New β-Hydroxyaspartate Derivatives Are Competitive Blockers for the Bovine Glutamate/Aspartate Transporter

Lebrun, Bruno; Sakaitani, Masahiro; Shimamoto, Keiko; Yasuda-Kamatani, Yoshimi; Nakajima, Terumi

doi:10.1074/jbc.272.33.20336

Cited by 74 publications

(61 citation statements)

References 34 publications

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“…These ¢ndings suggest that the behavior of the glutamate-gated anion conductance of EAAC1 is more reversible transporter-like than ligand-gated ion channel-like, since the latter channels are typically asymmetrically ligandgated from only one side of the membrane. The fact that TBOA blocks both the glutamate-induced and the glutamate-independent currents implies that TBOA, which is a potent blocker of inward glutamate transport [22], also interacts with the glutamate binding site on the intracellular side of EAAC1. Thus the geometry and speci¢city of the glutamate binding site exposed to the cytosol appears to be quite similar to that exposed to the extracellular side.…”

Section: Discussionmentioning

confidence: 99%

The anion conductance of the glutamate transporter EAAC1 depends on the direction of glutamate transport

Watzke

Grewer

2001

FEBS Letters

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The steady-state and pre-steady-state kinetics of glutamate transport by the neuronal glutamate transporter EAAC1 were determined under conditions of outward glutamate transport and compared to those found for the inward transport mode. In both transport modes, the glutamate-induced current is composed of two components, the coupled transport current and the uncoupled anion current, and inhibited by a specific nontransportable inhibitor. Furthermore, the glutamate-independent leak current is observed in both transport modes. Upon a glutamate concentration jump outward transport currents show a distinct transient phase that deactivates within 15 ms. The results demonstrate that the general properties of EAAC1 are symmetric, but the rates of substrate transport and anion flux are asymmetric with respect to the orientation of the substrate binding site in the membrane. Therefore, the EAAC1 anion conductance differs from normal ligand-gated ion channels in that it can be activated by glutamate and Na + from both sides of the membrane. ß

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Section: Discussionmentioning

confidence: 99%

The anion conductance of the glutamate transporter EAAC1 depends on the direction of glutamate transport

Watzke

Grewer

2001

FEBS Letters

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“…Glutamate uptake by high-affinity glutamate transporters can be differentiated from glutamate receptor binding and low-affinity glutamate transporters using low-Na ϩ solutions and a specific inhibitor of high-affinity glutamate transporters, TBOA (Lebrun et al, 1997;Shimamoto et al, 1998;Danbolt, 2001). Glutamate uptake in control and HFS-treated slices was measured at 7.5 and 180 min after HFS in Na ϩ -free solutions or TBOA (100 M).…”

Section: Namentioning

confidence: 99%

Different Mechanisms Exist for the Plasticity of Glutamate Reuptake during Early Long-Term Potentiation (LTP) and Late LTP

Pita-Almenar

Collado²,

Colbert³

et al. 2006

J. Neurosci.

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Regulation of glutamate reuptake occurs along with several forms of synaptic plasticity. These associations led to the hypothesis that regulation of glutamate uptake is a general component of plasticity at glutamatergic synapses. We tested this hypothesis by determining whether glutamate uptake is regulated during both the early phases (E-LTP) and late phases (L-LTP) of long-term potentiation (LTP). We found that glutamate uptake was rapidly increased within minutes after induction of LTP and that the increase in glutamate uptake persisted for at least 3 h in CA1 of the hippocampus. NMDA receptor activation and Na ϩ -dependent high-affinity glutamate transporters were responsible for the regulation of glutamate uptake during all phases of LTP. However, different mechanisms appear to be responsible for the increase in glutamate uptake during E-LTP and L-LTP. The increase in glutamate uptake observed during E-LTP did not require new protein synthesis, was mediated by PKC but not cAMP, and as previously shown was attributable to EAAC1 (excitatory amino acid carrier-1), a neuronal glutamate transporter. On the other hand, the increase in glutamate uptake during L-LTP required new protein synthesis and was mediated by the cAMP-PKA (protein kinase A) pathway, and it involved a different glutamate transporter, GLT1a (glutamate transporter subtype 1a). The switch in mechanisms regulating glutamate uptake between E-LTP and L-LTP paralleled the differences in the mechanisms responsible for the induction of E-LTP and L-LTP. Moreover, the differences in signaling pathways and transporters involved in regulating glutamate uptake during E-LTP and L-LTP indicate that different functions and/or sites may exist for the changes in glutamate uptake during E-LTP and L-LTP.

