Cardiac troponin T mutations: correlation between the type of mutation and the nature of myofilament dysfunction in transgenic mice
Cardiac troponin T mutations: correlation between the type of mutation and the nature of myofilament dysfunction in transgenic mice
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DOI：
10.1111/j.1469-7793.2001.0583c.xd
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发表时间：
2001-10-15
影响因子：
5.5
通讯作者：
Chandra, M
中科院分区：
文献类型：
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作者：
Montgomery, DE;Tardiff, JC;Chandra, M
1.人类家族性肥厚型心肌病（FHC）的异质性表明突变类型与心肌细胞病理生理学改变的性质之间存在联系。FHC相关的心肌肌钙蛋白T（cTnT）突变究竟如何导致心功能受损尚不清楚。我们测量了来自三个转基因（TG）小鼠心脏的清洁剂皮肤的心脏纤维束的稳态等长力和ATP酶活性，在这些转基因（TG）小鼠心脏中，天然cTnT分别被野生型（WT）cTnT、R92 Q突变型cTnT（R92 Q）和cTnT的C端缺失突变型（cTnT（DEL））取代50%、92%和6%。标准化的pCa-张力关系的R92 Q和cTnT（DEL）纤维表现出显着增加的敏感性钙在短（2.0妈妈）和长（2.3妈妈）肌节长度（SL）。在短SL下，WT、R92 Q和cTnTDEL纤维的pCa（50）值（代表pCa-张力关系的中点）分别为5.69 +/- 0.01、5.96 +/- 0.01和5.81 +/- 0.01。在长SL时，WT、R92 Q和cTnT（DEL）纤维的pCa（50）值分别为5.81 +/-0.01、6.08 +/- 0.01和5.95 +/- 0.01。对于R92 Q（92%）TG纤维，在短SL和长SL下半最大激活所需的pCa（Δ pCa（50））的差异为0.12 +/- 0.01，这显著小于先前报道的R92 Q（67%）TG纤维的ApCa（50）值0.29 +/- 0.02。在短SL时，R92 Q和cTnT（DEL）纤维的Ca 2+激活的最大张力显著降低（分别为24%和21%; P < 0.005），而Ca 2+激活的最大ATP酶活性没有相应的降低。因此，在短SL下，R92 Q和cTnTDEL纤维的张力成本分别增加了35%和29%（P < 0.001）。用重组突变cTnT（DEL）蛋白重建的纤维束仅产生由重组WT cTnT重建的纤维束产生的Ca 2+激活的最大力的37%，而Ca 2+敏感性没有明显变化。我们的数据表明，心脏功能的一个重要的突变相关效应是在肌丝水平上ATP利用效率低下的结果。此外，突变诱导的功能障碍的程度不仅取决于突变的性质，而且还取决于肌节中突变蛋白的浓度。
1. The heterogenic nature of familial hypertrophic cardiomyopathy (FHC) in humans suggests a link between the type of mutation and the nature of patho-physiological alterations in cardiac myocytes. Exactly how FHC-associated mutations in cardiac troponin T (cTnT) lead to impaired cardiac function is unclear.2. We measured steady-state isometric force and ATPase activity in detergent-skinned cardiac fibre bundles from three transgenic (TG) mouse hearts in which 50, 92 and 6% of the native cTnT was replaced by the wild type (WT) cTnT, R92Q mutant cTnT (R92Q) and the C-terminal deletion mutant of cTnT (cTnT(DEL)), respectively.3. Normalized pCa-tension relationships of R92Q and cTnT(DEL) fibres demonstrated a significant increase in sensitivity to Ca2+ at short (2.0 mum) and long (2.3 mum) sarcomere lengths (SL). At short SL, the pCa(50) values, representing the midpoint of the pCa-tension relationship, were 5.69 +/- 0.01, 5.96 +/- 0.01 and 5.81 +/- 0.01 for WT, R92Q and cTnTDEL fibres, respectively. At long SL, the pCa(50) values were 5.81 +/- 0.01, 6.08 +/- 0.01 and 5.95 +/- 0.01 for WT, R92Q and cTnT(DEL) fibres, respectively.4. The difference in pCa required for half-maximal activation (Delta pCa(50)) at short and long SL was 0.12 +/- 0.01 for the R92Q (92%) TG fibres, which is significantly less than the previously reported ApCa(50) value of 0.29 +/- 0.02 for R92Q (67%) TG fibres.5. At short SL, Ca2+-activated maximal tension in both R92Q and cTnT(DEL) fibres decreased significantly (24 and 21%, respectively; P < 0.005), with no corresponding decrease in Ca2+-activated maximal ATPase activity. Therefore, at short SL, the tension cost in R92Q and cTnTDEL fibres increased by 35 and 29%, respectively (P < 0.001).6. The fibre bundles reconstituted with the recombinant mutant cTnT(DEL) protein developed only 37% of the Ca2+-activated maximal force developed by recombinant WT cTnT reconstituted fibre bundles, with no apparent changes in Ca2+ sensitivity.7. Our data indicate that an important mutation-linked effect on cardiac function is the result of an inefficient use of ATP at the myofilament level. Furthermore, the extent of the mutation-induced dysfunction depends not only on the nature of the mutation, but also on the concentration of the mutant protein in the sarcomere.