scholarly journals Characterization of putrescine- and spermidine-transport systems of a rat pancreatic acinar tumoral cell line (AR4-2J)

1990 ◽  
Vol 269 (3) ◽  
pp. 629-632 ◽  
Author(s):  
T G Nicolet ◽  
J L Scemama ◽  
L Pradayrol ◽  
C Seva ◽  
N Vaysse
Keyword(s):  
Cell Line ◽  
Choline Chloride ◽  
The Other ◽  
Transport Systems ◽  
Lower Affinity ◽  
Polyamine Transport ◽  
Tumoral Cell ◽  
Cell Growth And Differentiation ◽  
The Difference

Polyamines are polycationic molecules essential for cell growth and differentiation. Recent work has focused on cell polyamine-transport systems as a way to regulate intracellular polyamine levels. In this study, we demonstrate the presence of two different active transporters for putrescine and spermidine in a rat tumoral cell line (AR4-2J). The first has a Km of 3.1 microM and a Vmax of 3.7 pmol/15 min per micrograms of DNA for putrescine and the second a Km of 0.42 microM and a Vmax of 4.7 pmol/15 min per micrograms of DNA for spermidine. Competition studies performed between the polyamines confirm the difference between these two carriers; one has an equal affinity for the three main polyamines, and the other has a lower affinity for putrescine. Amino acids do not share this transport system, which is Na(+)-independent. Choline chloride inhibits selectively and in a dose-responsive manner the uptake of putrescine without affecting that of spermidine. These data demonstrate that AR4-2J cells possess two polyamine transporters; one is specific for aminopropyl groups (spermidine and spermine), and the other is choline-sensitive, but cannot discriminate between aminobutyl (putrescine) and aminopropyl groups.

scholarly journals The STK2 gene, which encodes a putative Ser/Thr protein kinase, is required for high-affinity spermidine transport in Saccharomyces cerevisiae.

1997 ◽  
Vol 17 (6) ◽  
pp. 2994-3004 ◽  
Author(s):  
M Kaouass ◽  
M Audette ◽  
D Ramotar ◽  
S Verma ◽  
D De Montigny ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Fusion Gene ◽  
Transport Systems ◽  
Coding Region ◽  
Kinase Gene ◽  
Lower Affinity ◽  
High Affinity ◽  
Polyamine Transport ◽  
Exogenous Spermidine

Eukaryotic polyamine transport systems have not yet been characterized at the molecular level. We have used transposon mutagenesis to identify genes controlling polyamine transport in Saccharomyces cerevisiae. A haploid yeast strain was transformed with a genomic minitransposon- and lacZ-tagged library, and positive clones were selected for growth resistance to methylglyoxal bis(guanylhydrazone) (MGBG), a toxic polyamine analog. A 747-bp DNA fragment adjacent to the lacZ fusion gene rescued from one MGBG-resistant clone mapped to chromosome X within the coding region of a putative Ser/Thr protein kinase gene of previously unknown function (YJR059w, or STK2). A 304-amino-acid stretch comprising 11 of the 12 catalytic subdomains of Stk2p is approximately 83% homologous to the putative Pot1p/Kkt8p (Stk1p) protein kinase, a recently described activator of low-affinity spermine uptake in yeast. Saturable spermidine transport in stk2::lacZ mutants had an approximately fivefold-lower affinity and twofold-lower Vmax than in the parental strain. Transformation of stk2::lacZ cells with the STK2 gene cloned into a single-copy expression vector restored spermidine transport to wild-type levels. Single mutants lacking the catalytic kinase subdomains of STK1 exhibited normal parameters for the initial rate of spermidine transport but showed a time-dependent decrease in total polyamine accumulation and a low-level resistance to toxic polyamine analogs. Spermidine transport was repressed by prior incubation with exogenous spermidine. Exogenous polyamine deprivation also derepressed residual spermidine transport in stk2::lacZ mutants, but simultaneous disruption of STK1 and STK2 virtually abolished high-affinity spermidine transport under both repressed and derepressed conditions. On the other hand, putrescine uptake was also deficient in stk2::lacZ mutants but was not repressed by exogenous spermidine. Interestingly, stk2::lacZ mutants showed increased growth resistance to Li+ and Na+, suggesting a regulatory relationship between polyamine and monovalent inorganic cation transport. These results indicate that the putative STK2 Ser/Thr kinase gene is an essential determinant of high-affinity polyamine transport in yeast whereas its close homolog STK1 mostly affects a lower-affinity, low-capacity polyamine transport activity.

scholarly journals Transport systems for polyamines in the established renal cell line LLC-PK1. Polarized expression of an Na+-dependent transporter

