Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom.
PLoS One. 2012;7(7):e41975. doi: 10.1371/journal.pone.0041975. Epub 2012 Jul 27.
Dietary restriction (DR) extends lifespan in yeast, worms, flies and mammals, suggesting that it may act via conserved processes. However, the downstream mechanisms by which DR increases lifespan remain unclear. We used a gel based proteomic strategy to identify proteins whose expression was induced by DR in yeast and thus may correlate with longevity. One protein up-regulated by DR was Hsp12, a small heat shock protein induced by various manipulations known to retard ageing. Lifespan extension by growth on 0.5% glucose (DR) was abolished in an hsp12Δ strain, indicating that Hsp12 is essential for the longevity effect of DR. In contrast, deletion of HSP12 had no effect on growth under DR conditions or a variety of environmental stresses, indicating that the effect of Hsp12 on lifespan is not due to increased general stress resistance. Unlike other small heat shock proteins, recombinant Hsp12 displayed negligible in vitro molecular chaperone activity, suggesting that its cellular function does not involve preventing protein aggregation. NMR analysis indicated that Hsp12 is monomeric and intrinsically unfolded in solution, but switches to a 4-helical conformation upon binding to membrane-mimetic SDS micelles. The structure of micelle-bound Hsp12 reported here is consistent with its recently proposed function as a membrane-stabilising 'lipid chaperone'. Taken together, our data suggest that DR-induced Hsp12 expression contributes to lifespan extension, possibly via membrane alterations.
饮食限制（DR）延长了酵母、蠕虫、苍蝇和哺乳动物的寿命，这表明它可能通过保守的过程起作用。然而，DR 延长寿命的下游机制仍不清楚。我们使用基于凝胶的蛋白质组学策略来鉴定在酵母中由 DR 诱导表达的蛋白质，这些蛋白质可能与寿命相关。一种由 DR 上调的蛋白质是 Hsp12，它是一种小的热休克蛋白，由各种已知延缓衰老的操作诱导。在 hsp12Δ 菌株中，生长在 0.5%葡萄糖（DR）上的寿命延长被废除，表明 Hsp12 是 DR 长寿效应所必需的。相比之下，在 DR 条件下或各种环境胁迫下删除 HSP12 对生长没有影响，这表明 Hsp12 对寿命的影响不是由于增强了一般的应激抗性。与其他小热休克蛋白不同，重组 Hsp12 在体外显示出微不足道的分子伴侣活性，这表明其细胞功能不涉及防止蛋白质聚集。NMR 分析表明，Hsp12 在溶液中是单体和无规卷曲的，但在与模拟细胞膜的 SDS 胶束结合时会转变为 4 螺旋构象。这里报道的胶束结合 Hsp12 的结构与其最近提出的作为稳定膜的“脂质伴侣”的功能一致。总之，我们的数据表明，DR 诱导的 Hsp12 表达有助于延长寿命，可能通过改变膜来实现。
