Superoxide generation and tyrosine kinase.

NADPH oxidase is a multi-subunit enzyme complex responsible for superoxide generation in many cells, for example, B-lymphocytes and osteoclasts. NADPH oxidase is localized on the cell surface and generates superoxide extracellularly. After synthesis, components of this oxidase are transported to the cell membrane where the functional NADPH oxidase complex is assembled. The mechanism by which the membrane-bound components are transported to the cell surface of osteoclasts remains unclear. In this study, we examined the role of tyrosine kinase activity in the transport of NADPH oxidase components. When B-lymphocytes and osteoclasts were treated with herbimycin A, a specific inhibitor of tyrosine kinase, superoxide production was significantly decreased. The amount of p91, the catalytic subunit of NADPH oxidase, was decreased in the cellular membrane of herbimycin A treated cells compared to untreated controls. Similar results were obtained for the movement of a regulatory subunit of the NADPH oxidase complex, p47, in B-lymphocytes. Thus, inhibition of tyrosine kinase decreases superoxide production by disrupting the translocation of the NADPH oxidase complex.