Characterization of glycine transport in cultured M�ller glial cells from the retina

Gadea, Ana; López, Edith; López-Colomé, Ana Marı́a

doi:10.1002/(sici)1098-1136(199906)26:4<273::aid-glia1>3.0.co;2-z

Cited by 23 publications

(15 citation statements)

References 44 publications

(49 reference statements)

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“…2)). These affinity values and pharmacological specificity are in agreement with those previously determined for glycine transport in Mu¨ller radial glia from the retina (43), as well as with those reported for rat astrocytes and for GLYT1 transfected into HEK cells (3). We also detected a fraction of glycine accumulation, which was not inhibited by the compound blockage of GLYT1 and system A by sarcosine plus MeAIB.…”

Section: Discussionsupporting

confidence: 92%

“…2). The overlapping of the high-over the low-affinity component of the system, was accounted for as previously described (43). The kinetic constants obtained for the high-affinity system were Km 1 = 0.025±0.002 mM, and V 1 =0.346±0.03 nmol Âmg prot/min, and those for the low-affinity system were Km 2 =1.1±0.3 mM, and V 2 =1.86±0.2 nmol Âmg prot/min.…”

Section: Kinetic Constants and Ion Requirementsmentioning

confidence: 99%

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Characteristics and Regulation of Glycine Transport in Bergmann Glia

2005

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In the vertebrate CNS, glycine acts as an inhibitory neurotransmitter and as the obligatory coagonist of glutamate at N-methyl-D-aspartate receptors. These roles depend on extracellular glycine levels, regulated by Na+/Cl--dependent transporters GLYT1, present mainly in glial cells, and GLYT2, predominantly neuronal. In Bergmann glia, GLYT1 mediates both, glycine uptake and efflux, which, in turn, influences excitatory neurotransmission at Purkinje cell synapses. The biochemical properties of GLYTs and their regulation by signaling pathways in these cells are largely unknown. We characterized Gly uptake in confluent primary cultures of Bergmann glia from chick cerebellum. Transport was found to be energy- and Na+-dependent, and was resolved into a high (Km=25 microM) and a low affinity (Km=1.1 mM) components identified as GLYT1 and transport System A, respectively. Results show that high affinity transport by GLYT1 is regulated by calcium from intracellular stores, calmodulin, and myosin light chain kinase through an actin cytoskeleton-mediated action.

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Section: Discussionsupporting

confidence: 92%

Section: Kinetic Constants and Ion Requirementsmentioning

confidence: 99%

Characteristics and Regulation of Glycine Transport in Bergmann Glia

2005

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“…Under our experimental conditions, ouabain induced a massive [ 3 H] glycine release from retina, an effect, which is associated with inhibition of high affinity glycine uptake at least in cultured chick Müller glial cells [5]. The glycine releasing effect of ouabain may be mediated by reversal of the glycine transport system because NFPS, an irreversible inhibitor of GlyT-1, reduced this release.…”

Section: Alteration Of Intracellular Sodium Levels: Effects On [ 3 H]mentioning

confidence: 69%

“…Glycine is released from retinal amacrine cells and Müller glial cells and its synaptic and extrasynaptic concentrations are regulated by glycine transporter type-1 (GlyT-1) [3][4][5][6]. In physiological conditions, the GlyT-1 mediated uptake prevents accumulation of glycine extracellularly and thus minimizes the possibility of glycine/glutamate neurotoxicity triggered by overstimulation of NMDA receptors.…”

Section: Introductionmentioning

confidence: 99%

Some Operational Characteristics of Glycine Release in Rat Retina: The Role of Reverse Mode Operation of Glycine Transporter Type-1 (GlyT-1) in Ischemic Conditions

