Activation of UDP-galactose:globotriaosylceramide alpha 1-3-galactosyltransferase during PC12D cell differentiation induced by galactosylceramide

We measured the activities of UDP-galactose:globotriaosylceramide alpha 1-3-galactosyltransferase (alpha-GalTase) and protein kinase C (PKC) in PC12D pheochromocytoma (PC12D) cells which were induced to differentiation by nerve growth factor (NGF), forskolin (FRK), staurosporine (STP), retinoic acid (RA), 2-chloroadenosine (ClAd), and/or galactosylceramide (GalCer). NGF, STP, FRK, and RA were found to be stimulators for the PKC activity, whereas ClAd appeared to be an inhibitor of the enzyme. At the concentration of 25 microM, GalCer having normal fatty acids was found to be a stimulator, whereas GalCer having hydroxy fatty acids was ineffective in modulating the PKC activity. Interestingly, all stimulators of PKC activities, including GalCer having normal fatty acids, appeared to be activators for the alpha-GalTase activity. On the other hand, GalCer having alpha-hydroxy fatty acids had no effect and ClAd was found to be a potent inhibitor for the alpha-GalTase activity. These data suggest that alpha-GalTase activity during PC12D cell differentiation may be regulated by a PKC-dependent process.

Fucosyl-GM1 in human sensory nervous tissue is a target antigen in patients with autoimmune neuropathies

Several gangliosides of human nervous tissues have been reported to be potential target antigens in autoimmune neuropathies. To explain the diversity of clinical symptoms in patients with antiganglioside antibodies, we have searched for ganglioside antigens that are specific to individual nervous tissues such as motoneurons, peripheral motor nerves, and sensory nerves. Although the major ganglioside compositions were not different among human peripheral motor and sensory nerves, fucosyl-GM1 was found to be expressed in sensory nervous tissue but not in spinal cord, motor nerve, and sympathetic ganglia. Sera from several patients with sensory nerve involvement also reacted with fucosyl-GM1 as well as GM1. Thus, fucosyl-GM1 may be a responsible target antigen for developing sensory symptoms in some patients with autoimmune neuropathies.

Presence of cyclic AMP response element-binding protein in oligodendrocytes

Several lines of evidence indicate that cyclic AMP (cAMP) induces oligodendrocytes differentiation. However, the mechanism(s) of this stimulation remains unknown. Because in several cell types the transcriptional activity of various cAMP-responsive genes is regulated through a cis-acting DNA sequence known as cAMP response element (CRE), we investigated the possible presence of a CRE binding (CREB) protein in myelinating oligodendrocytes. A double-stranded oligonucleotide containing a tandem repeat of the CRE sequence was labeled with T4 kinase in the presence of [32P]ATP and then incubated with a nuclear protein extract from 14-day-old rat brain oligodendrocytes. The reaction mixture was then electrophoresed on nondenaturing polyacrylamide gels. The results indicated the presence of a protein that specifically binds to the CRE sequence. The results were supported by southwestern blotting assays in which the CRE probe bound to a approximately 45-kDa protein species. In separate experiments, it was shown that the 45-kDa protein can be phosphorylated in vitro by the catalytic subunit of protein kinase A. Developmental analysis of CREB protein expression indicated a peak at 14 days of age, preceding the peak of myelinogenesis.

Sulfated glucuronyl glycolipids and gangliosides in the optic nerve of humans

Pathologically delayed visual evoked potentials may be present in patients with neuropathy associated with IgM M-proteinemia, which is directed against myelin-associated glycoprotein and sulfated glucuronyl glycolipids (SGGLs), but there are no reports of these antigens in the optic nerve. We recently examined human optic nerve and occipital lobe tissues for the occurrence of SGGLs using the technique of immunostaining on thin-layer chromatographic plates and found them in the optic nerve, but not the occipital lobe. SGGLs in the optic nerve may represent target antigens for CNS involvement by the M-protein in patients with neuropathy. We also studied the ganglioside composition of the optic nerve and found it different from that of the brain. Human optic nerve is characterized by an abundance of the b-series gangliosides, including GD1b, GT1b, and GQ1b. GD1a, which is usually a major component of brain gangliosides, is only a minor species of the optic nerve ganglioside fraction.

