Activation of the cystic fibrosis transmembrane regulator (CFTR) chloride channel by protein kinases has been studied intensively. The mechanism of deactivation by protein phosphatases has received less attention, although it is equally important for physiological regulation of the channel. Characterization and identification of the phosphatases that regulate CFTR has become a priority in CF research because they are potential targets for pharmacotherapies. / The first goal of this project was to characterize the effects of purified phosphatases on single CFTR channels. I found that PP2A, PP2C and alkaline phosphatase all reduced channel activity in excised patches. PP1 and PP2B did not deactivate CFTR, despite having comparable phosphatase activity when assayed biochemically using a standard substrate. Deactivation by exogenous PP2C closely resembled the spontaneous rundown induced by endogenous phosphatase in CHO, BHK, and T84 cells. / Genistein and bromotetramisole (Br-t) have been proposed to activate CFTR by inhibiting phosphatases. The second goal of this project was to assess the role of phosphatases in CFTR activation by these drugs. Genistein did not affect phosphatase activities. By contrast Br-t inhibited all four types phosphatases (PP1, PP2A, PP2B and PP2C). Thus Br-t may activate the channel by inhibiting its dephosphorylation whereas genistein probably acts directly on CFTR. / These studies provide functional evidence that PP2C is the predominant phosphatase regulating CFTR, and clarify the role of phosphatases in CFTR activation by genistein and bromotetramisole.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.30119 |
| Date | January 1999 |
| Creators | Luo, Jiexin, 1968- |
| Contributors | Hanrahan, John W. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001681856, proquestno: MQ55077, Theses scanned by UMI/ProQuest. |
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