Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis
The hypothesis that glial cells synthesize proteins which are transferred to adjacent neurons was evaluated in the giant fiber of the squid (Loligo pealei). When giant fibers are separated from their neuron cell bodies and incubated in the presence of radioactive amino acids, labeled proteins appear...
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| Format: | Online |
| Language: | English |
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The Rockefeller University Press
1977
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| Online Access: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2110074/ |
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pubmed-2110074 |
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pubmed-21100742008-05-01 Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis Lasek, RJ Gainer, H Barker, JL Articles The hypothesis that glial cells synthesize proteins which are transferred to adjacent neurons was evaluated in the giant fiber of the squid (Loligo pealei). When giant fibers are separated from their neuron cell bodies and incubated in the presence of radioactive amino acids, labeled proteins appear in the glial cells and axoplasm. Labeled axonal proteins were detected by three methods: extrusion of the axoplasm from the giant fiber, autoradiography, and perfusion of the giant fiber. This protein synthesis is completely inhibited by puromycin but is not affected by chloramphenicol. The following evidence indicates that the labeled axonal proteins are not synthesized within the axon itself. (a) The axon does not contain a significant amount of ribosomes or ribosomal RNA. (b) Isolated axoplasm did not incorporate [(3)H]leucine into proteins. (c) Injection of Rnase into the giant axon did not reduce the appearance of newly synthesized proteins in the axoplasm of the giant fiber. These findings, coupled with other evidence, have led us to conclude that the adaxonal glial cells synthesize a class of proteins which are transferred to the giant axon. Analysis of the kinetics of this phenomenon indicates that some proteins are transferred to the axon within minutes of their synthesis in the glial cells. One or more of the steps in the transfer process appear to involve Ca++, since replacement of extracellular Ca++ by either Mg++ or Co++ significantly reduces the appearance of labeled proteins in the axon. A substantial fraction of newly synthesized glial proteins, possibly as much as 40 percent, are transferred to the giant axon. These proteins are heterogeneous and range in size from 12,000 to greater than 200,000 daltons. Comparisons of the amount of amino acid incorporation in glia cells and neuron cell bodies raise the possibility that the adaxonal glial cells may provide an important source of axonal proteins which is supplemental to that provided by axonal transport from the cell body. These findings are discussed with reference to a possible trophic effect of glia on neurons and metabolic cooperation between adaxonal glia and the axon. The Rockefeller University Press 1977-08-01 /pmc/articles/PMC2110074/ /pubmed/885913 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
| repository_type |
Open Access Journal |
| institution_category |
Foreign Institution |
| institution |
US National Center for Biotechnology Information |
| building |
NCBI PubMed |
| collection |
Online Access |
| language |
English |
| format |
Online |
| author |
Lasek, RJ Gainer, H Barker, JL |
| spellingShingle |
Lasek, RJ Gainer, H Barker, JL Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis |
| author_facet |
Lasek, RJ Gainer, H Barker, JL |
| author_sort |
Lasek, RJ |
| title |
Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis |
| title_short |
Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis |
| title_full |
Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis |
| title_fullStr |
Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis |
| title_full_unstemmed |
Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis |
| title_sort |
cell-to-cell transfer of glial proteins to the squid giant axon: the glia- neuron protein transfer hypothesis |
| description |
The hypothesis that glial cells synthesize proteins which are transferred to adjacent neurons was evaluated in the giant fiber of the squid (Loligo pealei). When giant fibers are separated from their neuron cell bodies and incubated in the presence of radioactive amino acids, labeled proteins appear in the glial cells and axoplasm. Labeled axonal proteins were detected by three methods: extrusion of the axoplasm from the giant fiber, autoradiography, and perfusion of the giant fiber. This protein synthesis is completely inhibited by puromycin but is not affected by chloramphenicol. The following evidence indicates that the labeled axonal proteins are not synthesized within the axon itself. (a) The axon does not contain a significant amount of ribosomes or ribosomal RNA. (b) Isolated axoplasm did not incorporate [(3)H]leucine into proteins. (c) Injection of Rnase into the giant axon did not reduce the appearance of newly synthesized proteins in the axoplasm of the giant fiber. These findings, coupled with other evidence, have led us to conclude that the adaxonal glial cells synthesize a class of proteins which are transferred to the giant axon. Analysis of the kinetics of this phenomenon indicates that some proteins are transferred to the axon within minutes of their synthesis in the glial cells. One or more of the steps in the transfer process appear to involve Ca++, since replacement of extracellular Ca++ by either Mg++ or Co++ significantly reduces the appearance of labeled proteins in the axon. A substantial fraction of newly synthesized glial proteins, possibly as much as 40 percent, are transferred to the giant axon. These proteins are heterogeneous and range in size from 12,000 to greater than 200,000 daltons. Comparisons of the amount of amino acid incorporation in glia cells and neuron cell bodies raise the possibility that the adaxonal glial cells may provide an important source of axonal proteins which is supplemental to that provided by axonal transport from the cell body. These findings are discussed with reference to a possible trophic effect of glia on neurons and metabolic cooperation between adaxonal glia and the axon. |
| publisher |
The Rockefeller University Press |
| publishDate |
1977 |
| url |
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2110074/ |
| _version_ |
1611410978412429312 |