The Notch ligand E3 ligase, Mind Bomb1, regulates glutamate receptor localization in Drosophila.
The Notch ligand E3 ligase, Mind Bomb1, regulates glutamate receptor localization in Drosophila.
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DOI：
10.1016/j.mcn.2015.11.004
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发表时间：
2016-01
期刊：
影响因子：
--
通讯作者：
Liebl FL
中科院分区：
文献类型：
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作者：
Sturgeon M;Davis D;Albers A;Beatty D;Austin R;Ferguson M;Tounsel B;Liebl FL
突触后致密物（PSD）是一种富含蛋白质的网络，对于突触后谷氨酸受体（GluRs）的定位和这些受体下游的信号传导很重要。虽然已经鉴定了数百种PSD蛋白，但许多蛋白在功能上没有特征。我们进行了反向遗传筛选突变，影响GluR本地化使用果蝇基因编码同源的哺乳动物PSD蛋白。42.8%的突变体分析表现出显着的变化，GluR定位在三龄幼虫神经肌肉接头（NMJ），模型突触，表达AMPA受体的同源物。我们确定了E3泛素连接酶，Mib 1，促进Notch信号，作为突触GluR定位的调节器。Mib 1正调节GluR亚基GluRIIA、GluRIIB和GluRIIC的定位。缺乏泛素连接酶活性的Mib 1的突变和Mib 1的普遍表达导致突触含GluRIIA受体的丧失。相反，在所有组织中Mib 1的过表达增加突触后GluRIIA水平。Mib 1的细胞水平对突触前运动神经元的结构也很重要。虽然Mib 1信号传导缺陷导致NMJ过度生长，但Mib 1的普遍过表达导致突触前运动神经元结和分支数量减少。这些突触的变化可能是次要的衰减mib1突变体中突触前运动神经元的谷氨酸释放的mib1突变体表现出显着减少囊泡相关蛋白半胱氨酸串蛋白和自发神经传递的频率。
The postsynaptic density (PSD) is a protein-rich network important for the localization of postsynaptic glutamate receptors (GluRs) and for signaling downstream of these receptors. Although hundreds of PSD proteins have been identified, many are functionally uncharacterized. We conducted a reverse genetic screen for mutations that affected GluR localization using Drosophila genes that encode homologs of mammalian PSD proteins. 42.8% of the mutants analyzed exhibited a significant change in GluR localization at the third instar larval neuromuscular junction (NMJ), a model synapse that expresses homologs of AMPA receptors. We identified the E3 ubiquitin ligase, Mib1, which promotes Notch signaling, as a regulator of synaptic GluR localization. Mib1 positively regulates the localization of the GluR subunits GluRIIA, GluRIIB, and GluRIIC. Mutations in mib1 and ubiquitous expression of Mib1 that lacks its ubiquitin ligase activity result in the loss of synaptic GluRIIA-containing receptors. In contrast, overexpression of Mib1 in all tissues increases postsynaptic levels of GluRIIA. Cellular levels of Mib1 are also important for the structure of the presynaptic motor neuron. While deficient Mib1 signaling leads to overgrowth of the NMJ, ubiquitous overexpression of Mib1 results in a reduction in the number of presynaptic motor neuron boutons and branches. These synaptic changes may be secondary to attenuated glutamate release from the presynaptic motor neuron in mib1 mutants as mib1 mutants exhibit significant reductions in the vesicle-associated protein cysteine string protein and in the frequency of spontaneous neurotransmission.