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“…L-THA is especially attractive for chemists and biologists owing to its broad clinical and material utility, including as an antimicrobial agent against various microorganisms (4), as an inhibitor of glutamate transporters (5), and as a functional moiety of polymethacrylamide polymers (6). Its derivatives also display competitive inhibitory activity for glutamate/ aspartate transporters (7,8) and antitumor activity (9).The synthesis of L-THA has typically relied on chemical methods, e.g., ammonolysis of DL-cis-epoxysuccinic acid (10) or hydroxylation of L-aspartic acid diesters using oxaziridine or oxodiperoxymolybdenum pyridine hexamethylphosphoric triamide (11). However, these methods are accompanied by the simultaneous formation of undesirable stereoisomers, including some amount of D-THA together with L-THA; thus, complex purification procedures are often required.…”

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confidence: 99%

One-Pot Production of l - threo -3-Hydroxyaspartic Acid Using Asparaginase-Deficient Escherichia coli Expressing Asparagine Hydroxylase of Streptomyces coelicolor A3(2)

Kino

Nakano

2015

Appl Environ Microbiol

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bWe developed a novel process for efficient synthesis of L-threo-3-hydroxyaspartic acid (L-THA) using microbial hydroxylase and hydrolase. A well-characterized mutant of asparagine hydroxylase (AsnO-D241N) and its homologous enzyme (SCO2693-D246N) were adaptable to the direct hydroxylation of L-aspartic acid; however, the yields were strictly low. Therefore, the highly stable and efficient wild-type asparagine hydroxylases AsnO and SCO2693 were employed to synthesize L-THA. By using these recombinant enzymes, L-THA was obtained by L-asparagine hydroxylation by AsnO followed by amide hydrolysis by asparaginase via 3-hydroxyasparagine. Subsequently, the two-step reaction was adapted to one-pot bioconversion in a test tube. L-THA was obtained in a small amount with a molar yield of 0.076% by using intact Escherichia coli expressing the asnO gene, and thus, two asparaginase-deficient mutants of E. coli were investigated. A remarkably increased L-THA yield of 8.2% was obtained with the asparaginase I-deficient mutant. When the expression level of the asnO gene was enhanced by using the T7 promoter in E. coli instead of the lac promoter, the L-THA yield was significantly increased to 92%. By using a combination of the E. coli asparaginase I-deficient mutant and the T7 expression system, a whole-cell reaction in a jar fermentor was conducted, and consequently, L-THA was successfully obtained from L-asparagine with a maximum yield of 96% in less time than with test tube-scale production. These results indicate that asparagine hydroxylation followed by hydrolysis would be applicable to the efficient production of L-THA.H ydroxylated amino acids occurring in nature possess important physiological functions as bioactive substances. For example, 5-hydroxy-L-tryptophan, which can be extracted from the African plant Griffonia simplicifolia, is clinically used for the treatment of depression, insomnia, headache, and obesity, owing to its ability to stimulate serotonin biosynthesis in the human brain (1). cis-4-Hydroxy-L-proline, which occurs in leaves of sandalwood, is a potent antitumor drug that prevents the folding of collagen triple helices in cancer cells (2). In addition, (4S)-4-hydroxy-L-isoleucine, which is contained in the seeds of fenugreek, is effective for the treatment of type II diabetes, since it promotes insulin secretion in a blood glucose-dependent manner (3). Moreover, derivatives of these hydroxylated amino acids can also be used in the synthesis of pharmaceuticals.3-Hydroxyaspartic acid is one such compound, and much attention has been paid to its synthesis and biological properties over the years. 3-Hydroxyaspartic acid contains two asymmetric centers at C-2 and C-3; thus, four stereoisomers are expected:, and D-erythro-3-hydroxyaspartic acid [(2R,3S)-form] (D-EHA) (see Fig. S1 in the supplemental material). L-THA is especially attractive for chemists and biologists owing to its broad clinical and material utility, including as an antimicrobial agent against various microorganisms (4), as an inhibitor of ...

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New β-Hydroxyaspartate Derivatives Are Competitive Blockers for the Bovine Glutamate/Aspartate Transporter

Cited by 74 publications

References 34 publications

The anion conductance of the glutamate transporter EAAC1 depends on the direction of glutamate transport

The anion conductance of the glutamate transporter EAAC1 depends on the direction of glutamate transport

Different Mechanisms Exist for the Plasticity of Glutamate Reuptake during Early Long-Term Potentiation (LTP) and Late LTP

One-Pot Production of l - threo -3-Hydroxyaspartic Acid Using Asparaginase-Deficient Escherichia coli Expressing Asparagine Hydroxylase of Streptomyces coelicolor A3(2)

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