Expression of glucose transporter isoform GLUT-2 and glucokinase genes in human brain.
The glucose transporter isoform-2 (GLUT-2) and glucokinase are considered to be components of a glucose sensor system controlling several key processes, and hence may modulate feeding behaviour. We have found GLUT-2 and glucokinase mRNAs in several brain regions, including the ventromedial and arcuate nuclei of the hypothalamus. GLUT-2, glucokinase and glucokinase regulatory protein mRNAs and proteins were present in these areas as determined by biochemical approaches. In addition, glucose-phosphorylating activity with a high apparent Km for glucose that displayed no product inhibition by glucose-6-phosphate was observed. Increased glycaemia after meals may be recognized by specific hypothalamic neurones due to the high Km of GLUT-2 and glucokinase. This enzyme is considered to be the true glucose sensor because it catalyses the rate-limiting step of glucose catabolism its activity being regulated by interaction with glucokinase regulatory protein, that functions as a metabolic sensor.
Roncero
Isabel
I
Department of Biochemistry and Molecular Biology, Faculty of Medicine, Madrid, Spain.
Alvarez
Elvira
E
Chowen
Julie A
JA
Sanz
Carmen
C
Rábano
Alberto
A
Vázquez
Patricia
P
Blázquez
Enrique
E
D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D001923:Brain Chemistry; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D015870:Gene Expression; D005941:Glucokinase / Q000096:biosynthesis* / Q000235:genetics*; D005947:Glucose / Q000737:chemistry / Q000493:pharmacokinetics; D051273:Glucose Transporter Type 2; D019298:Glucose-6-Phosphate / Q000737:chemistry; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis* / Q000235:genetics*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C485100:GCKR protein, human; D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C080906:glucokinase regulatory protein; D019298:Glucose-6-Phosphate; D005941:Glucokinase; D005947:Glucose