Endolysosomal defects in neurons are central to the pathogenesis of prion and other neurodegenerative disorders. In prion disease, prion oligomers traffic through the multivesicular body (MVB) and are routed for degradation in lysosomes or for release in exosomes, yet how prions impact proteostatic pathways is unclear. We found that prion-affected human and mouse brain showed a marked reduction in Hrs and STAM1 (ESCRT-0), which route ubiquitinated membrane proteins from early endosomes into MVBs. To determine how the reduction in ESCRT-0 impacts prion conversion and cellular toxicity in vivo, we prion-challenged conditional knockout mice (male and female) having Hrs deleted from neurons, astrocytes, or microglia. The neuronal, but not astrocytic or microglial, Hrs-depleted mice showed a shortened survival and an acceleration in synaptic derangements, including an accumulation of ubiquitinated proteins, deregulation of phosphorylated AMPA and metabotropic glutamate receptors, and profoundly altered synaptic structure, all of which occurred later in the prion-infected control mice. Finally, we found that neuronal Hrs (nHrs) depletion increased surface levels of the cellular prion protein, PrP^C, which may contribute to the rapidly advancing disease through neurotoxic signaling. Taken together, the reduced Hrs in the prion-affected brain hampers ubiquitinated protein clearance at the synapse, exacerbates postsynaptic glutamate receptor deregulation, and accelerates neurodegeneration.

SIGNIFICANCE STATEMENT Prion diseases are rapidly progressive neurodegenerative disorders characterized by prion aggregate spread through the central nervous system. Early disease features include ubiquitinated protein accumulation and synapse loss. Here, we investigate how prion aggregates alter ubiquitinated protein clearance pathways (ESCRT) in mouse and human prion-infected brain, discovering a marked reduction in Hrs. Using a prion-infection mouse model with neuronal Hrs (nHrs) depleted, we show that low neuronal Hrs is detrimental and markedly shortens survival time while accelerating synaptic derangements, including ubiquitinated protein accumulation, indicating that Hrs loss exacerbates prion disease progression. Additionally, Hrs depletion increases the surface distribution of prion protein (PrP^C), linked to aggregate-induced neurotoxic signaling, suggesting that Hrs loss in prion disease accelerates disease through enhancing PrP^C-mediated neurotoxic signaling.

神经元内溶酶体缺陷是朊病毒和其他神经退行性疾病发病机制的核心。在朊病毒疾病中，朊病毒寡聚体穿过多泡体（MVB）并在溶酶体中降解或在外泌体中释放，但朊病毒如何影响蛋白抑制途径尚不清楚。我们发现，受朊病毒影响的人和小鼠大脑中的 Hrs 和 STAM1 (ESCRT-0) 显着减少，这些蛋白将泛素化膜蛋白从早期内体传递到 MVB。为了确定ESCRT-0的减少如何影响体内朊病毒转化和细胞毒性，我们对从神经元、星形胶质细胞或小胶质细胞中删除了Hrs的朊病毒条件敲除小鼠（雄性和雌性）进行了攻击。神经元（而非星形胶质细胞或小胶质细胞）Hrs 耗尽的小鼠表现出生存期缩短和突触紊乱加速，包括泛素化蛋白的积累、磷酸化 AMPA 和代谢型谷氨酸受体的失调以及突触结构的深刻改变，所有这些都发生了后来在感染朊病毒的对照小鼠中。最后，我们发现神经元小时（nHrs）消耗增加了细胞朊病毒蛋白^PrPC的表面水平，这可能通过神经毒性信号传导导致疾病快速进展。总而言之，受朊病毒影响的大脑中小时数的减少阻碍了突触处泛素化蛋白的清除，加剧了突触后谷氨酸受体的失调，并加速了神经变性。

意义声明朊病毒病是一种快速进展的神经退行性疾病，其特征是朊病毒聚集体通过中枢神经系统扩散。早期疾病特征包括泛素化蛋白积累和突触丢失。在这里，我们研究了朊病毒聚集体如何改变小鼠和人类感染朊病毒的大脑中的泛素化蛋白清除途径（ESCRT），发现 Hrs 显着减少。使用神经元 Hrs (nHrs) 耗尽的朊病毒感染小鼠模型，我们发现低神经元 Hrs 是有害的，会显着缩短生存时间，同时加速突触紊乱，包括泛素化蛋白积累，表明 Hrs 损失会加剧朊病毒疾病的进展。此外，Hrs 消耗增加了朊病毒蛋白 (PrP ^C ) 的表面分布，与聚集诱导的神经毒性信号传导有关，表明朊病毒疾病中 Hrs 的缺失通过增强 PrP ^C介导的神经毒性信号传导而加速疾病的发生。