Muscle Contraction Regulates BDNF/TrkB Signaling to Modulate Synaptic Function through Presynaptic cPKCα and cPKCβI.
Muscle Contraction Regulates BDNF/TrkB Signaling to Modulate Synaptic Function through Presynaptic cPKCα and cPKCβI.
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DOI：
10.3389/fnmol.2017.00147
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发表时间：
2017
影响因子：
4.8
通讯作者：
Tomàs J
中科院分区：
文献类型：
--
作者：
Hurtado E;Cilleros V;Nadal L;Simó A;Obis T;Garcia N;Santafé MM;Tomàs M;Halievski K;Jordan CL;Lanuza MA;Tomàs J
神经营养因子脑源性神经营养因子（BDNF）通过原肌球蛋白相关激酶B受体（Trk B）调节神经肌肉系统中突触的维持和功能。BDNF对乙酰胆碱（ACh）释放的增强作用需要TrkB磷酸化和蛋白激酶C（PKC）活化。BDNF以活性依赖性方式分泌，但尚不清楚突触前和/或突触后活性是否增强BDNF在神经肌肉接头（NMJ）的体内表达。在这里，我们研究了神经和肌肉细胞活动是否通过BDNF/TrkB信号调节突触前常规PKC（cPKCα和βI）来调节NMJ的突触强度。为了区分突触前活动与肌肉收缩的影响，我们刺激大鼠膈肌的膈神经（1 Hz，30 min），有或无收缩（μ-芋螺毒素GIIIB消除）。然后，我们进行了ELISA，Western印迹，qRT-PCR，免疫荧光和电生理技术。我们发现，神经诱导的肌肉收缩：（1）增加成熟BDNF蛋白的水平，而不影响pro-BDNF蛋白或BDNF mRNA水平;（2）下调TrkB. T1，而不影响TrkB.FL或p75神经营养因子受体（p75）水平;（3）通过TrkB信号增加突触前cPKCα和cPKCβI蛋白水平;（4）增强cPKCα和cPKCβI的磷酸化。此外，我们证明，cPKCβI，这是专门位于运动神经末梢，增加活动诱导的乙酰胆碱释放。总之，这些结果表明，神经诱导的肌肉收缩是BDNF/TrkB信号通路的关键调节因子，逆行激活突触前cPKC亚型（特别是cPKCβI）以调节突触功能。这些结果表明，神经肌肉活动的减少，如发生在几种神经肌肉疾病，可能会影响BDNF/TrkB/PKC通路，连接突触前和突触后活动，以维持神经肌肉功能。
The neurotrophin brain-derived neurotrophic factor (BDNF) acts via tropomyosin-related kinase B receptor (TrkB) to regulate synapse maintenance and function in the neuromuscular system. The potentiation of acetylcholine (ACh) release by BDNF requires TrkB phosphorylation and Protein Kinase C (PKC) activation. BDNF is secreted in an activity-dependent manner but it is not known if pre- and/or postsynaptic activities enhance BDNF expression in vivo at the neuromuscular junction (NMJ). Here, we investigated whether nerve and muscle cell activities regulate presynaptic conventional PKC (cPKCα and βI) via BDNF/TrkB signaling to modulate synaptic strength at the NMJ. To differentiate the effects of presynaptic activity from that of muscle contraction, we stimulated the phrenic nerve of rat diaphragms (1 Hz, 30 min) with or without contraction (abolished by μ-conotoxin GIIIB). Then, we performed ELISA, Western blotting, qRT-PCR, immunofluorescence and electrophysiological techniques. We found that nerve-induced muscle contraction: (1) increases the levels of mature BDNF protein without affecting pro-BDNF protein or BDNF mRNA levels; (2) downregulates TrkB.T1 without affecting TrkB.FL or p75 neurotrophin receptor (p75) levels; (3) increases presynaptic cPKCα and cPKCβI protein level through TrkB signaling; and (4) enhances phosphorylation of cPKCα and cPKCβI. Furthermore, we demonstrate that cPKCβI, which is exclusively located in the motor nerve terminals, increases activity-induced acetylcholine release. Together, these results show that nerve-induced muscle contraction is a key regulator of BDNF/TrkB signaling pathway, retrogradely activating presynaptic cPKC isoforms (in particular cPKCβI) to modulate synaptic function. These results indicate that a decrease in neuromuscular activity, as occurs in several neuromuscular disorders, could affect the BDNF/TrkB/PKC pathway that links pre- and postsynaptic activity to maintain neuromuscular function.