A Survey of Stapling Methods to Increase the Affinity, Activity and Stability of Ghrelin Analogues

The growth hormone secretagogue receptor (GHSR) is a G protein-coupled receptor which regulates various important physiological and pathophysiological processes in the body. Ghrelin is the primary high affinity endogenous ligand for GHSR and has limited secondary structure in solution, which makes it proteolytically unstable. This inherent instability in ghrelin can be overcome by incorporating helix-inducing staples that stabilize its structure and improve affinity and activity. We present an analysis of different stapling methods at positions 12 and 16 of ghrelin(1-20) analogues with the goal of increasing proteolytic stability and to retain or improve affinity and activity towards GHSR. Ghrelin(1-20) analogues were modified with a wide range of chemical staples, including a lactam staple, triazole staple, hydrocarbon staple, Glaser staple, and xylene-thioether staple. Once synthesized, the analogue affinity and α-helicity were measured using competitive binding assays and circular dichroism spectroscopy, respectively. Generally, an increase in alpha-helicity using a flexible staple linker led to an improved affinity towards GHSR. Ghrelin(1-20) analogues with a lactam, triazole, and hydrocarbon staple resulted in helical analogues with stronger affinity towards GHSR than unstapled ghrelin(1-20), a compound that lacks helical character. Compounds were also investigated for their agonist activity through β-arrestin 1 & 2 recruitment BRET assays and for their metabolic stability through serum stability assays.

Name thesis:degree_name

M Sc

Discipline thesis:degree_discipline

Chemistry

Grantor dc:publisher

The University of Western Ontario

Year dc:date.issued

2022

Author dc:creator

• Esteban, Juan

Advisor dc:contributor.advisor

• Luyt, Leonard G.

• Ghrelin receptor
• GHSR-1a
• G-protein coupled receptors
• ghrelin receptor agonists
• cancer cachexia
• molecular imaging
• peptide staples
• helix-inducing staples
• solid-phase peptide synthesis

Language dc:language.iso

en_ca

Handle dc:identifier.uri

https://hdl.handle.net/20.500.14721/32421

OAI identifier oai:identifier

oai:uwo.scholaris.ca:20.500.14721/32421