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dc.contributor.advisorMcDonald, Fiona
dc.contributor.authorSwart, Marianne
dc.date.available2010-06-29T22:32:55Z
dc.date.copyright2010
dc.identifier.citationSwart, M. (2010). Localisation of the COMMD 1 and 3 Proteins (Thesis, Master of Science). University of Otago. Retrieved from http://hdl.handle.net/10523/344en
dc.identifier.urihttp://hdl.handle.net/10523/344
dc.description.abstractThe amiloride-sensitive epithelial sodium channel (ENaC), which is a key regulator of sodium (Na+) homeostasis, is expressed as a protein complex on the apical cell surface of many epithelial cells. ENaC is composed of three similar subunits named α-, β- and γENaC. Together these three subunits provide a regulated pathway for Na+ ions to enter epithelial cells from the lumen thus its activity at the cell surface requires tight regulation. In the distal nephron segments of the kidney this mode of regulation is especially important for maintaining total body Na+ and therefore extracellular fluid balance and arterial blood pressure. A number of factors have been identified as regulators of ENaC including COMMD1 (copper metabolism Murr1 domain 1). This protein factor, which belongs to a family of ten ubiquitously expressed proteins, is involved in a number of distinct cellular processes including inhibition of nuclear factor (NF-) κB. Previous work in our laboratory has shown that both COMMD1 and COMMD3 bind to all three ENaC subunits and subsequently mediate an inhibitory effect on the amiloride sensitive Na+ current generated by αβγENaC. Based on this knowledge it was hypothesised that in order for the COMMD proteins to have an effect on ENaC, colocalisation and co-expression of these two proteins to the same intracellular compartments and cell types are required in vivo. This was investigated using different mammalian cell lines that are derived from tissues in which COMMD proteins and/or mRNA have previously been identified, as well as in rat kidney. The specific objectives were addressed using Western blot analysis, immunocytochemistry (ICC) and immunohistochemistry (IHC). Here double label indirect IHC studies have shown for the first time that endogenously expressed COMMD1 and COMMD3 proteins colocalise with αENaC in the principal cells of the cortical and inner and outer medullary collecting ducts. This colocalisation was also shown to hold significance at the intracellular level. ENaC has previously been shown to localise to intracellular vesicular compartments that form part of the endosomal and recycling pathways. Here indirect ICC studies have provided evidence to show that endogenously expressed COMMD1 and COMMD3 proteins localise to the early endosomes. The absence of both COMMD1 and COMMD3 in the Golgi apparatus, which forms part of the secretory pathway, suggests that the COMMD proteins mediate their effects on ENaC in a post-Golgi compartment, possibly by initiating or promoting endocytosis of ENaC from the apical cell surface. In summary, these results provide strong evidence to suggest that the interaction between the COMMD proteins and ENaC is not only biochemically significant but also physiologically relevant thus implicating a possible regulatory role for the COMMD proteins on ENaC activity and therefore indirectly the regulation of Na+ homeostasis.en_NZ
dc.format.mimetypeapplication/pdf
dc.publisherUniversity of Otago
dc.rightshttp://www.otago.ac.nz/administration/policies/otago003228.htmlen_NZ
dc.rightsAll items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.rights.urihttp://www.otago.ac.nz/administration/policies/otago003228.html
dc.titleLocalisation of the COMMD 1 and 3 Proteinsen_NZ
dc.typeThesis
dc.date.updated2010-06-29T10:00:27Z
thesis.degree.disciplinePhysiologyen_NZ
thesis.degree.nameMaster of Scienceen_NZ
thesis.degree.grantorUniversity of Otago
thesis.degree.levelMasters Theses
otago.openaccessOpen
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