Inhibition of PKC phosphorylation of cTnI improves cardiac performance in vivo.
Inhibition of PKC phosphorylation of cTnI improves cardiac performance in vivo.
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DOI：
10.1152/ajpheart.00582.2003
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发表时间：
2004-06
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影响因子：
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通讯作者：
Brian B. Roman;P. Goldspink;Elyse Spaite;D. Urboniene;R. McKinney;David L. Geenen;R. J. Solaro
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作者：
Brian B. Roman;P. Goldspink;Elyse Spaite;D. Urboniene;R. McKinney;David L. Geenen;R. J. Solaro
蛋白激酶C（PKC）通过磷酸化包括肌丝蛋白在内的细胞内靶点来调节心肌细胞功能。体外心脏制备物研究产生的数据表明，肌钙蛋白I（TnI）的PKC磷酸化（主要通过PKC-β）可能会减慢心脏收缩和舒张速率（+dP/dt和-dP/dt）。为了在体内探索这一问题，我们使用转基因小鼠[突变TnI（mTnI）小鼠]，其中心脏TnI上的主要PKC磷酸化位点通过丙氨酸取代Ser（43）和Ser（45）而突变，并研究了基线时的原位血流动力学和增强的肌力。mTnI小鼠心脏的收缩力增加，+dP/dt和-dP/dt分别比FVB小鼠高30%和18%，与FVB小鼠相比，对异丙肾上腺素的反应可忽略不计，+dP/dt增加33%，-dP/dt增加26%。用苯丙氨酸和普萘洛尔治疗得到了类似的结果; FVB小鼠心脏显示出20%的发展压力增加，而肌钙蛋白I小鼠没有反应。心肌肌钙蛋白I的反磷酸化表明，PKC位点的突变与增强的PKA依赖性磷酸化相关，而与基础cAMP水平的变化无关。我们的研究结果表明，PKC依赖的磷酸化的TnI的基础以及增强状态下的心脏功能的调制的重要作用，并表明在原位跳动的心脏中的磷酸化位点的TnI的相互依赖性。
Protein kinase C (PKC) modulates cardiomyocyte function by phosphorylation of intracellular targets including myofilament proteins. Data generated from studies on in vitro heart preparations indicate that PKC phosphorylation of troponin I (TnI), primarily via PKC-epsilon, may slow the rates of cardiac contraction and relaxation (+dP/dt and -dP/dt). To explore this issue in vivo, we employed transgenic mice [mutant TnI (mTnI) mice] in which the major PKC phosphorylation sites on cardiac TnI were mutated by alanine substitutions for Ser(43) and Ser(45) and studied in situ hemodynamics at baseline and increased inotropy. Hearts from mTnI mice exhibited increased contractility, as shown by a 30% greater +dP/dt and 18% greater -dP/dt than FVB hearts, and had a negligible response to isoproterenol compared with FVB mice, in which +dP/dt increased by 33% and -dP/dt increased by 26%. Treatment with phenylephrine and propranolol gave a similar result; FVB mouse hearts demonstrated a 20% increase in developed pressure, whereas mTnI mice showed no response. Back phosphorylation of TnI from mTnI hearts demonstrated that the mutation of the PKC sites was associated with an enhanced PKA-dependent phosphorylation independent of a change in basal cAMP levels. Our results demonstrate the important role that PKC-dependent phosphorylation of TnI has on the modulation of cardiac function under basal as well as augmented states and indicate interdependence of the phosphorylation sites of TnI in hearts beating in situ.