Determination of the ligand pharmacophore required for secondary conformation activation of the human β1-adrenoceptor

Pinto de Sousa, Emanuel (2020) Determination of the ligand pharmacophore required for secondary conformation activation of the human β1-adrenoceptor. PhD thesis, University of Nottingham.

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Abstract

The β1-adrenergic receptor exists in at least two different agonist conformations: a primary conformation where endogenous catecholamines and β-blockers bind, and where agonist responses are blocked by low concentrations of antagonists and a secondary conformation, for which the precise nature is unknown, through which responses are more resistant to blockade by conventional primary conformation antagonists. Conventional agonists such as isoprenaline and cimaterol stimulate a response mainly through the primary conformation, while others such as alprenolol and oxprenolol can mediate a response through both conformations of the β1-AR, though the response mediated through the secondary conformation requires a higher concentration of ligand. Other ligands, such as CGP12177, behave as non-conventional agonist and bind with high affinity to the primary conformation (blocking the response of conventional agonist) but then, at much higher concentrations, stimulate a response through the secondary conformation. Only ligands with higher affinity for the primary conformation than for the secondary have been identified so far.

This project aims to identify the molecular features required to bind and stimulate a response at the secondary conformation of the β1-AR. This conformation has been studied so far with probes such as CGP12177 which bind the primary conformation at lower concentrations than the secondary conformation. The identification of a ligand with higher (if possible) or similar affinity for the secondary conformation would allow the better understanding of this conformation.

In this thesis, a set of alprenolol and oxprenolol N-alkyl analogues and alprenolol analogues bearing substituents in the aromatic ring were synthesised and pharmacologically characterised both through competitive radioligand binding assays and CRE-SPAP functional assays in CHO-β1 and CHO-β2 cells. Within these sets, bis alprenolol and bis oxprenolol ligands were identified as compounds able to bind to both conformations with similar affinities. The study of the individual enantiomers and meso compounds of these ligands and further modifications suggest the importance of the second aromatic core for the increase in affinity for the secondary conformation.

A potential photoreactive covalent antagonist was also synthesised to target the primary conformation and allow the better study of the secondary conformation of the β1-AR.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Mistry, Shailesh N.
Baker, Jillian G.
Keywords: G protein-coupled receptors(GPCR); β1-AR ; Alprenolol ; Oxprenolol
Subjects: Q Science > QP Physiology > QP351 Neurophysiology and neuropsychology
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID: 63154
Depositing User: Pinto de Sousa, Emanuel
Date Deposited: 09 Aug 2021 13:19
Last Modified: 09 Aug 2021 13:19
URI: http://eprints.nottingham.ac.uk/id/eprint/63154

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