Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling
Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling
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DOI：
10.1074/jbc.ra118.002081
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发表时间：
2018-07-06
影响因子：
4.8
通讯作者：
Redwood, Charles
中科院分区：
文献类型：
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作者：
Robinson, Paul;Liu, Xing;Redwood, Charles
导致肥厚型心肌病 (HCM) 的细丝调节蛋白突变会增加肌丝 Ca2+ 敏感性。小鼠模型表现出 Ca2+ 缓冲增加和心律失常，我们假设这些变化是突变的主要影响（独立于代偿性变化），并且 Ca2+ 缓冲增加和 Ca2+ 处理改变通过激活 Ca2+ 依赖性信号传导促进 HCM 发病机制。在这里，我们在一个模型系统中确定了 HCM 突变对细胞内 Ca2+ 处理和 Ca2+ 依赖性信号传导的主要影响，该模型系统拥有 Ca2+ 处理机制和收缩蛋白亚型，在不存在潜在混淆重塑的情况下密切反映了人类环境。使用腺病毒，我们在分离的豚鼠左心室心肌细胞中表达了人肌钙蛋白-T、肌钙蛋白-I和原肌球蛋白（分别为R92Q、R145G和D175N）的引起HCM的变体。 48 小时后，每个变体都定位于 I 带并约占总蛋白的 50%。 HCM 突变显着降低了 Ca2+ 结合的 K-d，导致突变心肌细胞具有更高的 Ca2+ 缓冲。我们观察到舒张期 [Ca2+] 增加，Ca2+ 再摄取减慢，同时基底肌节长度显着减少，松弛减慢。 HCM 突变细胞具有较高的钠/钙交换活性、肌浆网 Ca2+ 负载以及由受磷蛋白 Ca2+/钙调蛋白依赖性蛋白激酶 II (CaMKII) 磷酸化驱动的肌浆/内质网钙 ATP 酶 2 (SERCA2) 活性。在 CaMKII 介导的 RyR 磷酸化的驱动下，兰尼碱受体 (RyR) 泄漏/负载关系也增加。 Ca2+ 稳态的改变也增加了通过钙调神经磷酸酶/NFAT 和细胞外信号调节激酶途径的信号传导。改变的肌丝 Ca2+ 缓冲是信号级联的主要引发者，表明直接靶向肌丝 Ca2+ 敏感性为 HCM 提供了一种有吸引力的治疗方法。
Mutations in thin filament regulatory proteins that cause hypertrophic cardiomyopathy (HCM) increase myofilament Ca2+ sensitivity. Mouse models exhibit increased Ca2+ buffering and arrhythmias, and we hypothesized that these changes are primary effects of the mutations (independent of compensatory changes) and that increased Ca2+ buffering and altered Ca2+ handling contribute to HCM pathogenesis via activation of Ca2+-dependent signaling. Here, we determined the primary effects of HCM mutations on intracellular Ca2+ handling and Ca2+-dependent signaling in a model system possessing Ca2+-handling mechanisms and contractile protein isoforms closely mirroring the human environment in the absence of potentially confounding remodeling. Using adenovirus, we expressed HCM-causing variants of human troponin-T, troponin-I, and -tropomyosin (R92Q, R145G, and D175N, respectively) in isolated guinea pig left ventricular cardiomyocytes. After 48 h, each variant had localized to the I-band and comprised approximate to 50% of the total protein. HCM mutations significantly lowered the K-d of Ca2+ binding, resulting in higher Ca2+ buffering of mutant cardiomyocytes. We observed increased diastolic [Ca2+] and slowed Ca2+ reuptake, coupled with a significant decrease in basal sarcomere length and slowed relaxation. HCM mutant cells had higher sodium/calcium exchanger activity, sarcoplasmic reticulum Ca2+ load, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) activity driven by Ca2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylation of phospholamban. The ryanodine receptor (RyR) leak/load relationship was also increased, driven by CaMKII-mediated RyR phosphorylation. Altered Ca2+ homeostasis also increased signaling via both calcineurin/NFAT and extracellular signal-regulated kinase pathways. Altered myofilament Ca2+ buffering is the primary initiator of signaling cascades, indicating that directly targeting myofilament Ca2+ sensitivity provides an attractive therapeutic approach in HCM.