Adenosine uptake in pyrimidine 5′-nucleotidase deficient human erythrocytes via a high affinity transport system

1985 ◽  
Vol 41 (3) ◽  
pp. 366-368 ◽  
Author(s):  
T. Kagimoto ◽  
S. Tomino ◽  
K. Takatsuki
Keyword(s):  
Transport System ◽  
Human Erythrocytes ◽  
High Affinity ◽  
Adenosine Uptake

scholarly journals MOAT4, a novel multispecific organic-anion transporter for glucuronides and mercapturates in mouse L1210 cells and human erythrocytes

1996 ◽  
Vol 320 (1) ◽  
pp. 273-281 ◽  
Author(s):  
Manju SAXENA ◽  
Gary B HENDERSON
Keyword(s):  
Transport System ◽  
Organic Anion ◽  
High Sensitivity ◽  
Human Erythrocytes ◽  
Organic Anion Transporter ◽  
High Affinity ◽  
L1210 Cells ◽  
Anion Transporter ◽  
Dependent Transport ◽  
Inside Out

Glucuronides and mercapturates were examined as possible high-affinity substrates for a low-affinity ATP-dependent transport system for 2,4-dinitrophenyl S-glutathione (DNP-SG) in mouse L1210 cells. Initial inhibitor studies with inside-out vesicles revealed that the low-affinity transport of [3H]DNP-SG (Km 450 µM) exhibits a high sensitivity to N-acetyl 2,4-dinitrophenyl cysteine (NAc-DNP-Cys) (Ki 5.0 µM) and α-naphthyl β-D-glucuronide (naphthyl glucuronide) (Ki 8.5 µM). Direct transport measurements showed the presence of ATP-dependent uptake activities for NAc-DNP-[35S]Cys and naphthyl [14C] glucuronide, and Km values for half-maximal transport were comparable to the Ki values of these compounds for inhibition of [3H]DNP-SG transport. Transport of [3H]DNP-SG, NAc-DNP-[35S]Cys and naphthyl [14 C]glucuronide each showed the same sensitivity to various anions and anion conjugates. Inhibition was competitive and was most potent for bilirubin ditaurate, indoprofen, 4-biphenylacetic acid, 4-acridine 4β-D-glucuronide, N-acetyl leukotriene E4, 17β-oestradiol 3β-D-glucuronide and taurolithocholate 3-sulphate. Inside-out vesicles from human erythrocytes contain a comparable ATP-dependent transport system. These results show that NAc-DNP-Cys and naphthyl glucuronide are high-affinity substrates for a single system identified previously as a low-affinity transporter of DNP-SG. Substrate and inhibitor studies identify this system as a novel multispecific organic-anion transport system (MOAT4) that accommodates glucuronides and mercapturates and is distinct from other MOAT transporters. Human erythrocytes contain an additional ATP-dependent system for NAc-DNP-Cys (Km 33 µM) that does not transport monoglucuronides.

scholarly journals Nucleoside transport in human and sheep erythrocytes. Evidence that nitrobenzylthioinosine binds specifically to functional nucleoside-transport sites

1980 ◽  
Vol 190 (2) ◽  
pp. 377-383 ◽  
Author(s):  
S M Jarvis ◽  
J D Young
Keyword(s):  
Transport System ◽  
Binding Sites ◽  
Sheep Erythrocyte ◽  
Specific Interaction ◽  
Human Erythrocytes ◽  
Nucleoside Transport ◽  
Erythrocyte Membranes ◽  
Sheep Erythrocytes ◽  
High Affinity ◽  
Transport Site