Alterations of protein kinase C in rat hippocampus following traumatic brain injury

Calcium-dependent excitotoxic processes contribute significantly to pathologic responses to traumatic brain injury (TBI). TBI causes neuronal depolarization and excessive excitatory neurotransmitter release, which may lead to increases in intracellular calcium levels. However, responses of calcium-dependent enzymes such as protein kinase C (PKC) following TBI are poorly understood. Since PKC plays an important role in signal transduction and maintenance of normal neuronal function, we investigated changes in PKC activity and protein levels following fluid percussion brain injury in rats. We observed a 23.1% increase in PKC activity 1 h postinjury and 80.7% increase in PKC activity 3 h postinjury. There was no statistically significant change in PKC activity 5 min and 24 h after injury. PKC immunolabelling studies detected a significant increase in PKC levels in membrane fractions 3 h but not 1 h after injury. Thus PKC activation is transiently increased following TBI and may play an important role in pathophysiologic responses to TBI.

Modulation by glycosphingolipids of membrane-membrane interactions induced by myelin basic protein and melittin

The effect of glycosphingolipids (GSLs) with oligosaccharide chains of different length and charge on membrane-membrane interactions induced by myelin basic protein (MBP) or melittin (Mel) was comparatively investigated with small unilamellar vesicles. MBP induces a fast vesicle aggregation and close membrane apposition. Merging of lipid bilayers and vesicle fusion induced by MBP are slower and less extensive processes compared to membrane apposition. The changes of membrane permeability concomitant to these phenomena are small. The Trp region of MBP remains in a rather polar environment when interacting with vesicles; its accessibility to NO3- or acrylamide quenching depends on the type of GSLs in the membrane. The Trp region of Mel is inserted more deeply into the lipid bilayer and its accessibility to the aqueous quenchers is less dependent on variations of the oligosaccharide chain of the GSLs. Mel induces a faster and more extensive membrane apposition and bilayer merging than does MBP. Extensive vesicle disruption occurs in the presence of Mel. Negatively charged GSLs facilitate membrane proximity and vesicle aggregation but an increase of the oligosaccharide chain length of either neutral or acidic GSLs decreases the interaction among vesicles that are induced by either protein. This effect is independent of the different mode of insertion of MBP and Mel into the membrane. Our results suggest that the modulation by the oligosaccharide chain on the protein-induced interactions between bilayers containing GSLs is probably exerted beyond the level of local molecular interactions between the basic proteins and the lipids.

Isolated bovine spinal motoneurons have specific ganglioside antigens recognized by sera from patients with motor neuron disease and motor neuropathy

The gangliosides GM1 and GD1b have recently been reported to be potential target antigens in human motor neuron disease (MND) or motor neuropathy. The mechanism for selective motoneuron and motor nerve impairment by the antibodies directed against these gangliosides, however, is not fully understood. We recently investigated the ganglioside composition of isolated bovine spinal motoneurons and found that the ganglioside pattern of the isolated motoneurons was extremely complex. GM1, GD1a, GD1b, and GT1b, which are major ganglioside components of CNS tissues, were only minor species in motoneurons. Among the various ganglioside species in motoneurons, several were immunoreactive to sera from patients with MND and motor neuropathy. One of these gangliosides was purified from bovine spinal cord and characterized as N-glycolylneuraminic acid-containing GM1 [GM1(NeuGc)] by compositional analysis, fast atom bombardment mass spectra, and the use of specific antibodies. Among seven sera with anti-GM1 antibody activities, five sera reacted with GM1(NeuGc) and two did not. Two other gangliosides, which were recognized by another patient's serum, appeared to be specific for motoneurons. We conclude that motoneurons contained, in addition to the known ganglioside antigens GM1 and GD1b, other specific ganglioside antigens that could be recognized by sera from patients with MND and motor neuropathy.

