Membrane Lipid Control Of Ionotropic Glutamate Receptors

The goal of this project is to determine how ionotropic glutamate receptor operation is controlled by membrane lipids within a defined lipid environment. Studies of native and recombinant channels have demonstrated changes in channel function following exposure to a number of different lipid-derived modulators including PIP2 and lyso-lecithin as well as cis-unsaturated endocannabinoids and fatty acids such as arachidonic acid (AA) and docosahexaenoic acid (DHA).

These studies have revealed the potential for channel regulation in the context of native membranes of heterogeneous composition, but they leave open basic questions about how channel operation depends on specific bilayer properties including surface charge, head group identity, degree of fatty acyl saturation and cholesterol content.

To answer these questions directly, we are working to reconstitute functional glutamate receptor channels in liposomes from purified subunits expressed in yeast. This approach will allow us to evaluate receptor operation while systematically altering lipid composition to change the bilayer chemical and mechanical properties. In addition, the potential for rapid large scale screens of randomly generated mutants in yeast should greatly facilitate our search for channel residues that may be essential for fatty acid binding and/or modulation.

The work combines expertise from the Huettner and Nichols labs to pursue a multidisciplinary project involving protein chemistry, electrophysiology, and yeast genetics. How membrane composition controls ion channel operation is an under studied issue clearly relevant to a wide range of different channels and transporters that collectively determine cellular and network excitability. Understanding the mechanisms that underlie channel regulation by membrane constituents could help identify new targets and lead compounds for therapeutic control of excitability.