Zaklyazminskaya Elena V, Nefedova Victoria V, Koubassova Natalia A, Kotlukova Natalia P, Kopylova Galina V, Kochurova Anastasia M, Shchepkin Daniil V, Ryabkova Natalia S, Katrukha Ivan A, Kleymenov Sergey Y, Bershitsky Sergey Y, Matyushenko Alexander M, Tsaturyan Andrey K, Levitsky Dmitrii I
Petrovsky National Research Centre of Surgery, Moscow 119991, Russia.
Research Center of Biotechnology, A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow 119071, Russia.
Int J Mol Sci. 2024 Dec 5;25(23):13059. doi: 10.3390/ijms252313059.
Pediatric dilated cardiomyopathy (DCM) is a rare heart muscle disorder leading to the enlargement of all chambers and systolic dysfunction. We identified a novel de novo variant, c.88A>G (p.Lys30Glu, K30E), in the gene encoding the major cardiac muscle tropomyosin (Tpm) isoform, Tpm1.1. The variant was found in a proband with DCM and left ventricular non-compaction who progressed to terminal heart failure at the age of 3 years and 8 months. To study the properties of the mutant protein, we produced recombinant K30E Tpm and used various biochemical and biophysical methods to compare its properties with those of WT Tpm. The K30E substitution decreased the thermal stability of Tpm and its complex with actin and significantly reduced the sliding velocity of the regulated thin filaments over a surface covered by ovine cardiac myosin in an in vitro motility assay across the entire physiological range of Ca concentration. Our molecular dynamics simulations suggest that the charge reversal of the 30th residue of Tpm alters the actin monomer to which it is bound. We hypothesize that this rearrangement of the actin-Tpm interaction may hinder the transition of a myosin head attached to a nearby actin from a weakly to a strongly bound, force-generating state, thereby reducing myocardial contractility. The impaired myosin interaction with regulated actin filaments and the decreased thermal stability of the actin-Tpm complex at a near physiological temperature likely contribute to the pathogenicity of the variant and its causative role in progressive DCM.
小儿扩张型心肌病（DCM）是一种罕见的心肌疾病，会导致所有心腔扩大和收缩功能障碍。我们在编码主要心肌原肌球蛋白（Tpm）同工型Tpm1.1的基因中鉴定出一种新的从头变异，即c.88A>G（p.Lys30Glu，K30E）。该变异在一名患有DCM和左心室心肌致密化不全的先证者中被发现，该先证者在3岁8个月时进展为终末期心力衰竭。为了研究突变蛋白的特性，我们制备了重组K30E Tpm，并使用各种生化和生物物理方法将其特性与野生型Tpm的特性进行比较。在整个生理钙浓度范围内的体外运动分析中，K30E替代降低了Tpm及其与肌动蛋白复合物的热稳定性，并显著降低了调节性细肌丝在羊心肌肌球蛋白覆盖表面上的滑动速度。我们的分子动力学模拟表明，Tpm第30位残基的电荷反转改变了与其结合的肌动蛋白单体。我们假设肌动蛋白-Tpm相互作用的这种重排可能会阻碍附着在附近肌动蛋白上的肌球蛋白头部从弱结合状态转变为强结合的、产生力的状态，从而降低心肌收缩力。在接近生理温度下，肌球蛋白与调节性肌动蛋白丝的相互作用受损以及肌动蛋白-Tpm复合物的热稳定性降低，可能导致该变异的致病性及其在进行性DCM中的致病作用。
