Abstract
Tyrosine kinases play a prominent role in various intracellular signal transduction pathways. In this study, β2 integrin (CD11/CD18)-mediated adhesive interactions of human neutrophils (PMN) were mimicked by antibody cross-linking of CD11/CD18. Cross-linking of CD18 induced tyrosine phosphorylation of several proteins with apparent molecular masses of ~120, 78, 72, 65, and 56 kDa, respectively, as shown by anti-phosphotyrosine immunoblotting of whole cell lysates. Cross-linking of the α-subunits of the β2 integrins demonstrated that only cross-linking of Mac-1 but not LFA-1 or gp150/95 triggered tyrosine signaling. The tyrosine phosphorylations showed a rapid and transient time course. Comparison of the CD18-mediated tyrosine phosphorylation patterns with those induced by chemoattractants gave similar results. The observed tyrosine phosphorylation was specific, since binding and non-binding irrelevant primary antibodies had no effect. Furthermore, F(ab')2 fragments of the anti-CD18 antibody IB4 and addition of F(ab')2 fragments of secondary antibody were sufficient to induce tyrosine phosphorylation. Inhibition of tyrosine kinases by herbimycin A resulted in partial inhibition of the CD18-mediated tyrosine phosphorylation of the 120- and 65-kDa proteins and in complete inhibition of tyrosine phosphorylation of the 78- and 56-kDa proteins. In unstimulated PMN, the tyrosine phosphatase inhibitor sodium orthovanadate had no effect on tyrosine phosphorylation of the 120-kDa protein, but induced phosphorylation of the 78-, 72-, 65-, and 56-kDa proteins. These results indicate that the β2 integrin-mediated intracellular signaling cascade involves different tyrosine phosphorylation (and dephosphorylation) events, which may play a role in the regulation of PMN functions during inflammation.
Original language | English (US) |
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Pages (from-to) | 747-753 |
Number of pages | 7 |
Journal | Journal of Leukocyte Biology |
Volume | 59 |
Issue number | 5 |
DOIs | |
State | Published - May 1996 |
Externally published | Yes |
Keywords
- CD18
- integrin
- polymorphonuclear neutrophils
- signal transduction
ASJC Scopus subject areas
- Immunology and Allergy
- Immunology
- Cell Biology