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Methods for Cell-attached Capacitance Measurements in Mouse Adrenal Chromaffin Cell
Published on: October 22, 2014
Effects on capacitance by overexpression of membrane proteins
D Zimmermann1, A Zhou, M Kiesel
1Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
Biochemical and Biophysical Research Communications
|March 12, 2008
Summary
Functional Channelrhodopsin-2 (ChR2) overexpression in HEK293 cells increased plasma membrane capacitance. This capacitance increase is attributed to both microvilli changes and alterations in membrane properties due to ChR2 insertion.
Area of Science:
- Biophysics
- Cell Biology
- Membrane Biophysics
Background:
- Channelrhodopsin-2 (ChR2) is a light-gated ion channel crucial for optogenetics.
- Understanding ChR2's impact on cell membrane properties is essential for its application.
- HEK293 cells are a common model system for studying membrane protein expression.
Purpose of the Study:
- To investigate the biophysical effects of functional Channelrhodopsin-2 (ChR2) overexpression on HEK293 cell plasma membranes.
- To quantify changes in membrane capacitance and identify contributing factors.
Main Methods:
- Patch-clamp electrophysiology to measure membrane properties.
- Freeze-fracture electron microscopy to visualize membrane ultrastructure.
- Electrorotation measurements to assess cell membrane capacitance.
Main Results:
- ChR2 overexpression led to a significant increase in area-specific membrane capacitance (C(m)).
- Increased C(m) was partly due to enlarged or increased microvilli, evidenced by high capacitance under isotonic conditions.
- Even after microvilli loss, ChR2-expressing cells maintained higher C(m), suggesting ChR2's direct influence on membrane properties.
Conclusions:
- Functional ChR2 expression alters HEK293 cell membrane capacitance through both morphological changes (microvilli) and direct incorporation into the membrane.
- These findings provide insights into the biophysical consequences of ChR2 expression, relevant for optogenetic studies.
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