Potentiation of chemotactic peptide-induced superoxide generation by CD38 ligation in human myeloid cell lines.

CD38 is a type II transmembrane glycoprotein possessing an NAD+ glycohydrolase activity in its extracellular domain. We previously reported that the ligation of CD38 by a monoclonal antibody (mAb), HB-7, induces the tyrosine phosphorylation of cellular proteins including p120(c-cbl) in differentiated human myeloid cell lines and that the phosphorylated p120(c-cbl) is capable of binding to phosphatidylinositol (PI) 3-kinase. In the present study, we found that the agonistic anti-CD38 mAb markedly potentiates superoxide generation stimulated by chemotactic formyl-Met-Leu-Phe receptors in the CD38-producing cells. HB-7 neither generated superoxide by itself nor enhanced the cell response induced by phorbol 12-myristate acetate, indicating that the potentiating action of the anti-CD38 mAb is specific for the stimulation by the GTP-binding protein (G1)-coupled membrane receptors. The potentiation by HB-7 was abolished by prior treatment of the cells with a tyrosine kinase inhibitor, pertussis toxin, or a potent PI 3-kinase inhibitor, wortmannin. HB-7 also enhanced the product formation of PI 3-kinase in response to the chemotactic receptor stimulation, without significant changes in the receptor-stimulated accumulations of inositol-1,4,5-trisphosphate, arachidonate release, and intracellular Ca2+. These results indicate that the CD38-induced tyrosine phosphorylation has a cross-talk with the chemotactic receptor/G1-mediated signal transduction pathway resulting in the enhancement of superoxide generation, probably through the activation of PI 3-kinase.