SAG: a Schwann cell membrane glycoprotein

Dieperink, ME; O'Neill, Alison; Magnoni, Giacomo; Wollmann, RL; Heinrikson, R L; Zucher-Neely, HA; Stefansson, K.

doi:10.1523/jneurosci.12-06-02177.1992

Cited by 15 publications

(5 citation statements)

References 41 publications

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“…In addition to these abundant glycoproteins, the PNS myelin holds three other, very minor glycoproteins: Schwann cell membrane glycoprotein (SAG), found exclusively in PNS myelin, associated with Schwann cells (Dieperink et al, ); Schwann cell myelin protein (SMP), expressed in vivo exclusively by myelinating and nonmyelinating Schwann cells and oligodendrocytes (Dulac and Le Douarin, ; Dulac et al, ); and the oligodendrocyte‐myelin glycoprotein (OMgp), involved in the formation and maintenance of the myelin sheaths (Kottis et al, ; Vourc'h and Andres, ).…”

Section: Myelin Glycoproteinsmentioning

confidence: 99%

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Glycans of myelin proteins

Sędzik

Jastrzebski

Grandis

2014

J of Neuroscience Research

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Human P0 is the main myelin glycoprotein of the peripheral nervous system. It can bind six different glycans, all linked to Asn(93) , the unique glycosylation site. Other myelin glycoproteins, also with a single glycosylation site (PMP22 at Asn(36) , MOG at Asn(31) ), bind only one glycan. The MAG has 10 glycosylation sites; the glycoprotein OMgp has 11 glycosylation sites. Aside from P0, no comprehensive data are available on other myelin glycoproteins. Here we review and analyze all published data on the physicochemical structure of the glycans linked to P0, PMP22, MOG, and MAG. Most data concern bovine P0, whose glycan moieties have an MW ranging from 1,294.56 Da (GP3) to 2,279.94 Da (GP5). The pI of glycosylated P0 protein varies from pH 9.32 to 9.46. The most charged glycan is MS2 containing three sulfate groups and one glucuronic acid; whereas the least charged one is the BA2 residue. All glycans contain one fucose and one galactose. The most mannose rich are the glycans MS2 and GP4, each of them has four mannoses; OPPE1 contains five N-acetylglucosamines and one sulfated glucuronic acid; GP4 contains one sialic acid. Furthermore, human P0 variants causing both gain and loss of glycosylation have been described and cause peripheral neuropathies with variable clinical severity. In particular, the substitution T(95) →M is a very common in Europe and is associated with a late-onset axonal neuropathy. Although peripheral myelin is made up largely of glycoproteins, mutations altering glycosylation have been described only in P0. This attractive avenue of research requires further study.

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Section: Myelin Glycoproteinsmentioning

confidence: 99%

“…SAG is found in PNS and plays a role in myelination and stability of the myelin membrane. Bovine SAG contains HNK‐1 epitope, but rat SAG does not (Dieperink et al, ).…”

Section: Myelin Glycoproteinsmentioning

confidence: 99%

Glycans of myelin proteins

Sędzik

Jastrzebski

Grandis

2014

J of Neuroscience Research

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“…Since antibodies to the glycolipid galactocerebroside very efficiently block myelin formation by Schwann cells in vitro (Ranscht et al 1987), this molecule may be another likely candidate involved in the compensation for MAG or N-CAM. Other cell surface components of Schwann cells which might compensate for MAG or N-CAM are L1 (Wood et al 1990), Ecadherin (Fannon et al 1995), the Schwann cell membrane glycoprotein SAG (Dieperink et al 1992), the Schwann cell component P30 (Daston and Ratner 1991), the myelin and lymphocyte protein rMAL (SchaerenWiemers et al 1995) and plasmolipin (Gillen et al 1996). In conclusion, the formation of normal myelin in double mutants deficient in both MAG and N-CAM does not strictly argue against a compensatory role for N-CAM in the absence of MAG, but may reflect a high degree of flexibility in molecular compensation of the Schwann cell during myelin formation.…”

Section: Peripheral Nerve Myelin Is Normally Formed In the Absence Ofmentioning

confidence: 99%

Absence of the myelin-associated glycoprotein (MAG) and the neural cell adhesion molecule (N-CAM) interferes with the maintenance, but not with the formation of peripheral myelin

