FLUORESCEIN-TRP(25)-EXENDIN-4, A BIOLOGICALLY-ACTIVE FLUORESCENT-PROBE FOR THE HUMAN GLP-1 RECEPTOR

Exendin-4, a reptilian GLP-1 analogue, has been fluorescently labeled by covalently linking a fluorescein moiety onto the Trp residue yieldi ng fluorescein-Trp(25)-exendin-4 (FLEX). FLEX is equipotent to GLP-1(7 -36)-amide and exendin-4 as an inhibitor of [I-125] GLP-1 binding to t he human GLP-1 receptor stably expressed in CHO cells, and maintains f ull biological potency and efficacy as measured by the stimulation of cAMP accumulation in these cells. FLEX binding to CHO/hGLP-1R membrane s results in an increase in fluorescence anisotropy. The binding is sp ecific and saturable (K-d = 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. (C) 1997 Elsevier Science Inc.