Appetite-boosting property of pro-melanin-concentrating hormone(131-165) (neuropeptide-glutamic acid-isoleucine) is associated with proteolytic resistance

J Pharmacol Exp Ther. 2002 Aug;302(2):766-73. doi: 10.1124/jpet.302.2.766.

Abstract

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, MCH(1), MCH-R1, or MCH-1R) and MCH2 (SLT, MCH(2), 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 Ca(2+)(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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Appetite Stimulants / administration & dosage
  • Appetite Stimulants / pharmacology*
  • CHO Cells
  • Calcium Signaling / drug effects
  • Calcium Signaling / physiology
  • Cell Line
  • Cerebral Ventricles / drug effects
  • Cerebral Ventricles / physiology*
  • Cricetinae
  • Cyclic AMP / pharmacology
  • Feeding Behavior / drug effects*
  • Humans
  • Hypothalamic Hormones / administration & dosage
  • Hypothalamic Hormones / chemistry
  • Hypothalamic Hormones / pharmacology*
  • Injections, Intraventricular
  • Kidney
  • Kinetics
  • Male
  • Molecular Sequence Data
  • Peptide Fragments / administration & dosage
  • Peptide Fragments / pharmacology*
  • Protein Precursors / administration & dosage
  • Protein Precursors / chemistry
  • Protein Precursors / pharmacology*
  • Rats
  • Rats, Wistar
  • Transfection

Substances

  • Appetite Stimulants
  • Hypothalamic Hormones
  • Peptide Fragments
  • Protein Precursors
  • melanin-concentrating hormone precursors
  • Cyclic AMP