Betaine acts on a ligand-gated ion channel in the nervous system of the nematode C. elegans.

Prior to the advent of synthetic nematocides, natural products such as seaweed were used to control nematode infestations. The nematocidal agent in seaweed is betaine, an amino acid that functions as an osmolyte and methyl donor. However, the molecular mechanisms of betaine toxicity are unknown.

Molecular characterization and expression pattern of taurine transporter in zebrafish during embryogenesis.

Taurine and its transporter (TauT) are expressed in preimplantation embryos, but their role in embryogenesis is not known. To investigate the role of TauT during embryonic development, we cloned and functionally characterized the zebrafish TauT. The zebrafish TauT cDNA codes for a protein of 625 amino acids which is highly homologous to mammalian TauT.

Interaction of ibuprofen and other structurally related NSAIDs with the sodium-coupled monocarboxylate transporter SMCT1 (SLC5A8).

Purpose: Sodium-coupled monocarboxylate transporter 1 (SMCT1) is a Na+-coupled transporter for monocarboxylates. Many nonsteroidal anti-inflammatory drugs (NSAIDs) are monocarboxylates. Therefore, we investigated the interaction of these drugs with human SMCT1 (hSMCT1).

Heterologous expression systems for studying placental transporters.

We use two different heterologous expression systems to characterize the functional features of plasma membrane transporters cloned from placenta. The first is the vaccinia virus expression system that utilizes a recombinant vaccinia virus carrying a transgene for T7 RNA polymerase. Mammalian cells, when infected with this virus, are able to produce T7 RNA polymerase.

Electrophysiological characterization and modeling of the structure activity relationship of the human concentrative nucleoside transporter 3 (hCNT3).

We characterized the electrophysiology, kinetics, and quantitative structure-activity relationship (QSAR) of the human concentrative nucleoside transporter 3 (hCNT3) expressed in Xenopus laevis oocytes by measuring substrate-induced inward currents using a two-microelectrode voltage-clamp system. At membrane potentials between -30 and -150 mV, sodium activation of gemcitabine transport was sigmoidal, with a K0.5 of 8.

Cloning and functional identification of slc5a12 as a sodium-coupled low-affinity transporter for monocarboxylates (SMCT2).

We report in the present paper, on the isolation and functional characterization of slc5a12, the twelfth member of the SLC5 gene family, from mouse kidney. The slc5a12 cDNA codes for a protein of 619 amino acids. Heterologous expression of slc5a12 cDNA in mammalian cells induces Na+-dependent transport of lactate and nicotinate.

Sodium-coupled and electrogenic transport of B-complex vitamin nicotinic acid by slc5a8, a member of the Na/glucose co-transporter gene family.

SMCT (sodium-coupled monocarboxylate transporter; slc5a8) is a Na+-coupled transporter for lactate, pyruvate and short-chain fatty acids. Similar to these already known substrates of SMCT, the water-soluble B-complex vitamin nicotinic acid also exists as a monocarboxylate anion (nicotinate) under physiological conditions. Therefore we evaluated the ability of SMCT to mediate the uptake of nicotinate.

A Na+/Cl- -coupled GABA transporter, GAT-1, from Caenorhabditis elegans: structural and functional features, specific expression in GABA-ergic neurons, and involvement in muscle function.

GABA functions as an inhibitory neurotransmitter in body muscles and as an excitatory neurotransmitter in enteric muscles in Caenorhabditis elegans. Whereas many of the components of the GABA-ergic neurotransmission in this organism have been identified at the molecular and functional levels, no transporter specific for this neurotransmitter has been identified to date. Here we report on the cloning and functional characterization of a GABA transporter from C.

Expression of slc5a8 in kidney and its role in Na(+)-coupled transport of lactate.

We report here on the expression of slc5a8 in kidney and its relevance to Na(+)-coupled reabsorption of lactate. slc5a8 is the murine ortholog of SLC5A8, a candidate tumor suppressor gene, which we recently cloned from human intestine and demonstrated its functional identity as a Na(+)-coupled transporter for short-chain fatty acids and lactate. The slc5a8 cDNA, cloned from mouse kidney, codes for a protein consisting of 611 amino acids.

Functional identification of SLC5A8, a tumor suppressor down-regulated in colon cancer, as a Na(+)-coupled transporter for short-chain fatty acids.

