Regulation of the d-glucose transport system in isolated fat cells

1976 ◽  
Vol 11 (1) ◽  
pp. 51-63 ◽  
Author(s):  
Michael P. Czech
Keyword(s):  
Glucose Transport ◽  
Transport System ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Glucose Transport System

scholarly journals Effects of cytochalasin B, colchicine and vincristine on the metabolism of isolated fat-cells

1974 ◽  
Vol 140 (2) ◽  
pp. 185-192 ◽  
Author(s):  
Ernest G. Loten ◽  
Bernard Jeanrenaud
Keyword(s):  
Glucose Metabolism ◽  
Transport System ◽  
Cytochalasin B ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Prolonged Incubation ◽  
Glucose Transport System ◽  
End Products ◽  
Release Of Glycerol ◽  
Cytochalasin A

1. Colchicine and vincristine only slightly inhibit the metabolism of glucose to CO2 and lipids by isolated fat-cells. 2. Prolonged incubation with these agents causes no further inhibition. 3. Cytochalasin B, however, inhibits glucose metabolism to both CO2 and lipids in fat-cells. 4. However, at a concentration that causes a strong inhibition of glucose metabolism cytochalasin B is without effect on the metabolism of pyruvate, lactate or arginine to these end products. The uptake of labelled α-aminoisobutyrate is likewise not modified. Similarly it does not affect release of glycerol or free fatty acid, or the actions of adrenaline, insulin or caffeine on these parameters. At 10μg/ml it slightly lowers ATP concentrations, an effect that does not occur at 2μg/ml. 5. The transport of fructose into adipocytes by a specific fructose-transport system is also not affected by the agent, but the uptake of 2-deoxyglucose is strongly inhibited. It is concluded that cytochalasin B may specifically inhibit the glucose-transport system of isolated fat-cells. 6. Cytochalasin A has a much weaker action than cytochalasin B on glucose metabolism.

Effects of wheat germ agglutinin on insulin binding and insulin sensitivity of fat cells

1980 ◽  
Vol 238 (3) ◽  
pp. E267-E275
Author(s):  
J. N. Livingston ◽  
B. J. Purvis
Keyword(s):  
Insulin Sensitivity ◽  
Insulin Receptor ◽  
Glucose Transport ◽  
Transport System ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Insulin Binding ◽  
Fat Cells ◽  
Glucose Transport System ◽  
Stimulation Of

The plant lectin (wheat germ agglutinin, WGA) produces several alterations in the ability of fat cells to bind and respond to insulin. Although WGA markedly stimulated glucose oxidation, it caused only a modest stimulation of glucose transport. WGA (0.25-20 micrograms/ml) increased the binding of insulin by adipocytes, apparently by increasing the binding affinity of the insulin receptor. With low WGA concentrations (0.25-2.5 micrograms/ml), the elevation in binding was accompanied by an increase in the sensitivity of the adipocytes to insulin stimulation of glucose transport. However, the sensitivity of these cells to vitamin K5 and H2O2 was not altered. With higher WGA concentrations (5-20 micrograms/ml), stimulation of the glucose transport system by insulin, vitamin K5, or H2O2 was markedly inhibited, an effect that is reversed by the addition of ovomucoid. These findings suggest that low WGA concentrations increase the affinity of the insulin receptor and the insulin sensitivity of the cells. At higher concentrations, the lectin appears to act at another site(s) to inhibit the activation of the transport system by insulin or other agents.

