Glutamate forward and reverse transport: from molecular mechanism to transporter-mediated release after ischemia.

Glutamate transporters remove the excitatory neurotransmitter glutamate from the extracellular space after neurotransmission is complete, by taking glutamate up into neurons and glia cells. As thermodynamic machines, these transporters can also run in reverse, releasing glutamate into the extracellular space. Because glutamate is excitotoxic, this transporter-mediated release is detrimental to the health of neurons and axons, and it, thus, contributes to the brain damage that typically follows a stroke.

Global identification of DELLA target genes during Arabidopsis flower development.

Gibberellin (GA) plays important roles in regulating many aspects of plant development. GA derepresses its signaling pathway by promoting the degradation of DELLA proteins, a family of nuclear growth repressors. Although the floral organ identity is established in flowers of the GA-deficient mutant ga1-3, the growth of all floral organs is severely retarded.

Transport direction determines the kinetics of substrate transport by the glutamate transporter EAAC1.

Glutamate transport by the excitatory amino acid carrier EAAC1 is known to be reversible. Thus, glutamate can either be taken up into cells, or it can be released from cells through reverse transport, depending on the electrochemical gradient of the co- and countertransported ions. However, it is unknown how fast and by which reverse transport mechanism glutamate can be released from cells.

Two conformational changes are associated with glutamate translocation by the glutamate transporter EAAC1.

Glutamate is transported across membranes by means of a carrier mechanism that is thought to require conformational changes of the transport protein. In this work, we have determined the thermodynamic parameters of glutamate and the Na+ binding steps to their extracellular binding sites along with the activation parameters of rapid, glutamate-induced processes in the transport cycle by analyzing the temperature dependence of glutamate transport at steady state and pre-steady state. Our results suggest that glutamate binding to the transporter is driven by a negative reaction enthalpy (DeltaH0 = -33 kJ/mol), whereas the tighter binding of the non-transportable inhibitor TBOA is caused by an additional increase in entropy.

Cooperation of the conserved aspartate 439 and bound amino acid substrate is important for high-affinity Na+ binding to the glutamate transporter EAAC1.

The neuronal glutamate transporter EAAC1 contains several conserved acidic amino acids in its transmembrane domain, which are possibly important in catalyzing transport and/or binding of co/countertransported cations. Here, we have studied the effects of neutralization by site-directed mutagenesis of three of these amino acid side chains, glutamate 373, aspartate 439, and aspartate 454, on the functional properties of the transporter. Transport was analyzed by whole-cell current recording from EAAC1-expressing mammalian cells after applying jumps in voltage, substrate, or cation concentration.

[Therapeutic effect of glucose-6-phosphate polyclonal antibody on vasogenic brain edema in rats].

Objective: To observe the therapeutic effect of glucose-6-phosphate polyclonal antibody (G-6-P pAb) on vasogenic brain edema (VBE) in rats.

Methods: Sixty Wistar rats were randomly divided into normal control group, VBE group, mannitol-treated edema group, and G-6-P pAb-treated edema group. After establishment of rat models of VBE by intraperitoneal injection of phenylephrine in the latter 3 groups, mannitol was injected through the femoral vein in mannitol group and G-6-P pAb injected intraperitoneally in G-6-P pAb group.

Neutralization of the aspartic acid residue Asp-367, but not Asp-454, inhibits binding of Na+ to the glutamate-free form and cycling of the glutamate transporter EAAC1.

Substrate transport by the plasma membrane glutamate transporter EAAC1 is coupled to cotransport of three sodium ions. One of these Na(+) ions binds to the transporter already in the absence of glutamate. Here, we have investigated the possible involvement of two conserved aspartic acid residues in transmembrane segments 7 and 8 of EAAC1, Asp-367 and Asp-454, in Na(+) cotransport.

Individual subunits of the glutamate transporter EAAC1 homotrimer function independently of each other.

Glutamate transporters are thought to be assembled as trimers of identical subunits that line a central hole, possibly the permeation pathway for anions. Here, we have tested the effect of multimerization on the transporter function. To do so, we coexpressed EAAC1(WT) with the mutant transporter EAAC1(R446Q), which transports glutamine but not glutamate.

[Study of the expression membrane protein LASS2].

A human membrane protein LASS2 (Homo sapiens longevity assurance homologue 2 of yeast LAG1), which has important physiologic functions, was expressed in three different expression systems. Only the LASS2 protein carboxyl terminal hydrophilic fragment could be expressed in the prokaryote expression system and its polyclonal antibody was produced. The full length of LASS2 protein could be expressed successfully in both eukaryotic in vitro translation system and Bacuvirus expression system: Bac-to-Bac system.

[HRCA and application in detection of genetically modified plant].

In this article primary studies of the application of hyperbranched rolling cycle amplification (HRCA) in exogenous genes detection of transgenic plants were done. Four padlock probes were designed according to the sequences of four genes/DNA fragments that are used widely in transgenic plants; part of the sequence of pKK233 was chosen as the linking part of padlock probes and a pair of HRCA primers was designed according to the sequence of linking part. Study of the specificity of ligation in HRCA with isotope labeled padlock probes indicated padlock probes could be ringed effectively only when corresponding target DNA exited in the same reaction system and could not be ringed when there was no corresponding target DNA exited.

The conserved histidine 295 does not contribute to proton cotransport by the glutamate transporter EAAC1.

Transmembrane glutamate transport by the excitatory amino acid carrier (EAAC1) is coupled to the cotransport of three Na(+) ions and one proton. Previously, we suggested that the mechanism of H(+) cotransport involves protonation of the conserved glutamate residue E373. However, it was also speculated that the cotransported proton is shared in a H(+)-binding network, possibly involving the conserved histidine 295 in the sixth transmembrane domain of EAAC1.

[Long-term results of one stage tracheoesophageal end-side anastomosis voice restoration after total laryngectomy].

Objective: The purpose of this study is to discuss long-term results of one different kind of voice restoration after total laryngectomy with 10 years experience.

Method: One stage tracheoesophageal end-side anastomosis after total laryngectomy was performed in 36 patients from 1991-1996. The key technique of this operation is to make a tongue-ship flap(1.

[Advances in studies on transported flux and properties of riverine organic carbon].

Some lately advances in the study of riverine organic carbon were summarized in this paper. The transported flux of organic carbon from terrestrial ecosystems to the oceans via rivers, which is one of the most sensitive land surface processes in global climate change, has been changed in quantity due to the anthropogenic disturbance to it. The properties of riverine organic carbon, even in the same drainage, changed notably with the changes of hydrological processes in the drainage.

Molecular cloning, characterisation and tissue-specific expression of human LAG3, a member of the novel Lag1 protein family.

We identified and characterised the cDNA coding for human Lag3, a member of the novel eukaryotic Lag1 protein family which was related to the Saccharomyces cerevisiae longevity-assurance gene LAG1. The composite nucleotide sequence revealed a coding region of 1140 bp, a 5'-UTR of 210 bp and a 3'-UTR of 900 bp. The deduced sequence of 380 amino acids had six transmembrane regions and the conserved Lag1 motif.