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Kok, Zhi Yuan (2020) Optimisation of Peptide Linker-based Fluorescent Ligands for the Histamine H1 Receptor. PhD thesis, University of Nottingham.

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Abstract

The histamine H1 receptor (H1R) is a class A G protein-coupled receptor (GPCR) and as recent studies suggested, is involved in mediating cell proliferation and thus cancer progression. High affinity H1R-selective fluorescent ligands with optimum physicochemical properties would serve as a valuable tool to probe in further detail H1R-related cancer pharmacology and facilitate drug discovery. Fluorescent ligands comprise a receptor binding motif connected to an appropriate fluorophore via a linker moiety, which itself offers an opportunity to modulate the properties of the final compound. Whilst modulating the overall physicochemical properties of the fluorescent ligand, a peptide-based linker could interact with residues which line the ligand entry/exit route through its side chain functional groups, potentially improving the binding affinity of the overall conjugate as well as providing information on structure activity relationships (SARs) along the ligand entry/exit route.

An initial molecular docking study conducted on the H1R suggested an acidic amino acid (e.g. aspartic acid) within the peptide linker could potentially engage in salt bridge interactions with the basic residues of K179ECL2 and K1915.39; this however failed to generate a useable fluorescent ligand due to non-binding. This led to a more detailed screening approach to try and identify an optimised peptide linker. By incorporating the optimised peptide linker into several series of fluorescent compounds, a library of high affinity H1R fluorescent ligands was synthesised, where both Copper(I)-catalysed alkyne-azide cycloaddition (CuAAC) and conventional amide coupling approaches were employed for fluorophore attachment. The library afforded compounds with pKD values ranging from 7.6 to 8.4 determined using NanoBRET saturation binding experiments. Further investigation into the effects of the fluorophore on fluorescent ligand binding affinity suggested that the (E)-4-(2-(5,5-difluoro-7-(thiophen-2-yl)-5H-5λ^4,6λ^4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinin- 3-yl)vinyl)phenoxy-based fluorophore (BODIPY 630/650) was a key factor in increasing binding affinity of H1R fluorescent ligands, overriding the linker SAR. Molecular docking of these ligands into a H1R model based on the H1R crystal structure (PDB code: 3RZE) highlighted residues which could interact with the optimised peptidic linkers and potentially form additional binding site architecture for the fluorescent conjugate.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Kellam, Barrie Mistry, Shailesh N. Hill, Stephen J.
Keywords:	Histamine H1 receptor, fluorescent ligand, BODIPY
Subjects:	Q Science > QD Chemistry > QD450 Physical and theoretical chemistry Q Science > QP Physiology > QP501 Animal biochemistry
Faculties/Schools:	UK Campuses > Faculty of Science > School of Pharmacy
Item ID:	61521
Depositing User:	Kok, Zhi Yuan
Date Deposited:	08 Feb 2024 13:08
Last Modified:	08 Feb 2024 13:08
URI:	https://eprints.nottingham.ac.uk/id/eprint/61521

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