A study on the regulation of translocation of glucose transporters during hepatocarcinogenesis induced by 3'-Me DAB.
The mechanism of glucose transported (GT) expression on the plasma membranes of hepatoma cells in rats induced by 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) was studied. Cytochalasin B binding to plasma membrane fractions from control and 3'-MeDAB group in the absence of cold cytochalasin B showed 9,825 +/- 925 and 30,165 +/- 625 dpm/mg membrane protein. Scatchard plot analysis showed that the GTs present on the plasma membrane fractions in control and 3'-Me DAB groups were 5.0 and 16.0 pmol/mg membrane protein and their Kd values were 151 and 157 nM, respectively. These results suggest that the numbers of GTs in plasma membrane were increased in the 3'-Me DAB group compared to the control group. In contrast, the amounts of GTs in low density microsomal (LDM) fractions measured by a photoaffinity labeling technique using [3H]-cytochalasin B were 31,207 and 11,702 dpm/mg protein in the control and 3'-Me DAB group, respectively. These results suggest that GTs were translocated from LDM to plasma membranes during carcinogenesis. To confirm these results by an independent method 10% SDS-polyacrylamide gel electrophoresis was carried out. Gel slice No. 13 corresponding to MW of 45 kDa from plasma membrane fractions showed increased radioactivities in the 3'-Me DAB group compared to the control group. However, LDM fractions of the 3'-Me DAB group showed decreased radioactivities compared to the control group. Western blot analysis using anti-human RBC GT antibody present in the plasma membranes and LDM fractions from control and 3'-Me DAB groups did not show any significant difference, indicating low cross-reactivity between them. These results indicate that increased glucose transport seems to be more likely due to reciprocal redistribution of GTs between plasma membrane and LDM fractions.
Kim
Y S
YS
Department of Biochemistry, Yonsei University College of Medicine, Seoul, Korea.
Paik
E M
EM
Lee
M S
MS
Kim
K S
KS
Chai
K J
KJ
Ahn
Y H
YH
D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry; D003571:Cytochalasin B / Q000378:metabolism; D005947:Glucose / Q000032:analysis*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008297:Male; D008749:Methyldimethylaminoazobenzene; D008862:Microsomes, Liver / Q000737:chemistry*; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D051381:Rats
D009004:Monosaccharide Transport Proteins; D003571:Cytochalasin B; D008749:Methyldimethylaminoazobenzene; D005947:Glucose