SLC5A8, a tumor suppressor gene down-regulated in human colon cancer, codes for a transporter in the Na(+)/glucose cotransporter gene family, but the definitive functional identity of the transporter protein is not known. Since this gene is expressed abundantly in the colon where short-chain fatty acids are generated by bacterial fermentation, we tested the hypothesis that it codes for a Na(+)-coupled transporter for these fatty acids. The coding region of SLC5A8 mRNA was amplified from human intestine and expressed heterologously in Xenopus laevis oocytes.

Relevance of NAC-2, an Na+-coupled citrate transporter, to life span, body size and fat content in Caenorhabditis elegans.

We have cloned and functionally characterized an Na+-coupled citrate transporter from Caenorhabditis elegans (ceNAC-2). This transporter shows significant sequence homology to Drosophila Indy and the mammalian Na+-coupled citrate transporter NaCT (now known as NaC2). When heterologously expressed in a mammalian cell line or in Xenopus oocytes, the cloned ceNAC-2 mediates the Na+-coupled transport of various intermediates of the citric acid cycle.

Functional features and genomic organization of mouse NaCT, a sodium-coupled transporter for tricarboxylic acid cycle intermediates.

In the present study, we report on the molecular cloning and functional characterization of mouse NaCT (Na+-coupled citrate transporter), the mouse orthologue of Drosophila Indy. Mouse NaCT consists of 572 amino acids and is highly similar to rat and human NaCTs in primary sequence. The mouse nact gene coding for the transporter is approx.

Transport of amino acid-based prodrugs by the Na+- and Cl(-) -coupled amino acid transporter ATB0,+ and expression of the transporter in tissues amenable for drug delivery.

We evaluated the potential of the Na(+)- and Cl(-)-coupled amino acid transporter ATB(0,+) as a delivery system for amino acid-based prodrugs. Immunofluorescence analysis indicated that ATB(0,+) is expressed abundantly on the luminal surface of cells lining the lumen of the large intestine and the airways of the lung and in various ocular tissues, including the conjunctival epithelium, the tissues easily amenable for drug delivery. We screened a variety of beta-carboxyl derivatives of aspartate and gamma-carboxyl derivatives of glutamate as potential substrates for this transporter using heterologous expression systems.

Regulation of reduced-folate transporter-1 (RFT-1) by homocysteine and identity of transport systems for homocysteine uptake in retinal pigment epithelial (RPE) cells.

Reduced-folate transporter-1 (RFT-1) transports reduced-folates, such as N5-methyltetrahydrofolate (MTF), the predominant circulating form of folate. In RPE, RFT-1 is localized to the apical membrane and is thought to transport folate from RPE to photoreceptor cells. Folate is required for DNA, RNA, protein synthesis and the conversion of homocysteine (Hcy) to methionine.

Structure, function and immunolocalization of a proton-coupled amino acid transporter (hPAT1) in the human intestinal cell line Caco-2.

The human orthologue of the H(+)-coupled amino acid transporter (hPAT1) was cloned from the human intestinal cell line Caco-2 and its functional characteristics evaluated in a mammalian cell heterologous expression system. The cloned hPAT1 consists of 476 amino acids and exhibits 85 % identity with rat PAT1. Among the various human tissues examined by Northern blot, PAT1 mRNA was expressed most predominantly in the intestinal tract.

Structural and functional characteristics of two sodium-coupled dicarboxylate transporters (ceNaDC1 and ceNaDC2) from Caenorhabditis elegans and their relevance to life span.

We have cloned and functionally characterized two Na(+)-coupled dicarboxylate transporters, namely ceNaDC1 and ceNaDC2, from Caenorhabditis elegans. These two transporters show significant sequence homology with the product of the Indy gene identified in Drosophila melanogaster and with the Na(+)-coupled dicarboxylate transporters NaDC1 and NaDC3 identified in mammals. In a mammalian cell heterologous expression system, the cloned ceNaDC1 and ceNaDC2 mediate Na(+)-coupled transport of various dicarboxylates.

Functional identity of Drosophila melanogaster Indy as a cation-independent, electroneutral transporter for tricarboxylic acid-cycle intermediates.

Indy is a gene in Drosophila melanogaster which, when made dysfunctional, leads to an extension of the average adult life span of the organism. The present study was undertaken to clone the Indy gene-product and to establish its functional identity. We isolated a full-length Indy cDNA from a D.

Initial conditions of serotonin transporter kinetics and genotype: influence on SSRI treatment trial outcome.

Background: Fifty-one patients with major depression were classified for 5-HTT promoter region polymorphism and platelet 5-HTT kinetics before treatment with fluoxetine, and then examined for treatment outcome.

Methods: Dose was stratified from 1.25 mg to 40 mg per day to allow for the possibility that one genotype could express a lower-dose fluoxetine response.