| Project/Area Number |
04671477
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
内分泌・代謝学
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| Research Institution | Osaka University |
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Principal Investigator |
KAWAMORI Ryuzo First Dep. Med. Osaka University, Associate Professor, 医学部・第一内科, 講師 (00116021)
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| Co-Investigator(Kenkyū-buntansha) |
IMANO Eiichi Medical Staff, 医学部・第一内科, 医員
WATARAI Takao Medical Staff, 医学部・第一内科, 医員
IWAMA Norimichi Medical Staff, 医学部・第一内科, 医員
MORISHIMA Toyohiko Assistant Professor, 医学部・第一内科, 助手 (50221635)
KYAMASAKI Yoshimitsu Assistant Professor, 医学部・第一内科, 助手 (40201834)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1992: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Insulin receptor / Antophosphorylation / Phospho-tyrasine phosphatise (PTPase) / Baculovirus / バキュロウイルス |
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| Research Abstract |
To elucidate the mechanisms of the decreased autophophorylation of the insulin receptor in deabetes mellitus, we tried to express PTPase in Sf9 cells and examine the enzimatic property of PTPase.
Constructed expression plasmids, pVL1392-PTP and pVL1393-IR, were transfected to Sf9 cells with AcMNPV viral DNA by calcium phosphate precipitation. Recombinant viruses were screened with plaque hybridization method. Recombinant viruses were infected to Sf9 cells and PTPase were purified with WGA-agarose column.
To examine whether PTPase dephosphorylated the insulin receptor, PTPase was incubated with the ^<32>P-autophosphorylated insulin receptor of the rat liver. Ninety-five kD insulin receptor beta subunit was dephosphorylated by PTPase, suggesting that the autophosphorylated insulin receptor is a substrate for the PTPase in Vitro.
To examine whether increased PTPase inhibited autophosphorylation of the insulin receptor, PTPase was overexpressed in HepG2 cells using pcDL-SR alpha expression vector. Autophosphorylation of the insulin receptor from HepG2 cells in which PTPase was overexpressed was decreased compared with that of the insulin receptor from HepG2 cells to which only pcDL-SR alpha vector was transfected. This suggested that the PTPase dephosphorylates the insulin receptor in vivo.
To examine whether the expression of the PTPase in the liver of diabetic rats was increased, the PTPase mRNA of the liver and spleen was measured with Norther blot hybridization method. Contrary to our expectation, the PTPase mRNA in diabetic rats was not increased. These data suggested that the PTPase activity is regulated at the postiranslational step.
This research elucidated that the PTPase dephosphorylates the insulin receptor, and increased PTPase activity in the diabetic rats causes insulin resistance.
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