et al. 2015

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Rat posterior eyecups containing the retina were prepared, loaded with [(3)H]glycine and superfused in order to determine its release originated from glycinergic amacrine cells and/or glial cells. Deprivation of oxygen and glucose from the Krebs-bicarbonate buffer used for superfusion evoked a marked increase of [(3)H]glycine release, an effect that was found to be external Ca(2+)-independent. Whereas oxygen and glucose deprivation increased [(3)H]glycine release, its uptake was reduced suggesting that energy deficiency shifts glycine transporter type-1 operation from normal to reverse mode. The increased release of [(3)H]glycine evoked by oxygen and glucose deprivation was suspended by addition of the non-competitive glycine transporter type-1 inhibitor NFPS and the competitive inhibitor ACPPB further suggesting the involvement of this transporter in the mediation of [(3)H]glycine release. Oxygen and glucose deprivation also evoked [(3)H]glutamate release from rat retina and the concomitantly occurring release of the NMDA receptor agonist glutamate and the coagonist glycine makes NMDA receptor pathological overstimulation possible in hypoxic conditions. [(3)H]Glutamate release was suspended by addition of the excitatory amino acid transporter inhibitor TBOA. Sarcosine, a substrate inhibitor of glycine transporter type-1, also increased [(3)H]glycine release probably by heteroexchange shifting transporter operation into reverse mode. This effect of sarcosine was also external Ca(2+)-independent and could be suspended by NFPS. Energy deficiency in retina induced by ouabain, an inhibitor of the Na(+)-K(+)-dependent ATPase, and by rotenone, a mitochondrial complex I inhibitor added with the glycolytic inhibitor 2-deoxy-D-glucose, led to increase of retinal [(3)H]glycine efflux. These effects of ouabain and rotenone/2-deoxy-D-glucose could also be blocked by NFPS pointed to the preferential reverse mode operation of glycine transporter type-1 as a consequence of impaired cellular energy homeostasis. Immunohistochemical studies revealed that glycine transporter type-1, of which reverse mode operation assures [(3)H]glycine release, is expressed in amacrine cells in the inner nuclear and plexiform layers of the retina and also in Müller macroglia cells. We conclude that disruption of the balanced normal/reverse mode operation of glycine transporter type-1 is likely a significant factor contributing to neurotoxic processes of the retina. The possibility to inhibit glycine transporter type-1 mediated glycine efflux by drugs more potently than glycine uptake might offer some therapeutic potential for the treatment of various neurodegenerative disorders of the retina.

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“…GABA and glycine are relevant inhibitory transmitters in retinal synapses, because it was well established in the CNS, and many reports suggest a heterogeneous distribution of GABA/glycine receptors and transporters in the vertebrate retina (Honda et al, 1995;Wä ssle et al, 1998;Gadea et al, 1999). The organization and accessibility of the retina has made it the best-characterized system for examining the physiology and function of amino acid transporters, and it is an excellent model to study the effects of drugs on ischemia/ reperfusion in the CNS (Louzada-Junior et al, 1992;Eliasof et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Neurochemical Characterization of a Neuroprotective Compound fromParawixia bistriataSpider Venom That Inhibits Synaptosomal Uptake of GABA and Glycine

Beleboni¹,

Guizzo²,

Fontana³

et al. 2006

Mol Pharmacol

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The major contribution of this work is the isolation of a neuroprotective compound referred to as 2-amino-5-ureidopentanamide (FrPbAII) (M r ϭ 174) from Parawixia bistriata spider venom and an investigation of its mode of action. FrPbAII inhibits synaptosomal GABA uptake in a dose-dependent manner and probably does not act on Na ϩ , K ϩ , and Ca 2ϩ channels, GABA B receptors, or ␥-aminobutyrate:␣-ketoglutarate aminotransferase enzyme; therefore, it is not directly dependent on these structures for its action. Direct increase of GABA release and reverse transport are also ruled out as mechanisms of FrPbAII activities as well as unspecific actions on pore membrane formation. Moreover, FrPbAII is selective for GABA and glycine transporters, having slight or no effect on monoamines or glutamate transporters. According to our experimental glaucoma data in rat retina, FrPbAII is able to cross the blood-retina barrier and promote effective protection of retinal layers submitted to ischemic conditions. These studies are of relevance by providing a better understanding of neurochemical mechanisms involved in brain function and for possible development of new neuropharmacological and therapeutic tools.

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Characterization of glycine transport in cultured M�ller glial cells from the retina

Cited by 23 publications

References 44 publications

Characteristics and Regulation of Glycine Transport in Bergmann Glia

Characteristics and Regulation of Glycine Transport in Bergmann Glia

Some Operational Characteristics of Glycine Release in Rat Retina: The Role of Reverse Mode Operation of Glycine Transporter Type-1 (GlyT-1) in Ischemic Conditions

Neurochemical Characterization of a Neuroprotective Compound fromParawixia bistriataSpider Venom That Inhibits Synaptosomal Uptake of GABA and Glycine

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