NFAT is a nerve activity sensor in skeletal muscle and controls activity-dependent myosin switching
NFAT is a nerve activity sensor in skeletal muscle and controls activity-dependent myosin switching
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DOI：
10.1073/pnas.0308035101
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发表时间：
2004-07-20
影响因子：
11.1
通讯作者：
Schiaffino, S
中科院分区：
文献类型：
--
作者：
McCullagh, KJA;Calabria, E;Schiaffino, S
钙调磷酸酶（Cn）信号与骨骼肌中神经活动依赖的纤维类型规范有关，但下游效应通路尚未建立。我们研究了活化T细胞的转录因子核因子（NFAT）的作用，这是Cn的主要靶点，通过在再生和成年大鼠肌肉中使用体内转染的方法。用两种不同的NFAT依赖性报告器监测NFAT转录活性，发现慢肌比快肌更高。在慢肌中，去神经支配会降低NFAT的活性，而在去神经支配的肌肉中，用紧张性低频脉冲模式（模仿慢运动神经元的放电模式）电刺激NFAT会增加NFAT的活性，而不是用快速运动神经元的典型高频模式。为了确定NFAT的作用，我们用编码VIVIT的质粒转染再生和成年大鼠肌肉，VIVIT是cn介导的INFAT激活的特异性肽抑制剂。研究发现，VIVIT可阻断再生的慢比目鱼肌中运动神经元活动缓慢引起的慢肌球蛋白重链（MyHC-slow）的表达，抑制成人比目鱼肌中MyHC-slow转录本的表达和MyHC-slow启动子的活性。NFAT的作用被证实，一个组成型活性的INFATc1突变体刺激MyHC-slow，抑制成人快速肌肉中MyHC-2B启动子，并诱导再生肌肉中MyHC-slow的表达。这些结果支持了Cn-NFAT信号在体内骨骼肌中作为神经活动传感器并控制神经活动依赖性肌球蛋白转换的观点。
Calcineurin (Cn) signaling has been implicated in nerve activity-dependent fiber type specification in skeletal muscle, but the downstream effector pathway has not been established. We have investigated the role of the transcription factor nuclear factor of activated T cells (NFAT), a major target of Cn, by using an in vivo transfection approach in regenerating and adult rat muscles. NFAT transcriptional activity was monitored with two different NFAT-dependent reporters and was found to be higher in slow compared to fast muscles. NFAT activity is decreased by denervation in slow muscles and is increased by electrostimulation of denervated muscles with a tonic low-frequency impulse pattern, mimicking the firing pattern of slow motor neurons, but not with a phasic high-frequency pattern typical of fast motor neurons. To determine the role of NFAT, we transfected regenerating and adult rat muscles with a plasmid coding for VIVIT, a specific peptide inhibitor of Cn-mediated INFAT activation. VIVIT was found to block the expression of slow myosin heavy chain (MyHC-slow) induced by slow motor neuron activity in regenerating slow soleus muscle and to inhibit the expression of MyHC-slow transcripts and the activity of a MyHC-slow promoter in adult soleus. The role of NFAT was confirmed by the finding that a constitutively active INFATc1 mutant stimulates the MyHC-slow, inhibits the fast MyHC-2B promoter in adult fast muscles, and induces MyHC-slow expression in regenerating muscles. These results support the notion that Cn-NFAT signaling acts as a nerve activity sensor in skeletal muscle in vivo and controls nerve activity-dependent myosin switching.