Neurofilament protein is phosphorylated in the squid giant axon.

Pant, H. C.; Shecket, G.; Gainer, Harold; Lasek, Raymond J.

doi:10.1083/jcb.78.2.r23

Cited by 88 publications

(51 citation statements)

References 8 publications

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“…Previous SDS-PAGE and Western blot studies identified two major NF proteins in the squid giant axon, a high molecular weight phosphorylated protein, NF 220, a low molecular protein, NF 60 (Brown and Lasek 1990;Cohen et al 1987;Pant et al 1978), and a dephosphorylated form of NF220, approximately 190 kD, found together with NF60 in the cell bodies in the GFL (Tytell et al 1990). Subsequent molecular cloning studies in our laboratory revealed that there were two low molecular weight NF mRNAs in the GFL, an abundant NF60 mRNA and a small amount of a NF70 mRNA, in addition to a higher molecular weight mRNA corresponding to NF 190, all of which were formed from a single gene by alternative splicing (Szaro et al 1991;Way et al 1992).…”

Section: Resultsmentioning

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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Section: Resultsmentioning

confidence: 99%

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

et al. 2016

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“…A different type of neurofilament dynamics is governed in part by the phosphorylation state of the long, highly charged C-terminal tail regions of NF-M and NF-H, which are peripherally situated on the filament and may correspond to the sidearms of neurofilaments [Pant et al, 1978;Sharp et al, 1982;Leterrier et al, 1982;Hirokawa et al, 19841. The phosphorylation of many sites on the tail domains, which is mediated by one or more neuron-specific cytoskeletonassociated kinases Runge et al, 1981;Shecket and Lasek, 19821, is delayed until after neurofilaments have entered the axon and continues as neurofilaments are transported [Glicksman et al, 1987;Oblinger, 1987;Nixon et al, 19871.…”

Section: Neurofilament Dynamicsmentioning

confidence: 99%

Dynamics of neuronal intermediate filaments: A developmental perspective

Nixon

Shea

1992

Cell Motil. Cytoskeleton

217

159

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“…Recent observations that the major neurofflament proteins (NFPs) exhibit microheterogeneity (6, I0, 35, 36) and are modified by phosphorylation (35,40,56) indicate that neurofilament structure may be quite complex. Little is known, however, about the nature of this heterogeneity, the spatial organization of the several neurofilament protein forms within neurons and their processes, and whether the structural heterogeneity is related to functional complexity.…”

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confidence: 99%

Posttranslational modification of a neurofilament protein during axoplasmic transport: implications for regional specialization of CNS axons

Nixon¹,

Brown²,

Marotta³

1982

The Journal of Cell Biology

111

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The possibility that proteins are modified during axoplasmic transport in central nervous system axons was examined by analyzing neurofilament proteins (200,000, 140,000, and 70,000 mol wt) along the mouse primary optic pathway (optic nerve and optic tract). The major neurofilament proteins (NFPs) exhibited considerable microheterogeneity. At least three forms of the " 140,000" neurofilament protein differing in molecular weight by SDS PAGE (140,000-145,000 mol wt) were identified. The "140,000" proteins, and their counterparts in purified neurofilament preparations, displayed similar isoelectric points and the same peptide maps. The "140,000" NFPs exhibited regional heterogeneity when consecutive segments of the optic pathway were separately examined on polyacrylamide gels. Two major species (145,000 and 140,000 mol wt) were present along the entire length of the optic pathway. The third protein (143,000 mol wt) was absent proximally but became increasingly prominent in distal segments. After intravitreal injection of [(3)H]proline, newly synthesized radiolabeled proteins in the "140,000" mol wt region entered proximal mouse retinal ganglion cell (RGC) axons as two major species corresponding to the 145,000 and 14,000 mol wt NFPs observed on stained gels. When transported NFPs reached more distal axonal regions (30 d postinjection or longer), a 143,000 mol wt protein appeared that was similar in isoelectric point and peptide map to the 145,000 and 140,000 mol wt species. The results suggest that (a) the composition of CNS neurofilaments, particularly the "140,000" component, is more complex than previously recognized, that (b) retinal ganglion cell axons display regional differentiation with respect to these cytoskeletal proteins, and that (c) structural heterogeneity of "140,000" NFPs arises, at least in part, from posttranslational modification during axoplasmic transport. When excised but intact optic pathways were incubated in vitro at pH 7.4, a 143,000 NFP was rapidly formed by a calcium-dependent enzymatic process active at endogenous calcium levels. Changes in major proteins other than those in the 145,000-140,000 mol wt region were minimal. In optic pathways from mice injected intravitreally with L-[(3)H]proline, tritiated 143,000 mol wt NFP formed rapidly in vitro if radioactively labeled NFPs were present in distal RGC axonal regions (31 d postinjection). By contrast, no 143,000 mol wt NFP was generated if radioactively labeled NFPs were present proximally in RGC axons (6 d postinjection). The enzymatic process that generates 143,000 mol wt NFP in vitro, therefore, appears to have a nonuniform distribution along the RGC axons. The foregoing results and other observations, including the accompanying report (J. Cell Biol., 1982, 94:159-164), imply that CNS axons may be regionally specialized with respect to structure and function.

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Neurofilament protein is phosphorylated in the squid giant axon.

Cited by 88 publications

References 8 publications

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

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

Dynamics of neuronal intermediate filaments: A developmental perspective

Posttranslational modification of a neurofilament protein during axoplasmic transport: implications for regional specialization of CNS axons

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