scholarly journals Evidence for inherent differences in the system A carrier from normal and transformed liver tissue. Differential inactivation and substrate protection in membrane vesicles and reconstituted proteoliposomes.

1987 ◽  
Vol 262 (26) ◽  
pp. 12565-12569
Author(s):  
K L Dudeck ◽  
E E Dudenhausen ◽  
T C Chiles ◽  
P Fafournoux ◽  
M S Kilberg
Keyword(s):  
Liver Tissue ◽  
Membrane Vesicles ◽  
System A ◽  
Substrate Protection

scholarly journals The Hepatitis C Virus-Induced Membranous Web in Liver Tissue

Cells ◽  
2018 ◽  
Vol 7 (11) ◽  
pp. 191
Author(s):  
Emmanuelle Blanchard ◽  
Philippe Roingeard
Keyword(s):  
Immune Response ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Innate Immune Response ◽  
Liver Tissue ◽  
Hepatoma Cell ◽  
Membrane Vesicles ◽  
Innate Immune ◽  
Host Cell Membrane

Host cell membrane rearrangements induced by the hepatitis C virus (HCV) have been exclusively studied in vitro. These studies have shown that HCV induces double-membrane vesicles (DMVs), which probably serve to separate replication sites from the cytoplasmic sensors of the innate immune response. We report for the first time the observation of HCV-induced membrane rearrangements in liver biopsy specimens from patients chronically infected with HCV. Unlike observations performed in vitro, the membranous web detected in liver tissue seems essentially made of clusters of single-membrane vesicles derived from the endoplasmic reticulum and close to lipid droplets. This suggests that the DMVs could be a hallmark of laboratory-adapted HCV strains, possibly due to their ability to achieve a high level of replication. Alternatively, the concealment of viral RNA in DMVs may be part of innate immune response mechanisms particularly developed in hepatoma cell lines cultured in vitro. In any case, this constitutes the first report showing the differences in the membranous web established by HCV in vitro and in vivo.

Growth-dependent regulation of system A in SV40-transformed fetal rat hepatocytes

1988 ◽  
Vol 255 (3) ◽  
pp. C261-C270 ◽  
Author(s):  
M. E. Handlogten ◽  
M. S. Kilberg
Keyword(s):  
Cell Density ◽  
De Novo ◽  
Membrane Vesicles ◽  
Rat Hepatocytes ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Plasma Membrane Vesicles ◽  
Intact Cells ◽  
System A

Fetal RLA209-15 hepatocytes, transformed with a temperature-sensitive SV40 mutant, behave like fully differentiated cells at the growth-restrictive temperature of 40 degrees C. Conversely, incubation at the growth-permissive temperature of 33 degrees C results in a transformed phenotype characterized by rapid cell division and decreased production of liver-specific proteins. The results presented here demonstrate that the cells at 33 degrees C exhibited high rates of system A transport, but transfer to 40 degrees C reduced the activity greater than 50% within 24 h. This decline in transport was independent of cell density, although the basal rate of uptake was inversely proportional to cell density in rapidly dividing cells. Transfer of cells from 40 to 33 degrees C resulted in an enhancement of system A activity that was blocked by tunicamycin. Plasma membrane vesicles from cells maintained at either 33 or 40 degrees C retained uptake rates proportional to those in the intact cells; this difference in transport activity could also be demonstrated after detergent solubilization and reconstitution. Collectively, these data indicate that de novo synthesis of the system A carrier is regulated in conjunction with temperature-dependent cell growth in RLA209-15 hepatocytes.

K-Cl transport systems in rabbit renal basolateral membrane vesicles

1987 ◽  
Vol 252 (5) ◽  
pp. F883-F889 ◽  
Author(s):  
J. Eveloff ◽  
D. G. Warnock
Keyword(s):  
Carboxylic Acid ◽  
Renal Cortex ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Chloride Conductance ◽  
Transport Systems ◽  
Basolateral Membrane Vesicles ◽  
Transport Pathways ◽  
System A ◽  
Potassium Gradient

The transport pathways for chloride in basolateral membrane vesicles from the rabbit renal cortex were investigated. 36Cl uptake was stimulated by the presence of potassium in the uptake media compared with sodium or N-methyl-D-glucamine. In addition, potassium (86Rb) uptake was stimulated more by chloride than by nitrate or gluconate. Neither of these processes was further stimulated by potassium gradients plus valinomycin, suggesting the presence of an electrically neutral K-Cl cotransport system. A magnesium-induced chloride conductance was also found in the basolateral membrane vesicles. In the absence of magnesium, the chloride conductance was low; valinomycin and an inwardly directed potassium gradient did not stimulate 36Cl uptake, anthracene-9-carboxylic acid did not inhibit 36Cl uptake, and valinomycin did not stimulate chloride-dependent 86Rb uptake. However, in the presence of 1 mM magnesium, opposite results were obtained; valinomycin and an inwardly directed potassium gradient stimulated 36Cl uptake, anthracene-9-carboxylic acid inhibited 36Cl uptake, and valinomycin stimulated chloride-dependent 86Rb uptake. Therefore, an electrically neutral K-Cl cotransport and magnesium-induced chloride conductance were found in renal cortical basolateral membrane vesicles prepared from the rabbit renal cortex.

