title: Novel cyclic peptide agonist of high potency and selectivity for the type II vasoactive intestinal peptide receptor.
abstract: Ro 25-1392 [Ac-Glu8,OCH3-Tyr10,Lys12,Nle17,Ala19,A sp25,Leu26,-Lys27,28-vasoactive intestinal peptide(cyclo 21-25)] is a cyclic peptide analog of vasoactive intestinal peptide (VIP) that potently exerts cellular effects typical of VIP. The selectivity of Ro 25-1392 for type I (VIPR1) and type II (VIPR2) VIP receptors was investigated first in competitive binding studies using Chinese hamster ovary cell transfectants stably expressing recombinant human VIPR1 and VIPR2. Nonradioactive Ro 25-1392 was as potent a competitive inhibitor as VIP for the binding of 125I-VIP to VIPR2 transfectants (Ki = 9.6 +/- 1.0 and 16 +/- 1.7 nM, respectively; mean +/- S.E.M., n = 4). In contrast, Ro 25-1392 had a very low affinity for VIPR1, compared with VIP, and attained a maximum of only 40% mean inhibition of binding of 125I-VIP at 1 microM. The affinity of VIP (Ki = 3.4 +/- 1.5 nM, mean +/- S.E.M., n = 4) for binding to VIPR1 was 1000-fold greater than that of Ro 25-1392. Ro 25-1392 evoked concurrent and concentration-dependent increases in intracellular levels of calcium and cyclic AMP (EC50 = 3.0 +/- 0.4 nM, mean +/- S.E.M., n = 4) in VIPR2 transfectants, but not in VIPR1 transfectants. The VIP receptor specificity of Ro 25-1392 was confirmed by preincubation of Chinese hamster ovary transfectants with 0.1 microM Ro 25-1392 for 18 hr at 37 degrees C, to down-regulate each type of VIP receptor. Pretreatment of VIPR2 transfectants with Ro 25-1392 decreased Bmax by a mean of 58% and VIP-induced increases in the intracellular concentration of cyclic AMP by a mean of 65%. In contrast, there was no significant change in VIPR1 transfectants after pretreatment with Ro 25-1392. Ro 25-1392 thus is selectively recognized by VIPR2, with consequent initiation of cyclic AMP and Ca+2 signals and down-regulation of VIPR2. This potent analog of VIP may prove useful for investigations of VIPR2-mediated physiological effects of VIP and exploration of the roles of VIPR2 in diseases.
authors.affiliation: Department of Medicine, University of California, San Francisco, USA.
authors.forename: M
authors.initials: M
authors.lastname: Xia
authors.forename: S P
authors.initials: SP
authors.lastname: Sreedharan
authors.forename: D R
authors.initials: DR
authors.lastname: Bolin
authors.forename: G O
authors.initials: GO
authors.lastname: Gaufo
authors.forename: E J
authors.initials: EJ
authors.lastname: Goetzl
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D015536:Down-Regulation; D006801:Humans; D010456:Peptides, Cyclic / Q000378:metabolism / Q000494:pharmacology*; D011869:Radioligand Assay; D018005:Receptors, Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014162:Transfection; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D010456:Peptides, Cyclic; D018005:Receptors, Vasoactive Intestinal Peptide; C106005:Ro 25-1392; D014660:Vasoactive Intestinal Peptide