Protein kinase C-delta is a target of B-cell antigen receptor signaling

Protein kinase C (PKC) enzymes have been implicated as key intermediates in B-cell antigen receptor (BCR) signaling. Each of the 11 PKC isoforms may phosphorylate different substrates and regulate different cellular processes. In this report we show that PKC-delta (PKC-delta) is a target of BCR signaling. BCR engagement increased the amount of PKC-delta in the membrane-enriched particulate fraction of B-cells, suggesting that BCR activates PKC-delta. BCR ligation also caused substantial tyrosine phosphorylation of PKC-delta. We show that activation of phospholipase C by BCR is necessary for both PKC-delta membrane localization and tyrosine phosphorylation. In contrast, phorbol esters which mimic the action of diacylglycerol could recruit PKC-delta to cellular membranes but did not induce tyrosine phosphorylation of PKC-delta. These data suggest a model in which phospholipase C-dependent production of diacylglycerol recruits PKC-delta to cellular membranes where it is then phosphorylated by BCR-activated tyrosine kinases.