Molecular Mechanism of Synaptic Plasticity – Biochemistry and Imaging of Macromolecules in the Synapse
In the postsynaptic density of synapses, protein complexes formed of ion channels and soluble signaling proteins function in regulating synaptic transmission. My laboratory is interested in understanding the changes of these macromolecular machineries (i.e. changes in composition, conformation, and modification) in response to neuronal activity. Our primary focus will be on glutamate receptors and their macromolecular assemblies formed of scaffold proteins. We combine techniques in molecular and cellular methods, biochemistry, and imaging to accomplish the task. Studying the mechanisms of synaptic function is likely to tell us more about the normal physiology and pathology of the nervous system at the molecular level. We focus on the following three areas:
- Understanding the structural basis of AMPA receptor function using cryo-EM. Development of a purification method to isolate intact AMPA receptors from the brain allows us to study the structural basis for the function of these important ligand gated ion channels in the synapse. Based on the 35 Angstrom density map we published in 2005 and 2006, we are currently working on to obtain higher resolution structure of the intact tetrameric AMPA receptors using cryo electron microscopy. We expect to understand the accurate subunit arrangements within the tetrameric AMPA receptors and further obtain clues to the glutamate induced conformational changes.
- Molecular mechanism of the functional modulation of AMPA receptors by stargazin/TARP. Modulation of AMPA receptors affects synaptic plasticity at the cellular level and influences cognition at the level of behavior. Membrane proteins in the stargazin/TARP family are auxiliary subunits of native AMPA receptors in the brain and modulate ion channel functioning by slowing down the desensitization kinetics. Using high resolution molecular imaging (electron microscopy) and electrophysiological recordings, we intend to further identify the mechanism of the modulation of AMPA receptors by stargazin/TARP.
- Determining the modular organization of the synaptic plasticity machinery. Through the approaches taken by molecular cloning and protein identification through mass spectrometry, neuroscientists have the overall view about the variety of the molecules (mainly proteins) that exists in the synapse. It remains less known how these proteins assemble and exert their functions during synaptic plasticity. On the assumption that modular organization of macromolecules forms the basis of synaptic structure and function, we intend to isolate and characterize novel protein complexes involved in synaptic plasticity. By accumulating the information on the variety and function of macromolecular machinery in the synapse, we intend to provide an explanation for the modular organization of the synapse.