Overexpression of hexokinase I but not GLUT1 glucose transporter alters concentration dependence of glucose-stimulated insulin secretion in pancreatic beta-cell line MIN6.
The recently established pancreatic beta-cell line MIN6 retains the ability to secrete insulin in response to physiological glucose concentrations. To investigate the role of glucose transport and phosphorylation in glucose-stimulated insulin secretion by beta-cells, MIN6 cells were stably transfected with a rabbit GLUT1 glucose transporter cDNA or a rat hexokinase I cDNA cloned in an expression vector. Overexpression of GLUT1 increased 3-O-methylglucose uptake, but did not alter either glucose utilization or glucose-stimulated insulin secretion. In contrast, clones overexpressing hexokinase I exhibited enhanced glucose-stimulated insulin secretion at glucose concentrations below 10 mM with a concomitant increase in glucose utilization. Maximal insulin secretion as well as the maximal rate of glucose utilization were not altered in these clones. Insulin secretion stimulated by 2-ketoisocaproate, a non-glucose secretagogue, was not affected by hexokinase I expression. These results strongly suggest that the glucose phosphorylating step, but not glucose transport step, regulates glucose-stimulated insulin secretion by modulating the glycolytic rate in the beta-cell.
Ishihara
H
H
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Asano
T
T
Tsukuda
K
K
Katagiri
H
H
Inukai
K
K
Anai
M
M
Kikuchi
M
M
Yazaki
Y
Y
Miyazaki
J
J
Oka
Y
Y
D019325:3-O-Methylglucose; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D051272:Glucose Transporter Type 1; D006593:Hexokinase / Q000096:biosynthesis*; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007527:Isoenzymes / Q000096:biosynthesis; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000302:isolation & purification; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis / Q000302:isolation & purification; D011817:Rabbits; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection
D018076:DNA, Complementary; D051272:Glucose Transporter Type 1; D007328:Insulin; D007527:Isoenzymes; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495679:Slc2a1 protein, rat; D019325:3-O-Methylglucose; D006593:Hexokinase; D005947:Glucose