Apolipoprotein E receptors are required for Reelin-induced proteasomal degradation of the neuronal adaptor protein Disabled-1
Apolipoprotein E receptors are required for Reelin-induced proteasomal degradation of the neuronal adaptor protein Disabled-1
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DOI：
10.1074/jbc.m401770200
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发表时间：
2004-08-06
影响因子：
4.8
通讯作者：
Herz, J
中科院分区：
文献类型：
--
作者：
Bock, HH;Jossin, Y;Herz, J
细胞质衔接蛋白Disabled-1（Dab 1）是通过分泌分子Reelin调节发育中大脑中神经元定位所必需的。Reelin与神经元载脂蛋白E受体apoER 2和极低密度脂蛋白受体的结合诱导Dab 1的酪氨酸磷酸化以及随后的下游靶点如磷脂酰肌醇3（PI 3）-激酶和Nck β的活化或重新定位。Reelin信号传导的中断导致Dab 1蛋白在转基因小鼠的大脑中积累，这表明Reelin通过下调Dab 1表达水平来限制其自身在反应神经元中的作用。在这里，我们使用培养的原代胚胎神经元作为模型，以证明Reelin治疗的目标Dab 1蛋白水解降解的泛素-蛋白酶体途径。我们发现，Dab 1的酪氨酸磷酸化，但不是PI 3-激酶激活所需的蛋白酶体靶向。Dab 1激酶Fyn的遗传缺陷阻止Dab 1降解。Reelin诱导的Dab 1降解也依赖于apoER 2和极低密度脂蛋白受体，呈基因剂量依赖性。此外，蛋白酶体的药理学阻断防止在体外切片培养测定中形成适当的皮质板。我们的研究结果表明，通过神经元apoE受体的信号可以激活泛素-蛋白酶体机制，这可能对Reelin在神经发育过程中的作用和突触传递的调节有影响。
The cytoplasmic adaptor protein Disabled-1 (Dab1) is necessary for the regulation of neuronal positioning in the developing brain by the secreted molecule Reelin. Binding of Reelin to the neuronal apolipoprotein E receptors apoER2 and very low density lipoprotein receptor induces tyrosine phosphorylation of Dab1 and the subsequent activation or relocalization of downstream targets like phosphatidylinositol 3 (PI3)-kinase and Nckbeta. Disruption of Reelin signaling leads to the accumulation of Dab1 protein in the brains of genetically modified mice, suggesting that Reelin limits its own action in responsive neurons by down-regulating the levels of Dab1 expression. Here, we use cultured primary embryonic neurons as a model to demonstrate that Reelin treatment targets Dab1 for proteolytic degradation by the ubiquitin-proteasome pathway. We show that tyrosine phosphorylation of Dab1 but not PI3-kinase activation is required for its proteasomal targeting. Genetic deficiency in the Dab1 kinase Fyn prevents Dab1 degradation. The Reelin-induced Dab1 degradation also depends on apoER2 and very low density lipoprotein receptor in a gene-dose dependent manner. Moreover, pharmacological blockade of the proteasome prevents the formation of a proper cortical plate in an in vitro slice culture assay. Our results demonstrate that signaling through neuronal apoE receptors can activate the ubiquitin-proteasome machinery, which might have implications for the role of Reelin during neurodevelopment and in the regulation of synaptic transmission.