1990 ◽  
Vol 265 (2) ◽  
pp. 609-612 ◽  
Author(s):  
L Van Den Bosch ◽  
H De Smedt ◽  
L Missiaen ◽  
J B Parys ◽  
R Borghgraef
Keyword(s):  
Cell Line ◽  
Renal Cell ◽  
The Other ◽  
Transport Systems ◽  
Present Evidence ◽  
Cell Monolayers ◽  
Other Hand ◽  
Basolateral Side ◽  
Renal Cell Line ◽  
Polyamine Uptake

We present evidence for the existence of an Na(+)-dependent transporter and an Na(+)-independent transporter for polyamines in LLC-PK1 cells. Both transporters could be discriminated by their sensitivity to inhibitors, particularly rho-chloromercuriphenyl sulphate and various polycationic molecules. By using cell monolayers grown on a permeable filter support, we have found that the Na(+)-dependent polyamine uptake occurred preferentially from the basolateral side. The Na(+)-independent uptake, on the other hand, occurred to the same extent from either the apical or the basolateral side.

scholarly journals Cloning, expression, and characterization of the human eosinophil eotaxin receptor.

1996 ◽  
Vol 183 (5) ◽  
pp. 2349-2354 ◽  
Author(s):  
B L Daugherty ◽  
S J Siciliano ◽  
J A DeMartino ◽  
L Malkowitz ◽  
A Sirotina ◽  
...  
Keyword(s):  
Chemokine Receptor ◽  
Allergic Inflammation ◽  
The Other ◽  
Binding Affinities ◽  
Binding Studies ◽  
Human Eosinophil ◽  
Lower Affinity ◽  
Competition Binding ◽  
G Protein Coupled

Although there is a mounting body of evidence that eosinophils are recruited to sites of allergic inflammation by a number of beta-chemokines, particularly eotaxin and RANTES, the receptor that mediates these actions has not been identified. We have now cloned a G protein-coupled receptor, CC CKR3, from human eosinophils which, when stably expressed in AML14.3D10 cells bound eotaxin, MCP-3 and RANTES with Kds of 0.1, 2.7 and 3.1 nM, respectively. CC CKR3 also bound MCP-1 with lower affinity, but did not bind MIP-1 alpha or MIP-1 beta. Eotaxin, RANTES, and to a lessor extent MCP-3, but not the other chemokines, activated CC CKR3 as determined by their ability to stimulate a Ca(2+) -flux. Competition binding studies on primary eosinophils gave binding affinities for the different chemokines which were indistinguishable from those measured with CC CKR3. Since CC CKR3 is prominently expressed in eosinophils we conclude that CC CKR3 is the eosinophil eotaxin receptor. Eosinophils also express a much lower level of a second chemokine receptor, CC CKR1, which appears to be responsible for the effects of MIP-1 alpha.

scholarly journals Variable H+/substrate stoicheiometries in Rhodotorula gracilis are caused by a pH-dependent protonation of the carrier(s)

1982 ◽  
Vol 208 (2) ◽  
pp. 459-464 ◽  
Author(s):  
R Hauer ◽  
M Höfer
Keyword(s):  
Positive Charge ◽  
Low Ph ◽  
The Other ◽  
Transport Systems ◽  
Lower Affinity ◽  
High Affinity ◽  
High Sugar ◽  
Saturation Kinetics ◽  
Rhodotorula Gracilis ◽  
Ph Dependent

Two carrier-mediated systems transport sugars in the yeast Rhodotorula gracilis depending on the pH. One system, with higher affinity for sugars, catalyses a symport of protons with sugar, whereas the other system, having lower affinity, is independent of protons. This was shown in three different ways. (1) At low pH, where only the high-affinity system works, a H+/sugar stoicheiometry of 1 was found. An increase of the pH and of the sugar concentration, which allowed the low-affinity system to operate, brought about a drop of the stoicheiometry to values below 1. (2) During H+ symport the influx of positive charge was electrically compensated by an equivalent efflux of K+ from the cells. At high pH and high sugar concentrations this stoicheiometry of K+ and sugar decreased concomitant with the H+/sugar stoicheiometry. (3) At pH 7.5 both transport systems were operating, as shown by biphasic saturation kinetics. Under these conditions only the high-affinity transport was found to be electrogenic. These results agree with the theory of an electrogenic H+/sugar symport where changes in the affinity for substrate are brought about by reversible protonation and deprotonation of the carrier.

