Synthesis and Biological Characterization of Novel Fluorescent Analogs of Vasopressin

摘要

Since the original synthesis of vasopressin, hundreds of its analogs have been synthesized and studied. However, only a few fluorescent vasopressin analogs are available [1-4]. The need for suitable fluorescent tools to study intracellular trafficking of G protein-coupled receptors has resulted in the search of novel fluorescent vasopressin (VP) analogs for receptor-ligand interactions. We base our study on previous studies that show the feasability of using cyclic fluorescent VP analogs to observe intracellular binding studies between ligand and VP receptor type 2 (V2R). The aim of this study was to develop a cyclic fluorescent vasopressin analog with high affinity, and containing a fluorophore with a good quantum yield and low pH-sensitivity. Thus, our studies involve the synthesis and biological activities of analogs with Lys8 modifications. In these analogs, Lys~8 was coupled to spacers of different lengths on the ε-amine, followed by coupling of fluorophores, 5 or 6-carboxytetramethylrhodamine (TAMRA) at amino groups of these spacers. The N-terminus of some analogs were also altered to incorporate (2mefcapto)propionic acid which formed a disulfide linkage with Cys~6. The biological activities of these analogs were measured using receptor affinity binding assays and cAMP production in LLC-PK1 cells.