Center for Sleep and Circadian Neurobiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia.
Sleep. 2020 Jan 13;43(1). doi: 10.1093/sleep/zsz190.
Homer proteins mediate plasticity and signaling at the postsynaptic density of neurons and are necessary for sleep and synaptic remodeling during sleep. The goal of this study was to investigate the mechanisms of sleep regulation by Homer signaling. Using the Drosophila animal model, we demonstrate that knockdown of Homer specifically in the brain reduces sleep and that Drosophila Homer binds to the sole Drosophila mGluR, known as DmGluRA. This is the first evidence that DmGluRA, which bears greatest homology to group II mammalian metabotropic glutamate receptors (mGluRs), shares functional homology with group I mGluRs which couple to Homer proteins in mammals. As sleep is associated with the physical dissociation of Homer and mGluRs proteins at the synapse, we sought to determine the functional necessity of Homer × DmGluRA interaction in sleep regulation. Using the CRISPR/Cas9 gene editing system, we generated a targeted amino acid replacement of the putative binding site for Homer on DmGluRA to prevent Homer and DmGluRA protein binding. We found that loss of the conserved proline-rich PPXXF sequence on DmGluRA reduces Homer/DmGluRA associations and significantly reduces sleep amount. Thus, we identify a conserved mechanism of synaptic plasticity in Drosophila and demonstrate that the interaction of Homer with DmGluRA is necessary to promote sleep.
Homer 蛋白在神经元的突触后密度处介导可塑性和信号转导，并且是睡眠期间突触重构所必需的。本研究的目的是研究 Homer 信号转导对睡眠调节的机制。使用 Drosophila 动物模型，我们证明了 Homer 在大脑中的特异性敲低会减少睡眠，并且 Drosophila Homer 与唯一的 Drosophila mGluR（称为 DmGluRA）结合。这是第一个证据表明，DmGluRA 与哺乳动物的 I 组代谢型谷氨酸受体（mGluRs）具有最大同源性，与 Homer 蛋白结合具有功能同源性。由于睡眠与突触处 Homer 和 mGluR 蛋白的物理分离有关，我们试图确定 Homer × DmGluRA 相互作用在睡眠调节中的功能必要性。使用 CRISPR/Cas9 基因编辑系统，我们生成了针对 DmGluRA 上 Homer 结合位点的靶向氨基酸替换，以防止 Homer 和 DmGluRA 蛋白结合。我们发现，DmGluRA 上的保守脯氨酸丰富 PPXXF 序列的缺失减少了 Homer/DmGluRA 关联，并显著减少了睡眠时间。因此，我们在 Drosophila 中鉴定了一种突触可塑性的保守机制，并证明 Homer 与 DmGluRA 的相互作用对于促进睡眠是必需的。
