Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland; Institute of Biomedicine, University of Turku, Turku, Finland; Turku Bioscience Centre, University of Turku, 20520 Turku, Finland.
l'institut du thorax, INSERM, CNRS, University of Nantes, Nantes, France.
Biophys J. 2019 Oct 15;117(8):1467-1475. doi: 10.1016/j.bpj.2019.08.032. Epub 2019 Aug 31.
Mitral valve diseases affect ∼3% of the population and are the most common reasons for valvular surgery because no drug-based treatments exist. Inheritable genetic mutations have now been established as the cause of mitral valve insufficiency, and four different missense mutations in the filamin A gene (FLNA) have been found in patients suffering from nonsyndromic mitral valve dysplasia (MVD). The filamin A (FLNA) protein is expressed, in particular, in endocardial endothelia during fetal valve morphogenesis and is key in cardiac development. The FLNA-MVD-causing mutations are clustered in the N-terminal region of FLNA. How the mutations in FLNA modify its structure and function has mostly remained elusive. In this study, using NMR spectroscopy and interaction assays, we investigated FLNA-MVD-causing V711D and H743P mutations. Our results clearly indicated that both mutations almost completely destroyed the folding of the FLNA5 domain, where the mutation is located, and also affect the folding of the neighboring FLNA4 domain. The structure of the neighboring FLNA6 domain was not affected by the mutations. These mutations also completely abolish FLNA's interactions with protein tyrosine phosphatase nonreceptor type 12, which has been suggested to contribute to the pathogenesis of FLNA-MVD. Taken together, our results provide an essential structural and molecular framework for understanding the molecular bases of FLNA-MVD, which is crucial for the development of new therapies to replace surgery.
二尖瓣疾病影响约 3%的人口，是瓣膜手术最常见的原因，因为目前尚无基于药物的治疗方法。遗传性基因突变现已被确定为二尖瓣关闭不全的原因，在患有非综合征性二尖瓣发育不良 (MVD) 的患者中发现了纤连蛋白 A 基因 (FLNA) 的四个不同错义突变。纤连蛋白 A (FLNA) 蛋白在胎儿瓣膜形态发生过程中特别在内皮内皮细胞中表达，是心脏发育的关键。FLNA-MVD 致病突变聚集在 FLNA 的 N 端区域。FLNA 中的突变如何改变其结构和功能在很大程度上仍然难以捉摸。在这项研究中，我们使用 NMR 光谱和相互作用测定法研究了 FLNA-MVD 致病的 V711D 和 H743P 突变。我们的结果清楚地表明，这两种突变几乎完全破坏了突变所在的 FLNA5 结构域的折叠，并且还影响了邻近的 FLNA4 结构域的折叠。突变未影响邻近的 FLNA6 结构域的折叠。这些突变还完全消除了 FLNA 与蛋白酪氨酸磷酸酶非受体型 12 的相互作用，据认为这有助于 FLNA-MVD 的发病机制。总之，我们的研究结果为理解 FLNA-MVD 的分子基础提供了重要的结构和分子框架，这对于开发替代手术的新疗法至关重要。
