title: Elucidation of the vasoactive intestinal peptide pharmacophore for VPAC(2) receptors in human and rat and comparison to the pharmacophore for VPAC(1) receptors.
abstract: Vasoactive intestinal peptide (VIP) functions as a neurotransmitter involved in a number of physiological and pathological conditions. The actions of VIP are mediated through VPAC(1) and VPAC(2). In contrast to VPAC(1), which has been extensively studied, little is known about the pharmacology of VPAC(2). In this study we investigated the VIP pharmacophore for VPAC(2) by using alanine and D-amino acid scanning. We found significant species differences, and the human VPAC(2) (hVPAC(2)) expressed in Chinese hamster ovary (CHO) cells, which have been used in previous studies, differed significantly from the native hVPAC(2) in Sup T(1) cells and hVPAC(2) expressed in PANC1 cells. There was a close agreement between binding affinities and potencies for VPAC(2) activation. The amino acids whose backbone or side chain orientations were most important for high affinity potency are Asp(3), Phe(6), Thr(7), Tyr(10), Arg(12), Tyr(22), and Leu(23), whereas the side chains of Ser(2), Asp(8), Asn(9), Gln(16), Val(19), Lys(20), Lys(21), Asn(24), and Ser(25) are not essential. Comparison of the VIP pharmacophore between hVPAC(1) and hVPAC(2) demonstrated that the side chains of Thr(7), Tyr(10), Thr(11), and Tyr(22) were much more critical for high affinity for the hVPAC(2) than the hVPAC(1). In contrast, the orientation of the side chain of Asn(24) was more important for high affinity for the hVPAC(1). This study shows that in assessing the pharmacophore of VIP analogs for the VPAC(2), important species differences need to be considered as well as the expression system used. These results of our study should be useful for designing VPAC subtype-selective analogs, simplified analogs, and possibly metabolically stable analogs.
authors.affiliation: Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases/NIH, Building 10, 10 Center Drive, Bethesda, MD 20892, USA.
authors.forename: Hisato
authors.initials: H
authors.lastname: Igarashi
authors.forename: Tetsuhide
authors.initials: T
authors.lastname: Ito
authors.forename: Tapas K
authors.initials: TK
authors.lastname: Pradhan
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Mantey
authors.forename: Wei
authors.initials: W
authors.lastname: Hou
authors.forename: David H
authors.initials: DH
authors.lastname: Coy
authors.forename: Robert T
authors.initials: RT
authors.lastname: Jensen
mesh_terms: D000262:Adenylyl Cyclases / Q000096:biosynthesis / Q000235:genetics; D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D007457:Iodine Radioisotopes; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000494:pharmacology; D051381:Rats; D018005:Receptors, Vasoactive Intestinal Peptide / Q000737:chemistry / Q000187:drug effects*; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D014660:Vasoactive Intestinal Peptide / Q000819:agonists / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D000596:Amino Acids; D007457:Iodine Radioisotopes; D010455:Peptides; D010456:Peptides, Cyclic; D018005:Receptors, Vasoactive Intestinal Peptide; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; C089777:Ro 25-1553; D014660:Vasoactive Intestinal Peptide; D000262:Adenylyl Cyclases; D000409:Alanine