Elucidating the role of Staphylococcus epidermidis serine-aspartate repeat protein G in platelet activation
Elucidating the role of Staphylococcus epidermidis serine-aspartate repeat protein G in platelet activation
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DOI：
10.1111/j.1538-7836.2009.03495.x
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发表时间：
2009-08-01
影响因子：
10.4
通讯作者：
Cox, D.
中科院分区：
文献类型：
--
作者：
Brennan, M. P.;Loughman, A.;Cox, D.
背景资料：表皮葡萄球菌是人类皮肤的寄生虫，与感染性心内膜炎和植入医疗器械的感染有关。S.表皮炎通过未知的机制诱导血小板聚集。纤维蛋白原结合蛋白丝氨酸-天冬氨酸重复蛋白G（SdrG）存在于67-91%的临床菌株中。目的：确定SdrG是否在血小板活化中起作用，如果是的话，研究纤维蛋白原在这一机制中的作用。研究方法：SdrG在替代宿主乳酸乳球菌中表达，以研究其在没有其他葡萄球菌组分的情况下的作用。采用血小板粘附和血小板聚集试验。结果：L.表达SdrG的乳酸菌刺激血小板聚集（滞后时间：2.9 ± 0.5 min），而表达SdrG的乳酸菌刺激血小板聚集（滞后时间：2.9 ± 0.5 min）。乳酸对照则没有。L.乳酸SdrG诱导的聚集被α（IIb）β（3）拮抗剂和阿司匹林抑制。聚集依赖于纤维蛋白原和IgG以及血小板IgG受体Fc γ RIIa。用B β链纤维蛋白肽预孵育细菌可抑制聚集（延迟时间6倍），表明纤维蛋白原起桥接分子的作用。血小板粘附于L.乳酸SdrG在纤维蛋白原的情况下。α（IIb）β（3）拮抗剂可抑制粘附，表明这种直接相互作用涉及α（IIb）β（3）。使用纯化的SdrG片段的调查显示与B-结构域的直接相互作用。A-结构域的粘附涉及纤维蛋白原和IgG桥。结论：SdrG单独通过直接和间接机制足以支持血小板粘附和聚集。
Background: Staphylococcus epidermidis is a commensal of the human skin that has been implicated in infective endocarditis and infections involving implanted medical devices. S. epidermidis induces platelet aggregation by an unknown mechanism. The fibrinogen-binding protein serine-aspartate repeat protein G (SdrG) is present in 67-91% of clinical strains. Objectives: To determine whether SdrG plays a role in platelet activation, and if so to investigate the role of fibrinogen in this mechanism. Methods: SdrG was expressed in a surrogate host, Lactococcus lactis, in order to investigate its role in the absence of other staphylococcal components. Platelet adhesion and platelet aggregation assays were employed. Results: L. lactis expressing SdrG stimulated platelet aggregation (lag time: 2.9 +/- 0.5 min), whereas the L. lactis control did not. L. lactis SdrG-induced aggregation was inhibited by alpha(IIb)beta(3) antagonists and aspirin. Aggregation was dependent on both fibrinogen and IgG, and the platelet IgG receptor Fc gamma RIIa. Preincubation of the bacteria with B beta-chain fibrinopeptide inhibited aggregation (delaying the lag time six-fold), suggesting that fibrinogen acts as a bridging molecule. Platelets adhered to L. lactis SdrG in the absence of fibrinogen. Adhesion was inhibited by alpha(IIb)beta(3) antagonists, suggesting that this direct interaction involves alpha(IIb)beta(3). Investigation using purified fragments of SdrG revealed a direct interaction with the B-domains. Adhesion to the A-domain involved both a fibrinogen and an IgG bridge. Conclusion: SdrG alone is sufficient to support platelet adhesion and aggregation through both direct and indirect mechanisms.