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Title: Structural and computational studies of fibroblast growth factor receptor signalling complex formation
Author: Manrique Zuñiga, Santiago
ISNI:       0000 0004 6063 3950
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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Fibroblast growth factor receptor (FGFR) signalling plays a crucial role in embryogenesis, adult tissue development and tissue repair. It has been implicated in a wide range of human pathologies such as cancers and skeletal disorders which is the reason for a particular interest over recent years. Concerted efforts in academia and industry are targeting the FGFR signalling networks at different stages. The intracellular canonical downstream signalling pathways in healthy and pathogenic cells are relatively well understood. A definition of the precise mechanism for ligand induced FGFR dimerisation remains elusive. Structure biological efforts of the past 20 years have yielded a range of insightful but contradictory structures of FGFRs in complex with their ligands. It is key to solve uncertainties about the mode of extracellular and transmembrane receptor dimerisation in order to promote our abilities of targeted therapeutic manipulation of FGFR signalling in human physiology. The present study uses multiple methods from structural biology to shed more light on the effect of mutant FGFR transmembrane domains (TMDs) on signalling (Chapter 3) and on the architecture of the extracellular FGFR1 signalling complex (Chapter 4-6). Coarse-grained molecular dynamics simulations of FGFR3 and FGFR4 TMDs have confirmed inherent propensity to form symmetric dimers mediated by Gx3G motifs. Interestingly, disease related mutations do not map on the primary TMD dimer interfaces. Simulations of selected mutant TMDs show no significant effect on receptor dimerisation propensity. Atomistic simulations of the transmembrane FGFR3 Achondroplasia mutant reveal a significant shift of the dimer relative to the bilayer to allow interactions of the mutant Arg380 side chain with lipid head group phosphates. This finding supports mechanisms of signal transduction by conformational coupling across the membrane. Biophysical characterisation of the FGFR signalling complex was performed to work out a co-crystallisation strategy using receptors expressed in mammalian cells. Crystallographic experiments yielded a FGFR1 structure bound to its ligands, revealing a full signalling complex with an architecture that contradicts two well-established, crystal structure-derived models. The presented structure features a central, decasaccharide-mediated Fibroblast Growth Factor dimer, which recruits a receptor on each end to form a quasi-symmetric pentameric signalling complex. Further biophysical validation makes the newly presented structure the first model that is supported by structural data from the complex in solution.
Supervisor: Jones, E. Yvonne ; Sansom, Mark S. P. Sponsor: Wellcome Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available