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Journal Article

Effects on capacitance by overexpression of membrane proteins

MPS-Authors
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Zimmermann,  D.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Feldbauer,  K.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Terpitz,  U.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Haase,  W.
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Bamberg,  E.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Zimmermann, D., Zhou, A., Kiesel, M., Feldbauer, K., Terpitz, U., Haase, W., et al. (2008). Effects on capacitance by overexpression of membrane proteins. Biochemical and Biophysical Research Communications, 369(4), 1022-1026. doi:10.1016/j.bbrc.2008.02.153.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0024-D85C-2
Abstract
Functional Channelrhodopsin-2 (ChR2) overexpression of about 10(4)channels/mum(2) in the plasma membrane of HEK293 cells was studied by patch-clamp and freeze-fracture electron microscopy. Simultaneous electrorotation measurements revealed that ChR2 expression was accompanied by a marked increase of the area-specific membrane capacitance (C(m)). The C(m) increase apparently resulted partly from an enlargement of the size and/or number of microvilli. This is suggested by a relatively large C(m) of 1.15+/-0.08 microF/cm(2) in ChR2-expressing cells measured under isotonic conditions. This value was much higher than that of the control HEK293 cells (0.79+/-0.02 microF/cm(2)). However, even after complete loss of microvilli under strong hypoosmolar conditions (100 mOsm), the ChR2-expressing cells still exhibited a significantly larger C(m) (0.85+/-0.07 microF/cm(2)) as compared to non-expressing control cells (0.70+/-0.03 microF/cm(2)). Therefore, a second mechanism of capacitance increase may involve changes in the membrane permittivity and/or thickness due to the embedded ChR2 proteins.