Ghrelin receptor inverse agonists: identification of an active peptide core and its interaction epitopes on the receptor

TY - JOUR

T1 - Ghrelin receptor inverse agonists: identification of an active peptide core and its interaction epitopes on the receptor

AU - Holst, Birgitte

AU - Lang, Manja

AU - Brandt, Erik

AU - Bach, Anders

AU - Howard, Andrew

AU - Frimurer, Thomas M

AU - Beck-Sickinger, Annette

AU - Schwartz, Thue W

N1 - Keywords: Amino Acid Sequence; Amino Acid Substitution; Animals; Binding Sites; COS Cells; Cells, Cultured; Cercopithecus aethiops; Epitopes; Ghrelin; Humans; Ligands; Models, Molecular; Molecular Sequence Data; Mutant Proteins; Peptide Hormones; Peptides; Protein Binding; Receptors, G-Protein-Coupled; Receptors, Ghrelin; Structure-Activity Relationship; Substance P

PY - 2006

Y1 - 2006

N2 - [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.

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.

U2 - 10.1124/mol.106.024422

DO - 10.1124/mol.106.024422

M3 - Journal article

C2 - 16798937

SN - 0026-895X

VL - 70

SP - 936

EP - 946

JO - Molecular Pharmacology

JF - Molecular Pharmacology

IS - 3

ER -