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Degradation of cytoskeletal proteins and proteinases. Eiki KOMINAMI 1 , Takashi UENO 1 1Department of Biochemistry, Juntendo University School of Medicine pp.709-717
Published Date 1992/10/10
DOI https://doi.org/10.11477/mf.1431900267
  • Abstract
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Three cytoskeletal systems (microfilament, intermediate filament, and microtubule) are known to play an essential role in maintaining structural organization of the cell and conducting various cellular motile activities such as cell division, endocytosis, secretion, organelle transport, etc. In the nerve cell, these cytoskeletons are particularly developed in the dendrite and axon. Parallel arrays of numerous neurofilaments and microtubules run throughout the cytoplasm along the long axis of axon. Micro-tubules comprise principal cytoskeletons in the dendrite, too. Microfilaments are distributed beneath the plasma membrane at presynaptic region, dendrite, and axon. However, they are less conspicuous than neurofilaments and microtubules. It has been demonstrated that actin, tubulin, and neurofilament proteins that are major constituents of these three cytoskeletal systems are synthesized on free ribosomes of the cell body and transported via axonal flow into distal parts of the neuron. In contrast, very little is known on the mechanism by which these cytoskeletal proteins are degraded by cellular proteo-lytic machinery. Since the continuous assembly and disassembly of cytoskeletal proteins occur in various parts of living cells, it is reasonable to assume that free, monomeric cytoskeletal proteins and those incorporated in highly-organized structures of cytoskeleton have different life times because the suscepti-bility to proteases must be different between these two states. In the nerve cell, several factors which affect the stability of cytoskeletons must be considered for understanding life times of cytoskeletal pro-teins. i) Microtubule-associated proteins (MAPs) and various actin-binding proteins which would affect tertiary structure and polymerization-depolymerization cycle, of tubulin and actin. ii) Interaction be-tween cytoskeletons, in particular, between neurofilament and microtubule which is a principal deter-minant in cross-network formation of neuronal cytoskeletons. iii) Covalent modifications such as phos-phorylation and acetylation of cytoskeletal proteins which change the stability of neurofilaments and microtubules.


Copyright © 1992, Igaku-Shoin Ltd. All rights reserved.

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電子版ISSN 1882-1243 印刷版ISSN 0001-8724 医学書院

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