Functional analysis of titin/connectin N2-B mutations found in cardiomyopathy
Functional analysis of titin/connectin N2-B mutations found in cardiomyopathy
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DOI：
10.1007/s10974-005-9018-5
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发表时间：
2005-12-01
影响因子：
2.7
通讯作者：
Kimura, Akinori
中科院分区：
文献类型：
--
作者：
Matsumoto, Yuji;Hayashi, Takeharu;Kimura, Akinori
肥厚型心肌病和扩张型心肌病是特发性心肌病的两种主要临床表型。最近的分子遗传学分析显示，“特发性”心肌病是由肌节成分基因突变引起的。我们最近报道了在肥厚型心肌病或扩张型心肌病患者中发现的几个Titin/Connectin基因突变。肥厚型心肌病相关的Titin/Connectin突变(Arg740Leu)增加了与肌动蛋白的结合，而其他扩张型心肌病相关的Titin/Connectin突变(Ala743Val和Val54Met)分别降低了与肌动蛋白和TCAP/端粒素的结合。我们还报道了在肥厚型心肌病和扩张型心肌病中发现的肌联蛋白/连接素的N_2-B区的其他几个突变。由于N_2-B区只在心脏中表达，因此推测突变引起的功能改变会导致心肌病。在这项研究中，我们通过酵母双杂交实验研究了N_2-B区突变引起的功能变化。结果发现，肥厚型心肌病相关突变(Ser3799Tyr)增加了与FHL2蛋白的结合，而扩张型心肌病相关突变(Gln4053ter)则降低了与FHL2蛋白的结合。此外，在家族性DCM中还发现了IS2区域的另一种TTN突变(Arg25618Gln)。由于已知FHL2蛋白将代谢酶连接到肌动蛋白/连接蛋白的N_2-B和I_2区域，这些观察结果表明代谢酶在肌节的改变募集可能在心肌疾病的发病机制中起作用。
Hypertrophic cardiomyopathy and dilated cardiomyopathy are two major clinical phenotypes of "idiopathic" cardiomyopathy. Recent molecular genetic analyses have now revealed that "idiopathic" cardiomyopathy is caused by mutations in genes for sarcomere components. We have recently reported several mutations in titin/connectin gene found in patients with hypertrophic cardiomyopathy or dilated cardiomyopathy. A hypertrophic cardiomyopathy-associated titin/connectin mutation (Arg740Leu) was found to increase the binding to actinin, while other dilated cardiomyopathy-associated titin/connectin mutations (Ala743Val and Val54Met) decreased the binding to actinin and Tcap/telethonin, respectively. We also reported several other mutations in the N2-B region of titin/connectin found in hypertrophic cardiomyopathy and dilated cardiomyopathy. Since the N2-B region expresses only in the heart, it was speculated that functional alterations due to the mutations cause cardiomyopathies. In this study, we investigated the functional changes caused by the N2-B region mutations by using yeast-two-hybrid assays. It was revealed that a hypertrophic cardiomyopathy-associated mutation (Ser3799Tyr) increased the binding to FHL2 protein, whereas a dilated cardiomyopathy-associated mutation (Gln4053ter) decreased the binding. In addition, another TTN mutation (Arg25618Gln) at the is2 region was found in familial DCM. Because FHL2 protein is known to tether metabolic enzymes to N2-B and is2 regions of titin/connectin, these observations suggest that altered recruitment of metabolic enzymes to the sarcomere may play a role in the pathogenesis of cardiomyopathies.