Modulation of glucose transport by parathyroid hormone and insulin in UMR 106–01, a clonal rat osteogenic sarcoma cell line

1995 ◽  
Vol 14 (2) ◽  
pp. 263-275 ◽  
Author(s):  
D M Thomas ◽  
S D Rogers ◽  
M W Sleeman ◽  
G M Pasquini ◽  
F R Bringhurst ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Cell Line ◽  
Glucose Transport ◽  
Transport System ◽  
Osteogenic Sarcoma ◽  
Regulatory Subunit ◽  
Sarcoma Cell ◽  
Sarcoma Cell Line ◽  
Glucose Transport System ◽  
Umr 106

ABSTRACT This study characterizes the actions of insulin and parathyroid hormone (PTH) on the glucose transport system in the rat osteogenic sarcoma cell line UMR 106–01, which expresses a number of features of the osteoblast phenotype. Using [1,2-3H]2-deoxyglucose (2-DOG) as a label, UMR 106–01 cells were shown to possess a glucose transport system which was enhanced by insulin. In contrast, PTH influenced glucose transport in a biphasic manner with a stimulatory effect at 1 h and a more potent inhibitory effect at 16 h on basal and insulin-stimulated 2-DOG transport. To explore the mechanism of PTH action, a direct agonist of cAMP-dependent protein kinase (PKA) was tested. 8-Bromo-cAMP had no acute stimulatory effect but inhibited basal and insulin-stimulated 2-DOG transport at 16 h. This result suggested that the prolonged, but not the acute, effect of PTH was mediated by the generation of cAMP. Further studies with the cell line UMR 4–7, a UMR 106–01 clone stably transfected with an inducible mutant inactive regulatory subunit of PKA, confirmed that the inhibitory but not the stimulatory effect of PTH was mediated by the PKA pathway. Northern blot data indicated that the prolonged inhibitory effects of PTH and 8-bromo-cAMP on glucose transport were likely to be mediated in part by reduction in the levels of GLUT1 (HepG2/brain glucose transporter) mRNA.

scholarly journals Evidence for two asymmetric conformational states in the human erythrocyte sugar-transport system

1975 ◽  
Vol 145 (3) ◽  
pp. 417-429 ◽  
Author(s):  
J E Barnett ◽  
G D Holman ◽  
R A Chalkley ◽  
K A Munday
Keyword(s):  
Glucose Transport ◽  
Transport System ◽  
Human Erythrocyte ◽  
Partition Coefficients ◽  
External Medium ◽  
Sugar Transport ◽  
Conformational States ◽  
Glucose Transport System ◽  
Oil Water

6-O-methyl-, 6-O-propyl-, 6-O-pentyl- and 6-O-benzyl-D-galactose, and 6-O-methyl-, 6-O-propyl- and 6-O-pentyl-D-glucose inhibit the glucose-transport system of the human erythrocyte when added to the external medium. Penetration of 6-O-methyl-D-galactose is inhibited by D-glucose, suggesting that it is transported by the glucose-transport system, but the longer-chain 6-O-alkyl-D-galactoses penetrate by a slower D-glucose-insensitive route at rates proportional to their olive oil/water partition coefficients. 6-O-n-Propyl-D-glucose and 6-O-n-propyl-D-galactose do not significantly inhibit L-sorbose entry or D-glucose exit when present only on the inside of the cells whereas propyl-beta-D-glucopyranoside, which also penetrates the membrane slowly by a glucose-insensitive route, only inhibits L-sorbose entry or D-glucose exit when present inside the cells, and not when on the outside. The 6-O-alkyl-D-galactoses, like the other nontransported C-4 and C-6 derivatives, maltose and 4,6-O-ethylidene-D-glucose, protect against fluorodinitrobenzene inactivation, whereas propyl beta-D-glucopyranoside stimulates the inactivation. Of the transported sugars tested, those modified at C-1, C-2 and C-3 enhance fluorodinitrobenzene inactivation, where those modified at C-4 and C-6 do not, but are inert or protect against inactivation. An asymmetric mechanism is proposed with two conformational states in which the sugar binds to the transport system so that C-4 and C-6 are in contact with the solvent on the outside and C-1 is in contact with the solvent on the inside of the cell. It is suggested that fluorodinitrobenzene reacts with the form of the transport system that binds sugars at the inner side of the membrane. An Appendix describes the theoretical basis of the experimental methods used for the determination of kinetic constants for non-permeating inhibitors.

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.

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