O-acetylated gangliosides in bovine buttermilk. Characterization of 7-O-acetyl, 9-O-acetyl, and 7,9-di-O-acetyl GD3

Three O-acetylated gangliosides, G1, G2, and G3, were purified from bovine buttermilk by using chloroform/methanol extraction, Folch partitioning, chromatography on DEAE-Sephadex A-25, and Iatrobeads columns. The final yields of gangliosides G1, G2, and G3 were 2 mg, 37 mg, and 40 mg per 1.7 kg of the buttermilk powder, respectively. On the basis of immunostaining on high performance thin layer chromatography with specific monoclonal antibodies, mild alkaline treatment, gas-liquid chromatographic analysis, fast atom bombardment mass spectrometry, and proton nuclear magnetic resonance studies, G1 and G2 are characterized as O-acetylated GD3 and G3 as O-acetylated GT3, and the structures of these gangliosides are as follows: [formula: see text] The major fatty acids of these gangliosides were C18:0, C22:0, C23:0, and C24:0, and the long chain base was C18-sphingosine.

UDP-galactose:globotriaosylceramide alpha-galactosyltransferase activity in rat pheochromocytoma (PC12h) cells

The activity of alpha-galactosyltransferase in cultured rat pheochromocytoma subcloned (PC12h) cells was examined using Gb3 as the acceptor for the galactose from UDP-galactose. The major reaction product was identified as gal alpha 1-3Gb3 based on its mobility on thin-layer chromatographic (TLC) plates and susceptibility to specific galactosidases. The enzyme activity in PC12h cells was the highest at pH 7.0 while the presence of Triton CF-54 (0.1%) and Mn2+ (5 mM) was required for its full activity. The apparent Km values for Gb3 and UDP-galactose were 57 and 17 microM, respectively. The enzyme activity in PC12h cells was compared with that in parent PC12 cells, in which gal alpha 1-3Gb3 is not expressed in an appreciable amount. In the enzyme reaction with exogenous Gb3, the enzyme activity in PC12h cells was about 1.5-fold higher than that in PC12 cells. In the absence of exogenous Gb3, this difference became even more pronounced; gal alpha 1-3Gb3 was generated from endogenous Gb3 at a much higher rate in PC12h cells than in PC12 cells. These findings suggest that the higher level of the alpha-galactosyltransferase activity in PC12h cells may, at least in part, be responsible for the accumulation of unique neutral glycosphingolipids having gal alpha 1-3 terminal residues in the cells.

Neuraminidase activities in oligodendroglial cells of the rat brain

Neuraminidase activities in oligodendroglial cells were characterized using rats of different ages. Rat oligodendroglial cells had intrinsic neuraminidase activities directed toward GM3 and N-acetylneuramin(2-3)lactitol (NL). Developmental profiles of the neuraminidase activities toward the two substrates in oligodendroglial cells were different from each other. The neuraminidase activity toward GM3 increased rapidly with the onset of active myelination and, after 26 days of development, reached the adult level which was about 18 times higher than that in myelin. At the adult age, oligodendroglial cells had the highest neuraminidase activity toward GM3 among the individual brain cell types examined. The activity of NL-neuraminidase showed a less remarkable developmental profile, with a peak value at 26 days. The UDP-galactose:ceramide galactosyltransferase activity in oligodendroglial cells increased during the period of active myelination and, afterward, returned to the basal level. The enrichment and unique developmental profile in oligodendroglial cells of the neuraminidase activity toward GM3 suggest that this enzyme may play an important role in the formation and maintenance of the myelin sheath.

