The peptide hormone, ghrelin, exerts its physiological effects through a G-protein-coupled receptor called the ghrelin-R. The ghrelin-R displays a high degree of constitutive activity, signalling through the inositol phosphate pathway in the absence of bound agonist. TMs III and VI have been reported to be central to the activation of Family A GPCRs, with interactions between the two helices stabilising the ground state. During activation conformational rearrangements result in these interactions being broken, with new contacts forming and stabilising the active state. Investigation of the ghrelin-R constitutive activity gives an insight into the mechanisms involved in receptor activation. In this study the role of specific individual residues in the ghrelin-R has been investigated and the effect of disrupting or introducing intramolecular interactions was addressed. Site-directed mutagenesis and functional assays revealed that ghrelin-R constitutive activity can be increased and decreased with mutation of residues within the TM domains, specifically TMs III, VI and VII. The extracellular loops have been found to be involved in ligand binding and activation in a number of Family A GPCRs. The residues within ECL2 of the ghrelin-R were systematically mutated to alanine to determine their role. In particular, one residue, Asn196, was identified as being critical in ghrelin-R function and may be forming stabilising interactions which maintain ghrelin-R constitutive activity. The data presented in this thesis provide an insight into the structure and function of the ghrelin-R and the underlying molecular mechanisms of ghrelin-R constitutive activity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:527071 |
| Date | January 2011 |
| Creators | Kendrick, Rachel |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/1289/ |
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