Detection of secretory phospholipase A₂s related but not identical to type IIA isozyme in cultured mast cells

Abstract

We previously reported that BALB/cJ mouse-derived bone marrow-derived mast cells (BMMC) exhibited two sequential phases of prostaglandin D2 (PGD2) generation in response to Fc(epsilon) receptor I (Fc(epsilon)RI) crosslinking and cytokine stimulation, the late phase of which was suppressed by an antibody raised against type IIA secretory phospholipase A2 (sPLA2). Here we report that BMMC derived from C57BL/6J mice, which are genetically deficient in type IIA sPLA2, display both immediate and delayed PGD2 generation normally. Lysates of C57BL/6J-derived BMMC contained a Ca2+-dependent PLA2 that was absorbed to a column conjugated with anti-type IIA sPLA2 antibody and had a similar molecular mass of 14 kDa, as assessed by immunoblotting. Therefore we speculate that a sPLA2 similar to, but distinct from, type IIA sPLA2 would compensate for type IIA sPLA2 deficiency in C57BL/6J-derived BMMC. We found that the two type IIA-related sPLA2 family members, type V and type IIC sPLA2s, were expressed in BMMC as well as in rat mastocytoma RBL-2H3 cells.