Characterization of the melatoninergic MT3 binding site on the NRH:quinone oxidoreductase 2 enzyme.
Melatonin acts through a series of molecular targets: the G-protein coupled receptors, MT1 and MT2, and a third binding site, MT3, recently identified as the enzyme NRH:quinone oxydoreductase 2 (QR2). The relationship between the multiple physiological functions of melatonin and this enzyme remains unclear. Because of the relationship of QR2 with the redox status of cells, these studies could bring the first tools for a molecular rationale of the antioxidant effects of melatonin. In the present paper, we used a QR2-stably expressing cell line and hamster kidneys to compare the 2-[125I]-iodomelatonin and 2-[125I]-iodo-5-methoxycarbonylamino-N-acetyltryptamine binding data, and to characterize the MT3 binding site. We designed and tested compounds from two distinct chemicals series in a displacement assay of the two MT3 ligands, 2-[125I]-iodomelatonin and 2-[125I]-iodo-5-methoxycarbonylamino-N-acetyltryptamine from their cloned target. We also tested their ability to inhibit QR2 catalytic activity. These compounds were separated into two classes: those that bind within the catalytic site (and being inhibitors) and those that bind outside it (and therefore not being inhibitors). Compounds range from potent ligands (K(i) = 1 nM) to potent inhibitors (14 nM), and include one compound [NMDPEF: N-[2-(2-methoxy-6H-dipyrido[2,3-a:3,2-e]pyrrolizin-11-yl)ethyl]-2-furamide] active on both parameters in the low nanomolar range. To dissect the physio-pathological pathways in which QR2, MT3 and melatonin meet, one needs more compounds binding to MT3 and/or inhibitors of QR2 enzymatic activity. The compounds described in the present paper are new tools for such a task.
Mailliet
François
F
Division de Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, France.
Ferry
Gilles
G
Vella
Fanny
F
Berger
Sylvie
S
Cogé
Francis
F
Chomarat
Pascale
P
Mallet
Catherine
C
Guénin
Sophie-Pénélope
SP
Guillaumet
Gérald
G
Viaud-Massuard
Marie-Claude
MC
Yous
Saïd
S
Delagrange
Philippe
P
Boutin
Jean A
JA
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D008550:Melatonin / Q000378:metabolism*; D011808:Quinone Reductases / Q000378:metabolism*
C419642:NRH - quinone oxidoreductase2; D011808:Quinone Reductases; D008550:Melatonin