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 r eceptor (hGR), and its use in probing receptor structure and function. We demonstrate specificity of one of the antibodies, CIV395.7A, by im munofluorescence staining and immunoprecipitation analysis. In additio n, CIV395.7A specifically competes with glucagon for the hormone bindi ng site on the receptor, indicating that the antibody's specific recog nition epitope overlaps with the receptor's hormone binding domain. As a consequence, the mAB antagonizes glucagon-stimulated signal transdu ction as assayed by in vitro cAMP accumulation. Binding inhibition stu dies further reveal that the antibody specifically recognizes the huma n and rat GR, but not mouse. Using hGR/glucagon-like peptide I recepto r chimeras, we have localized the recognition epitope of the antibody to the membrane-proximal half of the a mine-terminal extension of the receptor, thus defining a domain on the receptor which is involved in glucagon binding.