Role of myelin-associated neuraminidase in the ganglioside metabolism of rat brain myelin

The role of myelin-associated neuraminidase in ganglioside metabolism was examined using rats of ages ranging from 17 to 97 days. The neuraminidase activity directed toward the ganglioside GM3 in the total myelin fraction was high during the period of active myelination and, thereafter, decreased rapidly to the adult level. The ganglioside composition became simpler during development with an increasing amount of GM1 and decreasing percentages of di- and polysialogangliosides. The decrease in the proportion of GD1a was most prominent, whereas relative amounts of GD1b and GT1b increased transiently before reducing to the adult levels. The heavy myelin subfraction contained higher percentages of di- and polysialo-species compared to the light myelin fraction at young and adult ages. The in vitro incubation of myelin of young rats under an optimal condition for neuraminidase action produced a profile of ganglioside changes similar to that observed in in vivo development. These results strongly suggest that myelin-associated neuraminidase may play a pivotal role in the developmental changes in the ganglioside composition of rat brain myelin.

Autoantibodies against Forssman glycolipids in Graves' disease and Hashimoto's thyroiditis

Sera from patients with Graves' disease and Hashimoto's thyroiditis have been shown to react with the Forssman glycolipid antigen (Gb5) using the techniques of high performance thin-layer chromatography (HPTLC) immunostaining and ELISA. Human monoclonal antibodies (MoAbs) have been prepared by fusion of human myeloma with peripheral lymphocytes from patients with Graves' disease. A MoAb, TRMo-4, reacted strongly and specifically with Gb5. These results suggest that anti-Forssman antibody may be involved in the pathogenesis of these autoimmune diseases. The detection of anti-Forssman glycolipid antibody may provide a useful means for clinical diagnosis and therapy.

Phosphorylation of nuclear proteins in myelinating oligodendrocytes and its control by cyclic AMP

Oligodendroglial nuclei isolated from rat brains at different stages of myelinogenesis (10, 18, and 30 days of age) were incubated with [gamma-32P]ATP and extracted with 0.75 M perchloric acid to yield a fraction of nonacidic chromatin proteins. The protein extracts were then analyzed by polyacrylamide gel electrophoresis. The phosphorylation pattern of these proteins was found to be different for different age groups. In 10-day-old rat oligodendrocytes the most extensive phosphorylation occurred in low molecular mass species (less than 30 kDa), in contrast to fractions obtained from 18- and 30-day-old rat oligodendrocytes which showed a significantly higher labeling of the proteins with molecular masses greater than 30 kDa. The phosphorylation of the latter species was greatly stimulated by the presence of cyclic AMP in the incubation media. The results suggest that the phosphorylation of specific nuclear proteins, which may play a regulatory role at different stages of oligodendroglial maturation and myelinogenesis, may be at least partially modulated by intracellular cyclic AMP.

Identification of glycoconjugates which are targets for anti-Gal(beta 1-3)GalNAc autoantibodies in spinal motor neurons

Human IgM anti-Gal(beta 1-3)GalNAc antibodies which bind to GM1 and GD1b, are implicated in the pathogenesis of predominantly motor neuropathy or motor neuron disease. By immunofluorescence microscopy, the human antibodies immunostain the surface of motor neurons from bovine spinal cord. The motor neurons are also immunostained by cholera toxin (CT), which is specific for GM1. Glycolipid analysis using thin-layer chromatography (TLC) and immunostaining reveals that the relative concentration of GM1 and GD1b in motor neurons is greatly reduced in comparison to whole spinal cord, and that other motor neuron gangliosides are unreactive with the anti-Gal(beta 1-3)GalNAc antibodies. By Western blot analysis, the antibodies react with several protein bands in motor neuron extracts, and many of the same proteins are also recognized by PNA. These data suggest that both glycoproteins and glycolipids might be targets for anti-Gal(beta 1-3)GalNAc antibodies in spinal motor neurons.

