Extracellular Fibrinogen-binding Protein (Efb) from Staphylococcus aureus Inhibits the Formation of Platelet-Leukocyte Complexes.
Extracellular Fibrinogen-binding Protein (Efb) from Staphylococcus aureus Inhibits the Formation of Platelet-Leukocyte Complexes.
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DOI：
10.1074/jbc.m115.678359
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发表时间：
2016-02-05
期刊：
影响因子：
--
通讯作者：
Pula G
中科院分区：
文献类型：
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作者：
Posner MG;Upadhyay A;Abubaker AA;Fortunato TM;Vara D;Canobbio I;Bagby S;Pula G
来自金黄色葡萄球菌的胞外纤维蛋白原结合蛋白（Efb）抑制血小板活化，但其作用机制尚未确定。在这项研究中，我们发现Efb的N-末端区域（Efb-N）促进血小板与纤维蛋白原的结合，并且Efb-N与血小板的结合通过两种独立的机制进行：纤维蛋白原介导的和纤维蛋白原不依赖的。通过对血小板内EFB相互作用蛋白的蛋白质组学分析和随后通过免疫印迹的下拉测定法的确认，我们确定了P-选择素和多聚体蛋白-1作为新的EFB相互作用伙伴。P-选择素和多聚素-1与Efb的相互作用不依赖于纤维蛋白原。我们重点关注EFB与P-选择素的相互作用。过量的P-选择素细胞外结构域显着损害Efb的活化血小板的结合，表明P-选择素是Efb的活化血小板表面的主要受体。Efb-N与P-选择素的相互作用抑制了P-选择素与其生理配体P-选择素糖蛋白配体-I（PSGL-1）的结合，在细胞裂解物和无细胞测定中均是如此。由于P-选择素-PSGL-1结合在血小板和白细胞之间的相互作用中的重要性，我们测试了人全血，发现Efb消除了血小板-单核细胞和血小板-粒细胞复合物的形成。总之，我们目前的证据表明，除了其记录的抗血栓形成活性，EFB可以发挥免疫调节作用，通过抑制P-选择素-PSGL-1依赖的血小板-白细胞复合物的形成。
Extracellular fibrinogen-binding protein (Efb) from Staphylococcus aureus inhibits platelet activation, although its mechanism of action has not been established. In this study, we discovered that the N-terminal region of Efb (Efb-N) promotes platelet binding of fibrinogen and that Efb-N binding to platelets proceeds via two independent mechanisms: fibrinogen-mediated and fibrinogen-independent. By proteomic analysis of Efb-interacting proteins within platelets and confirmation by pulldown assays followed by immunoblotting, we identified P-selectin and multimerin-1 as novel Efb interaction partners. The interaction of both P-selectin and multimerin-1 with Efb is independent of fibrinogen. We focused on Efb interaction with P-selectin. Excess of P-selectin extracellular domain significantly impaired Efb binding by activated platelets, suggesting that P-selectin is the main receptor for Efb on the surface of activated platelets. Efb-N interaction with P-selectin inhibited P-selectin binding to its physiological ligand, P-selectin glycoprotein ligand-1 (PSGL-1), both in cell lysates and in cell-free assays. Because of the importance of P-selectin-PSGL-1 binding in the interaction between platelets and leukocytes, we tested human whole blood and found that Efb abolishes the formation of platelet-monocyte and platelet-granulocyte complexes. In summary, we present evidence that in addition to its documented antithrombotic activity, Efb can play an immunoregulatory role via inhibition of P-selectin-PSGL-1-dependent formation of platelet-leukocyte complexes.