Reciprocal signals between microglia and neurons regulate α-synuclein secretion by exophagy through a neuronal cJUN-N-terminal kinase-signaling axis.
Reciprocal signals between microglia and neurons regulate α-synuclein secretion by exophagy through a neuronal cJUN-N-terminal kinase-signaling axis.
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DOI：
10.1186/s12974-016-0519-5
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发表时间：
2016-03-08
影响因子：
9.3
通讯作者：
Vilhardt F
中科院分区：
文献类型：
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作者：
Christensen DP;Ejlerskov P;Rasmussen I;Vilhardt F
从神经元分泌蛋白病性α-突触核蛋白（α-SNC）是帕金森病（PD）传播的一种可疑驱动力。我们以前曾暗示，自噬体的胞吐作用是分化的PC 12或SH-SY 5 Y神经细胞分泌α-SNC的主要机制。在这里，我们研究了与PD相关的不同形式的神经细胞应激相关的外食调节。我们确定cJUN-N-末端激酶（JNK）活性在含有α-SNC的自噬体的分泌命运中起关键作用。JNK 2或JNK 3的药理学抑制或遗传（shRNA）敲除分别减少分化的PC 12和SH-SY 5 Y细胞中的α-SNC分泌。相反，组成型活性丝裂原活化蛋白激酶激酶7（MKK 7）-JNK 2和-JNK 3构建体的表达增加分泌。cJUN的转录活性不是观察到的效果所必需的。我们在溶酶体融合缺陷（Lewy小体定位蛋白p25α或巴弗洛霉素A1过表达）后，通过外食增加α-SNC释放和JNK激活之间建立了因果关系。神经元ER或氧化应激后JNK激活与外食无关，但值得注意的是，我们证明小胶质细胞和神经元之间的相互信号传导调节α-SNC分泌。直接与表达α-SNC的PC 12神经元共培养或被动转移神经细胞条件培养基可上调小胶质细胞系的NADPH氧化酶活性。相反，活化的小胶质细胞分泌的炎性因子使PC 12细胞中JNK活化和α-SNC分泌增加数倍。虽然我们没有确定这些因素，但我们扩展了我们的观察结果，表明单一培养的神经元暴露于TNFα（活化小胶质细胞的经典促炎介质）足以增加α-SNC分泌，其机制依赖于JNK 2或JNK 3。在本文的继续中，我们表明IFNβ和TGFβ也增加了α-SNC从PC 12神经元的释放。我们暗示JNK家族的应激激酶参与调节外源性或内源性刺激后的外食和α-SNC的释放。在更广泛的范围内，我们的研究结果表明，小胶质细胞不仅造成旁观者损伤的神经元在晚期阶段的炎症性脑疾病，但也可能是积极的介质的疾病传播。
Secretion of proteopathic α-synuclein (α-SNC) species from neurons is a suspected driving force in the propagation of Parkinson’s disease (PD). We have previously implicated exophagy, the exocytosis of autophagosomes, as a dominant mechanism of α-SNC secretion in differentiated PC12 or SH-SY5Y nerve cells. Here we have examined the regulation of exophagy associated with different forms of nerve cell stress relevant to PD. We identify cJUN-N-terminal kinase (JNK) activity as pivotal in the secretory fate of autophagosomes containing α-SNC. Pharmacological inhibition or genetic (shRNA) knockdown of JNK2 or JNK3 decreases α-SNC secretion in differentiated PC12 and SH-SY5Y cells, respectively. Conversely, expression of constitutively active mitogen-activated protein kinase kinase 7 (MKK7)-JNK2 and -JNK3 constructs augment secretion. The transcriptional activity of cJUN was not required for the observed effects. We establish a causal relationship between increased α-SNC release by exophagy and JNK activation subsequent to lysosomal fusion deficiency (overexpression of Lewy body-localized protein p25α or bafilomycin A1). JNK activation following neuronal ER or oxidative stress was not correlated with exophagy, but of note, we demonstrate that reciprocal signaling between microglia and neurons modulates α-SNC secretion. NADPH oxidase activity of microglia cell lines was upregulated by direct co-culture with α-SNC-expressing PC12 neurons or by passive transfer of nerve cell-conditioned medium. Conversely, inflammatory factors secreted from activated microglia increased JNK activation and α-SNC secretion several-fold in PC12 cells. While we do not identify these factors, we extend our observations by showing that exposure of neurons in monoculture to TNFα, a classical pro-inflammatory mediator of activated microglia, is sufficient to increase α-SNC secretion in a mechanism dependent on JNK2 or JNK3. In continuation hereof, we show that also IFNβ and TGFβ increase the release of α-SNC from PC12 neurons. We implicate stress kinases of the JNK family in the regulation of exophagy and release of α-SNC following endogenous or exogenous stimulation. In a wider scope, our results imply that microglia not only inflict bystander damage to neurons in late phases of inflammatory brain disease but may also be active mediators of disease propagation.