1988 Fiscal Year Final Research Report Summary
Studies on Biogenesis of the Lysosomal Membranes.
| Project/Area Number |
62480459
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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 |
代謝生物化学
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| Research Institution | Kyushu University |
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Principal Investigator |
KATO Keitaro Faculty of Pharmaceutical Sciences, Kyushu University, 薬学部, 教授 (70037571)
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| Co-Investigator(Kenkyū-buntansha) |
HIMENO Masaru Faculty of Pharmaceutical Sciences, Kyushu University, 薬学部, 助教授 (50037602)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Lysosome / Acid Phosphatase / Endosomes / エンドゾーム / Mー6ーP受容体 / 細胞内輸送 / プロセシング |
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| Research Abstract |
To clarify the mechanisms of lysosome formation, it is essential to understand the biogenesis and the pathway of the intracellular transport of lysosomal membrane glycoproteins.In this project I attempted to study the biosynthesis of acid phosphatases(APase), which are located both in lysosomal matrix and membranes, and dipeptidyl peptidase IV(DPP-IV) which are located in the plasma membrane of bile canaliculi(Pl), lysosomal membranes(Ly) and contents(Lc).
50% of activity of the whole APases activity in rat liver lysosomes localizes in the lysosomal contents(C-APase) and the other is tightly associated with the lysosomal membranes(M-APase). Although C-APase(Mr. 48K) and M-APase(Mr. 67K) have a different molecular weight, these two enzyme have the same amino terminal sequences and show the same reactivity against antibodies prepared from rabbits immunized with the purified C-APase. In the in vivo experiment, after 30 min labeling with [^<35>S]methionine APase having a molecular weight of
… More
67 k was seen both in the golgi and the lysosomal membrane fraction. Appearance of C-APase in the lysosomal contents took a longer chase period. From these results, we could conclude that APase is synthesized on the rough er as a membrane integrated protein and transported into the lysosomes in a manner independent of the mannose-6-phosphate receptor system. After reaching the lysosomes, M-APase is solubilized into the lysosomal matrix by a limited proteolytic cleavage.
Concerning the biosynthesis of DPP-IV, after labeling rats with [^<35>S]me-thionine the plasma membranes, lysosomal membranes and contents were isolated from the rat liver homogenates. Thereafter, Pl-,Ly- and Lc-DPP-IV were separately purified and subjected to the measurement of the each radioactivities. It was revealed from the kinetic analysis that these three enzymes took 2h to reach their final destination. Since half life of Pl-DPP-IV and lysosomal ones are different, shuttling of the enzyme between the bile canaliculi membrane and lysosomal membranes seems not to occur. Less
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