Humboldt-Universität zu Berlin - Experimentelle Biophysik

Johannes Vierock

I am fascinated by the molecular mechanism of ion channels and transporters and the diversity of their applications in the exploding field of optogenetics. In motile algae channelrhodopsins achieve photoreception, highly selective ion conductance and light adaptation – all together, as a single protein. Each of these processes is mediated by the complex interplay of the light absorbing retinal chromophor and different specifically arranged amino acids. In my research I try to identify these key players and their interactions by combining sight-directed mutagenesis with time resolved functional measurements of the heterologously expressed protein. Specifically I am focusing on the molecular determinants of the high proton selectivity of channelrhdopsins, the functional characterization of different conducting states and the combination of different microbial rhodopsins with other ion channels in two component systems. Being a photoreceptor and an ion channel at the same time, channelrhodopsin activity can be remotely controlled by continuous light or short laser pulses and the resulting functional changes can be directly recorded by the Two-Electrode-Voltage-Clamp or the Patch Clamp technique with high precision and high temporal resolution. In addition ion specific imaging of local changes in ion concentration or protein purification and basic spectroscopic methods can be performed. Whereas a thorough characterization of specific channelrhodopsins - such as of the highly promising orange-light activated proton channel Chrimson - are crucial for the design and interpretation of optogenetic experiments, the disclosure of general mechanisms in the channelrhodopsin protein family allows the design of new optogenetic tools for basic research and medical applications.

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

*Ferenczi, E., *Vierock, J., Atsuta-Tsunoda, K.A., Tsunoda, S.P., Ramakrishnan, C., Gorini, C., Thompson, K., Lee, S.Y. Berndt, A., Perry, C., Minniberger, S., Vogt, A., Mattis, J., Prakash, R., Delp, S., Deisseroth, K.*, Hegemann, P.* (2016) Volume inhibition: modulation of excitability by extracellular protons Sci. Rep. 6, 23947; doi: 10.1038/srep23947.

*Zhang F, *Vierock J, Yizhar O, Fenno LE, Tsunoda S, Kianianmomeni A, Prigge M, Berndt A, Cushman J, Polle J, Magnuson J, Hegemann P, Deisseroth K. The microbial opsin family of optogenetic tools. Cell. 2011 Dec 23;147(7):1446-57. doi: 10.1016/j.cell.2011.12.004. PubMed PMID: 22196724.

http://download.cell.com/pdf/PIIS0092867411015029.pdf?intermediate=true