Unique interaction pattern for a functionally biased ghrelin receptor agonist

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

Bjørn Behrens Sivertsen, Manja Lang, Thomas M. Frimurer, Nicholas D. Holliday, Anders Bach, Sylvia Els, Maja Storm Engelstoft, Pia Steen Petersen, Andreas Nygaard Madsen, Thue W. Schwartz, Annette G. Beck-Sickinger, Birgitte Holst

Based on the conformationally constrained D-Trp-Phe-D-Trp (wFw) core of the prototype inverse agonist [D-Arg(1),D-Phe(5),D-Trp(7,9),Leu(11)]substance P, a series of novel, small, peptide-mimetic agonists for the ghrelin receptor were generated. By using various simple, ring-constrained spacers connecting the D-Trp-Phe-D-Trp motif with the important C-terminal carboxyamide group, 40 nm agonism potency was obtained and also in one case (wFw-Isn-NH(2), where Isn is isonipecotic acid) ~80% efficacy. However, in contrast to all previously reported ghrelin receptor agonists, the piperidine-constrained wFw-Isn-NH(2) was found to be a functionally biased agonist. Thus, wFw-Isn-NH(2) mediated potent and efficacious signaling through the Ga(q) and ERK1/2 signaling pathways, but in contrast to all previous ghrelin receptor agonists it did not signal through the serum response element, conceivably the Ga(12/13) pathway. The recognition pattern of wFw-Isn-NH(2) with the ghrelin receptor also differed significantly from that of all previously characterized unbiased agonists. Most importantly, wFw-Isn-NH(2) was not dependent on GluIII:09 (Glu3.33), which otherwise is an obligatory TM III anchor point residue for ghrelin agonists. Molecular modeling and docking experiments indicated that wFw-Isn-NH(2) binds in the classical agonist binding site between the extracellular segments of TMs III, VI, and VII, interacting closely with the aromatic cluster between TMs VI and VII, but that it does so in an opposite orientation as compared with, for example, the wFw peptide agonists. It is concluded that the novel peptide-mimetic ligand wFw-Isn-NH(2) is a biased ghrelin receptor agonist and that the selective signaling pattern presumably is due to its unique receptor recognition pattern lacking interaction with key residues especially in TM III.
TidsskriftThe Journal of Biological Chemistry
Sider (fra-til)20845-20860
Antal sider16
StatusUdgivet - 10 jun. 2011

ID: 33802480