Ion Channel Molecular Mechanisms
Research
Brief description of project/s
Ion channels have important roles in all cells but have a particularly prominent role in rapid signalling in nerves and muscle and are the targets for many clinically important drugs, including anaesthetics, anti-anxiety treatments and alcohol. We are interested in understanding the detailed molecular mechanisms underlying ion channel function, dysfunction in disease states and regulation by both physiological and pharmacological modulators. To tease apart these mechanisms and their significance we use a combination of computational molecular modelling, experimental structure-function studies of recombinantly expressed channels and animal models. Current projects include:
GABAA receptor; a) dysfunction in epilepsy, b) a target for novel steroid analgesics?
The GABAA receptor is the primary mediator of inhibitory currents in the brain that modulate neuronal activity. Mutations in GABAA receptors genes can lead to hyper-excitability and epilepsy. In collaboration with Dr Steve Petrou, we are investigating the molecular mechanisms linking the mutation to the disease. We are also investigating the molecular details of the interaction between neurosteroids and the GABAA receptor, with the goal of understanding the basis for the recently described analgesic activity of some synthetic steroids.
TRPV1 activation; a target for painful toxins?
TRPV1 was initially identified as the target for capsaicin, the "hot compound in chilies, and is important for pain-sensing, particularly sensing noxious heat. Recently, a toxin from a painful spider venom was also shown to target TRPV1. In collaboration with Peter McIntyre, we are investigating whether other painful toxins may also act on TRPV1 and their mechanism of action.
Modulation of ClC-1 by ATP; a role in fatigue?
ClC-1 has a similar role in muscle to that of the GABAA receptor in the brain, mediating inhibitory currents that modulate muscle excitability and activation. Mutations in the ClC-1 gene can lead to hyper-excitability and stiff or rigid muscles in the disease, myotonia congenita. We have shown recently that regulatory domains of ClC-1 control channel function in response to ATP (the energy currency of the cell) and acidosis, a mechanism that may be important for muscle fatigue during intense exercise. In collaboration with Graham Lamb, we are investigating further the molecular mechanism underlying this modulation and its physiological significance.
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Key References
2007:
Yang, Z., Ney, A., Cromer, B. A., Ng, H. L., Parker, M. W. & Lynch, J. W. (2007). Tropisetron modulation of the glycine receptor: femtomolar potentiation and a molecular determinant of inhibition. J Neurochem 100, 758-69.
Yang, Z., Cromer, B. A., Harvey, R. J., Parker, M. W. & Lynch, J. W. (2007). A proposed structural basis for picrotoxinin and picrotin binding in the glycine receptor pore. J Neurochem 103, 580-589.
Cromer, B. A., Gorman, M. A., Hansen, G., Adams, J. J., Coggan, M., Board, P. G. & Parker, M. W. (2007). Expression, purification, crystallization and preliminary X-ray of chloride intracellular channel 2 (CLIC2) Acta Cryst. F63, 961-963.
Cromer, B. A., Gorman, M. A., Hansen, G., Adams, J. J., Coggan, M., Littler, D. R., Brown, L. J., Mazzanti, M., Breit, S. N., Curmi, P. M. G., Dulhunty, A. F., Board, P. G. & Parker, M. W. (2007). Structure of the Janus Protein Human CLIC2 J Mol Biol 374, 719-731.
Bennetts, B., Parker, M. W. & Cromer, B. A. (2007). Inhibition of skeletal muscle CLC-1 chloride channels by low intracellular pH and ATP. J Biol Chem 282, 32780-32791.
Clayton, T., Chen, J. L., Ernst, M., L. Richter, L., Cromer, B. A., Morton, C. J., Ng, H., Kaczorowski, C., Helmstetter, F. J., Furtmüller, R., Ecker, G., Parker, M. W., Sieghart, W. & Cook, J. M. (2007). An updated unified pharmacophore model of the benzodiazepine binding site on γ-aminobutyric acidA receptors: correlation with comparative models. Current Medicinal Chemistry 14, 2755-2775.
Cromer, B. A. & McIntyre, P. (2008). Painful Toxins acting at TRPV1. Toxicon 51, 163-173
Last 5 years:
Bowser, D. N., Wagner, D. A., Czajkowski, C., Cromer, B. A., Parker, M. W., Wallace, R. H., Harkin, L. A., Mulley, J. C., Marini, C., Berkovic, S. F., Williams, D. A., Jones, M. V. & Petrou, S. (2002). Altered kinetics and benzodiazepine sensitivity of a GABAA receptor subunit mutation g2R43Q found in human epilepsy. Proc Natl Acad Sci U S A 99, 15170-5.
Cromer, B. A., Morton, C. J. & Parker, M. W. (2002). Anxiety over GABA(A) receptor structure relieved by AChBP. Trends Biochem Sci 27, 280-7.
Nevin, S. T., Cromer, B. A., Haddrill, J. L., Morton, C. J., Parker, M. W. & Lynch, J. W. (2003). Insights into the structural basis for zinc inhibition of the glycine receptor. J Biol Chem 278, 28985-92.
Smart, M. L., Gu, B., Panchal, R. G., Wiley, J., Cromer, B. A., Williams, D. A. & Petrou, S. (2003). P2X7 receptor cell surface expression and cytolytic pore formation are regulated by a distal C-terminal region. J Biol Chem 278, 8853-60.
Everitt, A. B., Luu, T., Cromer, B. A., Tierney, M. L., Birnir, B., Olsen, R. W. & Gage, P. W. (2004). Conductance of recombinant GABA (A) channels is increased in cells co-expressing GABA(A) receptor-associated protein. J Biol Chem 279, 21701-6.
Bennetts, B., Rychkov, G. Y., Ng, H. L., Morton, C. J., Stapleton, D., Parker, M. W. & Cromer, B. A. (2005). Cytoplasmic ATP-sensing domains regulate gating of skeletal muscle ClC-1 chloride channels. J Biol Chem 280, 32452-8.
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