Identification of a Cyanine-Dye Labeled Peptidic Ligand for Y1R and Y4R, Based upon the Neuropeptide Y C-Terminal Analogue, BVD-15.

Traceable truncated Neuropeptide Y (NPY) analogues with Y1 receptor (Y1R) affinity and selectivity are highly desirable tools in studying receptor location, regulation, and biological functions. A range of fluorescently labeled analogues of a reported Y1R/Y4R preferring ligand BVD-15 have been prepared and evaluated using high content imaging techniques. One peptide, [Lys(2)(sCy5), Arg(4)]BVD-15, was characterized as an Y1R antagonist with a pKD of 7.2 measured by saturation analysis using fluorescent imaging. The peptide showed 8-fold lower affinity for Y4R (pKD = 6.2) and was a partial agonist at this receptor. The suitability of [Lys(2)(sCy5), Arg(4)]BVD-15 for Y1R and Y4R competition binding experiments was also demonstrated in intact cells. The nature of the label was shown to be critical with replacement of sCy5 by the more hydrophobic Cy5.5 resulting in a switch from Y1R antagonist to Y1R partial agonist.