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Activation of large conductance background K+ channels by arachidonic acids in murine B cells
Author(s) -
Zheng Heifeng,
Nam Joo Hyun,
Kim Sung Joon
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.a540
Subject(s) - arachidonic acid , phosphatidylinositol , hyperpolarization (physics) , chemistry , depolarization , intracellular , phospholipase c , membrane potential , phospholipase a2 , cytosol , biochemistry , biophysics , microbiology and biotechnology , enzyme , biology , kinase , stereochemistry , nuclear magnetic resonance spectroscopy
Mouse B cells express a phosphatidylinositol 4,5‐bisphosphate (PIP 2 )‐inhibited large conductance background K + channels (BK bg ). In inside‐out membrane patches, the application of ATP inhibited BK bg due to the generation of PIP 2 by PI‐kinases. The activity of BK bg is low in cell‐attached (c‐a) conditions. Generation of arachidonic acid (AA) by phospholipase A 2 is involved in the apoptosis of immature B cells by antigen receptor stimulation. Some members of the cloned background K + channels are activated by AA. Similarly, the application of AA activated BK bg of B lymphocytes in c‐a as well as in i‐o patches. The facilitating effects of fatty acids became weaker as the acyl chain is more saturated; AA > oleic acid > plamitic acid. When the activity of BK bg was strongly inhibited by a direct application of PIP 2 (5 uM), the addition of AA hardly recovered BK bg activity. The facilitation of BK bg by AA was fully reversible and unaffected by the treatment with inhibitors of various metabolizing enzymes for AA. Consistent with the activation of BK bg , the application of AA induced strong hyperpolarization of membrane potential in WEHI‐231 cells. The intracellular [Ca 2+ ] of WEHI‐231 was increased by AA, which was partly diminished by KCl‐induced membrane depolarization. AA strongly augmented the store‐operated Ca 2+ entry in WEHI‐231. Besides the increase of BK bg , AA activated Ca 2+ permeable nonselective cation channels. Since the expression of PLA 2 is reportedly higher in immature than mature B lymphocytes, the increased driving force for Ca 2+ influx by AA might play a crucial role in the regulation and development of B lymphocytes.