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Cell volume and membrane stretch independently control K + channel activity
Author(s) -
Hammami Sofia,
Willumsen Niels J.,
Olsen Hervør L.,
Morera Francisco J.,
Latorre Ramón,
Klaerke Dan A.
Publication year - 2009
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2008.163550
Subject(s) - pipette , bk channel , biophysics , chemistry , hydrostatic pressure , piezo1 , membrane , potassium channel , membrane potential , patch clamp , mechanosensitive channels , xenopus , cell membrane , ion channel , biology , biochemistry , physics , receptor , gene , thermodynamics
A number of potassium channels including members of the KCNQ family and the Ca 2+ activated 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 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 hydrostatic pressure (suction) applied to the pipette. Thus, at a pipette pressure of −5.0 ± 0.1 mmHg the increase amounted to 381 ± 146% (mean ± s.e.m. , n = 6, P < 0.025). In contrast, in oocytes expressing the strongly volume‐sensitive KCNQ1 channel, the current was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude that stretch and volume sensitivity can be considered two independent regulatory mechanisms.