Effects on capacitance by overexpression of membrane proteins

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• 作者：D. Zimmermann ; A. Zhou ; M. Kiesel ; K. Feldbauer ; U. Terpitz ; W. Haase ; T. Schneider-Hohendorf ; E. Bamberg ; V.L. Sukhorukov
• 关键词：Patch-cl Electrorotation ; Freeze-fracture electron microscopy ; HEK293 ; Overexpression ; Membrane capacitance ; Channelrhodopsin-2
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2008
• 期刊代码：159_0006291x
• 类别：bio
• 出版时间：16 May 2008
• 卷：369
• 期：4
• 页码：1022-1026
• 文件大小：2369 K

摘要

Functional Channelrhodopsin-2 (ChR2) overexpression of about 10⁴ channels/μm² 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 μF/cm² in ChR2-expressing cells measured under isotonic conditions. This value was much higher than that of the control HEK293 cells (0.79 ± 0.02 μF/cm²). 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 μF/cm²) as compared to non-expressing control cells (0.70 ± 0.03 μF/cm²). Therefore, a second mechanism of capacitance increase may involve changes in the membrane permittivity and/or thickness due to the embedded ChR2 proteins.