Synergism of phosphorylation of 46K protein(s) and arachidonate release in the induction of superoxide anion production in guinea pig polymorphonuclear leukocytes.

The phosphorylation of 46K protein(s), which was generally observed in parallel with an activation of NADPH oxidase of guinea pig polymorphonuclear leukocytes (PMNL) in our previous studies (N. Okamura et al. (1984) Arch. Biochem. Biophys. 228, 270-277; T. Ohtsuka et al. (1987) J. Biochem. 101, 897-903), was increased by treatment with 1-oleoyl-2-acetylglycerol (OAG), even at low concentrations at which both superoxide anion (O2-) production and arachidonate release were little induced. On the other hand, exposure of PMNL to low concentrations of a calcium ionophore, A23187, stimulated arachidonate release without causing substantial O2- production and increase in phosphorylation of 46K protein(s). Simultaneous addition of the above-mentioned suboptimal concentrations of both OAG and A23187 markedly enhanced O2- production in PMNL. This enhancing effect may be ascribable to the increase in the phosphorylation of 46K protein(s) and arachidonate release, which are induced by the addition of OAG and A23187, respectively. Another arachidonate-releasing agent, N-formyl-methionylleucyl-phenylalanine (FMLP), also stimulated O2- production in accordance with an increase in the arachidonate release and protein phosphorylation. Simultaneous addition of OAG significantly enhanced the FMLP-induced O2- production, presumably by maintaining the 46K protein phosphorylation which would facilitate the effect of arachidonate released by FMLP. Thus, the present results suggest that phosphorylation of 46K protein(s) and arachidonate release synergistically induce O2- production in PMNL, although either of them alone hardly induces the production.