| Project/Area Number |
16590901
|
|---|
| 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) |
SEO Hisao Nagoya Univ., Res.Inst.Environ.Med., Professor, 環境医学研究所, 教授 (40135380)
OHMORI Sachiko Nagoya Univ., Res.Inst.Environ.Med., Research Associate, 環境医学研究所, 助手 (20233273)
HATTORI Kimihiko Nagoya Univ., Res.Inst.Environ.Med., Research Associate, 環境医学研究所, 助手 (90359745)
中川 光幸 三菱ウェルファーマ株式会社, 創薬基盤研究所長
NAKAGAWA Mitsuhide Mitsubishi Pharma Corporation, So-ken Kiban Laboratory, Chief
中川 幸光 三菱ウェルファーマ株式会社, 創薬基盤研究所, 所長
|
|---|
| Project Period (FY) |
2004 – 2005
|
| Project Status |
Completed (Fiscal Year 2005)
|
| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
|
|---|
| Keywords | DHCR24 / cholesterol / Akt / Bad / insulin / caveolae / caveolin-1 / apoptosis / hDiminuto / MEF |
|---|
| Research Abstract |
The DHCR24 gene encodes an enzyme catalyzing the last step of cholesterol biosynthesis, the conversion of desmosterol to cholesterol. To elucidate the physiological significance of cholesterol biosynthesis in mammalian cells, we investigated proliferation of mouse embryonic fibroblasts (MEFs) prepared from DHCR24-/- mice. Both DHCR24-/- and wild type MEFs proliferated in the presence of serum in culture media. However, the inhibition of external cholesterol supply by serum withdrawal induced apoptosis of DHCR24-/- MEFs, which was associated with a marked decrease in the intracellular and plasma membrane cholesterol levels, Akt inactivation, and Bad dephosphorylation. Insulin is an anti-apoptotic factor capable of stimulating the Akt-Bad cascade, and its receptor (IR) is enriched in caveolae, cholesterol-rich microdomains of plasma membrane. We thus analyzed the association of IR and caveolae in the cholesterol-depleted MEFs. Subcellular fractionation and immunocytochemical analyses revealed that the IR and caveolin-1 contents were markedly reduced in the caveolae fraction of the MEFs suggesting the disruption of caveolae, and that large amounts of IR were present apart from caveolin-1 on plasma membrane indicating the uncoupling of IR with caveolae. Consistent with these findings, insulin- dependent phosphorylations of insulin receptor substrate-1, Akt, and Bad were impaired in the cholesterol-depleted MEFs. However, this impairment was partial, because treatment of the MEFs with insulin restored Akt activation and prevented apoptosis. Cholesterol supply also prevented apoptosis. These results demonstrate that the cellular cholesterol biosynthesis is critical for the activation and maintenance of the Akt-Bad cell survival cascade in response to growth factors such as insulin.
|
