RT Journal Article
SR Electronic
T1 Ghrelin Receptor Inverse Agonists: Identification of an Active Peptide Core and Its Interaction Epitopes on the Receptor
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 936
OP 946
DO 10.1124/mol.106.024422
VO 70
IS 3
A1 Birgitte Holst
A1 Manja Lang
A1 Erik Brandt
A1 Anders Bach
A1 Andrew Howard
A1 Thomas M. Frimurer
A1 Annette Beck-Sickinger
A1 Thue W. Schwartz
YR 2006
UL http://molpharm.aspetjournals.org/content/70/3/936.abstract
AB [d-Arg1,d-Phe5,d-Trp7,9,Leu11]Substance P functions as a low-potency antagonist but a high-potency full inverse agonist on the ghrelin receptor. Through a systematic deletion and substitution analysis of this peptide, the C-terminal carboxyamidated pentapeptide wFwLX was identified as the core structure, which itself displayed relatively low inverse agonist potency. Mutational analysis at 17 selected positions in the main ligand-binding crevice of the ghrelin receptor demonstrated that ghrelin apparently interacts only with residues in the middle part of the pocket [i.e., between transmembrane (TM)-III, TM-VI and TM-VII]. In contrast, the inverse agonist peptides bind in a pocket that extends all the way from the extracellular end of TM-II (AspII:20) across between TM-III and TM-VI/VII to TM-V and TM-IV. The potency of the main inverse agonist could be improved up to 20-fold by a number of space-generating mutants located relatively deep in the binding pocket at key positions in TM-III, TM-IV and TM-V. It is proposed that the inverse agonists prevent the spontaneous receptor activation by inserting relatively deeply across the main ligand-binding pocket and sterically blocking the movement of TM-VI and TM-VII into their inward-bend, active conformation. The combined structure-functional analysis of both the ligand and the receptor allowed for the design of a novel, N-terminally Lys-extended analog of wFwLL, which rescued the high-potency, selective inverse agonism that was dependent upon both AspII:20 and GluIII:09. The identified pharmacophore can possibly serve as the basis for targeted discovery of also nonpeptide inverse agonists for the ghrelin receptor. The American Society for Pharmacology and Experimental Therapeutics