Biophysical characterisation of electrofused giant HEK293-cells as a novel electrophysiological expression system
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt (Germany)
- Lehrstuhl fuer Biotechnologie, University of Wuerzburg, Am Hubland, 97074 Wuerzburg (Germany)
- Lehrstuhl fuer Molekulare Pflanzenphysiologie und Biophysik, University of Wuerzburg, 97082 Wuerzburg (Germany)
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt (Germany) and Institute of Biophysical Chemistry, Biochemistry, Chemistry and Pharmacy, Johann-Wolfgang-GoeUniversity, Max-von-Laue Strasse 4, 60438 Frankfurt (Germany)
Giant HEK293 cells of 30-65 {mu}m in diameter were produced by three-dimensional multi-cell electrofusion in 75 mOsm sorbitol media. These strong hypotonic conditions facilitated fusion because of the spherical shape and smooth membrane surface of the swollen cells. A regulatory volume decrease (RVD), as observed at higher osmolalities, did not occur at 75 mOsm. In contrast to field-treated, but unfused cells, the increase in volume induced by hypotonic shock was only partly reversible in the case of fused giant cells after their transfer into isotonic medium. The large size of the electrofused cells allowed the study of their electrophysiological properties by application of both whole-cell and giant excised patch-clamp techniques. Recordings on giant cells yielded a value of 1.1 {+-} 0.1 {mu}F/cm{sup 2} for the area-specific membrane capacitance. This value was consistent with that of the parental cells. The area-specific conductivity of giant cells (diameter > 50 {mu}m) was found to be between 12.8 and 16.1 {mu}S/cm{sup 2}, which is in the range of that of the parental cells. Measurements with patch-pipettes containing fluorescein showed uniform dye uptake in the whole-cell configuration, but not in the cell-attached configuration. The diffusion-controlled uniform uptake of the dye into the cell interior excludes internal compartmentalisation. The finding of a homogeneous fusion was also supported by expression of the yellow fluorescent protein YFP (as part of the fusion-protein ChR2-YFP) in giant cells since no plasma-membrane bound YFP-mediated fluorescence was detected in the interior of the electrofused cells. Functional expression and the electrophysiological characterisation of the light-activated cation channel Channelrhodopsin 2 (ChR2) yielded similar results as for parental cells. Most importantly, the giant cells exhibited a comparable expression density of the channel protein in the plasma membrane as observed in parental cells. This demonstrates that electrofused cells can be used as a heterologous expression system.
- OSTI ID:
- 20854477
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 348, Issue 2; Other Information: DOI: 10.1016/j.bbrc.2006.07.112; PII: S0006-291X(06)01669-X; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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