Protein kinase C activator PMA reduces the Ca2+ response to antigen stimulation of adherent RBL-2H3 mucosal mast cells by inhibiting depletion of intracellular Ca2+ stores
✍ Scribed by John Kuchtey; Clare Fewtrell
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 324 KB
- Volume
- 181
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Activation of protein kinase C has been shown to reduce the Ca 2ϩ responses of a variety of cell types. In most cases, the reduction is due to inhibition of Ca 2ϩ influx, but acceleration of Ca 2ϩ efflux and inhibition of Ca 2ϩ store depletion by protein kinase C activation have also been described. For adherent RBL-2H3 mucosal mast cells, results from whole-cell patch clamp experiments suggest that protein kinase C activation reduces Ca 2ϩ influx, while experiments with intact, fura-2-loaded cells suggest that Ca 2ϩ influx is not affected. Here we present single-cell data from Ca 2ϩ imaging experiments with adherent RBL-2H3 cells, showing that antigen-stimulated Ca 2ϩ responses of phorbol 12-myristate 13-acetate (PMA)-treated cells are more transient than those of control cells. PMA also reduced the response to antigen in the absence of extracellular Ca 2ϩ , indicating that depletion of intracellular Ca 2ϩ stores is inhibited. If PMA was added after stores had been depleted by thapsigargin, a small decrease in [Ca 2ϩ ] i was observed, consistent with a slight inhibition of Ca 2ϩ influx. However, the major effect of PMA on the antigen-stimulated Ca 2ϩ response is to inhibit depletion of intracellular Ca 2ϩ stores. We also show that inhibition of protein kinase C did not enhance the Ca 2ϩ response to antigen, suggesting that inhibition of the Ca 2ϩ response by activation of protein kinase C does not contribute to the physiological response to antigen.