1995 Fiscal Year Final Research Report Summary
THE STUDIES ON MECHANISMS OF MEMBRANE RECOGNITION AND FUSION IN LYSOSOME FORMATION
| Project/Area Number |
06454678
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Cell biology
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
HIMENO Masaru Faculty of pharmaceutical Sciences Professor, 薬学部, 教授 (50037602)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIKAWA Toyoko Faculty of pharmaceutical Sciences Instructor, 薬学部, 助手 (50201314)
TANAKA Yoshitaka Faculty of pharmaceutical Sciences Instructor, 薬学部, 助手 (20217095)
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| Project Period (FY) |
1994 – 1995
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| Keywords | lysosome / endosome / lysosomal glycoproteins / fusion / N-ethylmaleimide sensitive factoe (NSF) |
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| Research Abstract |
To clarify the mechanisms of membrane recognition and fusion in lysosome formation, it is essential to understand the lysosome targeting siginal and sorting signal in lysosomal membrane glycoprotein and fusion mechanisms between lysosomes and endosomes. In this project l attempted to study the role of amino acids in ctoplasmic domain of LGP96, which was isolated from rat liver lysosomes as one of main constituent of lysosomal membrane glycoproteins and was cDNA cloned from rat liver cDNA library.
To idetify determinant responsible for lysosomal targeting of LGP96, the COS cells were transiently tranfected with plasmids encoding LGP96 and distribution of expressed LGP96 was examined by indirect immunofluorescence microscopy. The cells expressed with wild-type LGP96 represented endosome/lysosome-like stainig pattern distributed in perinuclear region, which overlapped at least partially with that of an endogemous lgp-A.The trancated form by deletion of 8 amino acids from the carboxyl-termi
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nus appeared in cell surface. This apparently suggeses the presence of determinant responsible for targeting LGP96 to the lysosomes in its cytoplasmic domain. We further examined the role of Fly, Tyr, and Phe in Gly-Tyr-Glu-Gln-Phe sequence at the carboxyl-terminus of LGP96, since Gly-Tyr-X-X-hydrophobic amino acid sequence is conserved in the known lysosomal membrabe proteins, and suppised tobe one of lysosomal targeting signals. The results suggest that Tyr and Phe residues in cytoplasmic domain of LGP96 may be critical for targeting to the endosomes rather than the lysosomes. We, therefore, would like to speculate that the mechanism by which LGP96 is transported from the late endosomes to the lysosomes may be the consequence of maturation of the late endosomes to the lysosomes.
The result s obtained from endosome-lysosome fusion experiment suggest the followings 1) endosome-endosome fusion requires NSF but endodome-lysosome fusion does not. 2) peripheral proteins on endosomes are essential for fusion of endosome-lysosome. Less
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