1995 Fiscal Year Final Research Report Summary
Purification and characterization of switching factor in hepatocyte signaling and its regulation
| Project/Area Number |
06670158
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General medical chemistry
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| Research Institution | The Tokyo Metropolitan Institute of Medical Science |
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Principal Investigator |
KAJIYAMA Yasuo The Tokyo Metropolitan Insitute of Medical Science Dept.of Biochemical Cell Research Researcher, 生命情報・研究部門, 研究員 (70250214)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Hepatocytes / Adhesion / Glycoconjugates / Ganglioside GM3 |
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| Research Abstract |
alpha_1-Adrenergic receptor-mediated response are overwhelming, or alpha_1-responses are dominant, in adult rat hepatocytes. Inversely, beta-responses are predominant over alpha1-responses in hepatocytes that have been cultured at a low-cell density (Adrenergic response "alpha*beta exchange"). We found "alpha*beta exchange" was not previously induced in cell-to-cell contact and we examined the adhesion of hepatocytes to terminal galactoside in detail during this project. As a result, it was suggested that adult hepatocytes were bound to terminal galactosides without binding specificity, and then alpha*beta exchange could not occur. Adhesion of hepatocytes to terminal galactoside was required by Mg^<2+> but not Ca^<2+>. In contrast, it was suggested that immature hepatocytes could not bind to the same sites because sialic acids were added to the galactosides on hepatocyte surfaces. However, we found it very difficult to isolate this unknown factor from hepatocyte surfaces. During the period of this project, we found that 24 day-hepatocytes after birth were strongly bound to ganglioside GM3. Therefore, we prepared a monoclonal antibody that would inhibit adhesion of hepatocytes to GM3. Then we examined the adhesion of hepatocytes to GM3 by using 6-18 mAb. As a result, it was suggested that 6-18 mAb recognized molecules that transiently founctioned on hepatocyte surfaces, but were expressed in rat of all ages on FACS analysis. From the result of fluorescent immunostaining, 6-18 mAb recognized molecules were localised from the periportal to pericentral regions of the lobule. We examined the binding specificity of the adhesion of hepatocytes to GM3. Hepatocytes recognized the terminal Siaalpha2-3 Gal-of GM3. This recognition was not required for divalent cations. Furthermore, from the result of western blotting analysis following immunoprecipitation, it was suggested that 6-18 mAb recognized molecules indicated 48 KDa. This molecule may be an unknown protein.
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