Ca2+ signalling mechanisms of the beta 2 integrin on neutrophils: involvement of phospholipase C gamma 2 and Ins(1,4,5)P3.
Engagement of beta 2 integrins triggers a tyrosine kinase-dependent intracellular mobilization and influx of Ca2+ in human neutrophils. However, the transduction pathway involved in generating this Ca2+ signal is obscure. In the present study we identified phospholipase C gamma 2 (PLC gamma 2) as one of the major proteins that was phosphorylated on tyrosine in response to beta 2 integrin activation. This beta 2 integrin-induced phosphorylation of PLC gamma 2 occurred in parallel with an increased accumulation of Ins(1,4,5)P3. The relevance of these observations for the beta 2 integrin-induced Ca2+ signal was investigated using an inhibitor of PLC signalling pathways, 1-(6-{[17 beta-3-methoxyoestra-1,3.5(10)-trien-17-yl] amino}hexyl)-1H-pyrrole-2,5-dione(U73122). U73122 dose-dependently (IC50, approx. 0.15 microM) inhibited both the beta 2 integrin-induced release of Ca2+ from intracellular stores and the subsequent influx of Ca2+ across the plasma membrane. These effects were not observed with the inactive analogue 1-(6-{[17 beta-3-methoxyoestra-1,3,5(10)-trien-17-yl] amino}hexyl)-pyrrolidine-2,5-dione (U73343). To gain further support for an involvement of PLC-induced Ins(1,4,5)P3 formation in the beta 2 integrin-induced Ca2+ signal, we searched for the molecular event(s) underlying the effects of U73122. Our experiments revealed that U73122 had no effect on either beta 2 integrin-induced tyrosine phosphorylation of PLC gamma 2 (or any of the other proteins) or on the formation of Ins(1,4,5)P3, but it reduced the Ins(1,4,5)P3-induced release of 45Ca2+ from intracellular stores of electropermeabilized cells. Taken together, the present data suggest that the beta 2 integrin-induced Ca2+ signal in human neutrophils is generated through activation of a PLC gamma 2-dependent pathway.
Hellberg
C
C
Department of Cell Biology, Linköping University, Sweden.
Molony
L
L
Zheng
L
L
Andersson
T
T
D018821:CD18 Antigens / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051966:Phospholipase C gamma; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D018821:CD18 Antigens; D004963:Estrenes; D007527:Isoenzymes; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D015544:Inositol 1,4,5-Trisphosphate; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium