Christiane Grimm
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The Neuro Technology Center at Columbia University, New York Biological Sciences 901 NWC Building
Email: cg3124@columbia.edu |
Characterization of red-shifted channelrhodopsin variants Channelrhodopsins (ChRs) are photosensitive channel proteins, which naturally occur in the eye spot of motile green algae. They unify the ability to perceive light and mediate ion currents in one small protein making them a perfect candidate for optogenetic approaches. Genetically-targeted to specific cells they modulate the ion permeability of the cell membrane in a precise and light-dependent manner; a feature which is widely used in the field of neuroscience to depolarize the membrane of neurons and thereby trigger action potentials with spatial and temporal precision. Today, the most commonly used variant is channelrhodopsin-2 from the unicellular green algae Chlamydomonas reinhardtii (C2), which is activated best with blue light. However, due to deeper penetration and reduced scattering in tissues, the use of red light for activation provides several advantages. This holds particularly true for in vivo application, where (non-invasive) light delivery can be a demanding challenge. Therefore, ChRs with a red-shifted activation compared to C2 are of special interest. My work is currently focused on the biophysical characterization of red-shifted ChRs like ReaChR and to some extend Chrimson. To achieve this, the proteins are expressed in HEK cells and whole-cell patch-clamp recording or confocal imaging is performed to investigate photocurrent properties, the photocycle or the expression/membrane targeting of the ChRs. Moreover, mutants are designed and characterized to create variants with novel properties like a more red-shifted action spectrum or slower/faster kinetics.
Publications
Vierock, J., Grimm, C., Nitzen, N., and Hegemann, P. (2017) Molecular determinants of proton selectivity and gating in the red-light activated channelrhodopsin Chrimson. Sci. Rep. 7(1):9928. doi: 10.1038/s41598-017-09600-8.
https://www.nature.com/articles/s41598-017-09600-8.pdf
Grimm C, Vierock J, Hegemann P, Wietek J.(2017) Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins. J Vis Exp. 2017 May 22;(123). doi: 10.3791/55497.
https://www.ncbi.nlm.nih.gov/pubmed/28570519
Krause, B.S., Grimm, C., Kaufmann, J.C.D., Schneider, F., Sakmar, T.P., and Hegemann, P. (2017) Complex Photochemistry within the Green-absorbing Channelrhodopsin. ReaChR. Biophys. J. 112, 1166-1175
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Schneider, F., Grimm, C. and Hegemann, P. (2015) Biophysics of Channelrhodopsin. Ann. Rev. Biophysics. 44, 167 – 186. http://www.annualreviews.org/doi/abs/10.1146/annurev-biophys-060414-034014