Table_1_Impaired synaptic incorporation of AMPA receptors in a mouse model of fragile X syndrome.XLSX

Fragile X syndrome (FXS) is the most common monogenetic cause of inherited intellectual disability and autism in humans. One of the well-characterized molecular phenotypes of Fmr1 KO mice, a model of FXS, is increased translation of synaptic proteins. Although this upregulation stabilizes in adulthood, abnormalities during the critical period of plasticity have long-term effects on circuit formation and synaptic properties. Using high-resolution quantitative proteomics of synaptoneurosomes isolated from the adult, developed brains of Fmr1 KO mice, we show a differential abundance of proteins regulating the postsynaptic receptor activity of glutamatergic synapses. We investigated the AMPA receptor composition and shuttling in adult Fmr1 KO and WT mice using a variety of complementary experimental strategies such as surface protein crosslinking, immunostaining of surface receptors, and electrophysiology. We discovered that the activity-dependent synaptic delivery of AMPARs is impaired in adult Fmr1 KO mice. Furthermore, we show that Fmr1 KO synaptic AMPARs contain more GluA2 subunits that can be interpreted as a switch in the synaptic AMPAR subtype toward an increased number of Ca2+−impermeable receptors in adult Fmr1 KO synapses.

脆性X综合征（FXS）是人类遗传性智力障碍和自闭症最常见的单基因原因。脆性X智力1基因敲除小鼠（Fmr1 KO小鼠），作为FXS的模型，其典型的分子表型之一是突触蛋白翻译水平的升高。尽管这种上调在成年期趋于稳定，但塑性关键期的不正常现象对电路形成和突触特性具有长期影响。利用从成年Fmr1 KO小鼠发育成熟的大脑中分离出的突触神经索进行的高分辨率定量蛋白质组学分析，我们揭示了调节谷氨酸能突触后受体活动的蛋白质丰度的差异。我们采用多种互补的实验策略，如表面蛋白交联、表面受体的免疫染色和电生理学等方法，研究了成年Fmr1 KO和野生型（WT）小鼠的AMPA受体组成和转运。我们发现成年Fmr1 KO小鼠的AMPA受体活动依赖性突触传递受损。此外，我们还发现Fmr1 KO突触中的AMPA受体含有更多的GluA2亚基，这可以解释为成年Fmr1 KO突触中突触AMPA受体亚型的切换，向增加Ca2+不可渗透受体数量的方向转变。