concanavalin-a and lysophosphatidylserine

Lysophosphatidylserine (1-acyl-2-lyso-PS) has been shown to stimulate histamine release from rat peritoneal mast cells (RPMC) triggered by FcepsilonRI (high affinity receptor for IgE) cross-linking, although the precise mechanism of lyso-PS production has been obscure. In the present study we show that phosphatidylserine-specific phospholipase A(1), PS-PLA(1), stimulates histamine release from RPMC through production of 2-acyl-1-lyso-PS in the presence of FcepsilonRI cross-linker. The potency of 2-acyl-1-lyso-PS was almost equal to that of 1-acyl-2-lyso-PS. A catalytically inactive PS-PLA(1), in which an active serine residue (Ser(166)) was replaced with an alanine residue did not show such activity. sPLA(2)-IIA, another secretory PLA(2) that is capable of producing lyso-PS in vitro, was also a poor histamine inducer against RPMC. PS-PLA(1) significantly stimulated histamine release from crude RPMC, indicating that lyso-PS is mainly derived from cells other than mast cells. In agreement with this phenomenon, the enzyme stimulated the histamine release more efficiently when RPMC were mixed with apoptotic Jurkat cells. Under these conditions, lyso-PS with unsaturated fatty acid was released from the apoptotic cells treated with PS-PLA(1). Finally, heparin, which has affinity for PS-PLA(1), completely blocked the stimulatory effect of the enzyme. In conclusion, PS-PLA(1) may bind to heparan sulfate proteoglycan, efficiently hydrolyze PS appearing on plasma membranes of apoptotic cells, and stimulate mast cell activation mediated by 2-acyl-1-lyso-PS.

Topics: Animals; Apoptosis; Brain; Catalysis; Cattle; Cell Membrane; Chromatography, High Pressure Liquid; Concanavalin A; Cross-Linking Reagents; Dose-Response Relationship, Drug; Flow Cytometry; Heparan Sulfate Proteoglycans; Heparin; Histamine; Humans; Hydrolysis; Jurkat Cells; Lysophospholipids; Mast Cells; Phospholipases A; Phospholipases A1; Rats; Recombinant Proteins; Serine

The correlations among the potentiating activity of various PS analogs on concanavalin A (Con A)-induced rat mast cell degranulation, the hemolytic activity and the incorporation into the mast cell membrane were studied. The following results were obtained. Lysophosphatidylserine (LysoPS) caused rat mast cell activation (degranulation) in the presence of Con A. The order of the activity was as follows: 1-stearoyl lysoPS = 1-palmitoyl lysoPS greater than 1-myristoyl lysoPS greater than 1-lauroyl lysoPS. The relative hemolytic activity of these compounds was similar to that observed in the mast cell activation. Dilauroyl PS, which shows similar hemolytic activity to 1-myristoyl lysoPS, did not activate mast cells appreciably. The relative activity of these phospholipids in the binding to mast cells was 1-stearoyl lysoPS greater than dilauroyl PS greater than 1-lauroyl lysoPS. Hemolytic activity, as well as activity on mast cells, of lysoPS analogs was well correlated to mast cell membrane incorporation, whereas such a correlation was not found with PS analogs. Dilauroyl PS could be accumulated in the mast cell membrane and showed hemolytic activity, but did not activate histamine secretion.

Topics: Animals; Cell Membrane; Concanavalin A; Hemolysis; Histamine Release; Lysophospholipids; Male; Mast Cells; Phosphatidylserines; Rats; Rats, Inbred Strains; Serotonin