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Zelluläre Biophysik (ICS-4)
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Ion homeostasis in cells and cell organelles

Intracellular ion concentrations regulate various cellular processes. Changes in the cytoplasmic Ca2+ concentration represent a key signal for many cellular processes; Na+, K+, H+ and Cl- gradients provide the driving force for electrical processes, permit the accumulation of nutrients and neurotransmitters and allow cellular volume regulation. Sensors based on fluorescent dyes and fluorescent proteins allow quantification of ion concentrations in intact living cells in various preparations. We develop novel fluorescent protein-based sensors, and spectroscopically and microscopically characterize genetically encoded as well as organic fluorescent sensor molecules. We put particular emphasis on Fluorescence Lifetime Imaging (FLIM) based on time-correlated single photon counting (TCSPC) to quantify absolute ionic concentrations in cell culture, primary cultures as well as in acute slice preparations from normal or genetically altered animals. We combine these techniques with heterologous expression and electrophysiology to elucidate the molecular mechanisms underlying ion homeostasis in cytoplasm, lysosomes and synaptic vesicles in normal and pathologically altered cells.

  1. M Cotlet, J. Hofkens, M. Maus, T. Gensch, J. Michiels, G. Dirix, M. Van Guyse, J. Vanderleyden, A. J. W. G. Visser, and F. C. De Schryver; Excited State Dynamics in the Enhanced Green Fluorescent Protein Mutant Probed by Picosecond Time-Resolved Single Photon Counting Spectroscopy. Journal of Physical Chemistry B 105:4999-5006 (2001)
    J. J. van Thor, T. Gensch, K. J. Hellingwerf, and L. Johnson. Phototransformation of the wild-type A. Victoria Green Fluorescent Protein with UV- and Visible light leads to decarboxylation of Glutamate-222. Nature Structural Biology 9:37-41 (2002)
  2. H. Kaneko, I. Putzier, S. Frings, U. B. Kaupp, and T. Gensch; Chloride accumulation in mammalian olfactory sensory neurons. Journal of Neuroscience 24:7931-7938 (2004)
  3. D. Gilbert, C. Franjic-Wuertz, K. Funk, T. Gensch, S. Frings, and F. Moehrlen; Differential maturation of chloride homeostasis in primary afferent neurons of the somatosensory system. International Journal of Developmental Neuroscience 25:479-489 (2007)
  4. K. Funk, A. Woitecki, C. Franjic-Wuertz, T. Gensch, F. Moehrlen, and S. Frings; Modulation of chloride homeostasis by inflammatory mediators in dorsal root ganglion neurons. Molecular Pain 4:32-43 (2008)
  5. S. Dangwal, , B.H. Rauch, T. Gensch, L. Dai, E. Bretschneider, C.F. Vogelaar, K. Schroer, and A.C. Rosenkranz; High glucose enhance thrombin response via protease-activated receptor-4 in human vascular smooth muscle cells. Arteriosclerosis, Thrombosis and Vascular Biology 31:624-633 (2011)
  6. M. Hoff, S. Balfanz, P. Ehling, T. Gensch, and A. Baumann; A single amino acid residue controls Ca(2+) signaling by an octopamine receptor from drosophila melanogaster. FASEB Journal 25:2482-2491 (2011)
  7. T. Gensch, and D. Kaschuba; Fluorescent genetically encoded calcium indicators and their in vivo application. in G. Jung (ed.), Fluorescent Proteins II. Application of Fluorescent Protein Technology, Springer Series on Fluorescence 12:125-161 (2012), Springer-Verlag Berlin Heidelberg
  8. A. Geiger, L. Russo, T. Gensch, T. Thestrup, S. Becker, K.-P. Hopfner, C. Griesinger, G. Witte, and O. Griesbeck. Correlating Calcium Binding, Förster Resonanxce Energy Transfer, and Conformational Change in the Biosensor TN-XXL.Biophysical Journal 102:2401 – 2410 (2012)
  9. M. Wingen, J. Potzkei, S. Endres, G. Casini, C. Rupprecht, C. Fahlke, U. Krauss, K.-E. Jaeger, T. Drepper, and T. Gensch. The photophysics of LOV-based fluorescent proteins – new tools for cell biology. Photochemical and Photobiological Sciences 13:875-883 (2014)
  10. C. Biskup, T. Gensch; Fluorescence Lifetime Imaging of ions in biological tissues. in “Fluorescence Lifetime Spectroscopy and Imaging. Principles and Applications in Biomedical Diagnostics” D. Elson, P.W.M. French and L. Marcu, eds. Taylor & Francis (2014).
  11. T. Gensch, V. Untiet, A. Franzen, P. Kovermann, and C. Fahlke. Determination of Intracellular Chloride Concentrations by Fluorescence Lifetime Imaging“ in Advanced Time-Correlated Single Photon Counting Applications W. Becker (ed.) Springer Series in Chemical Physics 111 Springer International Publishing Switzerland (2015).
  12. V. Untiet, L.M. Moeller, X. Ibarra-Soria, G. Sánchez-Andrade, M. Stricker, E.M. Neuhaus, D. W. Logan, T. Gensch, and M. Spehr. Elevated Cytosolic Cl− Concentrations in Dendritic Knobs of Mouse Vomeronasal Sensory Neurons. Chemical Senses 41:669-676 (2016)
  13. V. Untiet, P. Kovermann, N.J. Gerkau, T. Gensch, C.R. Rose, and Fahlke C. Glutamate Transporter-Associated Anion Channels Adjust Intracellular Chloride Concentrations during Glial Maturation. Glia (2017) 65:388-400.