Ac His1 [D-Phe2, K15, R16, L27] VIP (3-7)/GRF (8-27)--a VPAC1 receptor antagonist--is an inverse agonist on two constitutively active truncated VPAC1 receptors.
C-terminally truncated human VPAC(1) receptors were constructed and stably transfected in Chinese hamster ovary (CHO) cells. Selected clones expressing comparable receptor densities were studied for ligand's binding properties, basal and stimulated adenylate cyclase activity. The wild-type (1-457) receptor served as reference. The binding properties of all the constructions were preserved. As judged by the intrinsic activity of the partial agonist Q(3)-VIP, the shortest receptors have a moderate impairment of the coupling efficacy to G(alpha s) protein. Cells expressing the VPAC(1) (1-436) and (1-441) truncated receptors had a two- to three-fold higher basal adenylate cyclase activity than those expressing the wild-type or the VPAC(1) (1-444), (1-433), (1-429), (1-421) and (1-398) receptor. The stimulatory effect of VIP and other agonist was preserved. This suggested that VPAC(1) (1-436) and (1-441) receptors had a constitutive activity. The selective VPAC(1) receptor antagonist Ac His(1) [D-Phe(2), K(15), R(16), L(27)] VIP (3-7)/GRF (8-27) reduced by 60% the basal activity with an EC(50) value of 3 nM comparable to its IC(50) value for binding. This agonist behaved thus like an inverse agonist on the constitutively active VPAC(1) receptors generated by C-terminal truncation and expressed in CHO cells.
Vertongen
Pascale
P
Department of Biochemistry and Nutrition, School of Medicine, Université Libre de Bruxelles, Bât G/E, CP 611, B-1070 Bruxelles, Belgium. pvertong@ulb.ac.be
Langlet
Christelle
C
Langer
Ingrid
I
Gaspard
Nathalie
N
Robberecht
Patrick
P
D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D020128:Inhibitory Concentration 50; D007457:Iodine Radioisotopes; D008024:Ligands; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000494:pharmacology; D011487:Protein Conformation; D018005:Receptors, Vasoactive Intestinal Peptide / Q000737:chemistry* / Q000378:metabolism; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014162:Transfection; D014660:Vasoactive Intestinal Peptide / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*
D007457:Iodine Radioisotopes; D008024:Ligands; D010456:Peptides, Cyclic; D018005:Receptors, Vasoactive Intestinal Peptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D011994:Recombinant Proteins; D014660:Vasoactive Intestinal Peptide; D000262:Adenylyl Cyclases