Blanton R E, Licate L S
Department of Medicine, Case Western Reserve University, Cleveland.
Mol Biochem Parasitol. 1992 Apr;51(2):201-8. doi: 10.1016/0166-6851(92)90070-z.
Soon after infecting a mammalian host, cercariae of Schistosoma mansoni rapidly undergo a series of morphologic and biochemical adaptations associated with transformation to their next developmental stage, the schistosomulum. Few of these changes are associated with alterations in gene expression except for an apparent increase in protein synthesis. By pulse-labeling, we demonstrate that there is a gradual rise in methionine incorporation after transformation, and that the rise is not due to increasing amino acid uptake or increasing protein stability. This pattern of protein synthesis did not result from a general increase in transcription of mRNA. There was likewise no evidence of a rise in the availability of selected rate limiting components of the translational machinery such as rRNA or elongation factor 1 alpha as a mechanism for increasing levels of translation. Transcription of HSP 70 appears to be induced in both cercariae and schistosomula, though translation of this message was not detected. A comparison between the level of in vivo synthesis of proteins and the level of their corresponding mRNAs suggests that following transformation of cercariae to schistosomula the translation of most mRNAs is blocked and that this block is gradually reversed during the first 24 h.
曼氏血吸虫尾蚴感染哺乳动物宿主后不久，会迅速经历一系列形态和生化适应过程，以转变为下一发育阶段——童虫。除了蛋白质合成明显增加外，这些变化中很少与基因表达改变相关。通过脉冲标记，我们证明转变后蛋氨酸掺入量逐渐增加，且这种增加并非由于氨基酸摄取增加或蛋白质稳定性增加。这种蛋白质合成模式并非由mRNA转录普遍增加导致。同样没有证据表明翻译机制中选定的限速成分（如rRNA或延伸因子1α）的可用性增加是翻译水平提高的机制。HSP 70的转录似乎在尾蚴和童虫中均被诱导，尽管未检测到该信息的翻译。蛋白质体内合成水平与其相应mRNA水平的比较表明，尾蚴转变为童虫后，大多数mRNA的翻译被阻断，且这种阻断在最初24小时内逐渐逆转。
