Membrane phospholipid redistribution in cancer micro-particles and implications in the recruitment of cationic protein factors.
Membrane phospholipid redistribution in cancer micro-particles and implications in the recruitment of cationic protein factors.
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DOI：
10.3402/jev.v3.22653
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发表时间：
2014
影响因子：
16
通讯作者：
Zhao M
中科院分区：
文献类型：
--
作者：
Hou S;Grillo D;Williams CL;Wasserstrom JA;Szleifer I;Zhao M
肿瘤细胞来源的微粒子（MPs）在细胞和系统水平上起着重要的调节作用。这些活性部分归因于MPs携带的蛋白质因子。然而，MPs中隔离某些蛋白质因子的招募策略尚不清楚。在本研究中，我们使用外源性和内源性表达的磷脂结合探针，研究了膜磷脂在MPs中的分布，作为MPs中静电富集阳离子蛋白因子的潜在机制。我们在MPs的外表面检测到显著水平的外化磷脂酰乙醇胺（PE）。在MP膜的内部小叶中，伴随着更大密度的带负电荷的磷脂，特别是磷脂酰丝氨酸（PS）。MPs内表面PS的局部富集与多碱性区（PBR）依赖性的小gtpase的存在升高相关。通过采用一系列RhoA衍生物，包括组成活性和缺乏PBR的RhoA衍生物，我们可以证明，RhoA在MPs中的聚集依赖于PBR的存在。PBR序列单独与GFP融合的嵌合体显著增强了GFP在MPs中的定位，表明静电相互作用对RhoA向MPs募集的积极贡献。利用硅热力学模拟，我们表征了PBR与阴离子脂膜表面之间的静电相互作用。综上所述，膜磷脂在MPs中的重新分布对局部离子密度有影响，并且可能是膜相关蛋白以pbr依赖的方式向MPs静电招募的一个促进因素。
Cancer cell-derived micro-particles (MPs) play important regulatory roles on cellular and system levels. These activities are attributed in part to protein factors carried by MPs. However, recruitment strategies for sequestering certain protein factors in MPs are poorly understood. In the current study, using exogenous and endogenously expressed phospholipid-binding probes, we investigated the distribution of membrane phospholipids in MPs as a potential mechanism for electrostatically enriching cationic protein factors in MPs. We detected a significant level of externalised phosphatidylethanolamine (PE) at the outer surface of MPs. This was accompanied, in the inner leaflet of the MP membrane, by a greater density of negatively charged phospholipids, particularly phosphatidylserine (PS). The local enrichment of PS in the inner surface of MPs was correlated with an elevated presence of small GTPases in a polybasic region (PBR)-dependent fashion. By employing a series of RhoA derivatives, including constitutively active and RhoA derivatives lacking a PBR, we could demonstrate that the congregation of RhoA in MPs was dependent on the presence of the PBR. A chimer with the fusion of PBR sequence alone to GFP significantly enhanced GFP localisation in MPs, indicative of a positive contribution of electrostatic interactions in RhoA recruitment to MPs. Using in silico thermodynamic simulations, we characterised the electrostatic interactions between PBR and anionic lipid membrane surface. In summary, the redistribution of membrane phospholipids in MPs has an impact on the local ionic density, and is likely a contributing factor in the electrostatic recruitment of membrane-associated proteins to MPs in a PBR-dependent fashion.