| Project/Area Number |
07044229
|
|---|
| Research Category |
Grant-in-Aid for international Scientific Research
|
| Allocation Type | Single-year Grants |
|---|
| Section | Joint Research |
|---|
| Research Institution | University of Tokyo |
|---|
Principal Investigator |
KATADA Toshiaki Faculty of Pharmaceutical Sciences, University of Tokyo, Professor, 薬学部, 教授 (10088859)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ISHIKAWA Yoshihiro Department of Medicine, Harvard Medical School, ハーバード大学・医学部, 準教授
HOSHINO Shin-ichi Faculty of Pharmaceutical Sciences, University of Tokyo, 薬学部, 助手 (40219168)
HAZEKI Osamu Faculty of Pharmaceutical Sciences, University of Tokyo, 薬学部, 助教授 (80142751)
|
|---|
| Project Period (FY) |
1995 – 1996
|
| Project Status |
Completed (Fiscal Year 1996)
|
| Budget Amount *help |
¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 1996: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 1995: ¥3,700,000 (Direct Cost: ¥3,700,000)
|
|---|
| Keywords | GTP-binding proteins / Membrane receptors / Adenylyl cyclase / Phosphatidyl inositol 3-kinase / Wortmannin / Signal transduction / イノシトール脂質3キナーゼ / ワ-トマニン / シグナル伝達 |
|---|
| Research Abstract |
GTP-binding protein (G proteins) consisting of alpha, beta, gamma subunits, carry signals from membrane receptors to effectors such as enzymes or ion channels. G proteins dissociate into the GTP-bound alpha and betagamma subunits upon their interaction with agonist-receptor complex. In the present studies, we investigated mechanisms by which the activities of adenylyl cyclase and phosphatidylinositol (PI) 3-kinase are regulated by G proteins, especially the betagamma subunits.
In guinea pig neutrophils, the cellular cAMP formation by prostagladin (PG) E_1 was markedly potentiated by the chemoattractant formyl-Met-Leu-Phe (fMLP). This potentiation was abolished by prior treatment of the cells with pertussis toxin, but not by the prevention of fMLP-induced intracellular Ca^<2+> increase in the cells, indicating the direct involvement of the inhibitory G protein (G_i) in the fMLP-induced potentiation of cAMP formation. Adenylyl cyclase responsible for the G_i-induced potentiation was parti
… More
ally purified from the GTPgammaS-treated cell membranes with a forskolin-agarose column. The cyclase appeared to be a complex form with the GTPgammaS-bound alpha subunit of the stimulatory G_S protein (G_Salpha), but not with the betagamma subunits. The GTPgammaS-bound G_Salpha-stimulated cyclase activity was further enhanced by betagamma subunits. These results indicate that GTP-bound G_Salpha and betagamma subunits released from G_i synergistically stimulate adenylyl cyclase activity in neutrophils. In relation to this, we also found that the activity of PI 3-kinase is inhibited by wortmannin and that several types of PI 3-kinase are stimulated by bg subunits. Interestingly, a peptide containing phosphorylated Tyr and betagamma subunits synergistically activated a certain type of PI 3-kinase. Such synergistic activation was also observed in intact neutrophil-like cells upon their stimulation with insulin and fMLP.Thus, G_i activation appeared to have a cross-talk with Tyr-phosphorylation signaling pathway via betagamma subunits in PI 3-kinase. Less
|
