Minor proteins of CNS myelin fractions: are they intrinsic to the myelin sheath?

doi:10.1111/j.1471-4159.1977.tb09632.x

Cited by 6 publications

(1 citation statement)

References 29 publications

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“…This view was founded on studies in the 1970s, in which myelin was biochemically purified from nervous tissue and separated by polyacrylamide gel electrophoresis (PAGE). Upon protein staining using Coomassie Blue or other staining dyes, myelin purified from the brains of mammalian, avian, or reptilian species displayed only four to five bands (Zanetta et al, 1977;Quarles et al, 1978;Franz et al, 1981;Jeserich, 1983), which we now know represent one or several splice isoforms each of the transmembrane-tetraspan proteolipid protein (PLP), the cytosolic adhesion protein myelin basic protein (MBP), and the enzyme cyclic nucleotide phosphodiesterase (CNP, previously termed Wolfgram protein). Notably, the band pattern of central nervous system (CNS) myelin of several species of bony fish differed markedly from that of tetrapod myelin with respect to the number of bands and their molecular weight (Franz et al, 1981;Jeserich, 1983;Waehneldt et al, 1986;Kirschner et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Proteome Profile of Myelin in the Zebrafish Brain

Siems

Jahn

Hoodless

et al. 2021

Front. Cell Dev. Biol.

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The velocity of nerve conduction along vertebrate axons depends on their ensheathment with myelin. Myelin membranes comprise specialized proteins well characterized in mice. Much less is known about the protein composition of myelin in non-mammalian species. Here, we assess the proteome of myelin biochemically purified from the brains of adult zebrafish (Danio rerio), considering its increasing popularity as model organism for myelin biology. Combining gel-based and gel-free proteomic approaches, we identified > 1,000 proteins in purified zebrafish myelin, including all known constituents. By mass spectrometric quantification, the predominant Ig-CAM myelin protein zero (MPZ/P0), myelin basic protein (MBP), and the short-chain dehydrogenase 36K constitute 12%, 8%, and 6% of the total myelin protein, respectively. Comparison with previously established mRNA-abundance profiles shows that expression of many myelin-related transcripts coincides with the maturation of zebrafish oligodendrocytes. Zebrafish myelin comprises several proteins that are not present in mice, including 36K, CLDNK, and ZWI. However, a surprisingly large number of ortholog proteins is present in myelin of both species, indicating partial evolutionary preservation of its constituents. Yet, the relative abundance of CNS myelin proteins can differ markedly as exemplified by the complement inhibitor CD59 that constitutes 5% of the total zebrafish myelin protein but is a low-abundant myelin component in mice. Using novel transgenic reporter constructs and cryo-immuno electron microscopy, we confirm the incorporation of CD59 into myelin sheaths. These data provide the first proteome resource of zebrafish CNS myelin and demonstrate both similarities and heterogeneity of myelin composition between teleost fish and rodents.

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Section: Introductionmentioning

confidence: 99%

Proteome Profile of Myelin in the Zebrafish Brain

Siems

Jahn

Hoodless

et al. 2021

Front. Cell Dev. Biol.

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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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