TYROSINE PHOSPHORYLATION IN ACTIVATED HUMAN NEUTROPHILS - COMPARISON OF THE EFFECTS OF DIFFERENT CLASSES OF AGONISTS AND IDENTIFICATION OF THE SIGNALING PATHWAYS INVOLVED

The tyrosine phosphorylation responses initiated in human neutrophils by soluble and particulate agonists were characterized. Chemotactic fa ctors, hematopoietic growth factors, and inflammatory microcrystals st imulated in a time- and concentration-dependent manner the tyrosine ph osphorylation of distinct patterns of substrates: pp120, pp85, pp70, a nd pp60 in the case of chemotactic factors; pp155, pp130, pp120, pp85, pp60, and pp40 in the case of granulocyte macrophage-CSF; and pp130, pp120, pp70, and pp60 in the case of monosodium urate (MSU) crystals. Several of the single bands on one-dimensional blots (including pp40, pp70, and pp120) could be resolved into multiple spots on two-dimensio nal gels. The responses of several other chemotactic factors resembled bled those of FMLP. Cytokineplasts retained the capacity to respond t o FMLP, granulocyte-macrophage-CSF, or MSU crystals with a stimulation of tyrosine phosphorylation, and contained the major substrates detec ted in intact neutrophils. Several unrelated tyrosine kinase inhibitor s (herbimycin A, genistein, and erbstatin) strongly diminished the tyr osine phosphorylation response to chemotactic factors. Pertussis toxin abrogated the tyrosine phosphorylation response to FMLP, whereas prot ein kinase C (Ro 21-8220, chelerithryn) inhibitors were without effect . Chelation of intracellular calcium attenuated the tyrosine phosphory lation response to FMLP. These results indicate that G proteins play a crucial role in the coupling of chemotactic factor receptors to tyros ine phosphorylation and that this coupling occurs in parallel to that of phospholipase C. These results also underline the complexity of the transduction pathways implicated in the initiation of tyrosine phosph orylation.