Department Biology and Biotechnologies "Charles Darwin", Sapienza University of Rome, Center for Research in Neurobiology 'Daniel Bovet', 00185 Rome, Italy.
Department of Physiology and Pharmacology, Sapienza University of Rome, 00185 Rome, Italy.
Neurobiol Dis. 2018 Dec;120:139-150. doi: 10.1016/j.nbd.2018.08.026. Epub 2018 Sep 7.
An increasing number of rare mutations linked to autism spectrum disorders have been reported in genes encoding for proteins involved in synapse formation and maintenance, such as the post-synaptic cell adhesion proteins neuroligins. Most of the autism-linked mutations in the neuroligin genes map on the extracellular protein domain. The autism-linked substitution R451C in Neuroligin3 (NLGN3) induces a local misfolding of the extracellular domain, causing defective trafficking and retention of the mutant protein in the endoplasmic reticulum (ER). The activation of the unfolded protein response (UPR), due to misfolded proteins accumulating in the ER, has been implicated in pathological and physiological conditions of the nervous system. It was previously shown that the over-expression of R451C NLGN3 in a cellular system leads to the activation of the UPR. Here, we have investigated whether this protective cellular response is detectable in the knock-in mouse model of autism endogenously expressing R451C NLGN3. Our data showed up-regulation of UPR markers uniquely in the cerebellum of the R451C mice compared to WT littermates, at both embryonic and adult stages, but not in other brain regions. Miniature excitatory currents in the Purkinje cells of the R451C mice showed higher frequency than in the WT, which was rescued inhibiting the PERK branch of UPR. Taken together, our data indicate that the R451C mutation in neuroligin3 elicits UPR in vivo, which appears to trigger alterations of synaptic function in the cerebellum of a mouse model expressing the R451C autism-linked mutation.
越来越多与自闭症谱系障碍相关的罕见突变已在参与突触形成和维持的蛋白编码基因中被报道，如突触后细胞黏附蛋白神经连接蛋白。神经连接蛋白基因中的大多数自闭症相关突变位于细胞外蛋白结构域。神经连接蛋白 3（NLGN3）中的自闭症相关替代 R451C 导致细胞外结构域局部错误折叠，导致突变蛋白在内质网（ER）中的运输和保留缺陷。由于 ER 中积累的错误折叠蛋白，未折叠蛋白反应（UPR）的激活与神经系统的病理和生理状况有关。先前的研究表明，在细胞系统中过度表达 R451C NLGN3 会导致 UPR 的激活。在这里，我们研究了在自闭症内源性表达 R451C NLGN3 的敲入小鼠模型中，是否可以检测到这种保护细胞反应。我们的数据显示，与 WT 同窝仔相比，R451C 小鼠的 UPR 标志物在胚胎期和成年期均在上调，而在其他脑区则没有。与 WT 相比，R451C 小鼠的浦肯野细胞中的兴奋性微小电流的频率更高，通过抑制 UPR 的 PERK 分支可以挽救这种情况。总之，我们的数据表明，神经连接蛋白 3 中的 R451C 突变在体内引发 UPR，这似乎触发了表达 R451C 自闭症相关突变的小鼠模型中小脑突触功能的改变。
