RT Journal Article
SR Electronic
T1 The Third Intracellular Loop of the Rat and Mouse Cholecystokinin-A Receptors Is Responsible for Different Patterns of Gene Activation
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1381
OP 1388
DO 10.1124/mol.58.6.1381
VO 58
IS 6
A1 Roya Poosti
A1 Laure di Malta
A1 Didier Gagne
A1 Nicole Bernad
A1 Jean-Claude Galleyrand
A1 Chantal Escrieut
A1 Sandrine Silvente-Poirot
A1 Daniel Fourmy
A1 Jean Martinez
YR 2000
UL http://molpharm.aspetjournals.org/content/58/6/1381.abstract
AB It has previously been reported that the cholecystokinin analog JMV-180 behaves differently on the rat and the mouse cholecystokinin-A receptor (CCK-AR). In mice this analog acts as an agonist on low- and high-affinity sites of the CCK-AR, whereas in rats this compound acts as an agonist on high-affinity sites and as an antagonist on low-affinity sites. In an attempt to understand why the same compound behaves differently on these two CCK-A receptors, we cloned the cDNA encoding the mouse CCK-AR. We then investigated a cellular model able to mimic the effect that was observed in rats and mice. HeLa cells were transiently cotransfected with plasmids leading to expression of the rat or mouse CCK-AR in the presence of pFos-Luc as reporter plasmid; such a plasmid placed the regulatory part of the humanc-Fos gene upstream from the firefly luciferase structural gene (Luc). We then observed that the two CCK-A receptors behaved differently, not only in the presence of compound JMV-180 but also in the presence of cholecystokinin or even in absence of ligand; the rat CCK-AR was 2 to 3 times more potent than the mouse CCK-AR in inducing the reporter protein, whatever the ligand studied. This result was confirmed using the same kind of experiment with the reporter plasmid p(TRE)3-tk-Luc. Using various mutated receptors, we investigated the role of the putative third intracellular loop. We concluded that both the primary structure of the receptor and the cellular context are in part responsible for the differential behavior of these CCK-A receptors.