Search results for "transport systems"
showing 10 items of 33 documents
Direct Sensing of Nutrients via a LAT1-like Transporter in Drosophila Insulin-Producing Cells
2016
Summary Dietary leucine has been suspected to play an important role in insulin release, a hormone that controls satiety and metabolism. The mechanism by which insulin-producing cells (IPCs) sense leucine and regulate insulin secretion is still poorly understood. In Drosophila, insulin-like peptides (DILP2 and DILP5) are produced by brain IPCs and are released in the hemolymph after leucine ingestion. Using Ca2+-imaging and ex vivo cultured larval brains, we demonstrate that IPCs can directly sense extracellular leucine levels via minidiscs (MND), a leucine transporter. MND knockdown in IPCs abolished leucine-dependent changes, including loss of DILP2 and DILP5 in IPC bodies, consistent wit…
The Amino Acid Transporter JhI-21 Coevolves with Glutamate Receptors, Impacts NMJ Physiology, and Influences Locomotor Activity in Drosophila Larvae
2015
AbstractChanges in synaptic physiology underlie neuronal network plasticity and behavioral phenomena, which are adjusted during development. The Drosophila larval glutamatergic neuromuscular junction (NMJ) represents a powerful synaptic model to investigate factors impacting these processes. Amino acids such as glutamate have been shown to regulate Drosophila NMJ physiology by modulating the clustering of postsynaptic glutamate receptors and thereby regulating the strength of signal transmission from the motor neuron to the muscle cell. To identify amino acid transporters impacting glutmatergic signal transmission, we used Evolutionary Rate Covariation (ERC), a recently developed bioinforma…
Association between M467T and 114 C--A variants within the SLC3A1 gene and some phenotypical traits in cystinuria patients from Spain.
2000
Cystinuria is an inherited metabolic disease characterized by an abnormal urinary excretion of cystine and dibasic amino acids. Formation of renal calculi, recurrent infections and renal failure are the main complications of this disease. The SLC3A1 gene, which codes for a dibasic amino acid transporter protein, is involved in the pathogenesis of cystinuria. We investigated the possible association between molecular variants (M467T, E483X, T216 M and 114 C--A) within the SLC3A1 gene and some phenotypical traits in a Spanish area. The study population consisted of 45 cystinuria patients, 42 cystinuria relatives and 81 healthy control subjects. Only the M467T mutation was found in chromosomes…
Cationic amino acid transport across the blood-brain barrier is mediated exclusively by system y+.
2006
Cationic amino acid (CAA) transport is brought about by two families of proteins that are found in various tissues: Cat (CAA transporter), referred to as system y+, and Bat [broad-scope amino acid (AA) transporter], which comprises systems b0,+, B0,+, and y+L. CAA traverse the blood-brain barrier (BBB), but experiments done in vivo have only been able to examine the BBB from the luminal (blood-facing) side. In the present study, plasma membranes isolated from bovine brain microvessels were used to identify and characterize the CAA transporter(s) on both sides of the BBB. From these studies, it was concluded that system y+was the only transporter present, with a prevalence of activity on the…
CyaC, a redox-regulated adenylate cyclase of Sinorhizobium meliloti with a quinone responsive diheme-B membrane anchor domain.
2019
The nucleotide cyclase CyaC of Sinorhizobium meliloti is a member of class III adenylate cyclases (AC), a diverse group present in all forms of life. CyaC is membrane-integral by a hexahelical membrane domain (6TM) with the basic topology of mammalian ACs. The 6TM domain of CyaC contains a tetra-histidine signature that is universally present in the membrane anchors of bacterial diheme-B succinate-quinone oxidoreductases. Heterologous expression of cyaC imparted activity for cAMP formation from ATP to Escherichia coli, whereas guanylate cyclase activity was not detectable. Detergent solubilized and purified CyaC was a diheme-B protein and carried a binuclear iron-sulfur cluster. Single poin…
Voltage dependence of L-arginine transport by hCAT-2A and hCAT-2B expressed in oocytes from Xenopus laevis.
