Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.37 (CNPase)
 539 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of N-linked glycoproteins in the development of oligodendroglia has been studied in a culture system that initially contains the progenitor cell for oligodendroglia and type 2 astrocytes. The progenitor cells, derived from mixed glial primary cultures of newborn rat cerebrum, were studied under culture conditions that we have shown previously to induce oligodendroglial differentiation. Castanospermine was used to inhibit processing of N-linked glycoproteins by its inhibitory action on glucosidase I, the enzyme responsible for the initial trimming of glucose residues from the glucosylated high mannose core oligosaccharide derived from the dolichol pathway. Exposure to castanospermine had no effect on the initial commitment of the progenitors to oligodendroglial differentiation, i.e. 95% of both control and castanospermine-treated cells became galactocerebroside (GC) positive. However, the developmental inductions of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and glycerol-3-phosphate dehydrogenase (GPDH) and the elaboration of a network of fine interconnecting processes were prevented by the castanospermine exposure. No effect of castanospermine on cell number was observed. A major effect of the inhibitor on glycoprotein processing was manifested by an accumulation of high mannose glycoproteins, of abnormal oligosaccharide structure, compatible with the inhibition of glucosidase I.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glycoprotein processing is required for completion but not initiation of oligodendroglial differentiation from its bipotential progenitor cell. 128 24

The levels of GPC phosphocholine phosphodiesterase, pNP phosphocholine phosphodiesterase, CNPase, and UDP galactose: ceramide galactosyltransferase activities were estimated with pure cultures of oligodendrocytes and astrocytes; mixed primary glial cells cultures; C-6 cells; and CNS tissue of the dysmyelinating md rat, the jimpy mouse, and the quaking mouse. The highest activity of GPC and pNP phosphocholine phosphodiesterases as with CNPase and C gal T was found in the pure cultured oligodendrocytes. C-6 cells had very low or undetectable activities for these two phosphodiesterases but possessed very high CNPase activity. The activity of GPC phosphocholine phosphodiesterase was significantly decreased in the CNS tissue of the md rat and the jimpy and the quaking mouse. Similar reductions were observed for the pNP phosphocholine phosphodiesterase, CNPase, and C gal T activities. The selective cellular enrichment in oligodendrocytes of the GPC phosphocholine phosphodiesterase activity and decreases of its activity in three dysmyelinating mutants in the same ratio as for CNPase and C gal T suggest that GPC phosphocholine phosphodiesterase is a myelin marker enzyme and it may reflect the quantity of myelin and oligodendrocyte present.
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PMID:Glycerophosphorylcholine phosphocholine phosphodiesterase activity in cultured oligodendrocytes, astrocytes, and central nervous tissue of dysmyelinating rodent mutants. 131 6

Primary cultures of cerebral glia derived from neonatal rat brain were utilized to determine whether specific glycoproteins are involved in oligodendroglial and astrocytic differentiation. Specific emphasis was placed on the oligosaccharide portion of glycoproteins, and inhibitors of glycoprotein processing were studied. Castanospermine, an inhibitor of glucosidase I, and thereby formation of both complex glycoproteins and high mannose glycoproteins, and deoxymannojirimycin (DMM), an inhibitor of mannosidase I and thereby formation of complex glycoproteins, were utilized. Castanospermine exposure prevented the developmental inductions of the two oligodendroglial markers, 2',3'-cyclic nucleotide 3'-phosphohydrolase and glycerol-3-phosphate dehydrogenase. The effect of castanospermine on oligodendroglial differentiation was reversible. In contrast, castanospermine had no effect on the developmental inductions of the two astrocytic markers, glutamine synthetase and lactate dehydrogenase. DMM exposure had no effect on either oligodendroglial or astrocytic differentiation. Although both inhibitors caused a marked decrease in the formation of complex glycoproteins and an increase in high mannose structures, the oligosaccharide composition of these high mannose structures differed markedly. Castanospermine caused an increase in 'abnormal', apparently glucosylated high mannose structures and a decrease in all other 'normal' high mannose oligosaccharides, whereas DMM caused an increase in most high mannose structures, especially those migrating in the region of the Man7GlcNAc standard. The data indicate that oligodendroglial differentiation requires specific N-linked oligosaccharides, probably principally of the high mannose type, and that astrocytic differentiation can proceed normally despite marked alterations in both complex and high mannose glycoproteins.
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PMID:Specific N-linked oligosaccharides are required for oligodendroglial differentiation but probably not for astrocytic differentiation. 213 78