Electrogenic 2 Na/1 H antiport in crustacean epithelium is inhibited by a monoclonal antibody

1993 ◽  
Vol 264 (4) ◽  
pp. R804-R810
Author(s):  
H. Gert de Couet ◽  
L. Busquets-Turner ◽  
A. Gresham ◽  
G. A. Ahearn
Keyword(s):  
Brush Border ◽  
Membrane Vesicles ◽  
Structural Similarity ◽  
Protein Band ◽  
Monovalent Cation ◽  
Cation Binding ◽  
Western Blots ◽  
System A ◽  
Published Evidence

We have previously published evidence that suggests that Na/H exchange in crustacean and echinoderm epithelia occurs by an electrogenic antiporter protein with two external cation binding sites that accommodate Na, amiloride, or Ca and display a 2:1 monovalent cation antiport stoichiometry. The present study is an initial investigation into the molecular biology of this invertebrate electrogenic exchanger to ascertain its structural similarity to the analogous vertebrate electroneutral antiport system. A panel of monoclonal antibodies was prepared against components of lobster hepatopancreatic epithelial brush-border membranes and assayed immunohistochemically and by Western blotting. The antibodies were tested further in functional assays for their ability to interfere with electrogenic 2 Na/1 H antiport in isolated hepatopancreatic brush-border membrane vesicles. One cell line was identified producing an antibody that significantly inhibited the electrogenic exchange of cations by these membrane preparations and recognized a single protein band on Western blots of hepatopancreas, antennal gland, and gill epithelia corresponding to a molecular mass of 185 kDa. The existence of such an antibody probe may facilitate the purification of the electrogenic antiporter under denaturing conditions, in in vitro expression systems, or in prokaryotic expression libraries.

scholarly journals Substrate-specificity of glutamine transporters in membrane vesicles from rat liver and skeletal muscle investigated using amino acid analogues

1991 ◽  
Vol 278 (1) ◽  
pp. 105-111 ◽  
Author(s):  
S Y Low ◽  
P M Taylor ◽  
A Ahmed ◽  
C I Pogson ◽  
M J Rennie
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Rat Liver ◽  
Membrane Vesicles ◽  
Transport Processes ◽  
System A ◽  
Liver Membrane ◽  
Glutamine Transport ◽  
Fold Excess ◽  
Glutamine Uptake

We investigated the effects of glutamine and histidine analogues on glutamine transport processes in membrane vesicles prepared from rat liver (sinusoidal membrane) and skeletal muscle (sarcolemma). L-[14C]Glutamine is transported in these membranes predominantly by Systems N/Nm (liver and muscle respectively), and to a lesser extent by Systems A and L (e.g. about 60, 20 and 20% of total flux respectively via Systems N, A and L at 0.05 mM-glutamine in liver membrane vesicles). The glutamine anti-metabolites 6-diazo-5-oxo-L-norleucine and acivicin were relatively poor inhibitors of glutamine uptake into liver membrane vesicles (less than 25% inhibition at 20-fold excess) and appeared primarily to inhibit System A activity (i.e. N-methylaminoisobutyric acid-inhibitable glutamine uptake). In similar experiments azaserine (also a glutamine anti-metabolite) inhibited approx. 50% of glutamine uptake, apparently by inhibition of System A and also of System L (i.e. 2-amino-2-carboxybicyclo[2,2,1]heptane-inhibitable glutamine uptake). Glutamate gamma-hydroxamate, aspartate beta-hydroxamate, histidine and N'-methylhistidine were all strong inhibitors of glutamine uptake into liver membrane vesicles (greater than 65% inhibition at 20-fold excess), but neither homoglutamine nor N'-methylhistidine produced inhibition. L-Glutamate-gamma-hydroxamate was shown to be a competitive inhibitor of glutamine transport via System N (Ki approximately 0.6 mM). Glutamine uptake in sarcolemmal vesicles showed a similar general pattern of inhibition as in liver membrane vesicles. The results highlight limits on the substrate tolerance of System N; we suggest that the presence of both an L-alpha-amino acid group and a nitrogen group with a delocalized lone-pair of electrons (amide or pyrrole type), separated by a specific intramolecular distance (C2-C4 chain equivalent), is important for substrate recognition by this transporter.

