Group IID heparin‐binding secretory phospholipase A2 is expressed in human colon carcinoma cells and human mast cells and up‐regulated in mouse inflammatory tissues

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Abstract
Group IID secretory phospholipase A2 (sPLA2‐IID), a heparin‐binding sPLA2 that is closely related to sPLA2‐IIA, augments stimulus‐induced cellular arachidonate release in a manner similar to sPLA2‐IIA. Here we identified the residues of sPLA2‐IID that are responsible for heparanoid binding, are and therefore essential for cellular function. Mutating four cationic residues in the C‐terminal portion of sPLA2‐IID resulted in abolition of its ability to associate with cell surface heparan sulfate and to enhance stimulus‐induced delayed arachidonate release, cyclooxygenase‐2 induction, and prostaglandin generation in 293 cell transfectants. As compared with several other group II subfamily sPLA2s, which were equally active on A23187‐ and IL‐1‐primed cellular membranes, sPLA2‐IID showed apparent preference for A23187‐primed membranes. Several human colon carcinoma cell lines expressed sPLA2‐IID and sPLA2‐X constitutively, the former of which was negatively regulated by IL‐1. sPLA2‐IID, but not other sPLA2 isozymes, was expressed in human cord blood‐derived mast cells. The expression of sPLA2‐IID was significantly altered in several tissues of mice with experimental inflammation. These results indicate that sPLA2‐IID may be involved in inflammation in cell‐ and tissue‐specific manners under particular conditions.

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