Fluorescein-Trp25-Exendin-4, a Biologically Active Fluorescent Probe for the Human GLP-1 Receptor

Abstract

Chicchi, G. G., M. A. Cascieri, M. P. Graziano, T. Calahan and M. R. Tota. Fluorescein-Trp25-exendin-4, a biologically active fluorescent probe for the human Glp-1 receptor. Peptides 18(2) 319–321, 1997.—Exendin-4, a reptilian GLP-1 analogue, has been fluorescently labeled by covalently linking a fluorescein moiety onto the Trp residue yielding fluorescein-Trp25-exendin-4 (FLEX). FLEX is equipotent to GLP-1(7–36)-amide and exendin-4 as an inhibitor of [125I]GLP-1 binding to the human GLP-1 receptor stably expressed in CHO cells, and maintains full biological potency and efficacy as measured by the stimulation of cAMP accumulation in these cells. FLEX binding to CHO/hGLP-1R membranes results in an increase in fluorescence anisotropy. The binding is specific and saturable (Kd = 2.0 ± 0.4 nM), and GLP-1(7–36)-amide and exendin-4 are equipotent inhibitors of FLEX binding to the human GLP-1 receptor. Thus, FLEX is a potent, biologically active ligand that is useful for the study of the binding and functional characteristics of the human GLP-1 receptor.