2005 Fiscal Year Final Research Report Summary
Investigation of the regulation mechanism of tumor necrosis factor α converting enzyme by type II diacylglycerol kinases
| Project/Area Number |
16570119
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional biochemistry
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| Research Institution | Sapporo Medical University |
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Principal Investigator |
IMAI Shin-ichi Sapporo Medical University, School of Medicine, Instructor, 医学部, 助手 (20213209)
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| Project Period (FY) |
2004 – 2005
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| Keywords | diacylglyicerol kinase / diacylglyicerol / phosphatidic acid / isozyme / PH domain / tyrosine phosphorylation / oxidative stress |
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| Research Abstract |
Diacylglycerol kinase (DGK) plays an important role in signal transduction through modulating the balance between two signaling lipids, diacylglycerol and phosphatidic acid. We identified a tenth member of the DGK family designated DGKκ. The κ-isozyme (1271 amino acids, calculated molecular mass = 142 kDa) contains a pleckstrin homology domain, two cysteine-rich zinc finger-like structures and a separated catalytic region as have been found commonly in the type II isozymes previously cloned (DGKδ and DGKη). The new DGK isozyme has additionally 33 tandem repeats of Glu-Pro-Ala-Pro at the N terminus. Reverse transcriptase-PCR showed that the DGKκ mRNA is most abundant in the testis, and to a lesser extent in the placenta. DGKκ, when expressed in HEK293 cells, was persistently localized at the plasma membrane even in the absence of cell stimuli. Deletion analysis revealed that the short C-terminal sequence (amino acid residues 1199-1268) is necessary and sufficient for the plasma membrane localization. Interestingly, DGKκ, but not other type II DGKs, was specifically tyrosine-phosphorylated at Tyr-78 through the Src family kinase pathway and in H_2O_2-treated cells. Moreover, H_2O_2 selectively inhibited DGKκ activity in a Src family kinase-independent manner, suggesting that the isozyme changes the balance of signaling lipids in the plasma membrane in response to oxidative stress. The expression patterns, subcellular distribution, and regulatory mechanisms of DGKκ are distinct from those of DGKδ and DGKη despite high structural similarity, suggesting unique functions of the individual type II isozymes.
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