Phosphorylation of titin modulates passive stiffness of cardiac muscle in a titin isoform-dependent manner.
Phosphorylation of titin modulates passive stiffness of cardiac muscle in a titin isoform-dependent manner.
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TITIN的磷酸化可调节心脏肌肉的被动刚度，依赖性替丁同工型。
DOI：
10.1085/jgp.200409177
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发表时间：
2005-03
影响因子：
3.8
通讯作者：
Granzier, Henk L
中科院分区：
文献类型：
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作者：
Fukuda, Norio;Wu, Yiming;Nair, Preetha;Granzier, Henk L
我们研究了蛋白激酶A（PKA）对表达不同肌联蛋白亚型的皮肤心脏组织中被动力的影响，刚性（N2 B）和更柔顺（N2 BA）的钛蛋白。我们使用大鼠心室（RV）、牛左心室（BLV）和牛左心房（BLA）肌肉（被动力：RV > BLV > BLA，N2 B与N2 BA肌联蛋白的比例分别为90：10、40：60和10：90%），发现N2 B和N2 BA亚型都可以被PKA磷酸化。在松弛条件下，肌节长度增加，然后保持恒定30分钟，并测定峰值被动力，应力松弛和稳态被动力。PKA治疗后，所有肌肉类型的被动力均显著降低，其中RV的效果最大，BLA最低，BLV居中。拟合的应力松弛数据的总和的三个指数衰减函数显示，PKA钝化的应力松弛的幅度和加速其时间常数。为了研究PKA诱导的被动力的降低是否是由于肌钙蛋白-细丝相互作用的可能改变（例如，通过肌钙蛋白I磷酸化），我们使用已经用凝溶胶蛋白处理以提取细丝的RV制品进行了相同的实验。PKA减少被动力凝溶胶处理的RV制剂的幅度类似于在对照制剂中观察到的。PKA也被发现减少恢复力在皮肤心室肌细胞的大鼠已缩短到松弛长度以下。最后，我们研究了β-肾上腺素能受体激动剂异丙肾上腺素对完整大鼠心室肌小梁舒张力的影响。我们发现，异丙肾上腺素磷酸化肌联蛋白，它降低舒张力的程度相似，发现在皮肤的RV制剂。总之，这些结果表明，在β-肾上腺素能刺激，PKA增加心室顺应性的肌联蛋白亚型依赖性的方式。
We investigated the effect of protein kinase A (PKA) on passive force in skinned cardiac tissues that express different isoforms of titin, i.e., stiff (N2B) and more compliant (N2BA) titins, at different levels. We used rat ventricular (RV), bovine left ventricular (BLV), and bovine left atrial (BLA) muscles (passive force: RV > BLV > BLA, with the ratio of N2B to N2BA titin, ∼90:10, ∼40:60, and ∼10:90%, respectively) and found that N2B and N2BA isoforms can both be phosphorylated by PKA. Under the relaxed condition, sarcomere length was increased and then held constant for 30 min and the peak passive force, stress-relaxation, and steady-state passive force were determined. Following PKA treatment, passive force was significantly decreased in all muscle types with the effect greatest in RV, lowest in BLA, and intermediate in BLV. Fitting the stress-relaxation data to the sum of three exponential decay functions revealed that PKA blunts the magnitude of stress-relaxation and accelerates its time constants. To investigate whether or not PKA-induced decreases in passive force result from possible alteration of titin–thin filament interaction (e.g., via troponin I phosphorylation), we conducted the same experiments using RV preparations that had been treated with gelsolin to extract thin filaments. PKA decreased passive force in gelsolin-treated RV preparations with a magnitude similar to that observed in control preparations. PKA was also found to decrease restoring force in skinned ventricular myocytes of the rat that had been shortened to below the slack length. Finally, we investigated the effect of the β-adrenergic receptor agonist isoprenaline on diastolic force in intact rat ventricular trabeculae. We found that isoprenaline phosphorylated titin and that it reduced diastolic force to a degree similar to that found in skinned RV preparations. Taken together, these results suggest that during β-adrenergic stimulation, PKA increases ventricular compliance in a titin isoform-dependent manner.