Phenylarsine Oxide Modulates Intracellular Dynamics of Alkaline Phosphatase-Containing Granules in Human Neutrophils Stimulated with Phorbol Myristate Acetate or IgG-coated Latex Beads.

We studied the intracellular dynamics of alkaline phosphatase (ALPase) -containing granules in human neutrophils exposed to a phosphotyrosine phosphatase inhibitor, phenylarsine oxide (PAO). Unstimulated neutrophils showed ALPase activity in short rod-shaped intracellular compartments distributed dispersedly throughout the cytoplasm. Enzyme activity was observed in elongated tubular structures and vacuoles in cells stimulated with a protein kinase C activator, phorbol myristate acetate (PMA). When cells were exposed to PAO followed by stimulation with PMA, the enzyme activity was visualized in intracellular compartments, localized in the pericytoplasm, which were associated with the plasma membrane. A tyrosine kinase inhibitor, erbstatin, prevented this re-location of ALPase-containing granules. PAO also prevented the association of ALPase-containing granules with the limiting membrane of phagosomes containing IgG-coated latex beads. Biochemical studies demonstrated that the up-regulation of ALPase activity was not affected by exposure to PAO in cells stimulated with PMA, but was inhibited by erbstatin in cells exposed to PAO followed by stimulation with PMA. The present findings indicate that both tyrosine phosphorylation and phosphotyrosine dephosphorylation are involved in the intracellular dynamics of ALPase-containing granules, and demonstrate that the dynamical alterations of these granules are affected by different stimuli such as PMA or IgG-coated latex beads.