SHANK3 is a postsynaptic structural protein localized at excitatory glutamatergic synapses in which deletions and mutations have been implicated in patients with autism spectrum disorders (ASD). The expression of Shank3 ASD mutations causes impairments in ionotropic glutamate receptor-mediated synaptic responses in neurons, which is thought to underlie ASD-related behaviors, thereby indicating glutamatergic synaptopathy as one of the major pathogenic mechanisms. However, little is known about the functional consequences of ASD-associated mutations in Shank3 on another important set of glutamate receptors, group I metabotropic glutamate receptors (mGluRs). Here, we further assessed how Shank3 mutations identified in patients with ASD (one de novo InsG mutation and two inherited point mutations, R87C and R375C) disrupt group I mGluR (mGluR1 and mGluR5) expression and function. To identify potential isoform-specific deficits induced by ASD-associated Shank3 mutations on group I mGluRs, we surface immunolabeled mGluR1 and mGluR5 independently. We also induced mGluR-dependent synaptic plasticity (R,S-3,5-dihydroxyphenylglycine [DHPG]-induced long-term depression [LTD]) as well as N-methyl-D-aspartate receptor (NMDAR)-dependent LTD. ASD-associated mutations in Shank3 differentially interfered with the ability of cultured hippocampal neurons to express mGluR5 and mGluR1 at synapses. Intriguingly, all ASD Shank3 mutations impaired mGluR-dependent LTD without altering NMDAR-dependent LTD. Our data show that the specific perturbation in mGluR-dependent synaptic plasticity occurs in neurons expressing ASD-associated Shank3 mutations, which may underpin synaptic dysfunction and subsequent behavioral deficits in ASD.

中文翻译：

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自闭症相关的Shank3突变会改变mGluR的表达和mGluR依赖性但不是NMDA受体依赖性的长期抑郁症。

SHANK3是一种位于兴奋性谷氨酸能突触中的突触后结构蛋白，其中自闭症谱系障碍（ASD）患者涉及缺失和突变。Shank3 ASD突变的表达导致神经元的离子型谷氨酸受体介导的突触反应受损，这被认为是ASD相关行为的基础，从而表明谷氨酸能突触病是主要的致病机制之一。然而，关于Shunk3中与ASD相关的突变对另一组重要的谷氨酸受体（I组代谢型谷氨酸受体（mGluRs））的功能后果知之甚少。在这里，我们进一步评估了在ASD患者中如何识别Shank3突变（一个从头InsG突变和两个遗传点突变，R87C和R375C）破坏了I组mGluR（mGluR1和mGluR5）的表达和功能。为了确定I组mGluRs上由ASD相关的Shank3突变诱导的潜在亚型特异性缺陷，我们独立地对免疫标记的mGluR1和mGluR5进行表面处理。我们还诱导了mGluR依赖的突触可塑性（R，S-3,5-二羟基苯基甘氨酸[DHPG]引起的长期抑郁[LTD]）以及N-甲基-D-天冬氨酸受体（NMDAR）依赖的LTD。Shank3中与ASD相关的突变差异性地影响了培养的海马神经元在突触中表达mGluR5和mGluR1的能力。有趣的是，所有ASD Shank3突变都会损害mGluR依赖性LTD，而不会改变NMDAR依赖性LTD。我们的数据表明，mGluR依赖性突触可塑性中的特定扰动发生在表达ASD相关Shank3突变的神经元中，