Schumpert Charles A, Anderson Craig, Dudycha Jeffry L, Patel Rekha C
Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
Aging (Albany NY). 2016 Feb;8(2):402-17. doi: 10.18632/aging.100909.
The ability to appropriately respond to proteotoxic stimuli is a major determinant of longevity and involves induction of various heat shock response (HSR) genes, which are essential to cope with cellular and organismal insults throughout lifespan. The activity of NAD+-dependent deacetylase Sir2, originally discovered in yeast, is known to be essential for effective HSR and longevity. Our previous work on HSR inDaphnia pulicaria indicated a drastic reduction of the HSR in older organisms. In this report we investigate the role of Sir2 in regulating HSR during the lifespan of D. pulicaria. We cloned Daphnia Sir2 open reading frame (ORF) to characterize the enzyme activity and confirmed that the overall function of Sir2 was conserved in Daphnia. The Sir2 mRNA levels increased while the enzyme activity declined with age and considering that Sir2 activity regulates HSR, this explains the previously observed age-dependent decline in HSR. Finally, we tested the effect of Sir2 knockdown throughout adult life by using our new RNA interference (RNAi) method by feeding. Sir2 knockdown severely reduced both the median lifespan as well as significantly increased mortality following heat shock. Our study provides the first characterization and functional study of Daphnia Sir2.
对蛋白质毒性刺激做出适当反应的能力是寿命的一个主要决定因素，涉及多种热休克反应（HSR）基因的诱导，这些基因对于在整个生命周期中应对细胞和机体损伤至关重要。NAD+依赖的脱乙酰酶Sir2的活性最初在酵母中被发现，已知其对有效的热休克反应和寿命至关重要。我们之前关于蚤状溞热休克反应的研究表明，老年生物的热休克反应急剧降低。在本报告中，我们研究了Sir2在蚤状溞生命周期中调节热休克反应的作用。我们克隆了蚤状溞Sir2开放阅读框（ORF）以表征酶活性，并证实Sir2的整体功能在蚤状溞中是保守的。Sir2 mRNA水平随年龄增长而增加，而酶活性随年龄下降，考虑到Sir2活性调节热休克反应，这解释了之前观察到的热休克反应随年龄的下降。最后，我们通过使用新的喂食RNA干扰（RNAi）方法，测试了成年期敲低Sir2的效果。敲低Sir2严重缩短了平均寿命，并显著增加了热休克后的死亡率。我们的研究首次对蚤状溞Sir2进行了表征和功能研究。
