The Role of Putative Phosphatidylserine-Interactive Residues of Tissue Factor on Its Coagulant Activity at the Cell Surface
The Role of Putative Phosphatidylserine-Interactive Residues of Tissue Factor on Its Coagulant Activity at the Cell Surface
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DOI：
10.1371/journal.pone.0158377
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发表时间：
2016-06-27
期刊：
影响因子：
3.7
通讯作者：
Rao, L. Vijaya Mohan
中科院分区：
文献类型：
--
作者：
Ansari, Shabbir A.;Pendurthi, Usha R.;Rao, L. Vijaya Mohan
细胞膜外层的磷脂酰丝氨酸 (PS) 被认为在组织因子 (TF) 解密中发挥着关键作用。最近的分子动力学模拟研究表明，TF 胞外域可能直接与 PS 相互作用。为了研究 TF 与细胞表面磷脂直接相互作用对基础 TF 活性和解密后增强的 TF 活性的潜在作用，对 TF 胞外域中的一个或所有假定的 PS 相互作用残基进行突变，并测试其在细胞系统中的凝血活性。在9个选定的TF突变体中，其中5个——TFS160A、TFS161A、TFS162A、TFK165A和TFD180A——表现出与野生型TF相似的TF凝血活性。 TFK159A、TFS163A 和 TFK166A 三种突变体的比活性大幅降低。 164 位甘氨酸残基的突变显着消除了 TF 凝血活性，导致类似 90% 的抑制。与 TFG164A 相比，所有九个脂质结合残基一起突变并没有进一步降低 TF 的活性。用钙离子霉素或 HgCl2（两种常用于解密 TF 的试剂）处理 THP-1 细胞后，在野生型 TF 和所有 TF 突变体中观察到 TF 活性的类似倍数增加。总的来说，我们的数据表明，一些与 PS 相互作用有关的精选 TF 残基有助于细胞表面的 TF 凝固活性。然而，我们的数据还表明，假定的脂质结合区域之外的 TF 区域也可能有助于 TF 的 PS 依赖性解密。
Exposure of phosphatidylserine (PS) on the outer leaflet of the cell membrane is thought to play a critical role in tissue factor (TF) decryption. Recent molecular dynamics simulation studies suggested that the TF ectodomain may directly interact with PS. To investigate the potential role of TF direct interaction with the cell surface phospholipids on basal TF activity and the enhanced TF activity following the decryption, one or all of the putative PS-interactive residues in the TF ectodomain were mutated and tested for their coagulant activity in cell systems. Out of the 9 selected TF mutants, five of them -TFS160A, TFS161A, TFS162A, TFK165A, and TFD180A-exhibited a similar TF coagulant activity to that of the wild-type TF. The specific activity of three mutants, TFK159A, TFS163A, and TFK166A, was reduced substantially. Mutation of the glycine residue at the position 164 markedly abrogated the TF coagulant activity, resulting in similar to 90% inhibition. Mutation of all nine lipid binding residues together did not further decrease the activity of TF compared to TFG164A. A similar fold increase in TF activity was observed in wild-type TF and all TF mutants following the treatment of THP-1 cells with either calcium ionomycin or HgCl2, two agents that are commonly used to decrypt TF. Overall, our data show that a few select TF residues that are implicated in interacting with PS contribute to the TF coagulant activity at the cell surface. However, our data also indicate that TF regions outside of the putative lipid binding region may also contribute to PS-dependent decryption of TF.