Kinetics of metabotropic glutamate receptors

Project Description

G-protein-coupled receptors (GPCRs) constitute the largest and pharmacologically most important family of cell surface receptors. They become activated by binding of agonists to the orthosteric binding site, but may also be activated or modulated via presumably allosteric binding sites. Upon activation, GPCRs trigger a signaling cascade that begins by coupling to their cognate G-proteins, followed by activation of these G-proteins by binding of GTP and subsequent activation of effector proteins via the G-proteins’ α– or βγ -subunits, respectively.

The kinetics of this signaling machinery have been the subject of investigation for many years. However, only for the very specific case of the light receptor, rhodopsin, the activation has been determined with certainty at ≈1 ms. For all other GPCRs it is still essentially unknown how fast they can be activated. Using different approaches and receptors, activation times ranging from tens of ms to minutes have been reported.

Our own measurements using fluorescently labeled receptors in intact cells and activation with agonists by superfusion, have given activation times of ≈50 ms. This value may well overestimate the true activation times of GPCRs, notably because it is derived from a large number of receptors on a cell (or part of a cell) which are not fully synchronized. We now intend to develop optimized systems to measure the true activation kinetics and to investigate whether non-visual GPCRs might approach the switch times of rhodopsin. To do so, we intend to develop three distinct but related strategies for

a) light-triggered activation via caged agonists,

b) light-triggered activation via tethered photolabile agonists, and

c) concentration-jump induced activation and deactivation by a piezo device.

In each case, the readout will be via fluorescence resonance energy transfer (FRET) for receptor activation, based on sensor constructs bearing various types of fluorophores. The data will be globally fitted by complex Markovian models to quantify the kinetics of binding and unbinding as well as activation and deactivation. On the long run, this strategy will be expanded from the initial receptor activation process to the entire signaling chain.

Title Year Authors Journal Links
Related GPCRs couple differently to Gs: preassociation between G protein and 5-HT7 serotonin receptor reveals movement of Gαs upon receptor activation 2017 Andressen, K. W., Ulsund, A. H., Krobert, K. A., Lohse, M. J., Bünemann, M., and Levy, F. O. FASEB J More
beta-Arrestin biosensors reveal a rapid, receptor-dependent activation/deactivation cycle 2016 Nuber, S., Zabel, U., Lorenz, K., Nuber, A., Milligan, G., tobin, A. B., Lohse, M. J., and Hoffmann, C. Nature More
Kinetics and mechanism of G protein-coupled receptor activation 2014 Lohse, M.J., Maiellaro, I., and Calebiro, D. Curr Opin Cell Biol More
Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling 2012 Lohse, M.J., Nuber, S., and Hoffmann C. Pharmacol Rev More
Sequential inter- and intrasubunit rearrangements during activation of dimeric metabotropic glutamate receptor 1 2012 Hlavackova, V., Zabel, U., Frankova, D., Bätz, J., Hoffmann, C., Prezeau, L., Pin, J. P., Blahos, J., and Lohse, M. J. Sci Signal More
Differential regulation by cyclic nucleotides of the CNGA4 and CNGB1b subunits in olfactory cyclic nucleotide-gated channels 2012 Nache, V., Zimmer, T., Wongsamitkul, N., Schmauder, R., Kusch, J., Reinhardt, L., Bonigk, W., Seifert, R., Biskup, C., Schwede, F. and Benndorf, K. Sci Signal More
How subunits cooperate in cAMP-induced activation of homotetrameric HCN2 channels 2011 Kusch, J., Thon, S., Schulz, E., Biskup, C., Nache, V., Zimmer, T., Seifert, R., Schwede, F., and Benndorf, K. Nat Chem Biol More
Interdependence of receptor activation and ligand binding in HCN2 pacemaker channels 2010 Kusch, J., Biskup, C., Thon, S., Schulz, E., Nache, V., Zimmer, T., Schwede, F. and Benndorf, K. Neuron More
Conformational cross-talk between alpha2A-adrenergic and mu-opioid receptors controls cell signaling 2008 Vilardaga, J. P., Nikolaev, V. O., Lorenz, K., Ferrandon, S., Zhuang, Z., and Lohse, M. J. Nat Chem Biol More
Relating ligand binding to activation gating in CNGA2 channels 2007 Biskup, C., Kusch, J., Schulz, E., Nache, V., Schwede, F., Lehmann, F., Hagen, V. and Benndorf, K. Nature More
Molecular basis of inverse agonism in a G protein coupled receptor 2005 Vilardaga, J. P., Steinmeyer, R., Harms, G. S. and Lohse, M. J. Nat Chem Biol More
Measurement of the millisecond activation switch of G protein-coupled receptors in living cells 2003 Vilardaga, J. P., Bünemann, M., Krasel, C., Castro, M., and Lohse, M. J. Nat Biotechnol More