Chronic Hyperglycemia Increases the Density of Glucose Transporters in Human Erythrocyte Membranes*

Human erythrocyte membranes and partially purified nucleoside transporter (band 4.5 and 7) were photoaffinity labelled with 3H-labelled 6-[(4-nitrobenzyl)thio]-9-beta-D-ribofuranosylpurine under equilibrium binding conditions. Band 4.5 was the major site of radiolabelling in both preparations. These experiments provide additional evidence to implicate band 4.5 polypeptides in nucleoside permeation, proteins previously shown to be involved in hexose transport.

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Erythrocyte nucleoside and sugar transport Endo-β-galactosidase and endoglycosidase-F digestion of partially purified human and pig transporter proteins

Biochemical Journal ◽

10.1042/bj2400349 ◽

1986 ◽

Vol 240 (2) ◽

pp. 349-356 ◽

Cited By ~ 37

Author(s):

F Y Kwong ◽

S A Baldwin ◽

P R Scudder ◽

S M Jarvis ◽

M Y Choy ◽

...

Keyword(s):

Human Erythrocyte ◽

Cytochalasin B ◽

Sugar Transport ◽

Glucose Transporters ◽

Nucleoside Transporters ◽

Enzyme Treatment ◽

Erythrocyte Membranes ◽

Nucleoside Transporter ◽

Human Erythrocyte Membranes ◽

Beta Galactosidase

Nucleoside- and glucose-transport proteins isolated from human erythrocyte membranes were photoaffinity-labelled with [3H]nitrobenzylthioinosine and [3H]cytochalasin B, respectively, and subjected to endo-beta-galactosidase or endoglycosidase-F digestion. Without enzyme treatment the two radiolabelled transporters migrated on SDS/polyacrylamide gels with the same apparent Mr (average) of 55,000. Apparent Mr (average) values after endo-beta-galactosidase digestion were 47,000 and 48,000 for the nucleoside and glucose transporters respectively, and 44,000 and 45,000 respectively after endoglycosidase-F digestion. In contrast, endo-beta-galactosidase had no effect on the electrophoretic mobility of the nucleoside transporter isolated from pig erythrocytes. This transport system exhibited a higher Mr than the human protein, endoglycosidase-F treatment decreasing its apparent Mr (average) from 64,000 to 57,000. It is concluded that the human and pig erythrocyte nucleoside transporters are glycoproteins containing N-linked oligosaccharide. The data provide evidence of substantial carbohydrate and polypeptide differences between the human and pig erythrocyte nucleoside transporters, but evidence of molecular similarities between the human erythrocyte nucleoside and glucose transporters.

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Interaction of platelet plasma membranes with thrombin-activated platelets

Blood ◽

10.1182/blood.v57.2.305.305 ◽

1981 ◽

Vol 57 (2) ◽

pp. 305-312 ◽

Cited By ~ 2

Author(s):

HR Prasanna ◽

HH Edwards ◽

DR Phillips

Keyword(s):

Human Erythrocyte ◽

Plasma Membranes ◽

Membrane Binding ◽

Human Platelets ◽

Platelet Membrane ◽

Erythrocyte Membranes ◽

Functional Sites ◽

Activated Platelets ◽

Platelet Membranes ◽

Human Erythrocyte Membranes

Abstract This study described the binding of platelet plasma membranes to either control or thrombin-activated platelets. Glycoproteins in plasma membranes isolated from human platelets were labeled by oxidation with periodate followed by reduction with [3H]NaBH4. Labeled membranes were incubated with either control or thrombin-activated platelets. The amount of membranes bound was measured by separating platelets with bound membranes from solution by rapid centrifugation through 27% sucrose and determining the amount of radioactivity associated with platelets. Five- to sevenfold more membranes bound to thrombin- activated platelets than to control platelets. This enhanced binding of labeled membranes was completely inhibited by an excess of unlabeled platelet membranes. Human erythrocyte membranes had little affinity for either washed or thrombin-activated platelets and therefore did not compete for platelet-membrane binding. Binding of platelet membranes to thrombin-treated platelets was inhibited by prior incubation of the platelets with PGI2 suggesting that the enhanced binding of membranes was to activated platelets. This study demonstrates that the purified platelet membranes have functional sites that can mediate membrane binding to platelets and that quantitation of membrane binding appears to reflect the increased aggregation capability of activated platelets.

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