Cohesive axonal transport of the slow component b complex of polypeptides (original) (raw)
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The Journal of Cell Biology, 1985
The distribution of the proteins migrating with the slow components a (SCa) and b (SCb) of axonal transport were studied in cross-sections of axons with electron microscope autoradiography. Radiolabeled amino acids were injected into the hypoglossal nucleus of rabbits and after 15 d, the animals were killed. Hypoglossal nerves were processed either for SDS-polyacrylamide gel electrophoresis fluorography to identify and locate the two components of slow transport, or for quantitative electron microscope autoradiography. Proteins transported in SCa were found to be uniformly distributed within the cross-section of the axon. Labeled SCb proteins were also found throughout the axonal cross-section, but the subaxolemmal region of the axon contained 2.5 times more SCb radioactivity than any comparable area in the remainder of the axon.
Slow components of axonal transport: two cytoskeletal networks
The Journal of Cell Biology, 1980
Proteins are axonally transported at a relatively small number ofdiscrete rates. The available information indicates that each rate component represents the movement of highly ordered protein complexes. For example, although the range of transport rates spans three orders ofmagnitude, only five rate classes have been identified (31, 38, 45, 69, 70) and, each axonally transported protein is present in only one of these (64). The movement of particles in axons (11, 18) supports this hypothesis, as do the studies of Schwartz and his colleagues (24, 25) which have clearly shown that serotonin-containing vesicles are transported in an identified serotonergic neuron ofAplysia. Tubulin and neurofilament protein, the subunits of microtubules and neurofilaments, respectively, are also transported in axons (29, 41). The transport kinetics of these proteins suggest that they are associated in a structural complex, a microtubuleneurofilament network, that is transported in axons. These and other considerations have led to the "central theory of axonal transport," which states that proteins move as parts of cytologically identified structures (39). We have identified two slowly moving groups of proteins in guinea pig retinal ganglion cell axons (4). The slowest moving group, designated slow component a (SCa), consists of tubulin and neurofilament protein. The other group, designated slow component b (SCb), contains many polypeptides, one of which is actin (4, 71), the major constituent of actin microfilaments.
Slow axonal transport mechanisms move neurofilaments relentlessly in mouse optic axons
The Journal of Cell Biology, 1992
Pulse-labeling studies of slow axonal transport in many kinds of axons (spinal motor, sensory ganglion, oculomotor, hypoglossal, and olfactory) have led to the inference that axonal transport mechanisms move neurofilaments (NFs) unidirectionally as a single continuous kinetic population with a diversity of individual transport rates. One study in mouse optic axons (Nixon, R. A., and K. B. Logvinenko. 1986. J. Cell Biol. 102:647-659) has given rise to the different suggestion that a significant and distinct population of NFs may be entirely stationary within axons. In mouse optic axons, there are relatively few NFs and the NF proteins are more lightly labeled than other slowly transported slow component b (SCb) proteins (which, however, move faster than the NFs); thus, in mouse optic axons, the radiolabel of some of these faster-moving SCb proteins may confuse NF protein analyses that use one dimensional (1-D) SDS-PAGE, which separates proteins by size only. To test this possibility,...
Brain Research, 1977
We have determined that a genetically polymorphic polypeptide (H, molecular weight _ 195,000) of the rabbit nervous system is transported down the retinal ganglion cell axons at a velocity of 0.7-1.1 mm/day. The H-polypeptide and probably at least two additional polypeptides (molecular weights approximately 145,000 and 73,000) therefore compose a group of intra-axonally transported proteins which moves more slowly than the 4 groups previously described in these neurons. The polypeptides of this fifth group are similar in molecular weight to certain polypeptides transported slowly in other mammalian neuronsL * Whether the retinal ganglion cells are homogeneous or heterogeneous with respect to their transported proteins has not been directly determined.