Nitrobenzyl[35S]thioinosine binding and nitro[3H]benzylthioinosine binding to nucleoside-permeable and nucleoside-impermeable sheep erythrocyte membranes was investigated, and compared with that found for human erythrocytes. High-affinity nitrobenzylthioinosine-binding sites (apparent KD congruent to 1 nM) were present on human and nucleoside-permeable but not nucleoside-impermeable sheep erythrocyte membranes (8400 and 18 sites/cell for human and sheep nucleoside-permeable sheep erythrocytes was displaced by nitrobenzylthioguanosine and dipyridamole. Uridine, inosine and adenosine inhibited binding. The smaller number of nitrobenzylthioinosine sites on nucleoside-permeable cells compared with human erythrocytes corresponded to a considerably lower Vmax. for uridine influx in these cells (0.53 × 10(-20) mol/cell per s at 25 degrees C compared with 254 × 10(-20) mol/cell per s). It is suggested that high-affinity nitrobenzylthioinosine binding represents a specific interaction with functional nucleoside-transport sites. The uridine-translocation capacity for each transport site at 25 degrees C is 180 molecules/site per s for both nucleoside-permeable sheep cells and human erythrocytes (assuming a 1:1 interaction between nitrobenzylthioinosine and the nucleoside-transport system).

Affinity of calcium channel inhibitors, benzodiazepines, and other vasoactive compounds for the nucleoside transport system

1985 ◽  
Vol 63 (10) ◽  
pp. 1302-1307 ◽  
Author(s):  
James R. Hammond ◽  
Evan F. Williams ◽  
Alexander S. Clanachan
Keyword(s):  
Guinea Pig ◽  
Calcium Channel ◽  
Transport System ◽  
Human Erythrocytes ◽  
Nucleoside Transport ◽  
Rat Tissues ◽  
High Affinity ◽  
Cardiac Membranes ◽  
Transport Inhibitors ◽  
Calcium Channel Inhibitors

There is evidence to suggest that several different groups of drugs including the so-called coronary vasodilators, benzodiazepines, and calcium channel inhibitors may owe their vasoactivity, in part, to the potentiation of the vasorelaxant effects of endogenous adenosine. To measure the affinity of some of these agents for the membrane-located nucleoside transport system, competition binding assays have been performed using the high-affinity radioligand [3H]nitrobenzylthioinosine (NBMPR). Experiments were performed on human erythrocytes and cardiac membranes from guinea pigs and rats. Recognized nucleoside transport inhibitors had high affinity (<50 nM) for NBMPR recognition sites associated with the nucleoside transporter complex in human erythrocytes, whereas calcium channel inhibitors and benzodiazepines had predominantly low affinity (> 1 μM). Although some recognized transport inhibitors, such as dipyridamole, show marked differences in affinity for NBMPR sites in guinea pig and rat tissues, benzodiazepines and calcium channel blockers displayed no such species selectivity and had low affinity (> 1 μM) for NBMPR sites in both guinea pig and rat cardiac membranes. Consequently, it is unlikely that agents such as benzodiazepines and calcium channel inhibitors cause significant inhibition of adenosine transport, and hence potentiate adenosine actions, at the concentrations required to induce effects through occupation of their respective, specific high-affinity sites.

Regulation of the High-Affinity Nitrate Transport System in Wheat Roots by Exogenous Abscisic Acid and Glutamine

2007 ◽  
Vol 49 (12) ◽  
pp. 1719-1725 ◽  
Author(s):  
Chao Cai ◽  
Xue-Qiang Zhao ◽  
Yong-Guan Zhu ◽  
Bin Li ◽  
Yi-Ping Tong ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Transport System ◽  
Nitrate Transport ◽  
Wheat Roots ◽  
High Affinity

scholarly journals RCO-3 and COL-26 form an external-to-internal module that regulates the dual-affinity glucose transport system in Neurospora crassa

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Jinyang Li ◽  
Qian Liu ◽  
Jingen Li ◽  
Liangcai Lin ◽  
Xiaolin Li ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Neurospora Crassa ◽  
Glucose Transport ◽  
Transport System ◽  
Rational Design ◽  
Glucose Sensor ◽  
Glucose Transporters ◽  
Glucose Fluctuation ◽  
High Affinity ◽  
Glucose Transport System

