Cardiac Myosin-Binding Protein C Mutations and Hypertrophic Cardiomyopathy Haploinsufficiency, Deranged Phosphorylation, and Cardiomyocyte Dysfunction
Cardiac Myosin-Binding Protein C Mutations and Hypertrophic Cardiomyopathy Haploinsufficiency, Deranged Phosphorylation, and Cardiomyocyte Dysfunction
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DOI：
10.1161/circulationaha.108.838672
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发表时间：
2009-03-24
期刊：
影响因子：
37.8
通讯作者：
van der Velden, Jolanda
中科院分区：
文献类型：
--
作者：
van Dijk, Sabine J.;Dooijes, Dennis;van der Velden, Jolanda
背景：编码心肌肌球蛋白结合蛋白C （cMyBP-C）的MYBPC3基因突变是家族性肥厚性心肌病的常见原因。在本研究中，我们研究了MYBPC3（MYBPC3(mut)）移码突变的同质家族性肥厚性心肌病患者组中肌节的蛋白质组成和功能是否发生了改变。方法与结果：比较MYBPC3突变携带者（c. 2373dupG, n=7; c. 2864_2865delCT, n=4）和非失败供者（n=13）的心脏样本。使用针对cMyBP-C抗体的Western blots未在MYBPC3（mut）中发现截断的cMyBP-C。cMyBP-C蛋白在MYBPC3（mut）中的表达显著降低了33 +/- 5%。心肌MyBP-C在MYBPC3（mut）样品中的磷酸化水平与供体样品相似，而心肌肌钙蛋白I的磷酸化水平降低了84 +/- 5%，表明β -肾上腺素能途径的2种主要收缩靶蛋白的磷酸化水平存在差异。机械分离的triton -通透性心肌细胞的力测量表明，MYBPC3（mut）中肌细胞每横截面面积的最大力（20.2 +/- 2.7 kN/m(2)）比供体（34.5 +/- 1.1 kN/m(2)）有所下降。此外，MYBPC3(mut) （pCa(50)=5.62 +/- 0.04）的Ca2+敏感性高于供体（pCa(50)=5.54 +/- 0.02），这与心肌肌钙蛋白I磷酸化降低一致。用外源性蛋白激酶A治疗，模拟β -肾上腺素能刺激，并没有纠正最大力的降低，但消除了MYBPC3(mut) （pCa(50)=5.46 +/- 0.03）和供体（pCa(50)=5.48 +/- 0.02）之间Ca2+敏感性的初始差异。结论：移码型MYBPC3突变导致心肌细胞单倍体功能不全，收缩蛋白磷酸化紊乱，最大发力能力降低。MYBPC3（mut）中Ca2+敏感性的增强是由于继发于突变诱导功能障碍的肌钙蛋白I的低磷酸化。（Circulation. 2009; 119: 1473-1483.）
Background-Mutations in the MYBPC3 gene, encoding cardiac myosin-binding protein C (cMyBP-C), are a frequent cause of familial hypertrophic cardiomyopathy. In the present study, we investigated whether protein composition and function of the sarcomere are altered in a homogeneous familial hypertrophic cardiomyopathy patient group with frameshift mutations in MYBPC3 (MYBPC3(mut)).Methods and Results-Comparisons were made between cardiac samples from MYBPC3 mutant carriers (c. 2373dupG, n=7; c. 2864_2865delCT, n=4) and nonfailing donors (n=13). Western blots with the use of antibodies directed against cMyBP-C did not reveal truncated cMyBP-C in MYBPC3(mut). Protein expression of cMyBP-C was significantly reduced in MYBPC3(mut) by 33 +/- 5%. Cardiac MyBP-C phosphorylation in MYBPC3(mut) samples was similar to the values in donor samples, whereas the phosphorylation status of cardiac troponin I was reduced by 84 +/- 5%, indicating divergent phosphorylation of the 2 main contractile target proteins of the beta-adrenergic pathway. Force measurements in mechanically isolated Triton-permeabilized cardiomyocytes demonstrated a decrease in maximal force per cross-sectional area of the myocytes in MYBPC3(mut) (20.2 +/- 2.7 kN/m(2)) compared with donor (34.5 +/- 1.1 kN/m(2)). Moreover, Ca2+ sensitivity was higher in MYBPC3(mut) (pCa(50)=5.62 +/- 0.04) than in donor (pCa(50)=5.54 +/- 0.02), consistent with reduced cardiac troponin I phosphorylation. Treatment with exogenous protein kinase A, to mimic beta-adrenergic stimulation, did not correct reduced maximal force but abolished the initial difference in Ca2+ sensitivity between MYBPC3(mut) (pCa(50)=5.46 +/- 0.03) and donor (pCa(50)=5.48 +/- 0.02).Conclusions-Frameshift MYBPC3 mutations cause haploinsufficiency, deranged phosphorylation of contractile proteins, and reduced maximal force-generating capacity of cardiomyocytes. The enhanced Ca2+ sensitivity in MYBPC3(mut) is due to hypophosphorylation of troponin I secondary to mutation-induced dysfunction. (Circulation. 2009; 119: 1473-1483.)