Molecular Insight into the Effect of Lipid Bilayer Environments on Thrombospondin-1 and Calreticulin Interactions
Molecular Insight into the Effect of Lipid Bilayer Environments on Thrombospondin-1 and Calreticulin Interactions
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DOI：
10.1021/bi500662v
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发表时间：
2014-10-14
期刊：
影响因子：
2.9
通讯作者：
Song, Yuhua
中科院分区：
文献类型：
--
作者：
Wang, Lingyun;Murphy-Ullrich, Joanne E.;Song, Yuhua
血小板反应蛋白-1 (TSP1) 与细胞表面钙网蛋白 (CRT) 结合，刺激 CRT 与低密度脂蛋白 (LDL) 受体相关蛋白 (LRP1) 的结合，以发出粘着斑分解和细胞活动参与的信号。最近的一项研究表明，膜筏对于 TSP1 介导的粘着斑分解是必需的，但膜筏在介导 TSP1 CRT LRP1 信号传导中的分子作用尚不清楚。在这项研究中，我们通过原子详细的分子动力学模拟研究了脂质双层环境对 TSP1 和 CRT 相互作用的影响。结果表明，1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）双层和筏状脂质双层[POPC/胆固醇（CHOL）筏状脂质双层或POPC/CHOL/鞘磷脂（SM）筏状脂质双层]之间的脂质分子微观结构特性以及双层的介观力学性能和静电电位存在显着差异，并且差异为筏状脂质双层中的 SM 脂质增强了这种作用。这些双层特性差异影响 CRT 与双层的相互作用，进一步影响 CRT 构象和 TSPI CRT 相互作用。与 POPC 双层环境相比，筏状脂质双层稳定了 CRT 构象。 TSP1 与 CRT 的结合导致在筏状脂质双层环境中 CRT N 结构域的构象比 CRT P 结构域的构象更加“开放”，这可以促进 CRT 与 LRP1 的结合以参与下游信号传导。脂双层中的 SM 脂质增强了 CRT 通过与筏状脂双层中的 TSP1 结合而发生的开放构象变化。与 POPC 双层上的相比，CRT 的 N 结构域和 P 结构域与双层的直接相互作用有助于在筏状脂质双层上的 TSP1 CRT 复合物中形成更开放的 CRT 构象。 CRT 或 TSP1 CRT 复合物与脂质双层的相互作用也导致 CHOL 分子和/或脂质更加协调并聚集成筏状脂质双层中的斑块状区域。脂质和 CHOL 分子的协调和聚集反过来会影响 CRT 与膜筏的相互作用，从而改变 TSP1 CRT 相互作用和 CRT 构象变化，从而可能调节其与 LRP1 的相互作用。这项研究提供了关于脂质双层环境在 TSP1 CRT 相互作用和 CRT 构象变化中的作用的分子见解，这些变化预计将促进 CRT 与 LRP1 的结合以参与下游信号传导事件。
Thrombospondin-1 (TSP1) binding to cell surface calreticulin (CRT) stimulates the association of CRT with low-density lipoprotein (LDL) receptor-related protein (LRP1) to signal focal adhesion disassembly and engagement of cellular activities. A recent study demonstrated that membrane rafts are necessary for TSP1-mediated focal adhesion disassembly, but the molecular role of membrane rafts in mediating TSP1 CRT LRP1 signaling is unknown. In this study, we investigated the effect of lipid bilayer environments on TSP1 and CRT interactions via atomically detailed molecular dynamics simulations. Results showed that the microscopic structural properties of lipid molecules and mesoscopic mechanical properties and electrostatic potential of the bilayer were significantly different between a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer and a raftlike lipid bilayer [a POPC/cholesterol (CHOL) raftlike lipid bilayer or a POPC/CHOL/sphingomyelin (SM) raftlike lipid bilayer], and the difference was enhanced by SM lipids in a raftlike lipid bilayer. These bilayer property differences affect the interactions of CRT with the bilayer, further influencing CRT conformation and TSPI CRT interactions. A raftlike lipid bilayer stabilized CRT conformation as compared to a POPC bilayer environment. TSP1 binding to CRT resulted in a conformation for the CRT N-domain more "open" than that of the CRT P-domain in a raftlike lipid bilayer environment, which could facilitate binding of CRT to LRP1 to engage downstream signaling. The open conformational changes of CRT by binding to TSP1 in a raftlike lipid bilayer were enhanced by SM lipids in a lipid bilayer. The direct interactions of both the N- and P-domains of CRT with the bilayer contribute to the more open conformation of CRT in the TSP1 CRT complex on a raftlike lipid bilayer as compared to that on a POPC bilayer. The interactions of CRT or the TSP1 CRT complex with the lipid bilayer also caused CHOL molecules and/or lipids to be more coordinated and to aggregate into patchlike regions in the raftlike lipid bilayers. The lipid and CHOL molecule coordination and aggregation could in turn affect the interactions of CRT with the membrane raft, thereby altering TSP1 CRT interactions and CRT conformational changes that potentially regulate its interactions with LRP1. This study provides molecular insights into the role of lipid bilayer environments in TSP1 CRT interactions and in the CRT conformational changes that are predicted to facilitate binding of CRT to LRP1 to engage downstream signaling events.