Vol. 302, Issue 2, 766-773, August 2002

Appetite-Boosting Property of Pro-Melanin-Concentrating Hormone_131-165 (Neuropeptide-Glutamic Acid-Isoleucine) Is Associated with Proteolytic Resistance

Laurence Maulon-Feraille, Odile Della Zuana, Thomas Suply , Carole Rovere-Jovene, Valérie Audinot, Nigel Levens, Jean A. Boutin, Jacques Duhault and Jean-Louis Nahon

Institut de Pharmacologie Moléculaire et Cellulaire-Centre National de la Recherche Scientifique Unité Mixte de Recherche (L.M.-F., T.S., C.R.-J., J.-L.N.), Sophia-Antipolis, Valbonne, France; and Division Métabolisme (O.D.Z., N.L., J.D.) and Division de Pharmacologie Moléculaire et Cellulaire (T.S., V.A., J.A.B.), Institut de Recherches Servier, Suresnes, France

Melanin-concentrating hormone (MCH) is a cyclic neuropeptide, with a major role in stimulation of feeding behavior in mammals. MCH signals in the brain occur via two seven-transmembrane G protein-coupled receptors, namely MCH1 (SLC-1, MCH₁, MCH-R1, or MCH-1R) and MCH2 (SLT, MCH₂, MCH-R2, or MCH-2R). In this study, we demonstrate that the pro-MCH_131-165 peptide neuropeptide-glutamic acid-isoleucine (NEI)-MCH is more potent than MCH in stimulating feeding in the rat. Using rat MCH1-expressed human embryonic kidney 293 cells, we show that NEI-MCH exhibits 5-fold less affinity in a binding assay and 2-fold less potency in a cAMP assay than MCH. A similar 7- to 8-fold shift in potency was observed in a Ca²⁺_i assay using rat MCH1 or human MCH2-transfected Chinese hamster ovary cell models. This demonstrates that NEI-MCH is not a better agonist than MCH at either of the MCH receptors. Then, we compared the proteolysis resistance of MCH and NEI-MCH to rat brain membrane homogenates and purified proteases. Kinetics of peptide degradation using brain extracts indicated a t_1/2 of 34.8 min for MCH and 78.5 min for NEI-MCH with a specific pattern of cleavage of MCH but not NEI-MCH by exo- and endo-proteases. Furthermore, MCH was found highly susceptible to degradation by aminopeptidase M and endopeptidase 24.11, whereas NEI-MCH was fully resistant to proteolysis by these enzymes. Therefore, our results strongly suggest that reduced susceptibility to proteases of NEI-MCH compared with MCH account for its enhanced activity in feeding behavior. NEI-MCH represents therefore the first MCH natural functional "superagonist" so far described.