Studies on Subcellular Fractions Which Are Involved in Myelin Assembly: Labeling of Myelin Proteins by a Double Radioisotope Approach Indicates Developmental Relationships

Pereyra, Pedro M.; Braun, Peter E.; Greenfield, Seymour; Hogan, Edward L.

doi:10.1111/j.1471-4159.1983.tb09041.x

Cited by 29 publications

(11 citation statements)

References 20 publications

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“…For example, ing similarities, are nevertheless distinct. Our findings there is evidence that MBP is synthesized close to the have confirmed previous observations obtained from immyelin compartment (Benjamins et al, 1976; Colman et munocytochemical studies; they have shed new light on al., 1982; Pereyra et al, 1983). This accords with the the relationship between the plasma membrane and finding that B3.f OLG synthesize little MBP (Yim et al, myelin; and they have also sharpened old controversies 1986) just as mature oligodendrocytes in situ do not or opened new ones.…”

Section: Discussionsupporting

confidence: 81%

“…We believe that the availability of synthesize MBP (Sternberger, 1984). a highly purified fraction of oligodendrocyte plasma Studies with precursors have revealed that it takes 20 membrane should be instrumental in opening up new min (Pereyra et al, 1983) to 30 min (Benjamins et al, avenues of research on the plasma membrane itself and 1976; Benjamins, 1984;Colman et al, 1982) for PLP to on its transformation into myelin. get into myelin.…”

Section: Discussionmentioning

confidence: 99%

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Plasma membrane of cultured oligodendrocytes: III. Relatedness to myelin

Szuchet

Polak

Yim

et al. 1988

Glia

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We have compared highly purified fractions of oligodendrocyte plasma membrane to myelin by one- and two dimensional gel electrophoresis and found them to be distinct. The major myelin proteins--proteolipid protein (PLP), DM-20, and myelin basic protein (MBP), which dominate the sodium dodecyl sulfate polyacrylamide gel electrophoresis pattern of myelin--were minor components of the plasmalemma. However, 2',3', cyclic nucleotide phosphodiesterase (CNPase) and myelin-associated glycoprotein (MAG) were represented equally in both membranes. Labeling the cells with various precursors followed by isolation of plasmalemma revealed that newly synthesized PLP, DM-20, CNPase, and MAG were incorporated into the plasma membrane of "floating" oligodendrocytes (i.e., nonattached to substratum). This was not so with MBP. Nevertheless, scattered patches of MBP were localized on the plasma membrane of intact cells using the immunogold method at the electron microscopic level. The data are consistent with the notion that MBP is not a constituent of the plasma membrane of mature oligodendrocytes (the MBP patches on intact cells are likely remnants from past association with myelin) but is rapidly associated with the plasmalemma of myelinating oligodendrocytes (i.e., attached cells). It is suggested that phosphorylation of MBP provides the triggering signal for plasma membrane association. In order to analyze the minor proteins in myelin and compare them to the plasma membrane by two-dimensional gel electrophoresis, myelin was extracted with chloroform:methanol to remove PLP, DM-20, and MBP. Even in the absence of PLP, DM-20, and MBP the pattern of extracted myelin still differed from that of plasmalemma indicating that their minor protein compositions were not the same. Myelin was characterized by a group of proteins that clustered at pI 5.5-6.5 and Mr 40,000-60,000 of which alpha-tubulins, beta-tubulins, and actin are part: the plasmalemma had tubulins and actin but in different proportions. Our findings indicate that in addition to PLP, DM-20, and MPB, myelin is also enriched relative to the plasmalemma in another group of proteins.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Plasma membrane of cultured oligodendrocytes: III. Relatedness to myelin

Szuchet

Polak

Yim

et al. 1988

Glia

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“…Thus, specific radioactivity data from the fluorography scans can safely be referred to the corresponding proteins on the Western blots. 3H-leucine deposited intracranially has been dernonstrated to be nearly equivalent with a pulse label, with an average duration of less than 5 min and with no significant reutilization of the label Pereyra et al, 1983;Smith, 1968Smith, , 1972Wiggins and Morell, 1983). Therefore, this isotope and route of administration were used in the present study.…”

