Membrane Biophysics Lab

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Our research deals with the ion channels that underly the processes of neurotransmission and olfaction. Both involve the use of the patch-clamp technique, to directly record currents flowing through individual protein-channels, in order to investigate their channel properties. We also utilize site-directed mutagenesis to modify the molecular structure of those channels and to determine how their structure relates to their cellular and physiological function.

Current Projects

Structure-function studies of human glycine receptor channels
Individual nerve cells in the brain communicate with each other by means of synaptic neurotransmission. This is the process whereby one nerve cell releases a chemical, or neurotransmitter, that acts on a specific protein receptor in the receiving nerve cell. We are exploring the relationship between the molecular structure and the physiological function of these neurotransmitter receptor channels, and in particular those that respond to the two major inhibitory neurotransmitters, glycine and GABA. We are interested in how the receptor-channels respond to the binding of neurotransmitter by opening ("gating") and how the receptor-channels, once opened, allow small ions to permeate ("ion permeation") to generate an electrical signal in the receiving cell. We are particularly interested in how such channels distinguish between different ions and the structural determinants of this ion selectivity. We have been successful in converting the glycine receptor channel from being anion-selective to cation-selective. We are also investigating the role of “cytoplasmic portals” in the intracellular structure of the glycine receptor with respect to ion permeation. This research provides basic knowledge of how these neurotransmitter receptors operate as well as defining the functional consequences of various genetic diseases, such as hyperekplexia (startle disease), in which the genes for these receptor-channels are mutated.

The effects of flavonoids on the human glycine receptor channel
Many frequently encountered drugs act on neurotransmitter activated receptor-channels. Many sedatives and anaesthetics, for example, as well as alcohol and abused solvents, mediate much of their effects via direct actions on these receptor-channels. We are currently investigating flavonoids, a diverse family of plant-derived compounds, and how they act on these receptor-channels, using recombinant human glycine receptors (GlyRs) expressed in a cell line. We wish to determine both the structural basis for the actions, using mutagenesis, and how their mechanisms of action compare with other better studied modulators of GlyRs and GABAa receptor-channels. Ultimately, this research should provide basic knowledge on how different compounds can modify the properties of neurotransmitter-activated receptor-channels and provide a novel approach to aid the development of new sedative and anaesthetic drugs.

The properties of ion channels involved in olfactory transduction
Our ability to smell is due to odours in the air activating specific receptors in olfactory receptor neurons which then initiate a range of chemical processes inside these nerve cells, ultimately generating an electrical signal, which is then processed and detected as a smell. We are investigating the role of the different types of ionic channels present in olfactory receptor neurons, have in genrating this electrical signal and are investigating the properties of these important ion channels. In particular, we are exploring how the molecular structure affects the functional properties of one of these channels, the cyclic nucleotide-gate (CNG) ionic channel. More specifically, we are investigating what amino acids determine which ions, and how many, pass through these channels once they are activated by cyclic nucleotides. This work will provide important basic information on how these and similar channels function, how they contribute to the generation of the olfactory response and may also have some important implications for the development of biological odorant sensors for commercial uses.

Other Research and Software Development
Other research interests include biophysical modeling of ion permeation through channels and the problems incurred when evaluating the properties of ionic channels, including those which arise with electrical measurements in small cells, and the contribution and evaluation of liquid junction potentials in membrane potential measurements. Other interests include the role that unstirred-layers and unstirred regions adjacent to membranes have on membrane transport processes and other physiological functions. Additional projects involve the continued development of internationally marketed software (see:http://www.med.unsw.edu.au/PHBSoft), such as JPCalc, for research use in electrophysiological measurements, and experimental simulation programs, such as ArtMemW, MemPotW and MemCableW, for teaching electrophysiology.