Glycolipid changes in murine myelogenous leukemias: neutral glycolipids as markers for specific populations of leukemias

We have studied the glycolipid composition of six different murine myelogenous leukemias as well as that of T-cell leukemias and normal spleen cells. Neutral and acidic lipid fractions were isolated by column chromatography on DEAE-Sephadex and analyzed by high-performance thin-layer chromatography (HPTLC) and an HPTLC overlay method. Murine myelogenous leukemias were found to contain globo- and ganglio-series neutral glycolipids, e.g., glucosylceramide (Glc-cer), lactosylceramide (Lac-cer), globotriaosylceramide (Gb3), globoside (Gb4), Forssman glycolipid (Gb5), and asialo-GM1 (GA1). Monoblastic leukemia cells contained increased proportions of Gb3, Gb4, Gb5, and GA1. Monocytic and myelomonocytic leukemia cells contained increased proportions of Glc-cer and Lac-cer. Especially, Glc-cer accounted for approximately 60% of the total neutral glycolipids in monocytic leukemia cells. Gb3 was the major neutral glycolipid in reticulum cell neoplasm type A, and it accounted for approximately 75% of the neutral glycolipids. GA1 was the major neutral glycolipid in myeloblastic and granulocytic leukemia cells as well as T-cell leukemias. Especially, granulocytic leukemia cells contained predominantly GA1, and it accounted for approximately 80% of the total neutral glycolipids. The pattern of gangliosides in myelogenous leukemias was more complex when compared with that of the neutral glycolipids; murine myelogenous leukemias contained at least 13 gangliosides, including such major gangliosides as GM1, GM1b containing N-acetyl neuraminic acid and N-glycolyl neuraminic acid, and Ga1NAc-GM1b. Alterations of glycolipid composition in murine myeloid leukemias may be associated with cellular differentiation and maturation, and therefore these characteristic glycolipid species may be regarded as markers for specific populations of leukemia cells.

Induction of demyelination by intraneural injection of antibodies against sulfoglucuronyl paragloboside

Sulfoglucuronyl glycolipids (SGGLs) carry the glucuronyl 3-sulfate (HNK-1) epitope which is recognized by monoclonal IgM paraproteins from patients with demyelinating polyneuropathy. We report that intraneural injections of rat anti-SGGL antibodies induce demyelination in rat sciatic nerve, along with mild to moderate clinical symptoms. Morphologically, vesiculation and loosening of the myelin sheath were observed 3 h postinjection, followed by extensive demyelination and macrophage infiltration after 4 days. Since the anti-SGGL antibodies showed no cross-reactivity with other components in rat sciatic nerve, these results indicate that SGGLs alone can serve as the target antigens in demyelinating neuropathy.

Preliminary studies on sensitization of Lewis rats with sulfated glucuronyl paragloboside

A large number of patients with peripheral neuropathy and IgM paraproteinemia have IgM monoclonal antibodies which recognize a carbohydrate determinant shared by myelin-associated glycoprotein (MAG) and sulfated glucuronyl glycolipids (SGGLs). There is considerable evidence that these IgM monoclonal antibodies are responsible for demyelination in this disorder. To study the pathogenic role of SGGLs in this type of neuropathy, we sensitized Lewis rats with sulfated glucuronyl paragloboside (SGPG), a major SGGL. Fifty percent of the animals (8/16) developed neurological symptoms such as mild to moderate distal tail tone loss, with or without abnormal posture, along with development of anti-SGPG antibodies. These antibodies reacted with SGGLs, but not with rat MAG. Morphological studies showed: (1) axonal change in the lateral aspects of the dorsal columns in the spinal cord; and (2) damage to the endothelial cells in the spinal cord which suggested a breakdown of the blood-brain barrier. There was no obvious change in the peripheral nerve. Since no marked cellular infiltration was detected in these lesions, the clinicopathological findings observed could be induced by humoral mechanism, most likely anti-SGPG antibodies.

