Activation of human neutrophils by Mycobacterium tuberculosis H37Ra involves phospholipase C gamma 2, Shc adapter protein, and p38 mitogen-activated protein kinase

Recent studies have shown that human neutrophils play a significant protect ive role in mycobacteria infection. When encountered with mycobacteria, neu trophils exhibit the typical early bactericidal responses including phagocy tosis and generation of reactive oxygen intermediates (ROI), but the underl ying mechanisms are largely unknown. The present study shows that stimulati on of neutrophils with an attenuated strain of Mycobacterium tuberculosis H 37Ra (Mtb) led to a tyrosine kinase-dependent ROI production in these cells , Stimulation with Mtb induces a rapid and transient tyrosine phosphorylati on of several proteins, one of which was identified as phospholipase C gamm a 2 (PLC gamma 2), Several tyrosine-phosphorylated proteins were associated with the PLC gamma 2 precipitates from Mtb-stimulated neutrophils, of whic h pp46 was characterized as the Shc adapter protein. A role for PLC gamma 2 -Shc association in the generation of ROI is supported by the observations that stimulation with Mtb causes the activation of p38 mitogen-activated pr otein kinase (MAPK), a downstream target of the Shc/Ras signaling cascade, and that the effect of genistein on ROI production coincided with its abili ty to inhibit both PLC gamma 2-Shc association and p38 MAPK activation. Mor eover, pretreatment of neutrophils with a PLC inhibitor markedly suppresses the Mtb-stimulated ROI production as well as p38 MAPK activation in these cells. Taken together, these results indicate that stimulation of neutrophi ls with Mtb triggers the tyrosine phosphorylation of PLC gamma 2 and its as sociation with Shc, and that such association is critical for the Mtb-stimu lated ROI production through activating p38 MAPK.