Isolation of axonally transported glycoproteins with goldfish visual system myelin

Monticone, Robert E.; Elam, John S.

doi:10.1016/0006-8993(75)90241-3

Cited by 21 publications

(5 citation statements)

References 21 publications

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“…The possibility that the a form in the transported proteins is due to local synthesis by glia or other neurons, however, is a critical hypothesis to be tested. Transfer of axonally transported label to myelin-associated proteins has been shown to occur in garflish olfactory nerve (24). Transfer of labeled proteins in the opposite direction, from glia to axons, has also been seen in the squid giant axon (25).…”

Section: Discussionmentioning

confidence: 98%

Two different Na,K-ATPases in the optic nerve: cells of origin and axonal transport.

Specht¹,

Sweadner²

1984

Proc. Natl. Acad. Sci. U.S.A.

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Two molecular forms of Na,K-ATPase can be isolated from the central nervous system. The two forms can be distinguished by their sensitivities to cardiac glycosides and by the electrophoretic mobilities of their catalytic subunits, a and a(+). Because Na,K-ATPase is a membranebound enzyme, it would be predicted to move in the rapid phase of axonal transport, and this was used as a means to determine which form(s) is made by a defined neuron of the central nervous system. Retinal ganpglion cells were labeled in vivo by intravitreal injection of [3 Simethionine; the Na,KATPase that was axonally transported down the optic nerve was purified, and the a and a(+) forms were separated by electrophoresis and detected by fluorography. The two forms were synthesized in the retina in approximately equal amounts. The a(+) form was the predominant form transported from the retinal ganglion cells to the lateral geniculate nucleus and superior colliculus. The oligodendrocytes and other sheath cells of the excised optic nerve, in contrast, synthesized only the a form when incubated in vitro with [35S]methionine. The labeled Na,K-ATPase found at the nerve endings always included a small amount of the a form in addition to the a(+) form. The proportions of the two forms did not change with time after transport, and the presence of labeled a was not affected by infusion of cycloheximide to inhibit intracranial protein synthesis. Hence, although a(+) is the predominant form, the evidence suggests that small amounts of the a form are also made and transported by retinal ganglion cells.The ouabain-inhibited Na,K-ATPase is the enzyme responsible for active transport of Na' and K+ across the cell membrane (1), and is present in both neurons and glia. When isolated from the kidney, it is comprised of a catalytic subunit of Mr approximately 95,000 (a) and a smaller glycoprotein subunit (13) of unknown function. Preparations of Na,KATPase from the brain, however, have two biochemically distinct forms of the catalytic subunit, called a and a(+) (2). These differ in electrophoretic mobility in NaDodSO4-containing gels (2-4) and in sensitivity to cardiac glycosides (2, 5, 6). Purified axolemmal membrane from rat brain white matter contains only a(+) (2, 3), while cultured glia contain only a (2), which suggests that a(+) is characteristic of neurons and a, of nonneuronal cells. Neurons of the sympathetic nervous system contain only the a form, however, and synaptosomes from the cerebral cortex contain both forms (2). Although the presence of the a form in synaptosomes may be due to contamination with membrane of glial origin, the evidence is consistent with the hypothesis that neurons can express either form or both. A selective labeling technique is needed to determine which forms are expressed in different neurons of the central nervous system. The Na,K-ATPase of a defined population of neurons was examined by taking advantage of the axonal transport of newly synthesized radioactively labeled protein to sites distant from the cell b...

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Section: Discussionmentioning

confidence: 98%

Two different Na,K-ATPases in the optic nerve: cells of origin and axonal transport.

Specht¹,

Sweadner²

1984

Proc. Natl. Acad. Sci. U.S.A.

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“…Although there is some suggestive evidence to the contrary (14,28), it is generally believed that myelin proteins are a product of supportive glial ceils. Glycoproteins made in the neuronal perikar- The results are shown for mice injected for 8 days (A and D) or 72 days (B, C, E, and F).…”

Section: Discussionmentioning

confidence: 99%

Incorporation of glycoproteins into peripheral nerve myelin.

