title: A structure-function study of PACAP using conformationally restricted analogs: Identification of PAC1 receptor-selective PACAP agonists.
abstract: Pituitary adenylate cyclase-activating polypeptide (PACAP) has widespread physiological/pathophysiological actions and there is increased interest for its use therapeutically, especially in the CNS (neuroprotection). Unfortunately, no selective PACAP-analogs exist for PACAP-preferring PAC1-receptors, primarily because of its high sequence identity to VIP and particularly, because of the inability of structure-function studies to separate the pharmacophore of PAC1-R from VPAC1-R, which has high affinity for PACAP and VIP. The present study attempted to develop PAC1-R-selective agonists primarily by making conformationally restricted PACAP-analogs in positions important for receptor-selectivity/affinity. Forty-six PACAP-related-analogs were synthesized with substitutions in positions 1-4, 14-17, 20-22, 28, 34, 38 and receptor-selectivity determined in PAC1-R,VPAC1-R,VPAC2-R-transfected or native cells from binding or cAMP-generation experiments. Fifteen PACAP-analogs had 6-78-fold higher affinities for PAC1-R than VPAC1-R and 13 were agonists. Although binding-affinities correlated significantly with agonist potency, the degree of receptor-spareness varied markedly for the different PACAP-analogs, resulting in selective potencies for activating the PAC1 receptor over the VPAC1 receptor from 0- to 103-fold. In addition, a number of PACAP-analogs were identified that had high selectivity for PAC1-R over VPAC2-R as well as PACAP-analogs that could prove more useful therapeutically because of substitutions known to extend their half-lives (substitutions at potential sites of proteolysis and attachment of long-chain fatty acids). This study provides for the first time a separation of the pharmacophores for PAC1-R and VPAC1-R, resulting in PACAP-related analogs that are PAC1-R-preferring. Some of these analogs, or their modifications, could prove useful as therapeutic agents for various diseases.
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, United States.
authors.forename: Irene
authors.initials: I
authors.lastname: Ramos-Álvarez
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, United States.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Mantey
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, United States.
authors.forename: Taichi
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, United States.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Nuche-Berenguer
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, United States.
authors.forename: Paola
authors.initials: P
authors.lastname: Moreno
authors.affiliation: Center for Cancer Research, Office of the Director, NCI, National Institutes of Health, Bethesda, MD 20892-1804, United States.
authors.forename: Terry W
authors.initials: TW
authors.lastname: Moody
authors.affiliation: Peptide Research Laboratory, Department of Medicine, Tulane University Health Sciences Center, New Orleans, LA 70112-2699, United States.
authors.forename: Jerome L
authors.initials: JL
authors.lastname: Maderdrut
authors.affiliation: Peptide Research Laboratory, Department of Medicine, Tulane University Health Sciences Center, New Orleans, LA 70112-2699, United States.
authors.forename: David H
authors.initials: DH
authors.lastname: Coy
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, United States. Electronic address: robertj@bdg10.niddk.nih.gov.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Jensen
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000819:agonists* / Q000737:chemistry*; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / Q000378:metabolism*; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000378:metabolism; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I / Q000378:metabolism; D020521:Stroke / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
chemical_list: D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D014660:Vasoactive Intestinal Peptide
keywords: Neuroprotection; PACAP; Stroke; Structure–function study; Traumatic brain injury; Vasoactive intestinal peptide