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Mechanosensitive activation of K+ channel via phospholipase C-induced depletion of phosphatidylinositol 4,5-bisphosphate in B lymphocytes

Cited 22 time in Web of Science Cited 22 time in Scopus
Authors
Nam, Joo Hyun; Lee, Hoo-See; Nguyen, Yen Hoang; Kang, Tong Mook; Lee, Sung Won; Kim, Hye-Young; Kim, Sang Jeong; Earm, Yung E.; Kim, Sung Joon
Issue Date
2007-03-10
Publisher
Cambridge University Press
Citation
J Physiol. 2007 Aug 1;582(Pt 3):977-90. Epub 2007 Mar 8.
Keywords
AnimalsB-Lymphocytes/enzymology/*physiologyCell Line, TumorCell Membrane/physiology/ultrastructureElectrophysiologyGenes, ReporterLymphoma, B-CellMiceMicroscopy, ConfocalPhosphatidylinositol 4,5-Diphosphate/*physiologyPotassium Channels/*physiologyType C Phospholipases/*metabolism
Abstract
In various types of cells mechanical stimulation of the plasma membrane activates phospholipase C (PLC). However, the regulation of ion channels via mechanosensitive degradation of phosphatidylinositol 4,5-bisphosphate (PIP(2)) is not known yet. The mouse B cells express large conductance background K(+) channels (LK(bg)) that are inhibited by PIP(2). In inside-out patch clamp studies, the application of MgATP (1 mm) also inhibited LK(bg) due to the generation of PIP(2) by phosphoinositide (PI)-kinases. In the presence of MgATP, membrane stretch induced by negative pipette pressure activated LK(bg), which was antagonized by PIP(2) (> 1 microm) or higher concentration of MgATP (5 mm). The inhibition by PIP(2) was partially reversible. However, the application of methyl-beta-cyclodextrin, a cholesterol scavenger disrupting lipid rafts, induced the full recovery of LK(bg) activity and facilitated the activation by stretch. In cell-attached patches, LK(bg) were activated by hypotonic swelling of B cells as well as by negative pressure. The mechano-activation of LK(bg) was blocked by U73122, a PLC inhibitor. Neither actin depolymerization nor the inhibition of lipid phosphatase blocked the mechanical effects. Direct stimulation of PLC by m-3M3FBS or by cross-linking IgM-type B cell receptors activated LK(bg). Western blot analysis and confocal microscopy showed that the hypotonic swelling of WEHI-231 induces tyrosine phosphorylation of PLCgamma2 and PIP(2) hydrolysis of plasma membrane. The time dependence of PIP(2) hydrolysis and LK(bg) activation were similar. The presence of LK(bg) and their stretch sensitivity were also proven in fresh isolated mice splenic B cells. From the above results, we propose a novel mechanism of stretch-dependent ion channel activation, namely, that the degradation of PIP(2) caused by stretch-activated PLC releases LK(bg) from the tonic inhibition by PIP(2).
ISSN
0022-3751 (Print)
Language
English
URI
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17347270

https://hdl.handle.net/10371/29119
DOI
https://doi.org/10.1113/jphysiol.2007.128413
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College of Medicine/School of Medicine (의과대학/대학원)Dept. of Physiology (생리학교실)Journal Papers (저널논문_생리학교실)
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