Functional characterization of c-Mpl ectodomain mutations that underlie congenital amegakaryocytic thrombocytopenia
Functional characterization of c-Mpl ectodomain mutations that underlie congenital amegakaryocytic thrombocytopenia
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DOI：
10.3109/08977194.2013.874347
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发表时间：
2014-02-01
期刊：
影响因子：
1.8
通讯作者：
Murphy, James M.
中科院分区：
文献类型：
--
作者：
Varghese, Leila N.;Zhang, Jian-Guo;Murphy, James M.
细胞表面受体c-Mpl被细胞因子血小板生成素（TPO）激活，支持哺乳动物中的巨核细胞和血小板产生。在人类中，c-Mpl突变已被确定为先天性无巨核细胞血小板减少症（CAMT）的分子基础。在这里，我们表明，CAMT相关的突变c-Mpl主要导致有缺陷的受体介绍细胞表面上。相反，一个CAMT突变体c-Mpl，F104 S，在细胞表面上表达，但表现出缺陷的TPO结合和受体活化。使用突变分析，我们检查了c-Mpl的膜远端细胞因子受体同源模块（CRM）内与F104相邻的哪些残基包含TPO结合表位，揭示了预测的结构域1 E-F和A-B环以及结构域2 F '-G'环内的残基作为关键的TPO结合决定簇。这些研究强调了c-Mpl膜远端CRM对TPO结合的重要性，并表明干扰TPO结合的CRM内的突变可能引起CAMT。
Activation of the cell surface receptor, c-Mpl, by the cytokine, thrombopoietin (TPO), underpins megakaryocyte and platelet production in mammals. In humans, mutations in c-Mpl have been identified as the molecular basis of Congenital Amegakaryocytic Thrombocytopenia (CAMT). Here, we show that CAMT-associated mutations in c-Mpl principally lead to defective receptor presentation on the cell surface. In contrast, one CAMT mutant c-Mpl, F104S, was expressed on the cell surface, but showed defective TPO binding and receptor activation. Using mutational analyses, we examined which residues adjacent to F104 within the membrane-distal cytokine receptor homology module (CRM) of c-Mpl comprise the TPO-binding epitope, revealing residues within the predicted Domain 1 E-F and A-B loops and Domain 2 F'-G' loop as key TPO-binding determinants. These studies underscore the importance of the c-Mpl membrane-distal CRM to TPO-binding and suggest that mutations within this CRM that perturb TPO binding could give rise to CAMT.