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Cell volume and membrane stretch independently control K + channel activity.
Author(s) -
Hammami Sofia,
Willumsen Niels J,
Klaerke Dan A
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a539-b
Subject(s) - pipette , bk channel , biophysics , chemistry , membrane , xenopus , mechanosensitive channels , patch clamp , membrane potential , piezo1 , cell membrane , ion channel , cell , osmotic pressure , biochemistry , biology , receptor , gene
A number of K + channels including KCNQ1, IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch. To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in mammalian cells and Xenopus oocytes. Results from cell‐attached patch clamp studies (~50 μm 2 macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume‐insensitive BK current increases with increasing negative pipette pressure (suction). Thus, at a pipette pressure of −5.0±0.1 mmHg the increase amounted to 381±146 % (mean±SEM, n=6, P<0.025). In contrast, in oocytes expressing the strongly volume‐activated KCNQ1 channels, the current did not show any response to changes in membrane stretch. The results indicate that activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. Thus, we conclude that stretch‐ and volume‐sensitivity can be considered two independent regulatory mechanisms. Supported by the Oticon Foundation and DNSRC 272‐05‐0417.