Abstract 15784: Regulation of ITAM Receptor Signaling by Phospholipases PLA2G6 and PNPLA8 in Human Platelets

• Published in: Circulation (New York, N.Y.) N.Y.), 2019-11, Vol.140 (Suppl_1 Suppl 1), p.A15784-A15784
• Main Author: Abraham, Shaji
• Format: Article
• Language: English
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circ.140.suppl_1.15784

IntroductionReceptor FcγRIIA plays a significant role in immune-mediated thrombocytopenia and thrombosis disorders, such as heparin-induced thrombocytopenia, which adversely affects many patients with coronary and cerebrovascular arterial disease. We previously identified a role for ALOX12 in platelet FcγRIIA and GPVI signaling. ALOX12 produces 12(S) HETE from arachidonic acid (AA) following PLA2 action and affects platelet activation. GPVI as a collagen receptor is essential in hemostasis and thrombosis. While cPLA2 is important in thrombosis with atherosclerosis, the role of iPLA2 enzymes is less well understood.HypothesisPLA2G6 (iPLA2-β) and PNPLA8 (iPLA2-γ) contribute to the regulation of platelet activation by FcγRIIA and GPVI, ITAM receptors.Method and ResultsWe used specific pharmacological inhibitors to understand the role of PLA2G6 and PNPLA8 in human platelets. Inhibition of PLA2G6 by S-BEL and PNPLA8 by R-BEL decreased platelet aggregation following stimulation of FcγRIIA and GPVI receptors in washed human platelets. FKGK18, a chemically distinct inhibitor of iPLA2-β, also showed significant reduction in FcγRIIA-mediated aggregation. Further, R-BEL and S-BEL inhibited dense granule and α-granule secretion as assessed by ATP release assay and P-Selectin surface expression, respectively, for each receptor. Exogenous addition of ADP restored platelet aggregation in FcγRIIA-activated platelets in the presence of either R-BEL or S-BEL-induced inhibition. Combining the inhibitors with each at sub-inhibitory concentration was effective in blocking platelet activation, consistent with both PLA2G6 and PNPLA8 being important.ConclusionPLA2G6 and PNPLA8 play previously unrecognized roles in both FcγRIIA and GPVI signaling. Their molecular mechanisms and roles in hemostasis and thrombosis in vivo warrant further investigation.