Organotypic cultures of newborn rat brains were exposed to the neurotoxin kainic acid or the DNA synthesis inhibitor arabinoside C. The cultures were subsequently co-cultured and the myelination-related enzymatic activities, such as 2',3'-cyclic nucleotide phosphohydrolase and uridine diphosphate-galactose-ceramide galactosyl transferase, were determined under various culture conditions. The newly formed myelin basic protein in the cultured brain tissue was determined by the radioimmunoprecipitation method. The myelination-related enzymatic activities and the synthesis and accumulation of myelin basic protein in the co-cultured brain tissue were found compatible to the control cultures which were not exposed to either drug. The cultures which had been treated with either drug, but not subsequently co-cultured, were found to have decreased enzymatic activities and myelin basic protein synthesis. The experimental data suggest that myelinogenesis requires an interaction between functional neurons and oligodendroglial cells and further supports the hypothesis that the neuron exerts a regulatory effect on the glial myelination mechanism.
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PMID:Co-culture study of rat neuron-glial interaction: evidence of neuronal influence on myelination. 241 1

Methylmercury (MeHg) and triethyllead (Et3Pb) are known to cause neurologic impairment in human and in several animal models. In the developing central nervous system the formation of myelin is particularly vulnerable. To obtain more information on the toxic mechanisms related to dysmyelination, the effects of MeHg and Et3Pb on two marker enzymes of myelination was assessed in developing rats. From the 5th day of life intraperitoneal injections of MeHgCl or Et3PbCl at doses of 0.05 to 5 mg/kg body weight were administered to the rats three times a week. They were decapitated at the 21 to 23rd (group A) or at the 28 to 31st postnatal day (group B). The animals treated with 2 mg/kg MeHg or Et3Pb appeared normal and the rate of growth was unchanged compared with that of control rats. A decreased activity of the enzymes UDP galactose:ceramide galactosyltransferase (CGalT) and 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNP) was apparent already at doses of 0.1 mg/kg in group B rats. (MeHg, 18 and 16%, respectively; Et3Pb, 11 and 14%) and the values decreased further with increased toxic doses. In the MeHg-treated animals the exposure time was decisive for the effect; thus in group A of MeHg-treated animals the change in enzyme activities was minimal at doses which in group B had an inhibitor effect. The activities of brain acetylcholinesterase and succinate dehydrogenase were not affected. The results emphasize a common early effect of MeHg and Et3Pb on enzymes associated with myelination in the developing central nervous system.
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PMID:UDPgalactose:ceramide galactosyltransferase and 2',3'-cyclic-nucleotide 3'-phosphodiesterase activities in rat brain after long-term exposure to methylmercury or triethyllead. 298 18