Characterization Of The Active Site Of Urokinase With A Series Of Potent Inhibitory Amidines

1981 ◽  
Author(s):  
J D Geratz ◽  
S R Shaver ◽  
R R Tidwell
Keyword(s):  
Active Site ◽  
Factor Xa ◽  
Selective Inhibition ◽  
The Other ◽  
Plasminogen Activation ◽  
Steric Factors ◽  
The Difference ◽  
The One ◽  
Striking Contrast

Twenty amidine-substituted indole-like heterocycles were synthesized and examined for their blocking effect against human urokinase and a number of related arginine- or lysine- directed proteases. Kinetic analyses were carried out with the help of peptide anilide substrates and revealed a reversible competitive inhibitory pattern with each compound. The Ki values were therefore interpreted to reflect binding conditions at the active site of the enzymes.A highly potent inhibitor of urokinase was discovered in 5-amidino-l-(4-amidinobenzyl)indole which proved to be 18 times more effective on a molar basis than p-aminobenzamidine and 150 times more effective than benzamidine. The Ki value at 37°C and pH 8.3 was determined as 3.2 × 10-6 M. In striking contrast to the findings with the other proteases studied, urokinase was very sensitive to inhibition by 6-amidinoindoline (Ki 1.8 × 10-5 M), yet was much less susceptible to inhibition by the fully unsaturated analog 6-amidinoindole. Steric factors resulting from the difference in planarity between the two compounds are held responsible for this observation. In plasminogen activation assays the antiurokinase effect of the heterocycles mirrored their potency in the assays employing the synthetic urokinase substrate.The significant differences in the inhibitory activities of amidines against urokinase, on the one hand, and plasmin, thrombin and factor Xa, on the other hand, will be useful for experiments where selective inhibition of plasminogen activation is to be achieved. The compounds will also be of help in characterizing other tissue activators with respect to urokinase.

scholarly journals Immersion Calorimetry for the Characterization of PD Catalysts Supported on Activated Carbon

2009 ◽  
Vol 6 (4) ◽  
pp. 1221-1227
Author(s):  
Liliana Giraldo ◽  
Juan Carlos Moreno-Piraján
Keyword(s):  
Hydrogen Peroxide ◽  
Activated Carbon ◽  
Functional Groups ◽  
Activated Carbons ◽  
The Other ◽  
Pd Catalysts ◽  
Immersion Calorimetry ◽  
Characterization Techniques ◽  
The Difference

Activated carbons obtained from coconut peel were oxidized using hydrogen peroxide. Superficial characteristics of these carbons were determined through N2and CO2isotherms and functional groups were characterized by TPD. Finally, the microcalorimetry technique was used in order to obtain the immersion enthalpies in diverse liquids and established the relation between them and the results obtained by the other characterization techniques. The results suggested that the immersion calorimetry allow establishing the difference between the supports and the catalysts.

Characterization of a COS cell line deficient in polyamine transport

1994 ◽  
Vol 1221 (3) ◽  
pp. 279-285 ◽  
Author(s):  
Tapani Hyvönen ◽  
Nikolaus Seiler ◽  
Lo Persson
Keyword(s):  
Cell Line ◽  
Polyamine Transport

This, that and the other: locating the supernatural enemy in Old English

2015 ◽  
Vol 19 (2) ◽  
pp. 213-226
Author(s):  
ADAM MEARNS
Keyword(s):  
Old English ◽  
The Other ◽  
Modern Concept ◽  
Prototype Model ◽  
Semantic Structure ◽  
Anglo Saxon ◽  
Conceptual Category ◽  
Normative Function ◽  
The Difference

This article explores the concept of the supernatural and the characterization of monsters and devils in Old English (OE), using the framework of a prototype model of semantic structure. Although there is a lexical gap, with no OE word equivalent to Present-Day English supernatural, it is possible to identify a set of semantic traits that constitute a covert conceptual category similar to the modern concept and encompassing Anglo-Saxon monsters and devils. The essence of this category is ‘exclusion’. The difference between the modern and medieval concepts is that, for the Anglo-Saxons, the boundary of the supernatural was conceptually much ‘closer’ and conceived in less abstract terms, corresponding to the frontier between the civilized space of society and the unruly alien space beyond. Similarities in the words applied to them reflect the fact that supernatural beings shared this alien space with other more mundane outsiders, such as foreigners and criminals. As its most extraordinary members, however, Anglo-Saxon monsters and devils played an important role in delineating the boundaries of society by acting as a challenge or counterexample to the principles of proper behaviour and accepted beliefs from which that civilized space was constructed and therefore supporting the normative function of the Anglo-Saxons’ ‘sense of place’ in the terms of Convery et al. (2012).

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