2000
Membrane potential and currents were investigated with the two-electrode voltage-clamp technique in Xenopus laevisoocytes expressing hCAT-2A or hCAT-2B, the splice variants of the human cationic amino acid transporter hCAT-2. Both hCAT-2A- and hCAT-2B-expressing oocytes exhibited a negative extracellularl-arginine concentration ([l-Arg]o)-sensitive membrane potential, additive to the K+diffusion potential, when cells were incubated in Leibovitz medium (containing 1.45 mM l-Arg and 0.25 mM l-lysine). The two carrier proteins produced inward and outward currents, which were dependent on the l-Arg gradient and membrane potential. Ion substitution experiments showed that the hCAT-induced curren…
INFγ stimulates arginine transport through system y+L in human monocytes
2004
Freshly isolated human monocytes transport L-arginine mostly through a sodium independent, NEM insensitive pathway inhibited by L-leucine in the presence, but not in the absence of sodium. Interferon-gamma (IFNgamma) stimulates this pathway, identifiable with system y+L, and markedly enhances the expression of SLC7A7, the gene that encodes for system y+L subunit y+LAT1, but not of SLC7A6, that codes for the alternative subunit y+LAT2. System y+ plays a minor role in arginine uptake by monocytes and the expression of system y+-related genes, SLC7A1 and SLC7A2, is not changed by IFNgamma. These results demonstrate that system y+L is sensitive to IFNgamma.
Rapamycin stimulates arginine influx through CAT2 transporters in human endothelial cells
2007
In endothelial cells Tumor Necrosis Factor-alpha (TNFalpha) stimulates arginine transport through the increased expression of SLC7A2/CAT2 transcripts. Here we show that also rapamycin, an inhibitor of mTOR kinase, stimulates system y(+)-mediated arginine uptake in human endothelial cells derived from either saphenous (HSVECs) or umbilical veins (HUVECs). When used together with TNFalpha, rapamycin produces an additive stimulation of arginine transport in both cell models. These effects are observed also upon incubation with AICAR, a stimulator of Adenosine-Monophosphate-dependent-Protein Kinase (AMPK) that produces a rapamycin-independent inhibition of the mTOR pathway. Rapamycin increases …
Interference of L-arginine analogues with L-arginine transport mediated by the y+ carrier hCAT-2B.
1997
The inducible human cationic amino acid transporter hCAT-2B was expressed in Xenopus laevis oocytes, and this system was used to test the effect of several NO synthase (NOS) inhibitors and/or L-arginine analogues on L-arginine transport by this y+ carrier. L-NG-Methyl-L-arginine (L-NMA), asymmetrical L-NG, NG-dimethyl-L-arginine (L-ADMA), L-N5-(1-iminoethyl)-ornithine (L-NIO), L-NG-nitro-L-arginine (L-NNA), and L-NG-nitro-L-arginine methyl ester (L-NAME) all inhibited the inducible NOS II extracted from RAW 264.7 macrophages induced with bacterial lipopolysaccharide. L-NMA, L-ADMA, and L-NIO also competed with L-arginine for transport by hCAT-2B, whereas L-NNA and L-NAME did not. The two L-…
Car sharing demand estimation and urban transport demand modelling using stated preference techniques
2008
The research deals with the use of the stated preference technique (SP) and transport demand modelling to analyse travel mode choice behaviour for commuting urban trips in Palermo, Italy. The principal aim of the study was the calibration of a demand model to forecast the modal split of the urban transport demand, allowing for the possibility of using innovative transport systems like car sharing and car pooling. In order to estimate the demand model parameters, a specific survey was carried out inside the urban area of Palermo. The survey focused on the morning rush hour and involved mainly employees, self-employed workers and students (about 500 respondents) whose final destination was lo…