Type II secretory phospholipase A(2) associated with cell surfaces via C-terminal heparin-binding lysine residues augments stimulus-initiated delayed prostaglandin generation

Type II secretory phospholipase A(2) (sPLA(2)) has been shown to be induced by a variety of proinflammatory stimuli and, therefore, has been implicated in the inflammatory process. In order to determine whether association of sPLA(2) with cell surfaces via heparan sulfate proteoglycan is important for its effects on cellular functions, we have identified the critical domain in sPLA(2) for heparin and cell surface binding and examined its role in cellular prostaglandin (PG) biosynthesis. Replacement of several conserved Lys residues in the C-terminal region of mouse and rat sPLA(2)s by Glu resulted in a marked reduction of their capacities to bind to heparin and mammalian cell surfaces without affecting their enzymatic activities toward dispersed phospholipid as a substrate. CHO cells stably transfected with wild-type sPLA(2) released about twice as much arachidonic acid (AA) during culture for 10 h with fetal calf serum and interleukin-1 beta than cells transfected with vector alone, whereas the ability to enhance AA release was impaired in sPLA(2) mutants incapable of binding to cell surfaces. AA released by wild-type sPLA(2)-transfected CHO cells was metabolized to prostaglandin E(2) via prostaglandin endoperoxide H synthase (PGHS)-2 after IL-1 beta stimulation, revealing a particular functional linkage of sPLA(2) to PGHS-(2). In contrast, A23187-initiated immediate AA release over 30 min was not affected by sPLA(2) overexpression, Taken together, these results suggest that sPLA(2) expressed endogenously and anchored on cell surfaces via its C-terminal heparin-binding domain is involved in the PGHS-2-dependent delayed PG biosynthesis initiated by growth factors and cytokines during long term culture.