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Further characterisation of substrate, inhibitor and ancillary protein specificity of MCT1, MCT2, MCT4 and MCT6

The MonoCarboxylate Transporter (MCT) family of transmembrane proteins contain 14 members of which 6 have been functionally characterized. Of these characterised MCTs only MCTs 1-4 have been shown to transport lactate. These MCTs also facilitate the movement of pyruvate and ketone bodies across the plasma membrane (PM) in cotransport with a proton. For trafficking to and function at the PM MCTl, MCT3 and MCT4 require association with the monotopic ancillary glycoprotein basigin whereas MCT2 prefers association with embigin. This thesis has investigated the sensitivity of MCTl, MCT2 and MCT4 to the highly potent and selective MCTI inhibitor, ARC155858, discovered by AstraZeneca. Chimeras of MCTI and MCT4 were constructed and expressed in Xenopus laevis oocytes for transport studies to determine their inhibitor sensitivity. These identified a region between transmembrane domains (TMs) 7 and 10 of MCTI with which AR-C155858 binds from the cytoplasmic side. ARC155858 was shown to inhibit MCT2 but sensitivity was found to be dependent on the ancillary protein with which it is associated. Co-expression with embigin decreased the sensitivity of MCT2, but not MCTl, to AR-CI55858. The MCT C-terminus was shown to playa role in the interaction between MCT and ancillary protein which is secondary to interactions between the TM of the ancillary protein and TMs3 and 6 of the MCT. Additional studies were performed to characterise the substrate specificity of the orphan transporter, MCT6. Initial work suggested that products of pyruvate decarboxylation or polymerisation will provide lead compounds in the continuing search for the physiological substrate of MCT6, with formate another potential substrate. During this work it was also discovered that MCTI can catalyse the transport of specific dicarboxylates at low pH.
Date January 2010
CreatorsOvens, Matthew James
PublisherUniversity of Bristol
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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