Ingo Greger

Glutamate receptor dynamics, structure and function at synapses
Group Leader page

Project 1: Glutamate receptor dynamics, structure and function at synapses

Information transfer and storage in the nervous system occurs at synapses. AMPA-type glutamate-receptors (AMPARs) centrally contribute to synaptic plasticity, which underlies learning. Malfunction of these receptors underlies various neurological disorders such as epilepsy and neurodegeneration. My lab is utilizing various approaches, including structural biology, cell biology, electrophysiology and super-resolution imaging to understand mechanisms underlying AMPA-R regulation and signalling at synapses.

We will be capitalizing on our structural data to explore regulation of synaptic AMPA-Rs via the large receptor N-terminal domain (NTD) (Herguedas al., 2016). We will study the interaction between the NTD and synaptic proteins, including AMPA-R auxiliary subunits (Cais et al., 2014), and how this impacts on synaptic transmission and AMPAR clustering at synapses (Garcia-Nafria et al., 2016).

This multidisciplinary project investigates the impact of NTD dynamics on synaptic plasticity at various levels and thus provides an opportunity to employ a variety of approaches: In addition to extending our structural efforts using cryo-EM (electron-cryo microscopy), we will employ electrophysiology and super-resolution imaging. In collaboration with Prof. Ole Paulsen (Physiology Dept., University of Cambridge), there would be an opportunity to use optogentic approaches to selectively interfere with hippocampal activity in vitro and in vivo (Kohl et al. 2011).

References

Herguedas, B., García-Nafría, J., Cais, O., Fernández-Leiro, R., Krieger, J., Ho, H. and Greger. I.H. (2016)
Structure and organization of heteromeric AMPA-type glutamate receptors.
Science 352:aad3873.

García-Nafría, J., Herguedas, B., Watson, J.F. and Greger, I.H. (2016)
The dynamic AMPA receptor extracellular region: A platform for synaptic protein interactions.
J Physiol. doi: 10.1113/JP271844.

Kohl M et al. (2011)
Hemisphere-specific optogenetic stimulation reveals left-right asymmetry of hippocampal plasticity. ­
Nat. Neurosci
. 14, 1413-5.

Cais O et al. (2014)
Mapping the interaction sites between AMPA receptors and TARPs reveals a role for the receptor N-terminal domain in channel gating.
Cell Reports, 9, 728-40.


Project 2 : Supra-molecular organization and function of ionotropic glutamate receptors

Excitatory neurotransmission at chemical synapses in the vertebrate central nervous system is largely mediated by ionotropic glutamate receptors (iGluRs). All iGluRs are assembled from four multi-domain core subunits, which harbour binding sites for agonists and allosteric modulators and delineate a central ion channel pore across the neuronal plasma membrane. From a mechanistic point of view, the study of iGluRs has reached a very exciting stage. A series of full-length receptor structures, aided by an integrated analysis combining single-particle cryo-electron microscopy, X-ray crystallography and electrophysiology, have started to define most states of the iGluR gating cycle at intermediate resolution.

However, it is increasingly clear that, at neuronal synapses, these channels do not exist or function in isolation. The core iGluR subunits are embedded into supramolecular assemblies that include multiple extracellular, transmembrane and intracellular proteins beyond the four core subunits. Such complexes are known to modulate receptor trafficking and signalling, but in most cases a structure-based, mechanistic understanding of these processes is lacking.

This project will focus on the structural and functional analysis of iGluR complexes with extracellular proteins, spanning the synaptic cleft, building up on the ongoing collaboration between the groups of Ingo Greger and Radu Aricescu. Multiple options are available, centered around AMPA and kainate iGluR sub-families. This is an excellent opportunity to acquire training in human membrane protein structural biology, including single-particle cryo-EM and X-ray crystallography, combined with biophysical analyses, electrophysiology and super-resolution fluorescence microscopy.


References:

Mayer, M.L. (2016)
Structural biology of glutamate receptor ion channel complexes.
Curr Opin Struct Biol. 41:119-127.

Herguedas, B., García-Nafría, J., Cais, O., Fernández-Leiro, R., Krieger, J., Ho, H. and Greger, I.H. (2016)
Structure and organization of heteromeric AMPA-type glutamate receptors.
Science 352:aad3873.

García-Nafría, J., Herguedas, B., Watson, J.F., Greger, I.H. (2016)
The dynamic AMPA receptor extracellular region: A platform for synaptic protein interactions.
J Physiol. doi: 10.1113/JP271844.

Elegheert, J., Kakegawa, W., Clay, J.E., Shanks, N.F., Behiels, E., Matsuda, K., Kohda, K., Miura, E., Rossmann, M., Mitakidis, N., Motohashi, J., Chang, V.T., Siebold, C., Greger, I., Nakagawa, T., Yuzaki, M. and Aricescu, A.R. (2016)
Structural Basis for Integration of GluD Receptors within Synaptic Organizer Complexes.
Science 353:295-299.

Matsuda, K., Budisantoso, T., Mitakidis, N., Sugaya, Y., Miura, E., Kakegawa, W., Yamasaki, M., Konno, K., Uchigashima, M., Abe, M., Watanabe, I., Kano, M., Watanabe, M., Sakimura, K., Aricescu, A.R. and Yuzaki, M. (2016)
Trans-Synaptic Modulation of Kainate Receptor Functions by C1q-like Proteins.
Neuron 90:752-767.