The Arg451Cys-neuroligin-3 mutation associated with autism reveals a defect in protein processing
The Arg451Cys-neuroligin-3 mutation associated with autism reveals a defect in protein processing
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DOI：
10.1523/jneurosci.0468-04.2004
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发表时间：
2004-05-19
影响因子：
5.3
通讯作者：
Taylor, P
中科院分区：
文献类型：
--
作者：
Comoletti, D;De Jaco, A;Taylor, P
神经素是一个突触后跨膜蛋白家族，与突触前伙伴-神经素相关。神经素和神经素在突触连接的形成和分化中起着至关重要的作用。最近的一项研究报告称，在患有自闭症谱系障碍的兄弟姐妹中发现了神经胶质素-3 （NL3）的突变，这是一种x连锁基因，其中两个受影响的兄弟有一个点突变，用Cys取代了Arg451。为了在生化水平上表征突变，我们分析了突变蛋白的表达和活性。质谱分析表明，突变蛋白与天然蛋白之间的二硫键模式不存在异常二硫键，表明突变蛋白的二级结构是保守的。然而，突变单独影响蛋白质的表达和活性。Cys突变引起神经素运输缺陷，导致蛋白质在内质网中保留。这反过来又减少了NL3向细胞表面的传递。此外，到达细胞膜的一小部分蛋白质缺乏或明显降低了-神经素-1 （NX1beta）的结合活性。Arg451的其他替代品允许正常的细胞表达，但降低了对NX1beta的亲和力。我们的研究结果揭示了与自闭症谱系障碍相关的先天性突变的细胞表型和功能丧失。
The neuroligins are a family of postsynaptic transmembrane proteins that associate with presynaptic partners, the beta-neurexins. Neurexins and neuroligins play a critical role in initiating formation and differentiation of synaptic junctions. A recent study reported that a mutation of neuroligin-3 (NL3), an X-linked gene, was found in siblings with autistic spectrum disorder in which two affected brothers had a point mutation that substituted a Cys for Arg451. To characterize the mutation at the biochemical level, we analyzed expression and activity of the mutated protein. Mass spectrometry comparison of the disulfide bonding pattern between the native and the mutated proteins indicates the absence of aberrant disulfide bonding, suggesting that the secondary structure of the mutated protein is conserved. However, the mutation separately affects protein expression and activity. The Cys mutation causes defective neuroligin trafficking, leading to retention of the protein in the endoplasmic reticulum. This, in turn, decreases the delivery of NL3 to the cell surface. Also, the small fraction of protein that reaches the cell membrane lacks or has markedly diminished beta-neurexin-1 (NX1beta) binding activity. Other substitutions for Arg451 allow for normal cellular expression but diminished affinity for NX1beta. Our findings reveal a cellular phenotype and loss of function for a congenital mutation associated with autistic spectrum disorders.