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  • Title: Ca(2+)-induced translocation of protein kinase C during Ca(2+)-dependent histamine release from beta-escin-permeabilized rat mast cells.
    Author: Izushi K, Tasaka K.
    Journal: Pharmacology; 1992; 44(2):61-70. PubMed ID: 1373900.
    Abstract:
    When rat mast cells were cultured for a short period in plastic dishes and adhering cells were permeabilized with beta-escin and exposed to Ca2+ at concentrations higher than 10(-7) mol/l, histamine release was induced dose-dependently. Protein kinase C (PKC) activity in the crude extracts obtained from adhering mast cells was induced in the presence of Ca2+, phospholipid and diacylglycerol. The apparent Km value of PKC for Ca2+ was 0.33 mumol/l, and this Ca2+ concentration was equivalent to that which can elicit half the maximum of the Ca(2+0-induced histamine release. After permeabilization, approximately 80% of the total PKC activity remained in the cytosolic fraction. In the resting state, 95% of the total PKC activity was detected in the soluble fraction, and the rest was detected in the membrane fraction. When permeabilized mast cells were incubated with Ca2+ at micromolar concentrations, which are effective in releasing histamine, the total PKC activity did not change. However, the translocation of PKC took place from the cytosolic fraction to the membrane fraction, corresponding to Ca2+ concentrations in the medium. When the crude PKC extract of mast cells was incubated with phospholipid vesicles and centrifuged, the PKC activity in the supernatant was diminished; the amount of PKC binding to the vesicles was dependent upon Ca2+ concentrations in the medium. Calphostin C, a potent PKC inhibitor, interacts with PKC in a noncompetitive manner, and it does not inhibit Ca(2+)-induced translocation of PKC. It can be concluded that PKC is translocated into the cell membrane along with an increase in intracellular Ca2+ concentrations and the subsequent activation of PKC may be crucial for the process leading to histamine release.
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