Amalia Biron Research Institute of Thrombosis and Hemostasis, Chaim Sheba Medical Center, Tel Hashomer and Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
J Thromb Haemost. 2011 Jan;9(1):192-200. doi: 10.1111/j.1538-7836.2010.04087.x.
Studies of Glanzmann thrombasthenia (GT)-causing mutations has generated invaluable information on the formation and function of integrin αIIbβ(3).
To characterize the mutation in four siblings of an Israeli Arab family affected by GT, and to analyze the relationships between the mutant protein structure and its function using artificial mutations.
Sequencing disclosed a new A97G transversion in the αIIb gene predicting Asn2Asp substitution at blade 1 of the β-propeller. Alignment with other integrin α subunits revealed that Asn2 is highly conserved. No surface expression of αIIbβ(3) was found in patients' platelets and baby hamster kidney (BHK) cells transfected with mutated αIIb and WT β(3). Although the αIIbβ(3) was formed, the mutation impaired its intracellular trafficking. Molecular dynamics simulations and modeling of the αIIbβ(3) crystal indicated that the Asn2Asp mutation disrupts a hydrogen bond between Asn2 and Leu366 of a calcium binding domain in blade 6, thereby impairing calcium binding that is essential for intracellular trafficking of αIIbβ(3). Substitution of Asn2 to uncharged Ala or Gln partially decreased αIIbβ(3) surface expression, while substitution by negatively or positively charged residues completely abolished surface expression. Unlike αIIbβ(3), αVβ(3) harboring the Asn2Asp mutation was surface expressed by transfected BHK cells, which is consistent with the known lower sensitivity of αVβ(3) to calcium chelation compared with αIIbβ(3).
The new GT causing mutation highlights the importance of calcium binding domains in the β-propeller for intracellular trafficking of αIIbβ(3). The mechanism by which the mutation exerts its deleterious effect was elucidated by molecular dynamics.
对导致 Glanzmann 血小板无力症（GT）的突变的研究为整合素 αIIbβ(3) 的形成和功能提供了宝贵的信息。
对受 GT 影响的一个以色列阿拉伯家庭的四个兄弟姐妹的突变进行分析，并使用人工突变来分析突变蛋白结构与其功能之间的关系。
测序揭示了 αIIb 基因中的一个新的 A97G 颠换，预测β-三叶桨状结构的 1 号叶片上的天冬酰胺 2 取代为天冬氨酸。与其他整合素 α 亚基的比对表明，天冬酰胺 2 高度保守。在转染突变 αIIb 和 WT β(3) 的患者血小板和仓鼠肾细胞（BHK）中未发现 αIIbβ(3) 的表面表达。尽管形成了 αIIbβ(3)，但突变损害了其细胞内转运。αIIbβ(3) 晶体的分子动力学模拟和建模表明，天冬氨酸 2 取代破坏了位于叶片 6 中的钙结合域中天冬酰胺 2 和亮氨酸 366 之间的氢键，从而破坏了对 αIIbβ(3) 细胞内转运至关重要的钙结合。天冬酰胺 2 取代为不带电荷的丙氨酸或谷氨酰胺部分降低了 αIIbβ(3) 的表面表达，而取代为带负电荷或正电荷的残基则完全消除了表面表达。与 αIIbβ(3) 不同，转染 BHK 细胞表面表达携带天冬氨酸 2 取代的 αVβ(3)，这与已知的 αVβ(3 对钙螯合的敏感性低于 αIIbβ(3)一致。
新的 GT 致病突变强调了β-三叶桨状结构中的钙结合域对 αIIbβ(3) 细胞内转运的重要性。通过分子动力学阐明了突变产生有害影响的机制。