Degradation of dilauroylphosphatidylcholine by phospholipase A2 in monolayers containing glycosphingolipids

The ability of phospholipase A2 from porcine pancreas to degrade all of the available dilauroylphosphatidylcholine in mixed monolayers with galactocerebroside, sulfatide, or ganglioside GM1 was investigated at different constant surface pressures. Under the conditions used the interfacial glycosphingolipid composition was continuously enriched as the enzyme action proceeded. The total percentage of phospholipid degradation depends on the surface pressure and on the type of glycosphingolipid. The presence of sulfatide activates the enzyme while galactocerebroside and ganglioside GM1 are inhibitory. The extent of phospholipid hydrolysis is independent of the effect of glycosphingolipids on the enzyme velocity. This is so when the latter is measured either in conditions of constant glycosphingolipid composition and zero-order kinetics [Bianco, I.D., Fidelio, G.D., & Maggio, B. (1989) Biochem. J. 258, 95-99] or under variable surface composition as in the present work. The modulation of phospholipase A2 activity by glycosphingolipids operates at two independent levels. One controls the rate of enzyme activity, and the other modulates the total extent of substrate degradation. This depends on the initial interaction of the enzyme with the interface. The glycosphingolipid effect on the activity is different depending on whether the enzyme has access to the substrate from the subphase or is already adsorbed to the lipid interface.

Glycosphingolipids in the cerebrospinal fluid of patients with multiple sclerosis

Glycosphingolipids in cerebrospinal fluid (CSF) of individual patients with multiple sclerosis (MS) were analyzed using a glycolipid-overlay technique. The ganglioside composition of CSF of non-MS patients was characterized by an abundance of polysialo species, including GT1b and GQ1b. This pattern is completely different from that of human white or gray matter, in which mono- and disialogangliosides predominate. Increased levels of GM1, either associated with or without increases of other gangliosides, such as GD1a, were observed in 16% of the patients with MS (6 of 37 cases: 1 of 15 progressive progressive stage, 4 of 16 progressive stationary stage, and 1 of 6 relapsing stage). The concentration of GD3 was increased in 23% (3 of 13 cases), whereas 1 of 13 cases (8%) showed a dramatic increase of sulfoglucuronyl paragloboside (SGPG) associated with a high level of GD3. These changes may reflect the cellular changes associated with the known pathological lesions in MS, which are characterized by demyelination, gliosis, and/or remyelination with oligodendrocytic proliferation.

Purification and characterization of CMP-NeuAc:GM1 (Gal beta 1-4GalNAc) alpha 2-3 sialyltransferase from rat brain

A CMP-NeuAc:GM1 alpha 2-3 sialyltransferase (GD1a synthase, 2.4.99.2) has been purified from the Triton extract of rat brain. The enzyme was purified and resolved by affinity chromatography on CDP-Sepharose column by a linear NaCl gradient elution. Final purification was achieved by elution from a 'GM1-acid'-Sepharose column. SDS-PAGE of the enzyme revealed a single protein band with an apparent Mr 44 kDa. It catalyzed specifically the sialylation of GD1b, GM1 and asialo-GM1. Enzyme products were identified by TLC in three different solvent systems. The Km value for GM1 was 7.5 x 10(-2) M, and for CMP-NeuAc it was 6.5 x 10(-5) M.

Morphometric analysis of the developing optic nerve of the F1 heterotic mouse and its parental strains

During the period of active myelination, the CNS of the F1 hybrid mouse, derived from DBA/2J (D2) and C57BL/6J (B6) parental strains, displays levels of myelin-specific markers which are greater than in either parent. This so-called hypermyelination has been attributed to hybrid vigor or heterosis. Morphometric comparison of the optic nerves of F1 and parental strains revealed that the F1 contains larger myelinated axons and fewer premyelinated axons. These observations suggest that, compared with its parental strains, the F1 hybrid shows an early onset and accelerated rate of myelination.

NMR and computational studies of interactions between remote residues in gangliosides

Conformational preferences of the gangliosides GM1, GM1b, and GD1a have been investigated by using a systematic combination of NMR distance constraints and molecular mechanics calculations. These gangliosides share a common four-sugar core but differ in the number or placement of sialic acid residues attached to the core. Placement of the sialic acid residues is shown to influence the preferred core conformation. The origin of these effects is postulated to be intramolecular interactions of the sialic acid residues with other remote residues. In the case of GM1, hydrogen bonds between the internal sialic acid and an N-acetyl group on GalNAc are suggested. In the case of GD1a, a hydrogen-bonding network between the terminal and internal sialic acids is suggested to play a role.