Nostramo et al. identify a potential role for two novel RNA-protein granules, the P-body and stress granule, in the maintenance of normal protein homeostasis. These cytoplasmic granules are members of an ever-growing family of membraneless organelles in eukaryotic cells... The eukaryotic cell is highly compartmentalized, and contains a variety of both membrane-bound and membraneless organelles. The latter include the cytoplasmic ribonucleoprotein (RNP) granules, known as the processing body (P-body) and the stress granule. These RNP structures are thought to be involved in the storage of particular mRNAs during periods of stress. Here, we find that a mutant lacking both P-bodies and stress granules exhibits phenotypes suggesting that these structures also have a role in the maintenance of protein homeostasis. In particular, there was an increased occurrence of specific protein quality control (PQC) compartments in this mutant, an observation that is consistent with there being an elevated level of protein misfolding. These compartments normally house soluble misfolded proteins and allow the cell to sequester these polypeptides away from the remaining cellular milieu. Moreover, specific proteins that are normally targeted to both P-bodies and stress granules were found to instead associate with these PQC compartments in this granuleless mutant. This observation is interesting as our data indicate that this association occurs specifically in cells that have been subjected to an elevated level of proteotoxic stress. Altogether, the results here are consistent with P-bodies and stress granules having a role in normal protein homeostasis in eukaryotic cells.

中文翻译：

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深入了解 P 体和应激颗粒在蛋白质质量控​​制中的作用。

诺斯特拉莫等人。确定了两种新型 RNA 蛋白质颗粒（P 体和应激颗粒）在维持正常蛋白质稳态中的潜在作用。这些细胞质颗粒是真核细胞中不断增长的无膜细胞器家族的成员……真核细胞高度区室化，包含多种膜结合和无膜细胞器。后者包括细胞质核糖核蛋白（RNP）颗粒，称为处理体（P-体）和应激颗粒。这些 RNP 结构被认为参与应激期间特定 mRNA 的储存。在这里，我们发现缺乏 P 体和应激颗粒的突变体表现出的表型表明这些结构在维持蛋白质稳态中也发挥着作用。特别是，该突变体中特定蛋白质质量控​​制（PQC）区室的出现次数增加，这一观察结果与蛋白质错误折叠水平升高一致。这些区室通常容纳可溶性错误折叠蛋白质，并允许细胞将这些多肽与剩余的细胞环境隔离开。此外，在这种无颗粒突变体中，通常针对 P 体和应激颗粒的特定蛋白质被发现与这些 PQC 区室相关。这一观察结果很有趣，因为我们的数据表明这种关联特别发生在受到蛋白毒性应激水平升高的细胞中。总而言之，这里的结果与 P 体和应激颗粒在真核细胞正常蛋白质稳态中发挥作用是一致的。