TY - JOUR T1 - Different Vasoactive Intestinal Polypeptide Receptor Domains Are Involved in the Selective Recognition of Two VPAC<sub>2</sub>-Selective Ligands JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1280 LP - 1287 DO - 10.1124/mol.56.6.1280 VL - 56 IS - 6 AU - Maria G. Juarranz AU - Jean Van Rampelbergh AU - Philippe Gourlet AU - Philippe De Neef AU - Johnny Cnudde AU - Patrick Robberecht AU - Magali Waelbroeck Y1 - 1999/12/01 UR - http://molpharm.aspetjournals.org/content/56/6/1280.abstract N2 - A vasoactive intestinal polypeptide (VIP) analog, acylated on the amino-terminal histidine by hexanoic acid (C6-VIP), behaved as a VPAC2 preferring agonist in binding and functional studies on human VIP receptors, and radioiodinated C6-VIP was a suitable ligand for binding studies on wild-type and chimeric receptors. We evaluated the properties of C6-VIP, its analog AcHis1-VIP, and the VPAC2-selective agonist Ro 25-1553 on the wild-type VPAC1 and VPAC2 receptors and on the chimeric receptors exchanging the different domains between both receptors. VIP had a normal affinity and efficacy on the chimeras starting with the amino-terminal VPAC2 receptor sequence. The binding and functional profile of these chimeric receptors suggested that the high affinity of Ro 25-1553 for VPAC2 receptors is supported by the amino-terminal extracellular domain, whereas the ability to prefer C6-VIP over VIP is supported by the VPAC2 fifth transmembrane (TM5)-EC3 receptor domain. These results further support the hypothesis that the central and carboxyl-terminal regions of the peptide (modified in RO 25-1553) recognize the extracellular amino-terminal region domain, whereas the amino-terminal VIP amino acids bind to the TM receptor core. VIP had a reduced affinity and efficacy on the N-VPAC1/VPAC2 and on the N→EC2-VPAC1/VPAC2 chimeric receptors. C6-VIP behaved as a high-affinity agonist on these constructions. The antagonists [AcHis1,d-Phe2,Lys15,Arg16,Leu27]VIP(3-7)/GRF(8-27) and VIP(5-27) had comparable affinities for the wild-type receptors and for the two latter chimeras, supporting the hypothesis that these chimeras were properly folded but unable to reach the high-agonist-affinity, active receptor conformation in response to VIP binding. ER -