Weston, Cathryn (2013) The spatial and temporal regulation of the monomeric G protein, Ras 1. PhD thesis, University of Warwick.

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Abstract

A vast array of cellular processes are controlled by the highly conserved
guanine nucleotide-regulated molecular switches, such as Ras. The spatial and
temporal regulation of Ras signalling, both positively, through the action of
guanine nucleotide exchange factors (GEFs) and negatively, via interaction with
GTPase activating proteins (GAPs) is critical to maintain cell viability. Due to the
presence of multiple Ras isoforms, regulatory proteins and effectors, the study of
Ras signalling in higher eukaryotes is technically challenging. Fission yeast
provides a simple system in which to study Ras signalling containing a single Ras
homologue (Ras1) that modulates two distinct processes.
Ras1 signalling is terminated through GTP-hydrolysis accelerated by the
action of a GAP, Gap1. This thesis describes the development of a quantitative
FRET assay to visualise the dynamics of Ras1 activity within single cells. Using
this reporter, in combination with a variety of other quantitative techniques, the
role of the negative regulator during signal transduction was explored. These
results highlighted an important difference between the requirement for GTPhydrolysis
during signal propagation. Finally, use of the FRET reporter revealed
an alternative G protein state, within the Ras1 activation cycle. These data
question the accepted models of G protein signal propagation and prompt further
investigation into the roles of GTP-hydrolysis in signal transduction.
Several positive regulators of Ras1 have previously been described in
fission yeast. These proteins have been proposed to direct signalling via the
different Ras1 effectors. Using quantitative image analysis and pheromoneresponsive
reporter strains, this thesis presents data to suggest that it is not simply
a one-activator-one-effector response. Further, the role of the previously
uncharacterised, scaffold protein, Ral2 in mediating signal transduction is also
investigated. Finally the possibility that the heterotrimeric G protein, Gpa1 can
directly activate MAPK signalling to provide a pheromone-sensing mechanism
within fission yeast is discussed.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	G proteins, Ras proteins, Monomers, Cellular signal transduction, Guanosine triphosphatase
Official Date:	February 2013
Dates:	Date Event February 2013 Submitted
Institution:	University of Warwick
Theses Department:	Warwick Medical School
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Ladds, Graham; Davey, John
Extent:	xxix, 303 leaves : illustrations, charts.
Language:	eng

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