Quiescence is a cellular strategy for maintaining somatic stem cells in a specific niche in a low metabolic state without senescence for a long period of time. During development, neural stem cells (NSCs) actively proliferate and self‐renew, and their progeny differentiate into both neurons and glial cells to form mature brain tissues. On the other hand, most NSCs in the adult brain are quiescent and arrested in G0/G1 phase of the cell cycle. Quiescence is essential in order to avoid the precocious exhaustion of NSCs, ensuring a sustainable source of available stem cells in the brain throughout the lifespan. After receiving activation signals, quiescent NSCs reenter the cell cycle and generate new neurons. This switching between quiescence and proliferation is tightly regulated by diverse signaling pathways. Recent studies suggest significant involvement of cellular proteostasis (homeostasis of the proteome) in the quiescent state of NSCs. Proteostasis is the result of integrated regulation of protein synthesis, folding, and degradation. In this review, we discuss regulation of quiescence by multiple signaling pathways, especially bone morphogenetic protein and Notch signaling, and focus on the functional involvement of the lysosome, an organelle governing cellular degradation, in quiescence of adult NSCs.

中文翻译：

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溶酶体和维持成人神经干细胞静止的信号通路

静止是一种细胞策略，可将体干细胞维持在特定的生态位中，处于低代谢状态，且长时间不衰老。在发育过程中，神经干细胞（NSC）活跃地增殖和自我更新，它们的后代分化为神经元和神经胶质细胞，从而形成成熟的脑组织。另一方面，成年大脑中的大多数NSC都处于静止状态，并停滞在细胞周期的G0 / G1期。为了避免NSC的过早衰竭，确保整个生命周期中大脑中可用干细胞的可持续来源，静态是必不可少的。收到激活信号后，静止的NSC重新进入细胞周期并产生新的神经元。静止和增殖之间的这种切换受到多种信号通路的严格调控。最近的研究表明，细胞蛋白稳态（蛋白质组的稳态）大量参与了NSC的静止状态。蛋白质变形是蛋白质合成，折叠和降解的综合调控的结果。在这篇综述中，我们讨论了通过多种信号通路，特别是骨形态发生蛋白和Notch信号通路对静止的调节，并着重于溶酶体（一种控制细胞降解的细胞器）在成年NSC中的功能参与。