Tyrosine phosphorylation and translocation of phospholipase C-γ 2 in polymorphonuclear leukocytes treated with pervanadate

Abstract

We examined in detail the tyrosine phosphorylation of proteins, especially inositol phospholipid-specific phospholipase C (PLC) γ 2, during activation of respiratory burst of guinea pig polymorphonuclear leukocytes (PMNs) by pervanadate. The pervanadate, generated from a combination of H 2O 2 and orthovanadate, induced concomitantly tyrosine phosphorylation of 145, 120, 104, 76, 68, 60, 53, 42, 37, 28, and 25 kDa proteins and superoxide anion (O 2 −) production of PMNs. The pretreatment of PMNs with genistein caused an inhibition of tyrosine phosphorylation of these proteins, and also markedly depressed O 2 − production. Among the above proteins, a 145 kDa protein was found to be identical with the protein recognized by the anti-PLCγ 2 antibody on Western blots. PLCγ 2 was detected in the cytosol fraction but not in the membrane fraction of resting PMNs, whereas it was detected in both cytosol and membrane fractions of pervanadate treated PMNs. PLC activity of pervanadate treated PMNs was higher than that of resting cells. In addition, the enzyme activity of the cytosol fraction from the former cells was significantly lower than that from the latter cells, whereas the enzyme activity of membrane fraction from the former cells was significantly higher than that from the latter cells. These findings suggest that the tyrosine residue(s) of PLCγ 2 is phosphorylated and the enzyme is translocated from the cytosol to membrane fractions in PMNs by pervanadate treatment.