scholarly journals The anion-transfer system of erythrocyte membranes. N-(7-Nitrobenzofurazan-4-yl)taurine, a fluorescent substrate-analogue of the system

1981 ◽  
Vol 195 (2) ◽  
pp. 503-513 ◽  
Author(s):  
O Eidelman ◽  
M Zangvill ◽  
M Razin ◽  
H Ginsburg ◽  
Z I Cabantchik
Keyword(s):  
Transport System ◽  
Competitive Inhibition ◽  
Membrane Vesicles ◽  
Anion Transport ◽  
Erythrocyte Membranes ◽  
Fluorescent Substrate ◽  
System A ◽  
Highly Sensitive ◽  
Anion Transport System ◽  
Anion Transfer

The fluorescent probe Nbd-Tau [N-(7-nitrobenzofurazan-4-yl)taurine] was synthesized and evaluated as a potential substrate of the anion-transport system of human erythrocyte membrane. The probe inhibited Cl- exchange in a competitive manner from either surface of the membrane, displaying Ki values in the mM range at the inner surface and in the microM range at the outer surface. Inhibition from within cells was via interaction with Cl--transport sites, whereas from it was via interaction with sites of unidentified nature. Nbd-Tau efflux from cells was monitored fluorimetrically in a continuous mode by a novel method that circumvents separation of the cells from the medium. Using this method, it is shown that Nbd-Tau efflux fulfils the following criteria of a substrate of the anion transport system: (a) susceptibility to classical and specific inhibitors of the system; (b) competitive inhibition with Cl- for anion-transport sites; and (c) temperature coefficient comparable with that of Cl- exchange. The fluorometric method is highly sensitive, versatile, and kinetically informative. With minor modifications it can be used for measuring anion transport across “ghost” and isolated membrane vesicles.

scholarly journals Amino Acid (System A) Transporter Activity in Microvillous Membrane Vesicles from the Placentas of Appropriate and Small for Gestational Age Babies

1993 ◽  
Vol 34 (5) ◽  
pp. 661-665 ◽  
Author(s):  
Dhushy Maiiendran ◽  
Paul Donnai ◽  
Jocelyn D Glazier ◽  
Stephen W D'souza ◽  
Robert D H Boyd ◽  
...  
Keyword(s):  
Amino Acid ◽  
Gestational Age ◽  
Small For Gestational Age ◽  
Membrane Vesicles ◽  
Acid System ◽  
System A ◽  
Microvillous Membrane Vesicles

scholarly journals Sensitivity of system A and ASC transport activities to thiol-group-modifying reagents in rat liver plasma-membrane vesicles. Evidence for a direct binding of N-ethylmaleimide and iodoacetamide on A and ASC carriers

1990 ◽  
Vol 271 (2) ◽  
pp. 297-303 ◽  
Author(s):  
E Pola ◽  
J Bertran ◽  
A Roca ◽  
M Palacín ◽  
A Zorzano ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Rat Liver ◽  
Membrane Vesicles ◽  
Thiol Group ◽  
Transport Activity ◽  
Plasma Membrane Vesicles ◽  
Liver Plasma Membrane ◽  
System A ◽  
Alanine Transport

1. In the present study we have examined the sensitivity of A and ASC amino-acid-carrier activities in rat liver plasma-membrane vesicles to the thiol-group modifying reagents N-ethylmaleimide (NEM) and iodoacetamide (IA). To this end, the different Na(+)-dependent entities involved in alanine transport were assessed. 2. NEM inactivated Na(+)-dependent alanine transport as a result of the inhibition of both system A and ASC transport activities. The functional sensitivity of system A to NEM was greater than that of system ASC. 3. The presence of L-alanine (10 mM) during the exposure of vesicles to NEM afforded partial protection to system A, but not to the ASC, carrier. This effect was specific, since the presence of L-phenylalanine (10 mM) did not cause any protection. 4. Na+ did not protect A or ASC carriers against NEM inactivation; however, the presence of Na+ (100 mM-NaCl) and L-alanine (10 mM) during the exposure of the vesicles to NEM protected against inactivation of system A and ASC transport activities. The extent of protection was greater in the case of the system ASC transport activity than in the case of the A carrier. 5. IA also diminished Na(+)-dependent alanine transport by inhibition of A and ASC transport activities. Sodium and L-alanine afforded protection to both A and ASC transport activities from the inhibitory action of IA. The extent of protection induced by substrates was similar for both carriers. 6. It is concluded that there is one, or several, free thiol groups in A and ASC carriers, the integrity of which is essential for transport activity. Sensitivity to thiol-group-specific reagents and the pattern of protection with substrates against inactivation is different in A and ASC carriers. That suggests the existence of topological dissimilarities regarding the thiol-group containing site(s) in A and ASC amino acid carriers.

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