Lipid regulation of glucagon-like peptide-1 receptor in pancreatic beta-cells
File(s)
Author(s)
Oqua, Affiong Ika
Type
Thesis
Abstract
Glucagon-like peptide-1 receptor (GLP-1R), a key pharmacological target for treatment of type 2 diabetes and obesity, is a class B1 G protein-coupled receptor involved in the control of appetite and blood glucose levels via potentiation of insulin secretion from pancreatic beta-cells. Previously, cholesterol extraction from pancreatic beta-cells disrupted GLP-1R internalisation, clustering and cAMP responses. Therefore, the functional effects of the potential interactions between GLP-1R and its lipid microenvironment was studied.
This study highlighted that changes in the synthesis of complex sphingolipids using sphingomyelinase or eliglustat, caused changes in GLP-1R internalisation and a tendency for reduced cAMP signalling in pancreatic beta-cells. Reduced cholesterol synthesis using simvastatin increased GLP-1R-dependent cAMP signalling and insulin secretion in pancreatic islets. Increased cholesterol diet caused a decrease in the glucoregulatory effect of GLP-1R in vivo and reduced cAMP responses from extracted islets. Increased cholesterol levels ex vivo caused a reduction in cAMP signalling and insulin secretion from pancreatic islets.
This study identified potential sites/regions with high occupancy and residence times for cholesterol on GLP-1R using coarse grained molecular dynamic simulations. A screening of some key residues selected from these sites and detailed analyses of the effects of mutating one of these residues, valine 229 to alanine (V229A), highlighted the effects of changes in cholesterol binding to GLP-1R on receptor function. V229A mutant receptor caused changes in GLP-1R cholesterol interaction, plasma membrane activity, clustering, trafficking and signalling, causing improved insulin secretion in pancreatic beta-cells and islets.
In conclusion, this study highlighted the role of cholesterol in regulating GLP-1R function, identified relevant cholesterol binding sites on the receptor, and validated the effects of changes in cholesterol binding on receptor function. The results highlight the potential of GLP-1R cholesterol binding sites as locations that can be targeted for the rational design of novel allosteric modulators to fine-tune GLP-1R responses.
This study highlighted that changes in the synthesis of complex sphingolipids using sphingomyelinase or eliglustat, caused changes in GLP-1R internalisation and a tendency for reduced cAMP signalling in pancreatic beta-cells. Reduced cholesterol synthesis using simvastatin increased GLP-1R-dependent cAMP signalling and insulin secretion in pancreatic islets. Increased cholesterol diet caused a decrease in the glucoregulatory effect of GLP-1R in vivo and reduced cAMP responses from extracted islets. Increased cholesterol levels ex vivo caused a reduction in cAMP signalling and insulin secretion from pancreatic islets.
This study identified potential sites/regions with high occupancy and residence times for cholesterol on GLP-1R using coarse grained molecular dynamic simulations. A screening of some key residues selected from these sites and detailed analyses of the effects of mutating one of these residues, valine 229 to alanine (V229A), highlighted the effects of changes in cholesterol binding to GLP-1R on receptor function. V229A mutant receptor caused changes in GLP-1R cholesterol interaction, plasma membrane activity, clustering, trafficking and signalling, causing improved insulin secretion in pancreatic beta-cells and islets.
In conclusion, this study highlighted the role of cholesterol in regulating GLP-1R function, identified relevant cholesterol binding sites on the receptor, and validated the effects of changes in cholesterol binding on receptor function. The results highlight the potential of GLP-1R cholesterol binding sites as locations that can be targeted for the rational design of novel allosteric modulators to fine-tune GLP-1R responses.
Version
Open Access
Date Issued
2024-08-23
Date Awarded
2025-02-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Tomas Catala, Alejandra
Bernardino de la Serna, Jorge
Sponsor
Commonwealth Scholarship Commission
Publisher Department
Department of Metabolism, Digestion and Reproduction
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)