Gould¹

1977

The Journal of Cell Biology

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Peripheral nerve myelin contains a dominant low molecular weight glycoprotein (12,17,22,25,32) called Po (17). To study the metabolism of this glycoprotein, tritiated fucose was injected into the peripheral nerves of adult mice and developing rats, and the temporal distribution of label was examined by autoradiography and gel electrophoresis.Mice and rat pups, injected with fucose, were sacrificed from 1 h to 98 days later. Series of autoradiographs were prepared. At the shortest labeling periods, newly formed product was confined to juxtanuclear Schwann cell cytoplasm, in association with regions rich in Golgi apparatus. After longer labeling periods, silver grain levels in Schwann cell cytoplasm decreased; concomitantly, there was an increase of silver grains associated with myelin. In adult animals, label associated with myelin was concentrated over outer layers of thickly myelinated fibers. Even at the longest time intervals examined (72 and 98 days), this distribution of label was largely retained. In contrast, in developing animals, label became associated with inner layers of the thicker sheaths. At no time was label observed over axons.Gel electrophoresis revealed that tritiated fucose was a suitable precursor for the faster migrating peripheral nerve glycoprotein(s). At all times examined, there was a single major peak of radioactivity that co-migrated on sodium dodecyl sulfate (SDS) acrylamide gels with the Po protein (17). Sometimes, a faster migrating shoulder of radioactivity was noted. With increased labeling periods, there was an enrichment of radioactivity associated with Po, indicative of a relatively slow turnover rate.KEY WORDS peripheral nerve myelin glycoprotein metabolism 9 Po protein lateral diffusion EM autoradiographyMetabolism of choline-and inositol-labeled lipids of peripheral nerve myelin has recently been studied by quantitative autoradiography (10,15,16, and Gould, unpublished observations). It was demonstrated that these phospholipids migrate from synthetic sites in Schwann cell cytoplasm surrounding the myelin sheath into and through the myelin. Several days are needed for the innermost lamellae of thickly myelinated fibers to become as thoroughly labeled as the outer lamellae. From such a time-course and knowledge of the surface dimensions over which the phospholipids would travel, diffusion constants of between 10 -7 and 10 -~ cm"/s were determined. Peripheral nerve myelin contains two dominant glycoproteins having molecular weights of 23,000 326

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“…not nearly so prominent as in the various mammalian myelin fractions which have been examined (Matthieu et al, 1974;Everly et al, 1977). A very heterogeneous population of glycoproteins has also been reported in myelin fractions from another lower vertebrate, the gold fish (Monticone and Elam, 1975). The PAS stained glycoproteins in Xenopus sciatic nerve myelin were very similar to those in the rat, consisting of the PO protein and at least one smaller mol wt.…”

Section: Discussionmentioning

confidence: 78%

A biochemical comparison of Xenopus laevis and mammalian myelin from the central and peripheral nervous systems

et al. 1978

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Myelin purified from the central nervous system of Xenopus laevis contained the same major lipid and protein components as human myelin. However, some minor differences in the myelin proteins were noted. The Xenopus basic protein had a higher apparent mol wt. on sodium dodecyl sulfate gels than the corresponding mammalian protein. The absolute specific activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase in the Xenopus myelin was considerably higher than in mammals. There were differences in the high mol wt. proteins, and the glycoproteins in Xenopus myelin were more heterogeneous than those in mammals. Peripheral myelin from Xenopus sciatic nerve was compared with that from the rat. The lipids in the two types of myelin were similar. There was a major glycoprotein in the Xenopus myelin corresponding to the P0 protein and a basic protein of slightly larger mol wt. than the P1 protein of rat myelin.

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Isolation of axonally transported glycoproteins with goldfish visual system myelin

Cited by 21 publications

References 21 publications

Two different Na,K-ATPases in the optic nerve: cells of origin and axonal transport.

Two different Na,K-ATPases in the optic nerve: cells of origin and axonal transport.

Incorporation of glycoproteins into peripheral nerve myelin.

A biochemical comparison of Xenopus laevis and mammalian myelin from the central and peripheral nervous systems

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