Aquaporins (AQPs) are membrane channel proteins which facilitate rapid water transport across cell membranes. It is believed these channels are involved in many physiological processes including renal water conservation, neuro-homeostasis, digestion, regulation of body temperature and reproduction. At least 11 mammalian AQPs (AQP0 – AQP10) have been identified to date, making them potential therapeutic targets for drug intervention. Initial studies have shown that Hg<sup>2+</sup> irreversibly blocks water transport in AQP-1 by the formation of a mercaptide covalent bond with cysteine residue 189 deep within the pore. AQP-1 function can also be modified by tetraethylammonium chloride (TEA) (100 μM), which reversibly blocks water permeability in <i>Xenopus laevis</i> oocytes injected with AQP-12 and AQP-2 by 44 ± 11% and 49 ± 18% respectively. However, a specific reversible AQP inhibitor has so far not been reported. A 2.2 Å high resolution crystal structure of <i>Escherichia coli</i> glycerol facilitator (G1pF) was employed as a model for water transport through AQP-1. A number of compound libraries, based on the lead compounds of glycerol and TEA have been synthesised using a range of automated techniques. Several of these compounds have been screened as putative aquaplugs on <i>Xenopus laevis</i> oocytes injected with AQP-1, 2, 3, 4 and 5. Initial results suggest that it is possible to selectively block water throughput I AQP-1, using dimethyl ethyl hexadecanyl ammonium bromide (100 μM), by 80 ± 7% and AQP-2, using dimethyl ethyl decanyl ammonium bromide (100 μM), by 58 ± 16%. To our knowledge these are the first known selective blockers of AQP-1 and 2. These results have provided the basis to develop more focused lead compound optimisation which in turn should establish further qualitative structure-activity-relationship data to aid in our understanding of the mechanisms associated with water transport throughout the AQP family.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:642073 |
| Date | January 2005 |
| Creators | Brown, Fraser Kendall |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12913 |
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