Current address: The Institute for Neuromuscular Research, The Children's Hospital at Westmead, Westmead NSW 2145, Sydney, Australia
Identification of domains influencing assembly and ion channel properties in α7 nicotinic receptor and 5-HT3 receptor subunit chimaeras
Article first published online: 29 JAN 2009
2007 British Pharmacological Society
British Journal of Pharmacology
Volume 152, Issue 4, pages 501–512, October 2007
How to Cite
Gee, V. J., Kracun, S., Cooper, S. T., Gibb, A. J. and Millar, N. S. (2007), Identification of domains influencing assembly and ion channel properties in α7 nicotinic receptor and 5-HT3 receptor subunit chimaeras. British Journal of Pharmacology, 152: 501–512. doi: 10.1038/sj.bjp.0707429
- Issue published online: 29 JAN 2009
- Article first published online: 29 JAN 2009
- (Received May 9, 2007, Revised June 26, 2007, Accepted July 2, 2007)
- nicotinic receptor;
- 5-HT receptor;
- single-channel conductance
Background and purpose:
Nicotinic acetylcholine receptors (nAChRs) and 5-hydroxytryptamine type 3 receptors (5-HT3Rs) are members of the superfamily of neurotransmitter-gated ion channels. Both contain five subunits which assemble to form either homomeric or heteromeric subunit complexes. With the aim of identifying the influence of subunit domains upon receptor assembly and function, a series of chimaeras have been constructed containing regions of the neuronal nAChR α7 subunit and the 5-HT3 receptor 3A subunit.
A series of subunit chimaeras containing α7 and 5-HT3A subunit domains have been constructed and expressed in cultured mammalian cells. Properties of the expressed receptors have been examined by means of radioligand binding, agonist-induced changes in intracellular calcium and patch-clamp electrophysiology.
Subunit domains which influence properties such as rectification, desensitization and conductance have been identified. In addition, the influence of subunit domains upon subunit folding, receptor assembly and cell-surface expression has been identified. Co-expression studies with the nAChR-associated protein RIC-3 revealed that, in contrast to the potentiating effect of RIC-3 on α7 nAChRs, RIC-3 caused reduced levels of cell-surface expression of some α7/5-HT3A chimaeras.
Conclusions and implications:
Evidence has been obtained which demonstrates that subunit transmembrane domains are critical for efficient subunit folding and assembly. In addition, functional characterization of subunit chimaeras revealed that both extracellular and cytoplasmic domains exert a dramatic and significant influence upon single-channel conductance. These data support a role for regions other than hydrophobic transmembrane domains in determining ion channel properties.
British Journal of Pharmacology (2007) 152, 501–512; doi:10.1038/sj.bjp.0707429; published online 27 August 2007