Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Dr., Saskatoon, SK, S7N 5B4, Canada.
Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
Cell Stress Chaperones. 2018 Nov;23(6):1205-1217. doi: 10.1007/s12192-018-0926-x. Epub 2018 Jun 27.
Freeze tolerance is an adaptive response utilized by the wood frog Rana sylvatica to endure the sub-zero temperatures of winter. Survival of whole body freezing requires wood frogs to trigger cryoprotective mechanisms to deal with potential injuries associated with conversion of 65-70% of total body water into ice, including multiple consequences of ice formation such as cessation of blood flow and cell dehydration caused by water loss into ice masses. To understand how wood frogs defend against these stressors, we measured the expression of proteins known to be involved in the antioxidant defense and protein chaperone stress responses in brain and heart of wood frogs comparing freezing, anoxia, and dehydration stress. Our results showed that most stress proteins were regulated in a tissue- and stress-specific manner. Notably, protein levels of the cytosolic superoxide dismutase (SOD1) were upregulated by 1.37 ± 0.11-fold in frozen brain, whereas the mitochondrial SOD2 isoform rose by 1.38 ± 0.37-fold in the heart during freezing. Catalase protein levels were upregulated by 3.01 ± 0.47-fold in the brain under anoxia stress, but remained unchanged in the heart. Similar context-specific regulatory patterns were also observed for the heat shock protein (Hsp) molecular chaperones. Hsp27 protein was down-regulated in the brain across the three stress conditions, whereas the mitochondrial Hsp60 was upregulated in anoxic brain by 1.73 ± 0.38-fold and by 2.13 ± 0.57-fold in the frozen heart. Overall, our study provides a snapshot of the regulatory expression of stress proteins in wood frogs under harsh environment conditions and shows that they are controlled in a tissue- and stress-specific manner.
抗冻性是林蛙（Rana sylvatica）适应冬季低温的一种适应性反应。全身冷冻的生存需要林蛙触发抗冻保护机制，以应对与总身体水分的 65-70%转化为冰相关的潜在伤害，包括冰晶形成的多个后果，如血流停止和因水分流失到冰体而导致的细胞脱水。为了了解林蛙如何抵御这些压力源，我们测量了在比较冷冻、缺氧和脱水应激时，已知参与抗氧化防御和蛋白质伴侣应激反应的蛋白质在林蛙大脑和心脏中的表达。我们的结果表明，大多数应激蛋白以组织和应激特异性的方式被调节。值得注意的是，在冷冻大脑中，细胞质超氧化物歧化酶（SOD1）的蛋白水平上调了 1.37±0.11 倍，而线粒体 SOD2 同工型在冷冻心脏中上调了 1.38±0.37 倍。在缺氧应激下，大脑中的过氧化氢酶蛋白水平上调了 3.01±0.47 倍，但在心脏中不变。热休克蛋白（Hsp）分子伴侣也观察到类似的上下文特异性调节模式。Hsp27 蛋白在三种应激条件下均在大脑中下调，而线粒体 Hsp60 在缺氧大脑中上调了 1.73±0.38 倍，在冷冻心脏中上调了 2.13±0.57 倍。总的来说，我们的研究提供了林蛙在恶劣环境条件下应激蛋白调节表达的快照，并表明它们以组织和应激特异性的方式被控制。
