Kumar N, Koski G, Harada M, Aikawa M, Zheng H
Department of Immunology, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, MD 21205.
Mol Biochem Parasitol. 1991 Sep;48(1):47-58. doi: 10.1016/0166-6851(91)90163-z.
Induction of heat shock-related stress proteins Pfhsp and Pfgrp, similar in sequence to hsp70 (heat shock protein) and grp78 (glucose-regulated protein), respectively, was studied in culture-derived parasite Plasmodium falciparum. Elevation in temperature from 26 degrees C to 37 degrees C and higher caused significant induction of Pfhsp with a moderate effect on the synthesis of Pfgrp also. Synthesis of Pfgrp, however, was not induced by partial glucose deprivation. On the contrary, lack of glucose in the medium resulted in cessation of protein synthesis in the parasites. Other known inducers of grp synthesis in mammalian cells, i.e., calcium ionophore A23187 and inhibitors of glycosylation (tunicamycin, 2-deoxy glucose) were also without any apparent effect on the synthesis of Pfgrp. Heat shock-induced responses were transient in nature: removal of stress caused repression of these responses. The effect of glucose deprivation was only partially reversible with better recovery if parasites were subjected to glucose starvation at 26 degrees C than at 37 degrees C. Northern blot analysis and in vitro translation of mRNA revealed a parallel increase in the levels of mRNA for Pfhsp upon heat shock. Immuno-gold electron microscopy with cultured parasites revealed nuclear location of Pfhsp and primarily cytoplasmic (probably endoplasmic reticulum) location of Pfgrp. These findings suggest that SDEL (carboxy terminal sequence of Pfgrp) might play a similar role in the cellular localization of Pfgrp as does the sequence KDEL in mammalian cells and HDEL in yeast.
在体外培养的恶性疟原虫中，研究了与热休克蛋白hsp70（热休克蛋白）和grp78（葡萄糖调节蛋白）序列相似的热休克相关应激蛋白Pfhsp和Pfgrp的诱导情况。温度从26℃升高到37℃及更高会显著诱导Pfhsp，对Pfgrp的合成也有一定影响。然而，部分葡萄糖缺乏并不会诱导Pfgrp的合成。相反，培养基中缺乏葡萄糖会导致疟原虫蛋白质合成停止。哺乳动物细胞中其他已知的grp合成诱导剂，即钙离子载体A23187和糖基化抑制剂（衣霉素、2-脱氧葡萄糖）对Pfgrp的合成也没有明显影响。热休克诱导的反应本质上是短暂的：去除应激会导致这些反应受到抑制。如果疟原虫在26℃而非37℃下经历葡萄糖饥饿，葡萄糖缺乏的影响只是部分可逆的，且恢复情况更好。Northern印迹分析和mRNA的体外翻译显示，热休克后Pfhsp的mRNA水平平行增加。对培养的疟原虫进行免疫金电子显微镜观察发现，Pfhsp定位于细胞核，而Pfgrp主要定位于细胞质（可能是内质网）。这些发现表明，SDEL（Pfgrp的羧基末端序列）在Pfgrp的细胞定位中可能发挥与哺乳动物细胞中的KDEL序列和酵母中的HDEL序列类似的作用。
