Kampinga H H, Brunsting J F, Stege G J, Burgman P W, Konings A W
Department of Radiobiology, University of Groningen, The Netherlands.
Exp Cell Res. 1995 Aug;219(2):536-46. doi: 10.1006/excr.1995.1262.
Thermotolerance (TT) induced by sodium arsenite (A-TT: 100 microM, 1 h, 37 degrees C) was compared to heat-induced thermotolerance (H-TT: 15 min, 44 degrees C) using HeLa S3 cells. All four pretreatments led to comparable levels of thermotolerance and also induced resistance to arsenite-, ethanol-, and diamide-induced toxicity (clonogenic ability). Stress-induced expression of the major heat shock proteins (hsp27, hsc70(p73), hsp70(p72), and hsp90) was generally highest in H-TT cells and lowest in A-TT cells. Interestingly, the four types of TT cells showed distinct differences in certain aspects of resistance against thermal protein damage. Thermal protein denaturation and aggregation determined in isolated cellular membrane fractions was found to be attenuated when they were isolated from H-TT and A-TT cells but not when isolated from E-TT and D-TT cells. The heat resistance in the proteins of the membrane fraction corresponded with elevated levels of hsp70(p72) associated with the isolated membrane fractions. In the nuclear fraction, only marginal (not significant) attenuation of the formation of protein aggregates (as determined by TX-100 (in)solubility) was observed. However, the postheat recovery from heat-induced protein aggregation in the nucleus was faster in H-TT, E-TT, and D-TT cells, but not in A-TT cells. Despite the fact that elevated levels of hsp27, hsp70(p73), and hsp70(p72) were found in the TX-100 insoluble nuclear fraction derived from all TT cells, no correlation was found with the degree of resistance in terms of the accelerated recovery from nuclear protein aggregation. The only correlation between accelerated recovery from nuclear protein aggregates was that with total cellular levels of hsp27. The data indicate that heat-induced loss of clonogenic ability may be a multitarget rather than a single target event. A threshold of damage may exist in cells after exposure to heat; multiple sets of proteins in (different compartments of) the cell need to be damaged before this threshold is exceeded and the cell dies. As a consequence, stabilization of only one of these sets of proteins is already sufficient to render cells thermotolerant at the clonogenic level.
使用HeLa S3细胞，将亚砷酸钠诱导的热耐受（A-TT：100微摩尔，1小时，37℃）与热诱导的热耐受（H-TT：15分钟，44℃）进行比较。所有四种预处理均导致相当水平的热耐受，并且还诱导了对亚砷酸盐、乙醇和二酰胺诱导的毒性（克隆形成能力）的抗性。应激诱导的主要热休克蛋白（hsp27、hsc70（p73）、hsp70（p72）和hsp90）的表达通常在H-TT细胞中最高，在A-TT细胞中最低。有趣的是，四种类型的热耐受细胞在抗热蛋白损伤的某些方面表现出明显差异。当从H-TT和A-TT细胞中分离时，在分离的细胞膜组分中测定的热蛋白变性和聚集被发现减弱，但从E-TT和D-TT细胞中分离时则没有减弱。膜组分蛋白质的耐热性与与分离的膜组分相关的hsp70（p72）水平升高相对应。在核组分中，仅观察到蛋白质聚集体形成的轻微（不显著）减弱（通过TX-100不溶性测定）。然而，在H-TT、E-TT和D-TT细胞中，核中热诱导的蛋白质聚集后的热恢复更快，而在A-TT细胞中则不然。尽管在源自所有热耐受细胞的TX-100不溶性核组分中发现hsp27、hsp70（p73）和hsp70（p72）水平升高，但在从核蛋白聚集加速恢复方面未发现与抗性程度相关。从核蛋白聚集体加速恢复之间的唯一相关性是与hsp27的总细胞水平相关。数据表明，热诱导的克隆形成能力丧失可能是多靶点而非单靶点事件。细胞在受热后可能存在损伤阈值；在超过该阈值且细胞死亡之前，细胞（不同区室中的）多组蛋白质需要被损伤。因此，仅稳定这些蛋白质组中的一组就足以使细胞在克隆形成水平上具有热耐受性。
