Lepock J R, Cheng K H, Al-Qysi H, Kruuv J
Can J Biochem Cell Biol. 1983 Jun;61(6):421-7. doi: 10.1139/o83-057.
Exposure of mammalian cells to hyperthermic temperatures (ca. 41-45 degrees C) appears to act as a direct or triggering effect to produce some later response such as cell death, thermotolerance, or heat-shock protein synthesis. The high activation energy of cell killing indicates that the direct effect of hyperthermia might be a thermotropic transition in some cellular component, for this particular response. Both hyperthermic survival and growth data imply that the temperature for the onset of hyperthermic cell killing is 40-41.5 degrees C for Chinese hamster lung V79 cells. Studies using the electron spin resonance label 2,2-dimethyl-5-dodecyl-5-methyloxazolidine-N-oxide and the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene show the existence of lipid transitions at approximately 7-8 and 23-36 degrees C (or a broad transition between these temperatures) in mitochondria and whole cell homogenates, that correlate well with changes in growth and hypothermic killing. No lipid transition was detected near 40-41.5 degrees C that could correlate with hyperthermic killing in either mitochondrial or plasma membranes, but measurements of intrinsic protein fluorescence and protein fluorophore to trans-paranaric acid energy transfer demonstrate the existence of an irreversible transition in protein structure or arrangement above ca. 40 degrees C in both mitochondrial and plasma membranes. This transition is due to protein rearrangement and (or) unfolding such that there is increased exposure of protein tryptophan and tyrosine residues to polar groups and to paranaric acid. The strength of the transition implies that a significant fraction of total membrane protein is involved in this transition, which may be analogous to the heat-induced denaturation of water-soluble proteins. This alteration in membrane structure above ca. 40 degrees C could cause many of the observed changes in plasma membrane and mitochondrial function, which may further be involved in cellular responses to hyperthermia.
将哺乳动物细胞暴露于高温（约41 - 45摄氏度）似乎会产生直接或触发效应，从而引发一些后续反应，如细胞死亡、热耐受性或热休克蛋白合成。细胞杀伤的高活化能表明，高温的直接效应可能是某些细胞成分发生热致转变，从而引发这种特定反应。高温存活和生长数据均表明，中国仓鼠肺V79细胞发生高温细胞杀伤的起始温度为40 - 41.5摄氏度。使用电子自旋共振标记2,2 - 二甲基 - 5 - 十二烷基 - 5 - 甲基恶唑烷 - N - 氧化物和荧光探针1,6 - 二苯基 - 1,3,5 - 己三烯进行的研究表明，线粒体和全细胞匀浆中分别在约7 - 8摄氏度和23 - 36摄氏度（或这两个温度之间的宽泛转变）存在脂质转变，这与生长和低温杀伤的变化密切相关。在40 - 41.5摄氏度附近未检测到与线粒体或质膜高温杀伤相关的脂质转变，但对内在蛋白荧光以及蛋白荧光团到反式对硝基苯甲酸能量转移的测量表明，线粒体和质膜中在约40摄氏度以上存在蛋白质结构或排列的不可逆转变。这种转变是由于蛋白质重排和（或）展开，使得蛋白质色氨酸和酪氨酸残基更多地暴露于极性基团和对硝基苯甲酸。该转变的强度表明，总膜蛋白中有很大一部分参与了此转变，这可能类似于水溶性蛋白的热诱导变性。约40摄氏度以上膜结构的这种改变可能会导致质膜和线粒体功能出现许多观察到的变化，进而可能参与细胞对高温的反应。
