Nuclear localizations of phosphatidylinositol 5-phosphate 4-kinases a and ß are dynamic and independently regulated during starvation-induced stress.
Nuclear localizations of phosphatidylinositol 5-phosphate 4-kinases a and ß are dynamic and independently regulated during starvation-induced stress.
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磷脂酰肌醇 5-磷酸 4-激酶 a 和 α 的核定位在饥饿诱导的应激过程中是动态且独立调节的。
DOI：
10.1042/bcj20160380
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Droubi A
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文献类型：
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作者：
Droubi A
鸡B细胞系DT 40具有磷脂酰肌醇5-磷酸4-激酶（PI 5 P4 K）的两种亚型，α和β，它们可能以专性同源和异源二聚体的混合物形式存在。先前的工作使我们推测β亚型的重要作用可能是将更活跃的PI 5 P4 K α亚型靶向细胞核。在本研究中，我们通过在存在或不存在PI 5 P4 K β稳定或急性耗竭的情况下用荧光染料对PI 5 P4 K进行基因组标记来扩展这项工作。与我们最初的假设一致，我们发现当PI 5 P4 K β从细胞中稳定缺失时，PI 5 P4 K α主要（可能完全）在细胞质中。相反，当PI 5 P4 K β在1 h内被诱导性去除时，即使经过多次细胞分裂，PI 5 P4 K α仍保持其在细胞质和细胞核之间约50：50的野生型分布。这使我们推测PI 5 P4 K α与染色质相关。我们还发现，当细胞处于指数生长期时，PI 5 P4 K β主要位于细胞质中，但当细胞生长进入稳定期或血清饥饿时，PI 5 P4 K β易位到细胞核中。再一次，这并不伴随着PI 5 P4 K α定位的变化，我们使用体外模型表明，这是可能的，因为两种亚型之间的二聚化是动态的。鉴于营养剥夺后PI 5 P4 K β的这种变化，我们探索了暴露于这种应激的PI 5 P4 KB-null细胞的表型，发现它们可以比野生型对应物维持更大程度的营养剥夺，这可能是自噬上调的结果。
The chicken B-cell line DT40 has two isoforms of phosphatidylinositol 5-phosphate 4-kinase (PI5P4K), α and β, which are likely to exist as a mixture of obligate homo- and hetero-dimers. Previous work has led us to speculate that an important role of the β isoform may be to target the more active PI5P4Kα isoform to the nucleus. In the present study we expand upon that work by genomically tagging the PI5P4Ks with fluorochromes in the presence or absence of stable or acute depletions of PI5P4Kβ. Consistent with our original hypothesis we find that PI5P4Kα is predominantly (possible entirely) cytoplasmic when PI5P4Kβ is stably deleted from cells. In contrast, when PI5P4Kβ is inducibly removed within 1 h PI5P4Kα retains its wild-type distribution of approximately 50:50 between cytoplasm and nucleus even through a number of cell divisions. This leads us to speculate that PI5P4Kα is chromatin-associated. We also find that when cells are in the exponential phase of growth PI5P4Kβ is primarily cytoplasmic but translocates to the nucleus upon growth into the stationary phase or upon serum starvation. Once again this is not accompanied by a change in PI5P4Kα localization and we show, using anin vitromodel, that this is possible because the dimerization between the two isoforms is dynamic. Given this shift in PI5P4Kβ upon nutrient deprivation we explore the phenotype ofPI5P4KB-null cells exposed to this stress and find that they can sustain a greater degree of nutrient deprivation than their wild-type counterparts possibly as a result of up-regulation of autophagy.