Carenini

Montag

Cremer

et al. 1996

Cell and Tissue Research

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We have previously shown that mice deficient in the gene for the myelin-associated glycoprotein (MAG) develop normal myelin in the peripheral nerves, but show axon and myelin degeneration at eight months of age, suggesting that MAG is involved in the maintenance of axon-Schwann cell integrity. The search for molecules that might replace MAG during myelination revealed an overexpression of the neural cell adhesion molecule (N-CAM) at those aspects where MAG is detectable in wild type mice. To test whether N-CAM might compensate for MAG during myelination in MAG-deficient mice, double mutants deficient in both MAG and N-CAM (MAG-/N-CAM- mice) were generated by cross-breeding the single mutants. Whereas alterations of myelin development were not detectable in either of the single or double mutants, degeneration of myelin and axons occurred approximately 4 weeks earlier in MAG-/N-CAM- than in MAG- mutants. Furthermore, at 8 weeks of age, single fiber preparation and electron microscopy revealed that the number of profiles indicative of degeneration was substantially increased in MAG-/N-CAM- mutants when compared to MAG- mice. These data suggest that in MAG-deficient mice N-CAM does not compensate for MAG in myelin formation but partially substitutes for it in the maintenance of axon-myelin integrity.

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“…Several of these glycoproteins have been shown to be cell-adhesion molecules, such as N-CAM, L1, Ng-CAM, Nr-CAM, TAG-1, MAG, and others (10 -14). Based on these observations, the HNK-1 reactive carbohydrate has now been considered to be a marker of cell adhesion molecules in the nervous system (15). Previous studies have suggested that HNK-1 carbohydrate is involved in the organization of early neuronal settling and axonal outgrowth patterns (7, 16 -18).…”

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confidence: 99%

N-Acetylglucosaminyl Transferase Regulates the Expression of the Sulfoglucuronyl Glycolipids in Specific Cell Types in Cerebellum during Development

Chou

Jungalwala

1996

Journal of Biological Chemistry

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In the adult cerebellum, sulfoglucuronyl glycolipids (SGGLs) are specifically localized in Purkinje cells and their dendrites in the molecular layer. Other major cell types such as granule neurons and glial cells lack SGGLs. To explain the cell specific localization and the known biphasic expression of SGGLs, enzymic activities of four glycosyltransferases involved in the biosynthesis of SGGLs were studied in murine cerebellar mutants, in distinct cellular layers of rat cerebellum, and in isolated granule neurons during development. The enzymes studied were lactosylceramide: N-acetylglucosaminyl transferase (GlcNAc-Tr), lactotriaosylceramide:galactosyltransferase, neolactotetraosylceramide:glucuronyltransferase, and glucuronylglycolipid:sulfotransferase. In the cerebellum of Purkinje cell-deficient mutants, such as (pcd/pcd) and lurcher (Lc/؉) where Purkinje cells are lost, GlcNAc-Tr was absent, but the other three glycosyltransferase were not severely affected. This indicated that the latter three enzymes were localized in other cell types, such as in mature granule neurons and glial cells, in addition to that in Purkinje cells, and the lack of SGGLs in these mutants was due to absence of GlcNAc-Tr. Analyses of the enzymes in the specific micro-dissected cellular layers also showed that Purkinje cell layer and molecular layer (where Purkinje cell dendrites are localized) contained all four enzymes. However, granule neurons and glial cells in the white matter lacked GlcNAc-Tr, but expressed the other three enzymes. It was concluded that the absence of SGGLs in adult granule neurons and glial cells was due to specific deficiency of the GlcNAc-Tr. Although adult granule neurons lacked GlcNAc-Tr and therefore SGGLs, isolated granule neurons from the neonatal cerebellum contained all four enzymes necessary for the synthesis of SGGLs. With development, the activity of GlcNAc-Tr in the isolated granule neurons declined but the other enzymes were not as affected, indicating that immature granule neurons were capable of synthesizing SGGLs and with maturation the synthesis was down-regulated. This also explains the biphasic expression of SGGLs in the developing cerebellum.

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SAG: a Schwann cell membrane glycoprotein

Cited by 15 publications

References 41 publications

Glycans of myelin proteins

Glycans of myelin proteins

Absence of the myelin-associated glycoprotein (MAG) and the neural cell adhesion molecule (N-CAM) interferes with the maintenance, but not with the formation of peripheral myelin

N-Acetylglucosaminyl Transferase Regulates the Expression of the Sulfoglucuronyl Glycolipids in Specific Cell Types in Cerebellum during Development

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