CHARACTERISTICS OF GLUTAMINE vs GLUTAMATE TRANSPORT IN ISOLATED GLIA AND SYNAPTOSOMES

Weiler, C.T.; Nyström, Britta; Hamberger, Anders

doi:10.1111/j.1471-4159.1979.tb00384.x

Cited by 76 publications

(28 citation statements)

References 25 publications

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“…The observed pharmacologic profile of [3H]EAA uptake in striatum and cerebellum was generally consistent with previous reports Johnston, 1972, 1973;Bennett et al, 1973;Balcar et al, 1976;Johnston et al, 1979;Weiler et al, 1979;Vincent and McGeer, 1980;Marvizon et al, 1981;Naito and Ueda, 1985;Shousboe et al, in press]. Further, within a single region of brain, no marked differences were noted in the potency of compounds to inhibit [3H]EAA uptake.…”

Section: Discussionsupporting

confidence: 90%

“…Both high-and low-affinity uptake systems for GLU and LASP have been demonstrated in brain. High-affinity mechanisms, thought to be synaptically relevant, are temperature-dependent, regionally distributed in brain, enriched in synaptosomal fractions, and driven by a transmembrane sodium gradient [Bennett et al, 1973;Davies and Johnston, 1976;Balcar et al, 1976;Campbell and Shank, 1978;Weiler et al, 1979;Marvizon et al, 1981;Erecinska et al, 1983;Naito and Ueda, 19851. Whether exogenously accumulated GLU and LASP contribute to neurotransmitter pools of EAAs is not clear. Uptake systems for GLU and LASP are present on both neuronal and glial elements [Bennett et al, 1973;Balcar et al, 1976;Campbell and Shank, 1978;Marvizon et al, 1981;Erecinska et al, 1983;Naito and Ueda, 1985;Garthwaite and Garthwaite, 1985;Schousboe et al, in press].…”

Section: Discussionmentioning

confidence: 98%

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Heterogeneity of sodium‐dependent excitatory amino uptake mechanisms in rat brain

Ferkany

Coyle

1986

J of Neuroscience Research

127

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The pharmacologic and kinetic characteristics of sodium-dependent uptake of [3H]L-glutamate, [3H]D-aspartate, and [3H]L-aspartate into crude synaptosomal preparations of rat corpus striatum and cerebellum have been examined in vitro. In cerebellum the apparent Kts and Vmax for the three excitatory amino acids were identical whereas in striatal synaptosomes, the Vmax for [3H]L-glutamate was 30% greater (P less than or equal to .001) than for [3H]D-aspartate and 50% greater (P less than or equal to .001) than for [3H]L-aspartate. L-Amino adipic acid inhibited the uptake of the three amino acids in both regions of brain was 15- to 20-fold more potent in cerebellum than in striatum. In contrast, dihydrokainic acid inhibited transport processes in the corpus striatum but was without activity in cerebellar preparations. The neurotoxin kainic acid blocked only a portion (60%) of [3H]L-glutamate and [3H]D-aspartate uptake in cerebellum while completely inhibiting amino acid transport in corpus striatum. Three days post kainic acid lesion, [3H]D-aspartate uptake was attenuated more than [3H]L-glutamate uptake in the corpus striatum; destruction of corticostriatal afferents reduced [3H]L-glutamate to a greater extent than [3H]D-aspartate. Various lesions of the cerebellum affected excitatory amino acid transport processes to a similar extent. These results suggest that excitatory amino acid transport systems are pharmacologically distinct in different brain regions and may be heterogeneous within a single region.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 98%

Heterogeneity of sodium‐dependent excitatory amino uptake mechanisms in rat brain

Ferkany

Coyle

1986

J of Neuroscience Research

127

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“…This may reflect the difference in glutamine uptake by mitochondria as compared to synaptosomes [Weiler et al, 1979;Besagni et al, 1981;Minn, 19821. It should be noted that rates of I4CO2 production would be greatly affected by metabolic pool size and the observed differences in rates of oxidation by the subfractions may be due to differences in metabolic pool size between these two subcellular organelles. These data indicate that glutamine oxidation is also regulated differently by these two subcellular organelles and may reflect metabolic compartmentation [Balazs and Cremer, 1973;Berl et al, 19751.…”

