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Title: Regulation of uncoupling proteins : investigating mechanism and function
Author: Humphrey, D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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This study examines the interaction of fatty acids with nucleotide binding to UCP1, functional regulation of uncoupling in skeletal muscle mitochondria - which contain uncoupling protein 3 (UCP3) - and the role of the novel uncoupling proteins in ageing and ROS attenuation by expressing human UCP3 in Drosophila melanogaster. GDP binding to UCP1 in BAT mitochondria was studied using the fluorescent probe N-methylanthraniloyl guanosine-5-diphosphate (mant-GDP). Palmitate did not alter the affinity for mant-GDP or [3H]-GDP, but did cause a two-fold increase in the maximum number of binding sites (Bmax) of mant-GDP, inconsistent with a simple competitive interaction. Fatty acids also increased the susceptibility of UCP1 to trypsin digestion. A model was developed to explain these results: fatty acids induce a transition in UCP1 from a “protected” to an “open” conformation that is more accessible to mant-GDP. The “open” conformation binds but is not inhibited by nucleotides. Contrary to published reports, superoxide and HNE induced GDP-sensitive proton conductance equally in skeletal muscle mitochondria from wild type and UCP3 knockout mice suggesting other carriers can be induced to conduct protons. Interestingly, palmitate prevented GDP from inhibiting the induced proton conductance. These results indicate that an interaction between fatty acids and nucleotides exists for other members of the mitochondrial carrier family. Interestingly, hUCP3 expression in Drosophila decreased lifespan despite increasing mitochondrial uncoupling when targeted to neuronal tissue. Unexpectedly, targeting hUCP3 to neuronal secretory cells increased levels of insulin-like peptides (DILPs) suggesting that an up-regulation of insulin signalling is the cause of the shortened lifespan and demonstrating for the first time that increasing DILP levels can decrease lifespan in Drosophila.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available