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Researchers

Composition of Research Group
EProf Peter Barry, Emeritus and Conjoint Professor
Dr Andrew Moorhouse, Senior Lecturer
Dr Trevor Lewis, Lecturer
Dr Jane Carland, Vice Chancellor's Postdoctoral Fellow
Dr Jennie Cederholm, Postdoctoral Fellow
Mr S Sugiharto, P/T Research Assistant

Other Collaborators
Prof Peter R. Schofield, Garvan Institute of Medical Research
Dr Shin-Ho Chung, Dept of Theoretical Physics, The Australian National University
Prof Norio Akaike, Health Sciences University, Kumamoto, Japan.
Prof Junichi Nabekura, National Institute of Physiological Sciences, Okazaki, Japan
Profr Graham A R Johnston, Dept of Pharmacology, The University of Sydney
ProfJeremy Lambert, Dept Pathology and Neuroscience, University of Dundee, UK
Dr John Peters, Dept Pathology and Neuroscience, University of Dundee, UK

Research Support
From 1986, virtually continuous support by the National Health and Medical Research Council (NHMRC) of Australia and the Australian Research Council (ARC); Also University Research Support Program Grants (URSP) in 2001 and 2002, and a UNSW Faculty Research Grant in 2003. Current funding is provided by an NHMRC Program Grant (2003-2005), two ARC Discovery Grants (2003-5; 2005-2007) and a UNSW Faculty Research Grant (2005).

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Recent Publications (since 2000)

2005
Qu W., Moorhouse, A. J., Lewis, T. M., Pierce, K. D. and Barry, P. H. (2005). Mutation of the pore glutamate affects both cytoplasmic and external dequalinium block in the rat olfactory CNGA2 channel. Eur. Biophys. J. 34: 442-453.

Barry, P.H. and Lynch, J.W. (2005). Ligand-gated channels. IEEE Trans. Nanobiosci. 4: 70-80.

2004
Keramidas, A., Moorhouse, A.J., Schofield, P.R. and Barry, P.H. (2004). Ligand gated ion channels: Mechanisms underlying ion selectivity. Invited review for: Prog. Biophys. Molec. Biol., 86: 161-204.]

Carland, J.E., Moorhouse, A.J., Barry, P.H., Johnston, G.A.R. and Chebib, M. (2004). Charged residues at the 2' position of Human GABAC p1 receptors invert ion selectivity and influence open state probability. J. Biol. Chem. 279: 54153-54160.

Moorhouse, A.J., Li, S., Vickery, R.M., Hill, M.A. and Morley, J.W. (2004) A patch-clamp investigation of membrane currents in a novel mammalian retinal ganglion cell line. Brain Res. 1003: 205-208.

Katsurabayashi, S., Kubota, H., Moorhouse, A.J. and Akaike, N. (2004) Differential modulation of evoked and spontaneous glycine release from rat spinal cord glycinergic terminals by the cyclic AMP/protein kinase A transduction cascade. J. Neurochem. 91: 657-666.

Morris, R., Morgan, B.S., Lewis, T.M., Pierce, K.D., Pisano, A. and Schofield, P.R. (2004) In vivo delivery of plasmid DNA via retrograde transport to obtain cell-specific gene expression. J. Neurochem. 90: 1445-1452.

Absalom, N.L., Lewis, T.M. and Schofield, P.R. (2004) Mechanisms of channel gating of the ligand-gated ion channel superfamily inferred from protein structure. (Review) Exp. Physiol. 89:145-153.

2003
O’Mara, M., Barry, P.H. and Chung, S-H. (2003). A model of the glycine receptor deduced from Brownian dynamics studies. P.N.A.S. 100: 4310-4315.

Barry, P.H. (2003). Commentary. The relative contributions of cAMP and InsP3 pathways to olfactory responses in vertebrate olfactory receptor neurons and the specificity of odorants for both pathways. J. Gen. Physiol. 122: 247-250.

Lee, D J-S, Keramidas, A., Moorhouse, A.J., Schofield, P.R. and Barry, P.H. (2003). The contribution of proline 250 (P-2’) to pore diameter and ion selectivity in the human glycine receptor channel. Neurosci. Letts. 351(3): 96-200.

Akaike, N. and Moorhouse, A.J. (2003) Techniques: applications of the nerve-bouton preparation in neuropharmacology. TIPS 24: 44-47.

