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At least 1,261 records · Page 70Linked to original sources
PubMed1982

Rapid and precise down regulation of fast axonal transport of transmitter in an identified neuron.

Within 1 day after the removal of one branch of the bifurcated axon of an identified neuron in Aplysia, the cell body reduced its output of transmitter storage vesicles to adjust precisely for the decreased need. This adjustment terminated the initial consequence of the removal, the transport of an inappropriately large number of vesicles to the remaining synapses. The most likely cause of the reduction of transport of transmitter is the loss of information normally provided by the disconnected axon or synapses.

Animals↗
PubMed1999

Neuronal overexpression of APPL, the Drosophila homologue of the amyloid precursor protein (APP), disrupts axonal transport.

The two pathological hallmarks of Alzheimer's disease, amyloid plaques and neurofibrillary tangles, involve two apparently unrelated proteins, the amyloid precursor protein (APP) and Tau. Although it is known that aberrant processing of APP is associated with Alzheimer's disease, the definitive role of APP in neurons is not yet clear. Tau regulates microtubule stabilization and assembly in axons and is, thus, an essential component of the microtubule-associated organelle transport machinery. Although several groups have reported physical interaction between APP and Tau, and induction of Tau phosphorylation by APP and beta-amyloid peptide, the functional connection between APP and Tau is unclear. To explore the possibility that the functions of these two proteins may somehow converge on the same cellular process, we overexpressed APPL, the Drosophila homologue of APP, along with Tau in Drosophila neurons. Panneural coexpression of APPL and Tau resulted in adults that, upon eclosion, failed to expand wings and harden the cuticle, which is suggestive of neuroendocrine dysfunction. We analyzed axonal transport when Tau and APPL were coexpressed and found that transport of axonal cargo was disrupted, as evidenced by increased retention of synaptic proteins in axons and scarcity of neuropeptide-containing vesicles in the distal processes of peptidergic neurons. In an independent approach, we demonstrated genetic interaction and phenotypic similarity between APPL overexpression and mutations in the Kinesin heavy chain (Khc) gene, the product of which is a motor for anterograde vesicle trafficking.

Amyloid beta-Protein Precursor↗
PubMed1986

Binding, uptake and retrograde axonal transport of herpes virus suis in sympathetic neurons.

Newborn rat dissociated sympathetic neurons were grown in a chamber culture system, where a Teflon ring sealed with silicon grease separated the axonal plexus from the corresponding nerve cell bodies. The binding of 35S-labeled herpes virus suis (HVS) to the neurites was partially inhibited by an excess of unlabeled HVS as well as by concanavalin A, indicating the presence of specific binding sites for the virus. Specific binding was a prerequisite for the subsequent uptake and retrograde transport of HVS to the nerve cell bodies. Predominantly free nucleocapsids were detected by electron microscopy in the axons at the time of retrograde transport, both in culture and in vivo, suggesting the possibility that nucleocapsids without lipid membrane and not contained in cellular membrane compartments can be transported by retrograde axonal transport.

Animals↗
PubMed1976

Fast axonal transport in motor nerve regeneration.

This report describes the fast transport of [3H]-leucine-labeled proteins in regenerating rat sciatic motor nerves. A normal rate of fast transport (383 +/- 33 mm/day) was present in the regenerating sprouts, as well as in the central stumps. The rapidly transported proteins passed the level of axotomy without impediment, and accumulated in the endings of the regenerating sprouts, as shown by electron microscope autoradiography. In addition, transported proteins accumulated in terminal neuromas. The relative amount of protein-incorporated radioactivity in the crest of transport in the regenerating nerves was increased compared to control nerves. These results are interpreted to suggest that the mechanism of fast transport is the same in regenerating nerves was increased compared to control nerves. These results are interpreted to suggest that the mechanism of fast transport is the same in regenerating sprouts as in normal axons; during regeneration fast transport appears to add newly synthesized materials to the growing tip.

Animals↗
PubMed1995

Three distinct axonal transport rates for tau, tubulin, and other microtubule-associated proteins: evidence for dynamic interactions of tau with microtubules in vivo.

Microtubule-associated proteins (MAPs), such as tau, modulate neuronal shape and process outgrowth by influencing the stability and organization of microtubules. The dynamic nature of MAP-microtubule interactions in vivo, however, is poorly understood. Here, we have assessed the stability of these interactions by investigating the synthesis and axoplasmic transport of tau in relation to that of tubulin and other MAPs within retinal ganglion cells of normal adult mice in vivo. Using immunoprecipitation and Western blot analysis with anti-tau monoclonal and polyclonal antibodies, we unequivocally identified in optic axons a family of 50-60 kDa tau isoforms and a second 90-95 KDa tau family, the members of which were shown to contain the domain of tau encoded by exon 4A. To measure the rates of translocation of tau proteins in vivo, we injected mice with 35S-methionine intravitreously and, after 6-30 d, quantitated the radiolabeled tau isoforms immunoprecipitated from eight consecutive 1.1 mm segments of the nerve and optic tract and separated by electrophoresis. Linear regression analysis of protein transport along optic axons showed that the tau isoforms advanced at a rate of 0.2-0.4 mm/d, and other radiolabeled MAPs, identified by their association with taxol-stabilized microtubules, moved three- to fivefold more rapidly. By contrast, tubulins advanced at 0.1-0.2 mm/d, significantly more slowly than tau or other MAPs. These studies establish that tau is not cotransported with tubulin or microtubules, indicating that associations of tau with microtubules within axons are not as stable as previously believed. Our findings also reveal differences among various MAPs in their interactions with microtubules and provide evidence that assembly and reorganization of the microtubule network is an active process even after axons establish connections and fully mature.

Animals↗
PubMed1979

Comparison of the temperature-dependence of rapid axonal transport and microtubules in nerves of the rabbit and bullfrog.

1. The average velocity of transport of dopamine-beta-hydroxylase, an enzyme confined to unmyelinated adrenergic nerves, was measured in rabbit and bullfrog sciatic nerves or branches incubated in vitro at various temperatures. In parallel experiments, the number and density of microtubules were measured in cross-sections of randomly selected unmyelinated axons from another set of nerves incubated under the same conditions. 2. Average transport velocity was exponentially related to temperature over a wide range, but it fell abruptly towards zero at temperatures below 13 degrees C in the case of rabbit nerves and 10 degrees C in the case of frog nerves. 3. The number of microtubules per unmyelinated axon had declined considerably before the transport of dopamine-beta-hydroxylase was impaired. At 13 degrees C, axons in rabbit nerves lost 30% of their microtubules. Axons in bullfrog nerves were, if anything, more sensitive to cold, losing 35% of their microtubules at 15 degrees C and 65% of them at 10 degrees C. 4. Since the temperature-dependence of the axonal transport of dopamine-beta-hydroxylase is probably typical of rapid axonal transport in general, it was concluded that transport in unmyelinated axons can continue unaffected when a substantial fraction of the microtubular population has been lost. 5. Although these results could imply that microtubules are not essential for transport, they are equally compatible with the view that these organelles determine the capacity of the transport system and are normally present in excess.

Animals↗