Abstract Background Low- and high-affinity glucose transport system is a conserved strategy of microorganism to cope with environmental glucose fluctuation for their growth and competitiveness. In Neurospora crassa, the dual-affinity glucose transport system consists of a low-affinity glucose transporter GLT-1 and two high-affinity glucose transporters HGT-1/HGT-2, which play diverse roles in glucose transport, carbon metabolism, and cellulase expression regulation. However, the regulation of this dual-transporter system in response to environmental glucose fluctuation is not yet clear. Results In this study, we report that a regulation module consisting of a downstream transcription factor COL-26 and an upstream non-transporting glucose sensor RCO-3 regulates the dual-affinity glucose transport system in N. crassa. COL-26 directly binds to the promoter regions of glt-1, hgt-1, and hgt-2, whereas RCO-3 is an upstream factor of the module whose deletion mutant resembles the Δcol-26 mutant phenotypically. Transcriptional profiling analysis revealed that Δcol-26 and Δrco-3 mutants had similar transcriptional profiles, and both mutants had impaired response to a glucose gradient. We also showed that the AMP-activated protein kinase (AMPK) complex is involved in regulation of the glucose transporters. AMPK is required for repression of glt-1 expression in starvation conditions by inhibiting the activity of RCO-3. Conclusions RCO-3 and COL-26 form an external-to-internal module that regulates the glucose dual-affinity transport system. Transcription factor COL-26 was identified as the key regulator. AMPK was also involved in the regulation of the dual-transporter system. Our findings provide novel insight into the molecular basis of glucose uptake and signaling in filamentous fungi, which may aid in the rational design of fungal strains for industrial purposes.

Lead and calcium transport in human erythrocyte

1999 ◽  
Vol 18 (5) ◽  
pp. 327-332 ◽  
Author(s):  
J V Calderón-Salinas ◽  
M A Quintanar-Escorcia ◽  
M T González-Martínez ◽  
C E Hernández-Luna
Keyword(s):  
Transport System ◽  
Human Erythrocyte ◽  
Calcium Transport ◽  
Human Erythrocytes ◽  
The Other ◽  
Erythrocyte Ghosts ◽  
Passive Transport ◽  
Ca Uptake

In this paper we report the lead (Pb) and calcium (Ca) uptake by erythrocyte ghosts. In both cases the transport was carried out by a passive transport system with two kinetic components (Michaelis-Menten and Hill). Pb and Ca were capable of inhibiting the transport of the other metal in a non-competitive way. Under hyperpolarization, the uptakes of Ca and Pb were enhanced and the Michaelis-Menten component prevailed. Both Ca and Pb uptakes were inhibited by N-ethyl-maleimide to the same extent. These results indicate that Pb and Ca share the same permeability pathway in human erythrocytes and that this transport system is electrogenic.

scholarly journals Functional Characterization of a High-Affinity Choline Transport System in Human Keratinocytes

2002 ◽  
Vol 119 (1) ◽  
pp. 118-121 ◽  
Author(s):  
Kathrin Hoffmann ◽  
Franziska Grafe ◽  
Wolfgang Wohlrab ◽  
Reinhard H. Neubert ◽  
Matthias Brandsch
Keyword(s):  
Transport System ◽  
Functional Characterization ◽  
Human Keratinocytes ◽  
Choline Transport ◽  
High Affinity

scholarly journals Corrigendum to: A high affinity nitrate transport system from Chlamydomonas requires two gene products (FEBS 23233)

FEBS Letters ◽  
2000 ◽  
Vol 481 (1) ◽  
pp. 88-88
Author(s):  
Jing-Jiang Zhou ◽  
Emilio Fernández ◽  
Aurora Galván ◽  
Anthony J. Miller
Keyword(s):  
Transport System ◽  
Nitrate Transport ◽  
Gene Products ◽  
High Affinity
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