Section: Discussionmentioning

confidence: 99%

Metabolic relationships between proteins of myelin and paranodally shedded, partially degraded myelin fragments in the rabbit CNS

Persson¹,

Berthold²,

Rydmark³

et al. 1992

J of Neuroscience Research

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The "close-to-node" regions of myelinated nerve fibres, i.e., the paranodal end segments, are generally thought to be sites of high metabolic activity and myelin sheath turnover. Data on turnover rates of individual myelin constituents are conflicting but there exists a common belief that myelin is metabolized as independent molecules rather than as a unit. The occurrence of paranodal Marchi-positive bodies, with morphological and biochemical properties consistent with partially degraded myelin, prompted us to examine the temporal dynamics of the incorporation of radioactive precursor label in the major proteins of myelin and the Marchi-positive bodies. 3H-leucine was administered intrathecally in adult rabbits. After various survival times, the spinal cord was subfractionated by ultracentrifugation in a discontinuous two-step 0.32 M/0.85 M sucrose gradient. Myelin was collected from the interface and a floating fraction, heavily enriched in Marchi-positive bodies, was recovered on top of the 0.32 M sucrose. By scintillation counting and by gel fluorography combined with immunoblotting, a gradual appearance with time of partially degraded peptides of myelin-associated protein and 2',3'-cyclic nucleotide 3'-phosphodiesterase was seen in the floating fraction but not in myelin. The temporal dynamics of the specific activities of these two proteins and myelin-basic protein and proteolipid protein were consistent with a typical source-product relationship between myelin and the material in the floating fraction. In conjunction with earlier morphological and biochemical findings, these data may suggest that Marchi-positive bodies appear as a consequence of myelin catabolism.

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“…Following a relatively short transit time between their site of synthesis and site of deposition. MBPs accumulate in the myelin compartment [7]. In the CNS, maturation of a myelin sheath involves ensheathment of an axon by an oligodendroglial process followed by the formation of numerous lamellae arranged spirally around the axon.…”

Section: Introductionmentioning

confidence: 99%

In vivo Phosphorylation of Myelin Basic Proteins in Developing Mouse Brain: Evidence that Phosphorylation Is an Early Event in Myelin Formation

Ulmer¹,

Braun²

1983

Dev Neurosci

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Myelin basic proteins (MBPs) can be detected in 5-day mouse brain, even though there is very little myelin present. In addition to the 4 MBP components (with molecular weights of 14, 17, 18.5 and 21.5 kilodaltons), that are commonly observed, other larger MBP-related polypeptides are also present. We have investigated the possibility of MBP phosphorylation at early stages of development in order to establish the point at which this modification occurs in the assembly of myelin. In vivo isotope studies show that in the 5-day mouse brain 14-, 17-, 18.5- and 21.5- kilodalton MBPs are phosphorylated and that they may be present in an immature form of myelin. Larger MBP-related proteins with a molecular weight of 35 and 42 kilodaltons are also phosphorylated but appear to be present mostly in nonmyelin structures or compartments.

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Studies on Subcellular Fractions Which Are Involved in Myelin Assembly: Labeling of Myelin Proteins by a Double Radioisotope Approach Indicates Developmental Relationships

Cited by 29 publications

References 20 publications

Plasma membrane of cultured oligodendrocytes: III. Relatedness to myelin

Plasma membrane of cultured oligodendrocytes: III. Relatedness to myelin

Metabolic relationships between proteins of myelin and paranodally shedded, partially degraded myelin fragments in the rabbit CNS

In vivo Phosphorylation of Myelin Basic Proteins in Developing Mouse Brain: Evidence that Phosphorylation Is an Early Event in Myelin Formation

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