Nuclear Diacylglycerol Kinase-θ is Activated in Response to α-Thrombin

Lisa Bregoli, Joseph J. Baldassare, Daniel M. Raben

Research output: Contribution to journalArticle

Abstract

Currently, there is substantial evidence that nuclear lipid metabolism plays a critical role in a number of signal transduction cascades. Previous work from our laboratory showed that stimulation of quiescent fibroblasts with α-thrombin leads to the production of two lipid second messengers in the nucleus: an increase in nuclear diacylglycerol mass and an activation of phospholipase D, which catalyzes the hydrolysis of phosphatidylcholine to generate phosphatidic acid. Diacylglycerol kinase (DGK) catalyzes the conversion of diacylglycerol to phosphatidic acid, making it an attractive candidate for a signal transduction component. There is substantial evidence that this activity is indeed regulated in a number of signaling cascades (reviewed by van Blitterswijk, W. J., and Houssa, B. (1999) Chem. Phys. Lipids 98, 95-108). In this report, we show that the addition of α-thrombin to quiescent IIC9 fibroblasts results in an increase in nuclear DGK activity. The examination of nuclei isolated from quiescent IIC9 cells indicates that DGK-θ and DGK-δ are both present. We took advantage of the previous observations that phosphatidylserine inhibits DGK-δ (reviewed by Sakane, F., Imai, S., Kai, M., Wada, I., and Kanoh, H. (1996) J. Biol. Chem. 271, 8394-8401), and constitutively active RhoA inhibits DGK-θ (reviewed by Houssa, B., de Widt, J., Kranenburg, O., Moolenaar, W. H., and van Blitterswijk, W. J. (1999) J. Biol. Chem. 274, 6820-6822) to identify the activity induced by α-thrombin. Constitutively active RhoA inhibited the nuclear stimulated activity, whereas phosphatidylserine did not have an inhibitory effect. In addition, a monoclonal anti-DGK-θ antibody inhibited the α-thrombin-stimulated nuclear activity in vitro. These results demonstrate that DGK-θ is the isoform responsive to α-thrombin stimulation. Western blot and immunofluorescence microscopy analyses showed that α-thrombin induced the translocation of DGK-θ to the nucleus, implicating that this translocation is at least partly responsible for the increased nuclear activity. Taken together, these data are the first to demonstrate an agonist-induced activity of nuclear DGK-θ activity and a nuclear localization of DGK-δ.

Original languageEnglish (US)
Pages (from-to)23288-23295
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number26
DOIs
StatePublished - Jun 29 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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