Section: Discussionmentioning

confidence: 97%

Substrate oxidation by isolated rat brain mitochondria and synaptosomes

Tildón

Roeder

Stevenson

1985

J of Neuroscience Research

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The rates of [6-14C]-glucose oxidation by reconstituted systems of cytosol and mitochondria or cytosol and synaptosomes were essentially the same as the rate of oxidation of [3-14C]-3-hydroxybutyrate. However, the rate of [U-14C]-glutamine oxidation by mitochondria was 2.5 times that by synaptosomes. The addition of glutamine (5 mM) caused a reduction in the rates of oxidation [6-14C]-glucose of 20% and 40% by mitochondria and synaptosomes, respectively. Conversely, the addition of glucose (5 mM) had little or no effect on the rate of [U-14C]-glutamine oxidation by either organelle. Amino-oxyacetate decreased [U-14C]-glutamine oxidation by mitochondria more than 35% but had little or no effect on the rate of glutamine oxidation by synaptosomes. When glucose (5 mM) was added to [3-14C]-3-hydroxybutyrate, the rates of oxidation by the mitochondria and synaptosomes were increased by 65% and 77%, respectively. However, in the reverse situation the addition of 3-hydroxybutyrate decreased [6-14C]-glucose oxidation by synaptosomes (35%) but did not decrease the rate by mitochondria. These results suggest that differences in the rates of substrate utilization by mitochondria and synaptosomes and differences in substrate interactions in these two subcellular organelles may contribute to metabolic compartmentation in the brain.

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“…They can also function over a broad pH range and, in some situations, mediate amino acid release more than uptake (35,36). Kinetic studies have shown that distinct transport systems exist for glutamine in neurons and astrocytes (37)(38)(39). Uptake of glutamine by rat cerebellar granule cells, a predominantly glutamatergic nerve cell population, is primarily mediated by system A (40).…”

mentioning

confidence: 99%

Cloning and Functional Identification of a Neuronal Glutamine Transporter

Varoqui¹,

Zhu²,

Yao³

et al. 2000

Journal of Biological Chemistry

270

214

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Glutamine is the preferred precursor for the neurotransmitter pool of glutamate, the major excitatory transmitter in the mammalian central nervous system. We have isolated a complementary DNA clone (designated GlnT) encoding a plasma membrane glutamine transporter from glutamatergic neurons in culture, and its properties have been examined using the T7 vaccinia system in fibroblasts. When GlnT is transfected into CV-1 cells, L-glutamine is the preferred substrate. Transport is Na ؉ -dependent and inhibited by ␣-methylaminoisobutyric acid, a specific inhibitor of neutral amino acid transport system A. Kinetic analysis of glutamine uptake by GlnT is saturable, with a Michaelis constant (K m ) of 489 ؎ 88 M at pH 7.4. Glutamine uptake mediated by GlnT is pH-sensitive with a 5-fold greater efficiency of uptake at pH 8.2 than at pH 6.6. Only the maximal velocity of transport increases without a significant change in K m . The distribution of GlnT mRNA and protein in the central nervous system is widespread and is expressed on neurons that use glutamate as their neurotransmitter. In cultured cerebellar granule cells, GlnT is expressed only on neurons and is absent from astrocytes. GlnT expression increases concomitantly with the morphologic and functional differentiation of these cells in vitro, consistent with its role of supplying glutamatergic neurons with their neurotransmitter precursor. GlnT is the first member of the system A family of neutral amino acid transporters with 11 putative membrane-spanning domains and is a potential target to modulate presynaptic glutamatergic function.

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CHARACTERISTICS OF GLUTAMINE vs GLUTAMATE TRANSPORT IN ISOLATED GLIA AND SYNAPTOSOMES

Cited by 76 publications

References 25 publications

Heterogeneity of sodium‐dependent excitatory amino uptake mechanisms in rat brain

Heterogeneity of sodium‐dependent excitatory amino uptake mechanisms in rat brain

Substrate oxidation by isolated rat brain mitochondria and synaptosomes

Cloning and Functional Identification of a Neuronal Glutamine Transporter

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