Investigating the invasive and cytoprotective properties of the heme binding protein HRG-1 in cancer cells

dc.check.embargoformatBoth hard copy thesis and e-thesisen
dc.check.entireThesisEntire Thesis Restricted
dc.check.reasonThis thesis is due for publication or the author is actively seeking to publish this materialen
dc.contributor.advisorO'Connor, Rosemaryen
dc.contributor.authorFogarty, Fionola
dc.contributor.funderHealth Research Boarden
dc.contributor.funderScience Foundation Irelanden
dc.description.abstractThis thesis investigates the mechanisms by which HRG-1 contributes to the invasive and cytoprotective signalling pathways in cancer cells through its effects on VATPase activity and heme transport. Plasma membrane-localised V-ATPase activity correlates with enhanced metastatic potential in cancer cells, which is attributed to extrusion of protons into the extracellular space and activation of pH-sensitive, extracellular matrix degrading-proteases. We found that HRG-1 is co-expressed with the V-ATPase at the plasma membrane of certain aggressive cancer cell types. Modulation of HRG-1 expression altered both the localisation and activity of the VATPase. We also found that HRG-1 enhances trafficking of essential transporters such as the glucose transporter (GLUT-1) in cancer cells, and increases glucose uptake, which is required for cancer cell growth, metabolism and V-ATPase assembly. Heme is potentially cytotoxic, owing to its iron moiety, and therefore the trafficking of heme is tightly controlled in cells. We hypothesised that HRG-1 is required for the transport of heme to intracellular compartments. Importantly, we found that HRG-1 interacts with the heme oxygenases that are necessary for heme catabolism. HRG-1 is also required for trafficking of both heme-bound and nonheme-bound receptors and suppression of HRG-1 results in perturbed receptor trafficking to the lysosome. Suppression of HRG-1 in HeLa cells increases toxic heme accumulation, reactive oxygen species accumulation, and DNA damage resulting in caspasedependent cell death. Mutation of essential heme binding residues in HRG-1 results in decreased heme binding to HRG-1. Interestingly, cells expressing heme-binding HRG-1 mutants exhibit decreased internalisation of the transferrin receptor compared to cells expressing wildtype HRG-1. These findings suggest that HRG- 1/heme trafficking contributes to a hitherto unappreciated aspect of receptormediated endocytosis. Overall, the findings of this thesis show that HRG-1-mediated regulation of intracellular and extracellular pH through V-ATPase activity is essential for a functioning endocytic pathway. This is critical for cells to acquire nutrients such as folate, iron and glucose and to mediate signalling in response to growth factor activation. Thus, HRG-1 facilitates enhanced metabolic activity of cancer cells to enable tumour growth and metastasis.en
dc.description.sponsorshipHealth Research Board (PhD Scholars Programme in Cancer Biology (FF)); Science Foundation Ireland (PI Award: 06/INI/B107)en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Version
dc.identifier.citationFogarty, F. 2014. Investigating the invasive and cytoprotective properties of the heme binding protein HRG-1 in cancer cells. PhD Thesis, University College Cork.en
dc.publisherUniversity College Corken
dc.rights© 2014, Finola Fogarty.en
dc.titleInvestigating the invasive and cytoprotective properties of the heme binding protein HRG-1 in cancer cellsen
dc.typeDoctoral thesisen
dc.type.qualificationnamePhD Scholars Programme in Cancer Biologyen
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