Tyrosine phosphorylation of a 34-kDa protein induced by cross-linking a novel glycosylphosphatidylinositol-anchored glycoprotein (GPI-80) on human neutrophils that may regulate their adherence and migration.

We previously found a novel glycosylphosphatidylinositol (GPI)-anchored glycoprotein designated GPI-80 that modulates complement receptor 3 integrin-dependent adhesion and in vitro transendothelial migration of neutrophils. In this study, we show that antibody-mediated cross-linking of GPI-80 led to rapid tyrosine phosphorylation mainly of a 34-kDa protein (pp34). Chemical inhibitors, such as genistein, sodium orthovanadate, wortmannin, cytochalasin B, Ro 31-8220, and 1,2-bis(2-aminophenoxy)ethane-N,N,N',N',-tetraacetic acid inhibited this response, whereas pertussis toxin had no effect. These findings demonstrate that the tyrosine phosphorylation of pp34 by cross-linking GPI-80 in human neutrophils involves tyrosine kinases, tyrosine phosphatases, phosphatidylinositol 3-kinase, cytoskeleton reorganization, protein kinase C, and cytoplasmic calcium, but not heterotrimeric G proteins.