title: Spatial proximity between the VPAC1 receptor and the amino terminus of agonist and antagonist peptides reveals distinct sites of interaction.
abstract: Vasoactive intestinal peptide (VIP) plays a major role in pathophysiology. Our previous studies demonstrated that the VIP sequence 6-28 interacts with the N-terminal ectodomain (N-ted) of its receptor, VPAC1. Probes for VIP and receptor antagonist PG97-269 were synthesized with a photolabile residue/Bpa at various positions and used to explore spatial proximity with VPAC1. PG97-269 probes with Bpa at position 0, 6, and 24 behaved as high-affinity receptor antagonists (K(i)=12, 9, and 7 nM, respectively). Photolabeling experiments revealed that the [Bpa(0)]-VIP probe was in physical contact with VPAC1 Q(135), while [Bpa(0)]-PG97-269 was covalently bound to G(62) residue of N-ted, indicating different binding sites. In contrast, photolabeling with [Bpa(6)]- and [Bpa(24)]-PG97-269 showed that the distal domains of PG97-269 interacted with N-ted, as we previously showed for VIP. Substitution with alanine of the K(143), T(144), and T(147) residues located in the first transmembrane domain of VPAC1 induced a loss of receptor affinity (IC(50)=1035, 874, and 2070 nM, respectively), and pharmacological studies using VIP2-28 indicated that these three residues play an important role in VPAC1 interaction with the first histidine residue of VIP. These data demonstrate that VIP and PG97-269 bind to distinct domains of VPAC1.
authors.affiliation: INSERM U773/CRB3, Faculté de Médecine X. Bichat, 16 rue Henri Huchard, 75018 Paris, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Ceraudo
authors.forename: Régine
authors.initials: R
authors.lastname: Hierso
authors.forename: Yossan-Var
authors.initials: YV
authors.lastname: Tan
authors.forename: Samuel
authors.initials: S
authors.lastname: Murail
authors.forename: Christiane
authors.initials: C
authors.lastname: Rouyer-Fessard
authors.forename: Pascal
authors.initials: P
authors.lastname: Nicole
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Robert
authors.forename: Nadège
authors.initials: N
authors.lastname: Jamin
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Neumann
authors.forename: Patrick
authors.initials: P
authors.lastname: Robberecht
authors.forename: Marc
authors.initials: M
authors.lastname: Laburthe
authors.forename: Alain
authors.initials: A
authors.lastname: Couvineau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D019920:Photoaffinity Labels; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D010455:Peptides; D019920:Photoaffinity Labels; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I