Protein kinase C (PKC) changes in human basophils: IgE-mediated activation is accompanied by an increase in total PKC activity

We have examined the changes in protein kinase C (PKC) which follow IgE-mediated activation of basophils. Exposure to 0.1 μg/ml anti-IgE resulted in an increase in total cellular PKC (169 ± 23% of control, histamine release (HR) = 33 ± 7%, n = 12) which could be accounted for solely by the increase in membrane-associated PKC. These changes reached a maximum (280 ± 48%) 1.0 min after challenge and declined to 190 ± 38% after 5.0 min though histamine release was not complete until 5 to 10 min later. We found a good correlation between the increase in membrane-associated PKC and the eventual release of histamine (r(s) = 0.902). Donors whose basophils released < 5% total histamine (n = 3, HR = 3 ± 1%) showed a partial activation of PKC (173 ± 18%) though much less than the remaining donors (increase in PKC = 346 ± 59%, n = 9, HR = 43 ± 7%). We observed no redistribution of cytosolic PKC at any time following exposure to anti-IgE. In contrast, 0.1 μg/ml 2-O-tetradecanoyl-phorbol-13-acetate (HR = 36 ± 3%, n = 3) promoted an increase in total cellular PKC, the loss of 31 ± 4% of the cytosolic PKC and an 816 ± 183% increase in membrane-associated PKC. Activation of PKC by anti-IgE was only partially dependent on extracellular calcium. In the absence of calcium, the increase in PKC was approximately 65% (n = 4) of that noted in the presence of 1 mM calcium but these levels were sustained over much longer periods, failing to return to base line after 30 min. Higher than normal concentrations of calcium (5 to 10 mM) promoted rapid increases in PKC activity and accelerated the return to base line (back to prechallenge levels by 5 min). Suboptimal concentrations of anti-IgE (0.01 μg/ml) attenuated the changes in membrane associated PKC and altered the kinetics of the response. The time required to reach maximum activity increased from 1.0 to 5.0 min with a corresponding decrease in the rate at which histamine was released. Higher concentrations of anti-IgE (1.0 μg/ml) promoted a rapid increase in PKC (maximum increase in PKC = 501 ± 59%, time = 0.5 min, HR = 28 ± 2%) followed by an equally rapid return to base line levels. Even the most striking responses to anti-IgE (increase in PKC = 562 ± 69%, HR = 64 ± 2%, n = 3) gave no evidence that cytosolic PKC underwent translocation to the membrane suggesting that the IgE-induced changes in basophil PKC differ from those observed in other secretory cells.