The phosphotyrosine phosphatase inhibitor vanadyl hydroperoxide induces morphological alterations, cytoskeletal rearrangements and increased adhesiveness in rat neutrophil leucocytes.

The functional consequences of treating rat neutrophils with the potent tyrosine phosphatase inhibitor vanadyl hydroperoxide (pervanadate) has been investigated. Pervanadate induced rapid increases in cellular protein phosphotyrosine content in a dose-dependent manner. This treatment also resulted in a change in morphology of the cells from a rounded to a polarised morphology, with many cells exhibiting uropods, pseudopodia and increased membrane activity. Pervanadate induced a transient actin polymerisation and reorganisation similar to that in agonist-stimulated cells. The pervanadate-induced increases in tyrosine phosphorylation, shape change and actin polymerisation were inhibited by the tyrosine kinase inhibitors tyrphostin and erbstatin, indicating that these phenomena were mediated by the constitutive activity of cellular tyrosine kinases. Double fluorescence experiments demonstrated that there was a co-localisation of tyrosine phosphorylated proteins with F-actin in both pervanadate- and agonist-stimulated neutrophils. Pervanadate also induced spreading of neutrophils on tissue culture substrata with concurrent changes in F-actin localisation including unusual F-actin-containing structures. These results demonstrate that morphological changes and cytoskeletal reorganisation in neutrophils are regulated by tyrosine phosphorylation, and that inhibition of tyrosine phosphatase activity in neutrophils is sufficient to activate motile machinery of these cells. These results suggest that an alternative pathway involved in neutrophil stimulation might be via inhibition of endogenous tyrosine phosphatases rather than activation of tyrosine kinases.