Journal of Cell Biology, 1980
Polypeptide H (mol wt 195,000) is axonally transported in rabbit retinal ganglion cells at a velocity of 0.7--1.1 mm/d, i.e., in the most slowly moving of the five transport groups described in these neurons. To identify the organelle with which H is associated, we purified H, prepared antibodies directed against it, and adsorbed the antibodies onto Formvar-coated electron microscope grids. When the resulting "immuno-affinity grids" were incubated with extracts of spinal cord and then examined in the electron microscope, they contained as many as 100 times more 100-A filaments than did grids coated similarly with nonimmune IgG. The ability of the anti-H IgG to specifically adsorb filaments to grids was completely blocked by incubating the IgG with polypeptide H. The 100-A filaments adsorbed to anti-H immunoaffinity grids could be specifically decorated by incubating them with anti-H IgG. These observations demonstrate that H antigens (and most likely H itself) are associat...
Axonal transport of macromolecules I. Protein migration in the central nervous system
Experimental Brain Research, 1971
The avian visual system has been used to study the transport of proteins and their precursors along the optic tract. Various labeled compounds were injected into a single eye of new hatched chicks. The radioactivity of components in the optic lobe that was contralateral to, and innervated by, the injected eye was compared to radioactivity in the ipsilateral lobe, not innervated by the treated eye. Proteins migrating from the ganglion cells of the retina to the optic tectum seemed to be relatively stable and may be rich in praline and glycine. Microtubular protein migrated at a rate similar to nonmicrotubule soluble protein, and slower than particulate protein. With the exception of y-aminobutyric acid, transport of free amino acids occurred to only a minor extent. Following monocular injection of tritiated fucose, a rapid asymmetry in the specific activities of protein from contralateral and ipsilateral lobes, was established. Thus the more rapidly migrating proteins may be attached to glycosidic residues. The carbohydrate moeity of these glycoproteins is attached in the nerve cell body, prior to their axonal transport to the optic tectum. There was no evidence for transneuronal transfer of protein as in no cai;e was a differential in specific activity observed in labeled protein from paired cerebral hemispheres.
Imaging axonal transport in the rat visual pathway
Biomedical Optics Express, 2013
A technique was developed for assaying axonal transport in retinal ganglion cells using 2 µl injections of 1% cholera toxin b-subunit conjugated to AlexaFluor488 (CTB). In vivo retinal and post-mortem brain imaging by confocal scanning laser ophthalmoscopy and post-mortem microscopy were performed. The transport of CTB was sensitive to colchicine, which disrupts axonal microtubules. The bulk rates of transport were determined to be approximately 80-90 mm/day (anterograde) and 160 mm/day (retrograde). Results demonstrate that axonal transport of CTB can be monitored in vivo in the rodent anterior visual pathway, is dependent on intact microtubules, and occurs by active transport mechanisms.
Brain Research, 1977
Rapid movements of intra-axonal organelles in acutely isolated single myelinated fibers from bullfrog sciatic nerve were visualized by dark-field microscopy. The movements were recorded by cinemicrography, and analyzed by computer-based methods. The movements are saltatory and bidirectional, but each particle moves mainly in a single direction. For more than 90~ of the particles, the predominant movement direction is retrograde, i.e. toward the cell body. Quantitative measurements on a variety of parameters of the organelle movements are presented. Different particles in the same axon show a broad range of mean speeds. The average mean speed of movement in the retrograde direction at 28 °C was 1.08 #m/sec (S.D. = 0.41), equivalent to an axonal transport rate of 93 mm/day. Disperse distributions were also found for other parameters such as the instantaneous velocities of individual particles. Quantal velocities, periodic movement patterns, and specific 'channels' were not detected. When the data from a population of particles is treated statistically, the average mean speed, the distribution of velocities, and other statistical parameters are found to be similar in different axons studied at the same temperature. Direct microscopical observation of axonal organelle movement is a technique which provides information about axonal transport which is different from and complementary to that obtained from enzyme accumulation or radioactive tracer methods.