2000 Fiscal Year Final Research Report Summary
MEMBRANE DOMAINS IN SECRETORY GRANUES OF RAT PAROTID ACINAR CELLS
| Project/Area Number |
11671856
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional basic dentistry
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| Research Institution | NIHON UNIVERSITY |
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Principal Investigator |
YOKOYAMA Miki NIHON UNIVERSITY SCHOOL OF DENTISTRY AT MATSUDO LECTURER, 松戸歯学部, 講師 (70191533)
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| Project Period (FY) |
1999 – 2000
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| Keywords | RAT PAROTID / SECRETORY GRANULES / MEMRANE DOMAINS / CHOLESTEROL / GLYCOLIPIDS |
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| Research Abstract |
Recent advances in membrane biology suggest the glycolipids- and cholesterol-rich membrane microdomains as lateral structural components of the plasma membranes. These microdomains are called as lipid rafts and have been proposed to function as platforms for both signal transduction and membrane trafficking. Rafts are considered to be formed by tight packing of long and mostly saturated acyl chains of glycolipids interspaced by cholesterol. The components of lipid rafts are biochemically separated as DRMs (detergent-resistant membranes) or DIGs (detergent-insoluble glycolipids-enriched domains) based on their insolubility in the detergent Triton X-100 in the cold. Because of their high lipid content, DRMs can be isolated in the low density fraction after gradient centrifugation. DRMs concentrate glycosyl-phosphatidylinositol-anchored proteins (GPI-anchored proteins), some transmembrane proteins including influenza hemagglutinin, and also intracellular signaling proteins such as dually acylated Src-PTKs Lck, Lyn and Fyn or heterotrimeric GTP-binding proteins and phosphatidylinositol bisphosphate. Rafts are therefore likely to act as scaffolding for both extracellular proteins and intracellular molecules. In the immune system, the requirement of lipid rafts for tyrosine phosphorylation mediated via high affinity Fc receptor for IgE (FceRI) and TCR has been reported. However, the requirement of lipid rafts for FcγR-mediated tyrosine phosphorylation has not been investigated.
In the present study, we investigated the role of lipid rafts in FcγR-signaling in retinoic acid-differentiated HL60 cells (RA-HL60 cells). Our results suggest that lipid rafts are crucial machinery in which clustering of FCγRIIa induces the activation of Src-PTKs to initiate the tyrosine phosphorylation pathway. We have also tried to identify lipid raft in the secretory granules of rat parotid acinar cells.
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[Publications] Hara-Yokoyama, M., Nagatsuka, Y., Katsumata, O., Irie, F., Kontani, K., Hoshino, S., Katada, T., Ono, Y., Fujita-Yoshigaki, J., Sugiya, H., Furuyama, S., and Hirabayashi, Y.: "Complex Gangliosides as Cell Surface Inhibitors for the Ecto-NAD^+ Glycohydrolase of CD38"Biochemistry. 40(4). 888-895 (2001)
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