BINDING OF HUMAN PHOSPHOLIPASE A(2) TYPE-II TO PROTEOGLYCANS - DIFFERENTIAL EFFECT OF GLYCOSAMINOGLYCANS ON ENZYME-ACTIVITY

Phospholipase A(2) acting on low density lipoproteins in the extracell ular arterial intima may form proinflammatory lipid mediators. Human n onpancreatic secretory phospholipase A(2) has three regions that may a ssociate with sulfated glycosaminoglycans. The apoB-100 molecule in lo w density lipoproteins also has glycosaminoglycan binding regions that could mediate its retention in the arterial intima. Here we report th at human nonpancreatic phospholipase A(2) isolated from a transfected cell line binds to glycosaminoglycans secreted by cultured human arter ial smooth muscle cells. A gel mobility shift assay showed that the af finity of phospholipase A(2) for glycosaminoglycans from a heparan sul fate/chondroitin sulfate proteoglycan was higher than for chondroitin sulfate glycosaminoglycans from a larger versican-like proteoglycan. A ffinity chromatography confirmed these results. All glycosaminoglycans tested, at concentrations up to 100 mu M, increased the activity of p hospholipase A(2) toward phosphatidylcholine liposomes. Above this con centration, heparan sulfate and heparin inhibited the enzyme. Heparin and chondroitin 6-sulfate increased phospholipase A(2) activity on ion , density lipoproteins up to 4-fold at 100 mu M, whereas heparan sulfa te had no effect. The results indicate that human nonpancreatic secret ory phospholipase A(2) interacts with proteoglycans via their glycosam inoglycan moiety and that the enzyme activity may be modulated by the association of the enzyme and its substrate to the sulfated polysaccha rides.