GTP-BINDING PROTEINS ARE INVOLVED IN THE MODULATED ACTIVITY OF HUMAN NEUTROPHILS TREATED WITH THE PANTON-VALENTINE LEUKOCIDIN FROM STAPHYLOCOCCUS-AUREUS

Significant amounts of leukotriene B-4 (LTB(4)) are generated by human polymorphonuclear neutrophils (PMNs) after incubation with the Panton -Valentine leukocidin (Luk-PV) from Staphylococcus aureus V8 strains. We showed that GTP-binding proteins (G proteins) are involved in the L uk-PV-activated signal transduction of PMNs, ADP-ribosylation of heter otrimeric G proteins by cholera and pertussis toxins decreased the Luk -PV-induced LTB(4)-generation. In contrast, ADP-ribosylation of the lo w-molecular-weight G proteins rho and rac by Clostridium botulinum exo enzyme C3 increased the Luk-PV-induced LTB, synthesis. The subsequent stimulation of Luk-PV-treated PMNs by either calcium ionophore A23187, sodium fluoride, or formylmethionyl-leucyl-phenylalanine was signific antly inhibited. This decrease was paralleled by a loss of G-protein f unctions, including GTPase activity and GTP-binding capacity. An incre ase of G-protein functions was obtained with low amounts of Luk-PV. In addition to the modulated G-protein functions, ADP-ribosylation of 24 -, 40-, and 45-kDa proteins by Luk-PV was detected. As shown in contro l experiments, the ADP-ribosylated 24-kDa proteins were not substrates for C. botulinum exoenzyme C3. Introduction of ras p21 into digitonin -permeabilized PMNs was without effect on subsequent Luk-PV stimulatio n. In addition, the translocation of ras p21, ras GAP, and 5-lipoxygen ase into the membrane of Luk-PV-treated PMNs, as well as the expressio n of chemotactic membrane receptors for LTB(4) and formylmethionyl leu cyl phenylalanine,,vas significantly diminished.