Molecular and Functional Aspects of Ion Channels, Receptors, and Transporters; Mouse Genetic Models for Neuroscience Diseases

The Lester group continues our work on ion channels, receptors, and transporters. The group has continued to analyze several strains of knock-in mice generated in its laboratory for two ligand-gated channels, the nicotinic alpha4 receptor and the serotonin 5-HT3 receptor. The nicotinic receptor work is enhanced by a promising new strain, Leu9'Ala. This work has generated interesting insights into nicotine addiction, neurodegenerative disease, and epilepsy. Strains that contain GFP tags on their nicotinic receptors, and that duplicate mutations underlying human epilepsies, are under construction. The epilepsy mutations in nicotinic receptors are also under study in oocyte expression systems. The Lester group has also started to explore the possible role of the alpha7 nicotinic receptor in Alzheimer's disease, again using mouse models. The hypersensitive 5-HT3 receptor knock-in mice have generated insights into murine urologic syndrome.

The group’s work on selective silencing of mammalian neurons has generated a promising set of techniques and reagents based on ligand-activated chloride channels. It is now developing "proof of concept" transgenic mouse strains.

The Lester group continues its joint work with the Dougherty group, in Caltech's Chemistry Division, on aspects of ion channel structure-function. The group has  brought novel techniques to these studies, including mass spectrometry and fluorescence. It works on unnatural amino-acid mutagenesis. The group has now studied the cation-pi interaction that helps agonists bind to several cys-loop receptors and has now extended unnatural amino-acid incorporation to mammalian cells.

With the Dougherty group and with Neurion Pharmaceuticals in Pasadena, the Lester group has started to analyze the binding of blocking drugs to the hERG potassium channel, also using unnatural amino acid mutagenesis. The channel is important because it underlies many instances of drug-induced long-QT syndrome. It is beginning unnatural amino acid experiment on G protein-coupled receptors.

The Lester group collaborates with both Dougherty and Doug Rees, also in the Chemistry Division, on bacterial ion channels of known atomic-scale structure. It gathered data at bandwidths more than an order of magnitude greater than usual; but some gating transitions are still too fast to measure. It is seeking the origin of voltage sensitivity in the MscS channel.

Work continues on quantitative aspects of transporter function, primarily measured with fluorescence and with knock-in mice, and fluorescence is being used to analyze the mobility of GABA transporters. As an interesting side benefit of the GABA transporter knock-in mouse, a knockout mouse for the same molecule has been generated and analyzed. The late Norman Davidson led a subgroup working on aspects of synaptic plasticity, particularly those that depend on A kinase stimulation. Members of this subgroup are now analyzing their data and preparing papers for publication.

Source: http://www.bbe.caltech.edu/content/henry-lester