The Neurobiology Lab - Collaborations

 

Research Collaborations:

Department of Mathematics
School of Molecular and Microbial Biosciences
Department of Anatomy and Histology
Department of Pharmacology

Department of Mathematics

Associate Professor Bill Gibson
Dr Les Farnell - Senior Research Associate
Greg Lemon - Ph.D. student

http://www.maths.usyd.edu.au/u/billg

Research:

Theoretical models of intra- and inter-cellular communication in neural systems and in smooth muscle

The unifying theme of our work is the role of calcium ions (Ca2+) as a principal second messenger in cellular communication. We have developed theoretical methods, including Monte Carlo simulation, for studying the entry, diffusion and binding of Ca2+ in single neurons and the resulting exocytosis and facilitation of transmitter release.

We are also modelling the action of metabotropic receptors: these initiate a G-protein cascade leading to the production of inositol 1,4,5-trisphosphate (IP3) and the release of Ca2+ from internal stores, This release mediates the contractile process in smooth muscle and also IP3 diffusion is important for intracellular communication in a number of other systems, including glia.

Figure 1 - Profile of Ca2+ bound to fixed buffer 4.5 ms
after opening of Ca2+ channels in the plasmalemma
following an action potential.

Selected recent publications:

Lemon G, Gibson WG, Bennett MR, (2003). Metabotropic receptor activation, desensitization and sequestration - I: modelling calcium and inositol 1,4,5-trisphosphate dynamics following receptor activation. J. Theor. Biol. 223: 93-111.

Lemon G, Gibson WG, Bennett MR, (2003). Metabotropic receptor activation, desensitization and sequestration - II: modelling the dynamics of the pleckstrin homology domain. J. Theor. Biol. 223: 113-129.

Bennett MR, Farnell L, Gibson WG, (2000). The probability of quantal secretion near a single calcium channel of an active zone. Biophys. J., 78: 2201-2221.

Bennett MR, Farnell L, Gibson WG, (2000). The probability of quantal secretion within an array of calcium channels of an active zone. Biophys. J., 78: 2222-2240.

 



School of Molecular and Microbial Biosciences

Justin Henandez
Associate Professor Arthur Conigrave
Professor Max Bennett

Identification of protein binding partners of the key ionotropic receptor P2X1.

The P2X1 gene product takes the form of two transmembrane domain protein subunits in which both the N- and C-termini are intracellular. Together, several P2X1 subunits form oligomeric complexes in the plasma membrane. Once assembled P2X1 oligomers behave as ATP/ADP receptors that mediate fast neurotransmission at various sites in the autonomic nervous system.

Local expression of the receptor protein to specific regions of the post-synaptic membrane is critical for receptor function and hence neurotransmission. However, the mechanism by which the receptor molecules are expressed at specific sites is currently unclear. Specific interactions with one or more cytoskeletal proteins, which are known to form complex networks on the intracellular face of the plasma membrane, might explain the basis for discrete expression of P2X1 receptors at synapses.

Yeast two-hybrid analysis has been used to identify two potential cytoskeletal protein binding partners of P2X1; one of these candidates binds to an N-terminal peptide of P2X1, the other binds to its C-terminus. Specific interactions between the intracellular N- and C-termini of P2X1 with these proteins in the cytoskeleton might be used as a scaffold to direct its localized expression.

The candidate protein partners of P2X1 are now being examined directly for evidence of protein-protein interactions by co-expression with full length P2X1 (or its N- or C-termini). The gene products have been tagged with specific peptide tags (including HA and c-myc) and subcloned into the mammalian expression vector pcDNA3.1. Successful expression of the P2X1 protein and its candidate cytoskeletal binding partners in human HEK-293 cells has been confirmed by Western blotting of cell lysates. Experiments to test for the existence of specific interactions between P2X1 and its candidate binding partners are currently in progress using co-immunoprecipitation analysis.




Dr Kevin Keay

Department of Anatomy and Histology
The University of Sydney

 




Dr Hilary Lloyd

Department of Pharmacology
The University of Sydney

 


 


 


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