An evaluation of Hsp90 as a mediator of cortical patterning in Tetrahymena
An evaluation of Hsp90 as a mediator of cortical patterning in Tetrahymena
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DOI：
10.1111/j.1550-7408.2001.tb00297.x
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发表时间：
2001-03-01
影响因子：
2.2
通讯作者：
Keeling, PJ
中科院分区：
文献类型：
--
作者：
Frankel, J;Williams, NE;Keeling, PJ
这项研究提出了两个问题：1)Hsp90是否参与四膜虫皮质模式的调节。2)如果是，这一调控中的具体缺陷是否可以归因于Hsp90分子的功能不足。为了回答问题1，我们比较了Hsp90的特异性抑制剂格尔达那霉素对两个四膜虫种梨形毛虫和嗜热毛虫的种群增长和口腔器官发育的影响。我们观察到，格尔达霉素在很低的浓度下抑制了这两个物种的种群增长，并且它对梨形毛虫的口腔模式的影响比对嗜热毛虫的影响要严重得多。这些影响与高温对同一物种的影响是平行的，并对第一个问题提供了初步肯定的答案。为了回答问题2，我们确定了编码Hsp90分子的基因的碱基序列，这些基因在两种四膜虫中都是在高温下诱导的，在四草履虫中也是如此。对两种四膜虫Hsp90分子推导的氨基酸序列进行了广泛的比较分析，结果表明，根据我们目前对Hsp90的了解，这两种蛋白质具有相同的功能。对Hsp90氨基酸序列的系统发育分析表明，这两个四膜虫Hsp90分子从它们最近的共同祖先经历了类似数量的氨基酸替换，这些替换都不对应于该分子的任何已知功能关键区。因此，没有证据表明梨形虫热休克蛋白90分子的功能受损；皮质模式控制中的缺陷更可能是由调节对热休克蛋白90反应的机制缺陷(S)引起的，正如卢瑟福和林德奎斯特的“热休克蛋白90电容器”模型所预期的那样。
This study asks two questions: 1) whether Hsp90 is involved in the regulation of cortical patterning in Tetrahymena. and 2) if it is, whether specific defects in this regulation can he attributed to functional insufficiency of the Hsp90 molecule. To address question 1, we compared the effects of a specific inhibitor of Hsp90, geldanamycin, on population growth and on development of the oral apparatus in two Tetrahymena species, T. pyriformis and T. thermophila. We observed that geldanamycin inhibits population growth in both species at very low concentrations, and that it has far more severe effects on oral patterning in T. pyriformis than in T. thermophila. These effects are parallel to those of high temperature in the same two species, and provide a tentative affirmative answer to the first question. To address question 2, we ascertained the base sequence of the genes that encode the Hsp90 molecules which are induced at high temperatures in both Tetrahymena species, as well as corresponding sequences in Paramecium tetraurelia. Extensive comparative analyses of the deduced amino acid sequences of the Hsp90 molecules of the two Tetrahymena species indicate that on the basis of what we currently know about Hsp90 both proteins are equally likely to be functional. Phylogenetic analyses of Hsp90 amino acid sequences indicate that the two Tetrahymena Hsp90 molecules have undergone a similar number of amino acid substitutions from their most recent common ancestor, with none of these corresponding to any known functionally critical region of the molecule. Thus there is no evidence that the Hsp90 molecule of T. pyriformis is functionally impaired; the flaw in the control of cortical patterning is more likely to be caused by defects in mechanism(s) that mediate the response to Hsp90, as would be expected fr om the "Hsp90 capacitor" model of Rutherford and Lindquist.