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Coupling of the Human Y2 Receptor for Neuropeptide Y and Peptide YY to Guanine Nucleotide Inhibitory Proteins in Permeabilized SMS‐KAN Cells

Abstract: Using guanine nucleotides, pertussis toxin, and specific antisera against the COOH‐terminals of the α‐subunits of Gi1/2, Gi3, and Go, the binding and biological response of the Y2 receptor (Y2R) for peptide YY (PYY) was probed in SMS‐KAN neuroblastoma cells. The specific binding of radiolabeled PYY exhibited a single apparent dissociation constant, KD = 76 pM for intact cells and KD = 906 pM for permeabilized cells. However, other data suggested existence of multiple receptor affinity states. A shift in KD and a decrease in apparent number of binding sites (Bmax) was observed in permeabilized cells when incubated with guanine nucleotides. By contrast, in membrane preparations guanine nucleotides induced only a decrease in Bmax. In intact cells, agonist exposure inhibited the intracellular accumulation of forskolin‐stimulated cyclic AMP by 80% (IC50 = 420 nM) compared with 94% inhibition (IC50 = 380 nM) in permeabilized cells. In permeabilized cells, preincubation with antisera against αi1/2 and αi3 blocked the functional response of PYY, with anti‐αi3 being the most potent; whereas anti‐αo failed to affect the cyclic AMP levels. These results suggest that permeabilized SMS‐KAN cells serve as a good model system for analysis of Y2R binding kinetics and functional response and that the Y2R interacts directly with several different Gis (but not Go).