1999 Fiscal Year Final Research Report Summary
Intracellular sorting of glucose transporter and insulin action
| Project/Area Number |
10044296
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
内分泌・代謝学
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| Research Institution | Yamaguchi University |
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Principal Investigator |
OKA Yoshitomo Yamaguchi University School of Medicine, Professor, 医学部, 教授 (70175256)
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| Co-Investigator(Kenkyū-buntansha) |
OKUYA Shigeru Yamaguchi University School of Medicine, Research Associate,, 医学部, 助手 (20214083)
TANIZAWA Yukio Yamaguchi University Hospital, Assistant Professor,, 医学部・附属病院, 講師 (00217142)
MATSUTANI Akira Yamaguchi University School of Medicine, Associate Professor, 医学部, 助教授 (10190464)
KATAGIRI Hideki Tokyo University Hospital, Clinical Fellow,, 医学部・附属病院, 医員(臨床)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Insulin / Glucose transport / GLUT4 / PI3 kinase / Akt / PH domain / Grp1 / PDK1 |
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| Research Abstract |
Insulin rapidly stimulates glucose transport activity in muscle and adipose tissue. This increase in glucose transport activity is primarily due to translocation of glucose transporter GLUT4 from intracellular compartment to the plasma membrane. We have shown that activation of PI3 kinase is crucial for insulin-stimulation of glucose transport, based on our findings that overexpression of p110a catalytic subuniti of PI3 kinase and dominant negative p85 subunit mimic and inhibit, respectively, this insulin action. We have also studied signals downstream of PI3 kinase. Insulin stimulation phosphorylates AKt1 at both Thr308 and Ser473, leading to activation of various signals including those towards glucose metabolism. To investigate the role of PDK1 on the phosphorylation state of AKt1, the wild-type PDK1 (wt-PDK1) and its kinase dead mutant (kd-PDK1) were expressed in CHO-IR cells using adenovirus gene transduction system. Immunoblotting using antiphosphorylated AKt1 antibody revealed that Thr308 was maximally phosphorylated already at 1 min by insulin stimulation but almost completely dephosphorylated at 5 min. Insulin-stimulated phosphorylation state of Thr308 was markedly increased in CHO-IR cells overexpressing wt-PDK1 at 1 min, but it returned to the basal level at 5 min. On the contrary, insulin-stimulated phosphorylation state of Thr308 was maintained even at 15 min in cells overexpressing kd-PDK1, suggesting that kd-PDK1 overexpression inhibited insulin-stimulated phosphatase activity. Insulin-stimulated Ser473 phosphorylation was not affected by overexpression of we-PDK1 or kd-PDK1.
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