Protein synthesis in the isolated giant axon of the squid.

Giuditta, Antonio; Dettbarn, Wolf‐D.; Brzin, Miro

doi:10.1073/pnas.59.4.1284

Cited by 111 publications

(64 citation statements)

References 9 publications

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“…These studies confirmed and extended previous observations (20) indicating that squid giant fibers separated from their neuron cell bodies are capable of incorporating labeled amino acids into proteins, some of which appear in the axon (42). The appearance of these labeled proteins in the axon raised an interesting question regarding the site at which these proteins were synthesized.…”

supporting

confidence: 78%

“…Although the possibility of endogenous axonal protein synthesis has frequently been raised in the literature (15,20,35), no evidence has been provided which convincingly supports this suggestion. None of the previous studies on protein synthesis in isolated nerve fibers have determined whether the newly synthesized axonal proteins were synthesized in the axon or in the glial cells.…”

Section: Does Protein Synthesis Occur Within the Squid Giant Axon?mentioning

confidence: 70%

“…A contemporary proof of this theory is provided by the demonstration that axonal proteins are synthesized in the nerve cell body and transported within the axon (40). Although this historical trend has focused attention almost exclusively on the neuron cell body and axonal transport as the source of axonal proteins, a small but persistent literature has raised the possibility that proteins are supplied to the axon by mechanisms which exist locally at the level of the axon (4,15,20,35,42,55,56,60,61). These reports have convincingly demonstrated that amino acids are incorporated into axonal proteins in nerve fibers separated from their cell bodies and have awakened interest in the possibility that the glial cells might play a contributory role in the supply of macromolecules to the axon (see Singer, reference 60, for review).…”

Section: Discussionmentioning

confidence: 99%

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Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis

Lasek¹,

Gainer²,

Barker³

1977

The Journal of Cell Biology

186

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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 [aH]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 §247 significantly reduces the appearance of labeled proteins in the axon. A substantial fraction of newly synthesized glial proteins, possibly as much as 40%, 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.It has often been suggested that adjacent cells communicate with one another via the actual intercellular transfer of molecules including macromolecules. The possibility that molecular transfer may play a role in intercellular regulation has taken on added credibility since the discovery and

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supporting

confidence: 78%

Section: Does Protein Synthesis Occur Within the Squid Giant Axon?mentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

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Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis

Lasek¹,

Gainer²,

Barker³

1977

The Journal of Cell Biology

186

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“…It was shown almost 50 years ago that when isolated squid giant axons are incubated in radioactive amino acids there are abundant newly synthesized proteins found in the axoplasm (Giuditta et al 1968). There were two possible interpretations of this finding: 1) that this was due to de novo protein biosynthesis in the axoplasm, and 2) that radioactive proteins were synthesized in the adaxonal Schwann cells and then transported into the giant axon.…”

Section: Introductionmentioning

confidence: 91%

“…12 When isolated squid giant axons are incubated in radioactive amino acids there are substantial amounts of newly synthesized radioactive protein found in the axoplasm of the giant axon (Giuditta et al 1968;Lasek et al 1977;Lasek et al 1974). This phenomenon is illustrated in Fig.…”

Section: Does the Squid Giant Axon Synthesize Nf Proteins?mentioning

confidence: 99%

Squid Giant Axon Contains Neurofilament Protein mRNA but does not Synthesize Neurofilament Proteins

et al. 2016

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When isolated squid giant axons are incubated in radioactive amino acids, abundant newly synthesized proteins are found in the axoplasm. These proteins are translated in the adaxonal Schwann cells and subsequently transferred into the giant axon. The question as to whether any de novo protein synthesis occurs in the giant axon itself is difficult to resolve because the small contribution of the proteins possibly synthesized intra-axonally is not easily distinguished from the large amounts of the proteins being supplied from the Schwann cells. In this paper we reexamine this issue by studying the synthesis of endogenous neurofilament (NF) proteins in the axon. Our laboratory previously showed that NF mRNA and protein is present in the squid giant axon, but not in the surrounding adaxonal glia. Therefore, if the isolated squid axon could be shown to contain newly synthesized NF protein de novo, it could not arise from the adaxonal glia. The results of experiments in this paper show that abundant 3H-labeled NF protein is synthesized in the squid giant fiber lobe containing the giant axon's neuronal cell bodies, but despite the presence of NF mRNA in the giant axon, no labeled NF protein is detected in the giant axon. This lends support to the Glia-Axon Protein Transfer Hypothesis which posits that the squid giant axon obtains newly synthesized protein by Schwann cell transfer and not through intra-axonal protein synthesis, and further suggests that the NF mRNA in the axon is in a translationally repressed state.

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