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At least 1,657 records · Page 92Linked to original sources
PubMed2000

Subcellular localization and axonal transport of the survival motor neuron (SMN) protein in the developing rat spinal cord.

The subcellular localization of the survival motor neuron (SMN) protein, encoded by the spinal muscular atrophy determining gene, was investigated in motor neurons of the developing and adult rat spinal cord by light and electron microscopy immunocytochemistry. The experiments were carried out with a panel of anti-SMN antibodies, all recognizing an SMN-specific protein band at 39 kDa in HeLa cells and rat spinal cord protein extracts. SMN protein expression decreased during postnatal spinal cord development, but it remained unchanged in distribution and intensity in motor neurons at all ages examined. SMN protein was mainly organized in immunoreactive aggregates sparse in the nucleoplasm and cytoplasm of both mature and developing motor neurons, and it was more rarely localized within the endoplasmic reticulum and in apposition to the external mitochondrial membrane. Most strikingly, the SMN protein was found in association with cytoskeletal elements in spinal dendrites and axons, where it was particularly evident during postnatal development. The present findings suggest that SMN protein may be transported via axoplasmic flow in maturing neurons. Given the RNA-binding activity of SMN, the SMN protein could be involved in the transport of specific mRNAs in axons and dendrites of motor neurons. The reduced transport of specific mRNAs within motor neurons during development could play a role in the motoneuronal degeneration and impaired axonal sprouting observed in spinal muscular atrophy.

Animals↗
PubMedDate not supplied

Neuronotoxicity of axonally transported toxic lectins, abrin, modeccin and volkensin in rat peripheral nervous system.

In an attempt to find new and more useful suicide transport agents, the cytotoxic lectins abrin, modeccin and volkensin were pressure microinjected into peripheral nerves (vagus, hypoglossal and sciatic) of adult rats. After 33 h-5 days survival, the brainstems, spinal cords and corresponding sensory ganglia were examined histologically. All three lectins produced profound chromatolysis, and destruction of sensory and motor neurons projecting axons through the injected nerves. Volkensin and modeccin were significantly more potent than any previously reported suicide transport agent. It is concluded that abrin, modeccin and volkensin are effective, unselective suicide transport agents in the rat peripheral nervous system but none is clearly superior to ricin for making restricted sensory and motor neuron ablations. However, modeccin and volkensin are fundamentally different from any previously reported suicide transport agents with respect to spread within the CNS which destroyed neurons adjacent to those initially taking up and transporting the toxin. Possibly this is due to the different oligosaccharide binding specificity of modeccin and volkensin compared to other suicide transport agents. Modeccin and/or volkensin may prove useful in making lesions of CNS interneurons using the suicide transport strategy.

Abrin↗
PubMed1985

Fast axonal transport in the visual pathway of the chick and rat.

Young chickens and rats were injected intravitreally with [3H]proline and sacrificed at short intervals thereafter. Regression lines calculated for the plotted points (survival time, transport distance) revealed a transport rate of 329 mm/day in the chick and 350 mm/day in the rat. Both rates are close to those reported for peripheral axons (410 +/- 50 mm/day).

Animals↗
PubMed1995

Induction of heat-shock protein-70 messenger RNA and protein following systemic kainate injection in the rat: evidence of protein axonal transport.

Induction of heat-shock protein-70 was studied using in situ hybridization and immunohistochemistry in the adult rat at different times following intraperitoneal injection of kainate. Marked expression of heat-shock protein-70 messenger RNA was observed during the first 24 h, followed by residual signal at 48 h. Inducible heat-shock protein-70 protein was found in sensitive areas not subjected to early cell death, including the lateral, dorsal and cingular cortices, lateral amygdala, thalamus and hippocampus at 12, 24 and 48 h after injection. In the hippocampus, inducible heat-shock protein-70 immunoreactivity was contained in the soma and proximal dendritic region of neurons of CA3, hilus and CA1 at 12 h, and within the entire dendritic arbor at 24 h. Heat-shock protein-70 immunoreactivity decreased in the cell bodies at four days, but delicate immunostaining appeared in the dorsal fornix, fimbria, and ventral and dorsal hippocampal commissures, as well as in the strata oriens and radiatum of CA3, and part of the stratum radiatum of CA1. Inducible heat-shock protein-70 immunoreactivity at day 7 was mainly localized in the strata oriens and radiatum of CA1 and CA3, and inner one-third of the molecular layer of the dentate gyrus, in which the ipsilateral and commissural hippocampal pathways terminate. These findings show that, in the hippocampus, inducible heat-shock protein-70 is synthesized in the cytoplasm of neurons and subsequently transported at slow rates (about 2-5 mm/day) through the axons to appropriate terminals in the ipsilateral and contralateral hippocampus. A similar pattern is observed for sensitive neurons (heat-shock protein-70 immunoreactive) in the neocortex and thalamus, and labelling of corticocortical, corticostriatal and intrathalamic (between the dorsal and the reticular nuclei) fibres. Since inducible heat-shock protein-70 keeps native proteins unfolded to prevent abnormal configuration following diverse insults, heat-shock protein-70 is proposed as a marker of transient impaired assembly of native proteins in sensitive neurons and axons following intraperitoneal kainate injection.

Animals↗
PubMed2002

Axonal transport of mitochondria to synapses depends on milton, a novel Drosophila protein.

A protein required to localize mitochondria to Drosophila nerve terminals has been identified genetically. Photoreceptors mutant for milton show aberrant synaptic transmission despite normal phototransduction. Without Milton, synaptic terminals and axons lack mitochondria, although mitochondria are numerous in neuronal cell bodies. In contrast, synaptic vesicles continue to be transported to and concentrated at synapses. Milton protein is associated with mitochondria and is present primarily in axons and synapses. A likely explanation of the apparent trafficking defect is offered by the coimmunoprecipitation of Milton and kinesin heavy chain. Transfected into HEK293T cells, Milton induces a redistribution of mitochondria within the cell. We propose that Milton is a mitochondria-associated protein required for kinesin-mediated transport of mitochondria to nerve terminals.

Animals↗
PubMed1975

Effect of inhibiting protein synthesis on axonal transport of membrane glycoproteins in an identified neuron of Aplysia.

Intrasonic injection of L-[3H]fucose into R2, the cholinergic giant neuron in the abdominal ganglion of the marine molluse, Aplysia californica, labeled 5 major glycoprotein membrane components, 3 of which were preferentially exported into the axon. Brief exposure to anisomycin, a potent inhibitor of protein synthesis in Aplysia, almost completely blocked the appearance of [3H]glycoprotein in the axon; but fucosylation of proteins in the cell body was only partially inhibited. Polyacrylamide gel electrophoresis showed that the 5 normal components were present in the cell body of inhibited neurons. Thus, synthesis and insertion of glycoproteins into membranes do not guarantee export from the cell body: presumably completion of transportable organelles requires continuous synthesis of new proteins. Longer exposure before injection resulted in reduced amounts of four of the glycoproteins, but one component continued to be formed. Anisomycin can be used to resolve export of glycoproteins out of the cell body from subsequent movement along the axon. When we exposed R2 to anisomycin after injection, [3H]glycoproteins, which had already entered the axon, were translocated along the axon normally; they were distributed in waves, the most distal moving at 50-60 mm/day.

Acetylcholine↗