Jeong, H.J., Jang, I.S., Moorhouse, A.J, and Akaike, N. (2003) Activation of presynaptic glycine receptors facilitates glycine release from presynaptic terminals synapsing onto rat spinal sacral dorsal commissural nucleus neurons. J. Physiol. (Lond.) 550: 373-383.

Kubota, H., Katsurabayashi, S., Moorhouse, A.J., Murakami, N., Koga, H. and Akaike, N. (2003) GABAB receptor transduction mechanisms, and crosstalk between protein kinases A and C, in GABAergic terminals synapsing on to rat nucleus basalis of Meynert's neurons. J. Physiol. (Lond.) 551: 263-276.

Lewis, T.M., Schofield, P.R., and McClellan, A.M.L. (2003) Kinetic determinants of agonist potency at the recombinant human glycine receptor. J. Physiol. (Lond.) 549: 361-374.

Absalom, N.L., Lewis, T.M., Kaplan, W., Pierce, K.D., and Schofield, P.R. (2003) Role of charged residues in coupling ligand binding and channel activation in the extracellular domain of the glycine receptor. J. Biol. Chem. 278: 50151-50157.

2002
Keramidas, A., Moorhouse, A.J., Pierce, K., Schofield, P.R. and Barry, P.H. (2002). Cation-selective mutations in the M2 domain of the inhibitory glycine receptor channel reveal determinants of ion-charge selectivity. J. Gen. Physiol. 119: 393-410.

Moorhouse, A.J., Keramidas, A., Zaykin, A., Schofield, P.R. and Barry, P.H. (2002). Single channel analysis of conductance and rectification in cation-selective, mutant glycine receptor-channels. J. Gen. Physiol. 119: 411-425.

Rees, M.I., Lewis, T.M., Kwok, J.B.J., Mortier, G., Govaert, P., Snell, R.G., Schofield, P.R. and Owen, M.J. (2002) Hyperekplexia associated with compound heterozygote mutations in the -subunit of the human inhibitory glycine receptor (GLRB). Hum. Mol. Gen. 11:853-860.

2001
Friedrich, O. Ehmer, T., Uttenweiler, D., Vogel, M., Barry, P.H., Fink, R.H.A. (2001) Numerical Analysis of Ca2+ depletion in the transverse tubular system (TTS) of mammalian muscle. Biophys. J., 80: 2046-2055.

Kaur, R., Zhu, X.O., Moorhouse, A.J., Barry, P.H. (2001). IP3-gated channels and their occurrence relative to CNG channels in the soma and dendritic knob of rat olfactory receptor neurons. J. Membrane Biol, 181: 91-105.

Qu, W., Moorhouse, A.J., Cunningham, A.M. and Barry, P. H. (2001) Anomalous mole fraction effects in recombinant and native cyclic nucleotide-gated channels in rat olfactory receptor neurons. Proc. Roy. Soc. Lond. Ser. B. 268: 1395-1403.

Rees, M., Lewis, T.M., Vafa, B., Ferrie, C., Corry, P., Muntoni, F., Jungbluth, H., Stephenson, J.B.P., Kerr, M., Snell, R.G., Schofield, P.R. and Owen, M.J. (2001) Compound heterozygosity and nonsense mutations in the α1-subunit of the inhibitory glycine receptor in hyperekplexia. Hum. Gen. 109: 267-270.

2000
Qu, W., Moorhouse, A.J., Rajendra, S. and Barry, P.H. (2000). Very negative potential for half-inactivation of, and effects of anions on, voltage-dependent sodium currents in acutely isolated rat olfactory receptor neurons. J. Membrane Biol., 175: 123-138.

Keramidas, A., Moorhouse, A.J., French, C.R., Schofield, P.R. and Barry, P.H. (2000). M2 pore mutations convert the glycine receptor channel from being anion to cation selective. Biophys. J.: 78: 247-259.

Qu, W., Zhu, X. O., Moorhouse, A.J., Bieri, S., A. M. Cunningham, A. M. and Barry, P.H. (2000). Ion Permeation and Selectivity of Wild-Type Recombinant Rat CNG (rOCNC1) Channels Expressed in HEK293 Cells. J. Membrane Biol., 178: 137-150.