Excitation-contraction (EC) coupling is the process by which Ca<sup>2+</sup> is released from the sarcoplasmic reticulum (SR) and is fundamental to cardiac and skeletal muscle function. The SR contains many uncharacterised ion channels and proteins which may influence EC coupling and in this thesis I have investigated the biophysical properties of some of these channels. I have demonstrated that the single-channel gating and conducting properties of SR K<sup>+</sup> channels from various mammalian species (rabbit, sheep and mouse) are very similar. I investigated the actions of possible physiological regulators of these channels and demonstrated that luminal Ca<sup>2+</sup> and Mg<sup>2+</sup> can block K<sup>+</sup> flux in a voltage-dependent manner, while luminal Ca<sup>2+</sup>, Ni<sup>2+</sup>, and alkaline pH can reduce Po by additional mechanisms. I also characterised the single-channel properties of the various SR anion channels that are observed after incorporating mammalian SR vesicles into artificial membranes. The trimeric intracellular cation channels (TRIC-A and TRIC-B) and Mitsugumin 23 (MG23) are suggested to be SR cation channels. I have therefore utilised Tric-a KO and Mg23 KO mice to study SR membranes devoid of TRIC-A and MG23. Additionally, I have begun to investigate the single-channel properties of purified c. elegans TRIC-B1 and human TRIC-A. I found that SR K<sup>+</sup> channel function was altered in SR from Tric-a KO or Mg23 KO tissue, however the underlying mechanisms for the observed changes appear to be complex. My initial studies of the purified TRIC-A and TRIC-B proteins show that they are permeable to K<sup>+</sup>, Ca<sup>2+</sup>, choline, and Cl<sup>-</sup>, properties which deviate from those of SR K<sup>+</sup> channels from rabbit, mouse and sheep. This may reflect species differences or alterations to protein function caused during the purification process or that SR K<sup>+</sup> channels remain an unidentified class of ion channel.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:748987 |
| Date | January 2018 |
| Creators | Eberhardt, David Richard |
| Contributors | Sitsapesan, Rebecca |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:9b89bdc9-95aa-42c5-aa78-3087ca47074a |
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