Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Affiliated Senior High School of National Taiwan Normal University, Taipei, Taiwan.
PLoS Biol. 2023 Aug 31;21(8):e3002274. doi: 10.1371/journal.pbio.3002274. eCollection 2023 Aug.
Dendritic spines, the tiny and actin-rich protrusions emerging from dendrites, are the subcellular locations of excitatory synapses in the mammalian brain that control synaptic activity and plasticity. Dendritic spines contain a specialized form of endoplasmic reticulum (ER), i.e., the spine apparatus, required for local calcium signaling and that is involved in regulating dendritic spine enlargement and synaptic plasticity. Many autism-linked genes have been shown to play critical roles in synaptic formation and plasticity. Among them, KLHL17 is known to control dendritic spine enlargement during development. As a brain-specific disease-associated gene, KLHL17 is expected to play a critical role in the brain, but it has not yet been well characterized. In this study, we report that KLHL17 expression in mice is strongly regulated by neuronal activity and KLHL17 modulates the synaptic distribution of synaptopodin (SYNPO), a marker of the spine apparatus. Both KLHL17 and SYNPO are F-actin-binding proteins linked to autism. SYNPO is known to maintain the structure of the spine apparatus in mature spines and contributes to synaptic plasticity. Our super-resolution imaging using expansion microscopy demonstrates that SYNPO is indeed embedded into the ER network of dendritic spines and that KLHL17 is closely adjacent to the ER/SYNPO complex. Using mouse genetic models, we further show that Klhl17 haploinsufficiency and knockout result in fewer dendritic spines containing ER clusters and an alteration of calcium events at dendritic spines. Accordingly, activity-dependent dendritic spine enlargement and neuronal activation (reflected by extracellular signal-regulated kinase (ERK) phosphorylation and C-FOS expression) are impaired. In addition, we show that the effect of disrupting the KLHL17 and SYNPO association is similar to the results of Klhl17 haploinsufficiency and knockout, further strengthening the evidence that KLHL17 and SYNPO act together to regulate synaptic plasticity. In conclusion, our findings unravel a role for KLHL17 in controlling synaptic plasticity via its regulation of SYNPO and synaptic ER clustering and imply that impaired synaptic plasticity contributes to the etiology of KLHL17-related disorders.
树突棘，从树突伸出的微小富含肌动蛋白的突起，是哺乳动物大脑中兴奋性突触的亚细胞位置，控制着突触活动和可塑性。树突棘包含一种特殊形式的内质网（ER），即棘器，它是局部钙信号所必需的，并且参与调节树突棘扩张和突触可塑性。许多与自闭症相关的基因已被证明在突触形成和可塑性中起着关键作用。其中，KLHL17 已知在发育过程中控制树突棘的扩张。作为一种大脑特异性疾病相关基因，KLHL17 预计在大脑中发挥关键作用，但尚未得到很好的描述。在这项研究中，我们报告说，KLHL17 在小鼠中的表达受到神经元活动的强烈调节，KLHL17 调节突触素（SYNPO）的突触分布，SYNPO 是棘器的标志物。KLHL17 和 SYNPO 都是与自闭症相关的 F-肌动蛋白结合蛋白。SYNPO 已知在成熟的棘器中维持棘器的结构，并有助于突触可塑性。我们使用扩展显微镜的超分辨率成像表明，SYNPO 确实嵌入到树突棘的 ER 网络中，KLHL17 与 ER/SYNPO 复合物紧密相邻。使用小鼠遗传模型，我们进一步表明，Klhl17 杂合不足和敲除导致含有 ER 簇的树突棘减少，并且在树突棘处钙事件发生改变。相应地，活性依赖性树突棘扩张和神经元激活（反映为细胞外信号调节激酶（ERK）磷酸化和 C-FOS 表达）受损。此外，我们表明破坏 KLHL17 和 SYNPO 关联的效果类似于 Klhl17 杂合不足和敲除的结果，进一步加强了 KLHL17 和 SYNPO 共同作用以调节突触可塑性的证据。总之，我们的研究结果揭示了 KLHL17 通过调节 SYNPO 和突触 ER 聚类来控制突触可塑性的作用，并暗示了突触可塑性受损可能导致 KLHL17 相关疾病的发病机制。
