Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29423, USA.
Biochem J. 2010 Oct 1;431(1):31-8. doi: 10.1042/BJ20100307.
Recent work, especially in the yeast Saccharomyces cerevisiae, has demonstrated that mRNA movement from active translation to cytoplasmic granules, termed mRNA'p-bodies' (processing bodies), occurs in concert with the regulation of translation during cell stress. However, the signals regulating p-body formation are poorly defined. Recent results have demonstrated a function for sphingolipids in regulating translation during heat stress, which led to the current hypothesis that p-bodies may form during heat stress in a sphingolipid-dependent manner. In the present study, we demonstrate that mild-heat-stress-induced formation of p-bodies, as determined by localization of a GFP (green fluorescent protein)-tagged Dcp2p and RFP (red fluorescent protein)-tagged Edc3p to discrete cytoplasmic foci. Sphingoid base synthesis was required for this effect, as inhibition of sphingoid base synthesis attenuated formation of these foci during heat stress. Moreover, treatment of yeast with the exogenous sphingoid bases phyto- and dihydro-sphingosine promoted formation of p-bodies in the absence of heat stress, and the lcb4/lcb5 double-deletion yeast, which accumulates high intracellular levels of sphingoid bases, had large clearly defined p-bodies under non-stress conditions. Functionally, inhibition of sphingolipid synthesis during heat stress did not prevent translation stalling, but extended translation arrest, indicating that sphingolipids mediate translation initiation. These results are consistent with the notion that p-bodies serve not only in mRNA degradation, but also for re-routing transcripts back to active translation, and that sphingolipids play a role in this facet of the heat-stress response. Together, these results demonstrate a critical and novel role for sphingolipids in mediating p-body formation during heat stress.
最近的研究工作表明，尤其是在酵母酿酒酵母中，mRNA 从活跃翻译到细胞质颗粒的运动，称为 mRNA“p 体”（处理体），与细胞应激时翻译的调节同时发生。然而，调节 p 体形成的信号尚未明确。最近的研究结果表明，神经酰胺在热应激期间调节翻译具有功能，这导致了当前的假设，即在热应激期间，p 体可能以神经酰胺依赖性的方式形成。在本研究中，我们通过 GFP（绿色荧光蛋白）标记的 Dcp2p 和 RFP（红色荧光蛋白）标记的 Edc3p 定位到离散的细胞质焦点，证明了轻度热应激诱导的 p 体形成。鞘氨醇碱基合成是这种效应所必需的，因为鞘氨醇碱基合成的抑制削弱了这些焦点在热应激期间的形成。此外，用外源性鞘氨醇碱基植物鞘氨醇和二氢鞘氨醇处理酵母，在没有热应激的情况下促进了 p 体的形成，并且 lcb4/lcb5 双缺失酵母，其积累了高细胞内鞘氨醇碱基水平，在非应激条件下具有大而清晰定义的 p 体。功能上，热应激期间鞘脂合成的抑制并没有阻止翻译停滞，但延长了翻译停顿，表明鞘脂介导翻译起始。这些结果与 p 体不仅在 mRNA 降解中起作用，而且还将转录物重新路由回活跃翻译的观点一致，并且鞘脂在热应激反应的这一方面发挥作用。总之，这些结果表明鞘脂在热应激期间介导 p 体形成中具有关键和新颖的作用。
