Henle K J, Monson T P, Stone A
Department of Medicine and Physiology/Biophysics, University of Arkansas for Medical Sciences, Little Rock 72205.
J Cell Physiol. 1990 Feb;142(2):372-8. doi: 10.1002/jcp.1041420221.
The cellular heat shock response leads to the enhanced synthesis of a family of heat shock proteins and the development of thermotolerance. In CHO cells, however, heat shock also leads to enhanced synthesis of a 50 kD glycoprotein and elevated activity of N-acetylgalactosaminyltransferase (GalNAcT). In this study we showed increased GalNAcT activity during thermotolerance expression in all of five mammalian cell lines included in the study. However, there was no simple correlation between cellular heat sensitivity of unheated control cells and basal levels of GalNAcT activity, measured toward the same exogenous acceptor apomucin. Although GalNAcT was elevated in thermotolerant cells, GalNAcT activity itself did not exhibit thermotolerance in terms of reduced sensitivity to heat inactivation. The increase in GalNAcT activity after heating was similar in exponentially growing and plateau-phase cultures and was inhibited neither by cycloheximide nor actinomycin D. However, the inhibitors by themselves also increased GalNAcT activity in unheated control cells. Chemical inducers of thermotolerance (arsenite and diamide) increased GalNAcT activity, but the increase was modest when compared to that following hyperthermia. In addition to GalNAcT, two other glycosyltransferases with specificity for O-glycans, alpha 1,2-fucosyltransferase and alpha 2,6-sialyltransferase, also showed increased activity after hyperthermia and during thermotolerance development. Together with previously published data, these results support the hypothesis that heat-induced activation of O-glycan-specific glycosyltransferases plays a physiological role in the cellular heat shock response and in thermotolerance development.
细胞热休克反应会导致一类热休克蛋白的合成增加以及耐热性的形成。然而，在CHO细胞中，热休克还会导致一种50kD糖蛋白的合成增加以及N-乙酰半乳糖胺基转移酶（GalNAcT）的活性升高。在本研究中，我们发现，在所研究的全部五种哺乳动物细胞系中，耐热性表达过程中GalNAcT活性均增加。然而，对于相同的外源性受体脱辅基粘蛋白，未加热的对照细胞的细胞热敏感性与GalNAcT活性的基础水平之间并无简单的相关性。尽管GalNAcT在耐热细胞中升高，但就对热失活的敏感性降低而言，GalNAcT活性本身并未表现出耐热性。加热后GalNAcT活性的增加在指数生长期和平台期培养物中相似，且不受环己酰亚胺或放线菌素D的抑制。然而，这些抑制剂本身也会增加未加热对照细胞中的GalNAcT活性。耐热性的化学诱导剂（亚砷酸盐和二酰胺）会增加GalNAcT活性，但与热疗后的增加相比，增加幅度较小。除了GalNAcT外，另外两种对O-聚糖具有特异性的糖基转移酶，α1,2-岩藻糖基转移酶和α2,6-唾液酸基转移酶，在热疗后以及耐热性形成过程中也表现出活性增加。结合先前发表的数据，这些结果支持了以下假设：热诱导的O-聚糖特异性糖基转移酶激活在细胞热休克反应和耐热性形成中发挥生理作用。
