Morin Pier, Storey Kenneth B
Institute of Biochemistry and Department of Chemistry, College of Natural Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6.
Arch Biochem Biophys. 2007 May 1;461(1):59-65. doi: 10.1016/j.abb.2007.01.035. Epub 2007 Feb 23.
Mammalian hibernation is characterized by prolonged torpor bouts interspersed by brief arousal periods. Adequate antioxidant defenses are needed both to sustain cell viability over weeks of deep torpor and to defend against high rates of oxyradical formation associated with massive oxygen-based thermogenesis during arousal. The present study shows that up-regulation of peroxiredoxins contributes to antioxidant defense during torpor in thirteen-lined ground squirrels, Spermophilus tridecemlineatus. Expression levels of three isozymes of the 2-Cys peroxiredoxin (Prdx) family were quantified by Western blotting, the results showing 4.0- and 12.9-fold increases in Prdx1 protein in brown adipose tissue (BAT) and heart, respectively, during hibernation compared with euthermia. Comparable increases in Prdx2 were 2.4- and 3.7-fold whereas Prdx3 rose by 3.1-fold in heart of torpid animals. Total 2-Cys peroxiredoxin enzymatic activity also rose during hibernation by 1.5-fold in heart and 3.5-fold in BAT. Furthermore, RT-PCR showed that prdx2 mRNA levels increased by 1.7- and 3.7-fold in BAT and heart, respectively, during hibernation. A partial nucleotide sequence of prdx2 from ground squirrels was obtained by PCR amplification, the deduced amino acid sequence showing 96-97% identity with Prdx2 from other mammals. Some unique amino acid substitutions were identified that might contribute to stabilizing Prdx2 conformation at the near 0 degrees C body temperatures during torpor.
哺乳动物的冬眠特征是长时间的蛰伏期，其间穿插着短暂的觉醒期。在深度蛰伏的数周内维持细胞活力以及抵御觉醒期间与大量基于氧气的产热相关的高氧自由基形成速率，都需要足够的抗氧化防御机制。本研究表明，过氧化物还原酶的上调有助于十三条纹地松鼠（Spermophilus tridecemlineatus）蛰伏期间的抗氧化防御。通过蛋白质印迹法对2-半胱氨酸过氧化物还原酶（Prdx）家族的三种同工酶的表达水平进行了定量分析，结果显示，与正常体温时相比，冬眠期间棕色脂肪组织（BAT）和心脏中Prdx1蛋白分别增加了4.0倍和12.9倍。Prdx2在BAT和心脏中的相应增加分别为2.4倍和3.7倍，而蛰伏动物心脏中的Prdx3增加了3.1倍。冬眠期间，心脏中2-半胱氨酸过氧化物还原酶的总酶活性也增加了1.5倍，BAT中增加了3.5倍。此外，逆转录-聚合酶链反应（RT-PCR）显示，冬眠期间BAT和心脏中prdx2 mRNA水平分别增加了1.7倍和3.7倍。通过聚合酶链反应（PCR）扩增获得了地松鼠prdx2的部分核苷酸序列，推导的氨基酸序列与其他哺乳动物的Prdx2显示出96-97%的同一性。还鉴定出了一些独特的氨基酸取代，这些取代可能有助于在蛰伏期间接近0摄氏度的体温下稳定Prdx2的构象。
