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An investigation into Glucagon receptor pharmacology
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Barkan, Kerry (2017) An investigation into Glucagon receptor pharmacology. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3152896~S15
Abstract
The glucagon receptor (GCGR), a family B G protein-coupled receptor (GPCR), plays an important role in regulating blood glucose levels through its ability to bind the 29 amino acid peptide hormone, glucagon (GCG). Antagonising GCG action is a potential therapeutic option for reducing hepatic glucose production. However, GCG-based therapy is currently limited to acute emergency treatment of hypoglycemia in patients with type 1 diabetes (T1D) (Habegger et al., 2010). Further insight into GCGR-mediated signalling pathways and mechanism of activation may provide the basis for therapeutic development.
We investigated the ligand stimulated GCGR signalling using multiple assays including those measuring cAMP accumulation, ERK1/2 phosphorylation and intracellular Ca2+ (Ca2+ i) mobilisation. Through site directed mutagenesis and FACS analysis for the investigation of cell-surface expression, we identified several important residues. They included K16812.49, L16912.50 , H17012.51 and T1722.45 of the ICL1 region (G1651.63 -T1722.45 ) as potential determinant in signalling bias at the GCGR through Gq/11-coupling, C1712.44 as a critical determinant of GCGR expression and R1732.46 as an essential residue for G protein-coupling. Helix 8 residue E4068.49 was implicated in maintaining GCGR in an inactive state. Finally, TM4 residues G2714.49 , L2774.55 and V2804.58 were found to plays an important role in successful translation and/or trafficking of GCGR and (Ca2+ i) mobilisation.
The GCGR-mediated pERK1/2 response way found to be both Gq/11 and β-arrestin1/2 mediated, whereas it was independent of PKA or Gβγ-subunits. The GCG analogue TH-GCG, contrary to previous reports (Wakelam et al., 1986, Lenzen et al., 1990), was characterised as a partial agonist at the GCGR, inducing a robust cAMP response but fails to induce a detectable Ca2+ i or IP1 response. We also identified a RAMP2-dependent potentiation of the GCG stimulated cAMP response at the GCGR.
The research described in this thesis has produced novel data that contributes to a clearer understanding of GCGR pharmacology.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QP Physiology | ||||
Library of Congress Subject Headings (LCSH): | Glucagon, Blood sugar, Hypoglycemia, Diabetes -- Treatment | ||||
Official Date: | September 2017 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Ladds, Graham | ||||
Sponsors: | Biotechnology and Biological Sciences Research Council (Great Britain) | ||||
Extent: | xxi, 354 leaves : illustrations, charts. | ||||
Language: | eng |
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