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 an in vitro model, 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 of PI5P4K B-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.
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Research Article|
July 12 2016
Nuclear localizations of phosphatidylinositol 5-phosphate 4-kinases α and β are dynamic and independently regulated during starvation-induced stress
Alaa Droubi;
*Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
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Simon J. Bulley;
*Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
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Jonathan H. Clarke;
Jonathan H. Clarke
*Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
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Robin F. Irvine
Robin F. Irvine
4
*Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
4To whom correspondence should be addressed (email rfi20@cam.ac.uk).
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Publisher: Portland Press Ltd
Received:
December 17 2015
Revision Received:
May 14 2016
Accepted:
May 16 2016
Accepted Manuscript online:
May 16 2016
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society
2016
Biochem J (2016) 473 (14): 2155–2163.
Article history
Received:
December 17 2015
Revision Received:
May 14 2016
Accepted:
May 16 2016
Accepted Manuscript online:
May 16 2016
Citation
Alaa Droubi, Simon J. Bulley, Jonathan H. Clarke, Robin F. Irvine; Nuclear localizations of phosphatidylinositol 5-phosphate 4-kinases α and β are dynamic and independently regulated during starvation-induced stress. Biochem J 15 July 2016; 473 (14): 2155–2163. doi: https://doi.org/10.1042/BCJ20160380
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