half of the amino-terminal extension of the receptor, thus defining a domain on the receptor which is involved in glucagon binding.