| Project/Area Number |
14571062
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Endocrinology
|
|---|
| Research Institution | Nagoya University |
|---|
Principal Investigator |
KAMBE Fukushi Nagoya Univ., Res.Inst.Environ.Med., Assoc.Prof., 環境医学研究所, 助教授 (00211871)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
IMAI Tsuneo Nagoya Univ., School of Med., Lecturer, 医学部, 講師 (80252245)
OHMORI Sachiko Nagoya Univ., Res.Inst.Environ.Med., Res.Associate, 環境医学研究所, 助手 (20233273)
SEO Hisao Nagoya Univ., Res.Inst.Environ.Med., Prof., 環境医学研究所, 教授 (40135380)
舟橋 啓臣 名古屋大学, 医学部, 講師 (50135357)
|
|---|
| Project Period (FY) |
2002 – 2003
|
| Project Status |
Completed (Fiscal Year 2003)
|
| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2003: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2002: ¥1,900,000 (Direct Cost: ¥1,900,000)
|
|---|
| Keywords | Diminuto / DHCR24 / insulin / Akt / Bad / caveolin / ステロイド / ミトコンドリア |
|---|
| Research Abstract |
We demonstrated that the human diminuto gene is overexpressed in benign cortisol-producing adrenocortical adenomas, and that its reduced expression is associated with increased apoptosis of adjacent normal cells. It was then reported that Diminuto catalyzes the last step of cholesterol biosynthesis, the conversion of desmosterol to cholesterol. To explore physiological function of Diminuto in mammalian cells, we investigated proliferation and apoptosis of mouse embryonic fibroblasts (MEF) prepared from diminuto-KO mice. Both KO-MEF and wild-type (WT)-MEF proliferated in the presence of 10% serum. However, serum withdrawal induced apoptosis of KO-MEF, but not WT-MEF. Interestingly, insulin rescued KO-MEF from the apoptosis, indicating that cholesterol depletion in KO-MEF by serum withdrawal might impair insulin-dependent cell survival signaling such as PI3K-Akt-Bad cascade. Indeed, phospho-Akt (S473) and Bad (S136) were more rapidly dephosphorylated in KO-MEF after serum withdrawal than those in WT-MEF. Furthermore, insulin-dependent phosphorylation of Akt and Bad in KO-MEF was much less in WT-MEF. The impaired insulin action was ascribed to cholesterol loss of plasma membrane, because treatment of WT-MEF with cyclodextrin, which selectively depletes cell surface of cholesterol, also impaired the insulin action. Since functional insulin receptor (IR) has been shown to be present in caveolae, the cholesterol-rich microdomain of plasma membrane, we isolated caveolae and examined IR and caveolin contents. It was demonstrated that IR and caveolin contents were reduced in KO-MEF. Taken together, these observations demonstrate that Diminuto plays an important role in insulin signaling and cell survival by controlling cholesterol biosynthesis and caveolae function.
|
