Lysophosphatidylserine enhances exogenous type II phospholipase A2-induced activation of rat serosal mast cells

We have previously shown that exogenous type II phospholipase A2 (PLA2) alone elicits degranulation of mast cells, including rat serosal mast cells (SMC) and mouse bone marrow-derived mast cells (BMMC). Here we report that lysophosphatidylserine (lysoPS), a co-factor for activation of rodent SMC in response to some tyrosine kinase-coupled agonists, enhanced type II PLA2-elicited histamine release from rat SMC. In contrast, mouse BMMC was insensitive to lysoPS. Our findings demonstrate a novel route for activation of SMC in that type II PLA2 can act as a direct activator of SMC with enhancement by lysoPS, which is generated from membrane phosphatidylserine possibly by the action of the same enzyme.