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Cytochalasin B-sensitive, sodium ion-dependent glucose transport in intestinal microvillous membrane
1Department of Biochemistry, Hamamatsu University School of Medicine, Handa-cho, Japan.
Abstract:
It was found that sodium ion-dependent glucose uptake by microvillous membrane (MVM) vesicles was partially inhibited by cytochalasin B with a half-maximum inhibition at ca. 10 microM. The MVM was photolabeled with [3]cytochalasin B. The Kd value and the maximum number of binding sites for cytochalasin B were ca. 8 microM and 70 pmol/mg protein, respectively. SDS-PAGE of the photolabeled MVM revealed 2 binding components. One was 86 K in Mr and the other 42 K. The binding of cytochalasin B to the 86 K component was affected neither by cytochalasin E nor by the presence of 0.5 M NaCl, but was depressed in the presence of 2-deoxy-D-glucose or phlorizin, which had no effect on the labeling of the 42 K component. These and other data suggested that the 86 K component might be responsible for a cytochalasin B-sensitive glucose transport in intestinal epithelial MVM.
Insights
Cytochalasin B partially inhibits glucose uptake in intestinal microvillus membrane (MVM) vesicles. Further research identified an 86 K protein component potentially responsible for this cytochalasin B-sensitive glucose transport.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Glucose uptake is crucial for intestinal absorption.
- Microvillus membrane (MVM) vesicles are key sites for nutrient transport.
- Cytochalasin B is a known inhibitor of glucose transport.
Purpose of the Study:
- To investigate the mechanism of sodium-ion dependent glucose uptake in intestinal MVM.
- To identify the specific protein components involved in cytochalasin B-sensitive glucose transport.
Main Methods:
- Utilized cytochalasin B to inhibit glucose uptake in MVM vesicles.
- Photolabeled MVM vesicles with [3]cytochalasin B.
- Analyzed protein binding using SDS-PAGE.
- Investigated the effects of competing molecules on cytochalasin B binding.
Main Results:
- Cytochalasin B partially inhibited glucose uptake with a half-maximum inhibition at approximately 10 microM.
- Photolabeling revealed two binding components in MVM: 86 K and 42 K.
- The 86 K component showed specific binding characteristics, being depressed by glucose analogs (2-deoxy-D-glucose, phlorizin), suggesting its role in glucose transport.
- The 42 K component's labeling was unaffected by these glucose analogs.
Conclusions:
- An 86 K protein component in intestinal epithelial MVM is likely responsible for cytochalasin B-sensitive glucose transport.
- This finding contributes to understanding the molecular basis of intestinal glucose absorption.