Previous data suggest the existence of discrete pools of inositol lipids, which are components of a nuclear phosphoinositide (PI) cycle. However, it is not known whether the contents of these pools are regulated during cell proliferation. In the present study we demonstrate that the mass levels of three important constituents of the nuclear PI cycle are regulated during the cell cycle. Radioactive label incorporation into PtdIns(4,5)P2 was seen to increase dramatically as synchronized cells entered S-phase. This did not coincide with any significant changes in the nuclear mass levels of this lipid, suggesting that the rate of turnover of this molecule was increased. Levels of PtdIns4P, the major substrate for PtdIns(4,5)P2 production by Type I PtdInsP kinases (PIPkins), were regulated during the cell cycle and indicated a complex relationship between these two lipids. An alternative substrate for PtdIns(4,5)P2, PtdIns5P, phosphorylated by Type II PIPkins, was present in nuclei at much smaller amounts than the PtdIns4P, and thus is unlikely to contribute significantly to PtdIns(4,5)P2 turnover. However, a large increase in nuclear PtdIns5P mass was observed when murine erythroleukaemia cells are in G1, and this could represent a potential pool of nuclear inositol lipid that has a specific signalling role. Analysis of extracted lipid fractions indicated the absence of any PtdIns3P in these nuclei.
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August 2001
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Research Article|
July 25 2001
Inositol lipids are regulated during cell cycle progression in the nuclei of murine erythroleukaemia cells
Jonathan H. CLARKE;
Jonathan H. CLARKE
∗Department of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
†Department of Pharmacology, Cambridge University, Tennis Court Road, Cambridge CB2 1QJ, U.K.
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Andrew J. LETCHER;
Andrew J. LETCHER
†Department of Pharmacology, Cambridge University, Tennis Court Road, Cambridge CB2 1QJ, U.K.
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Clive S. D'SANTOS;
Clive S. D'SANTOS
∗Department of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Jonathan R. HALSTEAD;
Jonathan R. HALSTEAD
∗Department of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Robin F. IRVINE;
Robin F. IRVINE
†Department of Pharmacology, Cambridge University, Tennis Court Road, Cambridge CB2 1QJ, U.K.
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Nullin DIVECHA
Nullin DIVECHA
1
∗Department of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
1To whom correspondence should be addressed (e-mail ndivecha@nki.nl).
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Publisher: Portland Press Ltd
Received:
March 22 2001
Revision Received:
May 11 2001
Accepted:
May 23 2001
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2001
2001
Biochem J (2001) 357 (3): 905–910.
Article history
Received:
March 22 2001
Revision Received:
May 11 2001
Accepted:
May 23 2001
Citation
Jonathan H. CLARKE, Andrew J. LETCHER, Clive S. D'SANTOS, Jonathan R. HALSTEAD, Robin F. IRVINE, Nullin DIVECHA; Inositol lipids are regulated during cell cycle progression in the nuclei of murine erythroleukaemia cells. Biochem J 1 August 2001; 357 (3): 905–910. doi: https://doi.org/10.1042/bj3570905
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