Developmental changes in protein N-glycosylation activity have been studied using cultures of dissociated fetal rat brain cells as an in vitro model system. These cultures undergo an initial phase of neurite outgrowth and cell proliferation (4-6 days in culture), followed by a period of cellular differentiation. N-Glycosylation activity has been measured by assaying the incorporation of [2-3H]mannose into dolichol-linked oligosaccharides and glycoprotein over a period of 1-25 days in culture. This study revealed a marked induction of N-glycosylation activity beginning at approximately 1 week of culture. [2-3H]Mannose incorporation into the oligosaccharide-lipid intermediate fraction and glycoprotein reached maximal values between 12 and 16 days of culture and declined thereafter. The major dolichol-linked oligosaccharide labeled by the brain cell cultures was shown to be Glc3Man9GlcNAc2 by HPLC analysis. Parallel incorporation studies with [3H]leucine showed that the increase in protein N-glycosylation was relatively higher than a concurrent increase in cellular protein synthesis observed during the induction period. Maximal labeling of glycoprotein corresponded to the period of glial differentiation, as indicated by a sharp rise in the marker enzymes, 2',3'-cyclic nucleotide 3'-phosphohydrolase (an oligodendroglial marker) and glutamine synthetase (an astroglial marker). The results describe a developmental activation of the N-glycosylation pathway and suggest a possible relationship between N-linked glycoprotein assembly and the growth and differentiation of glial cells.
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PMID:Induction of N-glycosylation activity in cultured embryonic rat brain cells. 333 55

The incorporation of 35SO4(2-) and [3H]galactose into myelin-associated lipids, the activity of enzymes catalyzing the synthesis of these lipids, and the activity of 2',3'-cyclic nucleotide phosphohydrolase were determined in primary cultures of dissociated cells from brains of 15-day embryonic mice. These biochemical parameters of myelination were barely detectable before about 10 days in culture, but their activity increased in parallel after this time and reached a maximum at about 40 days in culture. The activities of the selected enzymes in homogenates of the cultured cells at their optimum age were of the same order of magnitude as the same enzymes derived from fresh brain. Scanning electron microscopic studies showed that the cells after adhering to the surface by the 4th day form aggregates and extensive membranes; the aggregates increase in size and coalesce to form nests of cells by the 15th day; the surface of the aggregates becomes smoother until by the 43rd day the entire surface is covered by and cells are buried in a membrane-like substance. These biochemical measurements and morphological data suggest that the cultures of dissociated cells from brain of 15 day embryonic mice provide a useful system for studying myelination and its regulation in vitro.
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PMID:Investigations on myelination in vitro: biochemical and morphological changes in cultures of dissociated brain cells from embryonic mice. 736 98

The N20.1 immortalized cell line has several characteristics of differentiating oligodendrocytes (OLs), including expression of the glycolipids galactocerebroside (GalC) and sulfatide, and the myelin proteins CNPase and myelin basic protein (MBP) (1,2). Addition of 1-100 microM forskolin to elevate cyclic AMP (cAMP) levels changed cell morphology from irregular and flattened to a more rounded birefringent cell with multiple branched processes. GalC and sulfatide were detected immunocytochemically after permeabilization in the untreated cells and levels appeared to increase slightly following exposure to forskolin. Further analysis showed that most of the glycolipid was internal, with virtually no detectable levels on the cell surface in untreated cells and a very slight change following treatment with forskolin. Synthesis of the two lipids as measured by [H3]galactose incorporation doubled within 24 hours of treatment with forskolin. Levels of message for UDP-galactose: ceramide galactosyl transferase (CGT), a key enzyme in the synthesis of GalC and sulfatide, were compared with those of MBP and proteolipid protein (PLP), before and after elevation of cAMP. No changes were observed in levels of mRNA for CGT and PLP after 24 hours, with a possible increase by 48 hours. In contrast, levels of MBP message dropped precipitously by 24 hours; this was accompanied by an increase in levels of message for suppressed cAMP-inducible POU (SCIP). Thus CGT transcription is regulated independently of MBP and SCIP in N20.1 cells. Analysis of MBP levels by immunocytochemistry and Western blot showed little or no change in protein levels at 24 and 48 hours, in contrast to the sharp decrease in message levels by 24 hours, indicating a relatively long half life for MBP in this cell line. Thus, the N20.1 cells are an informative model for examining regulation of expression of myelinotypic proteins and GalC, as well as the transport of this lipid to the plasma membrane.
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PMID:Effects of cyclic AMP on expression of myelin genes in the N20.1 oligodendroglial cell line. 948 58