Evidence that glucokinase regulatory protein is expressed and interacts with glucokinase in rat brain.
Our previous description of functional glucokinase isoforms in the rat brain has opened new questions concerning the presence of glucokinase regulatory protein in the brain and the functional role of its interactions with glucokinase. In this study, we found glucokinase regulatory protein mRNA in rat brain, pancreatic islets and liver. In addition, we found two other variant splicing isoforms, both identified in hypothalamus, pancreatic islets and liver. In situ hybridization studies revealed the presence of glucokinase regulatory protein mRNA, the highest number of positive cells being found in the paraventricular nucleus of the hypothalamus. Glucokinase regulatory protein gene expression gave rise to a protein of 69 kDa mainly in nuclear and soluble cell fractions. Glutathione S-transferase protein fused either to rat liver or human pancreatic islet glucokinase were able to precipitate glucokinase regulatory protein from liver or hypothalamic extracts in the presence of fructose-6-phosphate, the amount of protein co-precipitated being decreased with fructose-1-phosphate. These findings suggest that the presence of glucokinase and glucokinase regulatory protein in the rat brain would facilitate the adaptation of this organ to fluctuations in blood glucose concentrations, and both proteins may participate in glucose-sensing and metabolic regulation in the central nervous system.
Alvarez
Elvira
E
Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Spain. eao513@eucmax.sim.ucm.es
Roncero
Isabel
I
Chowen
Julie A
JA
Vázquez
Patricia
P
Blázquez
Enrique
E
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D015139:Blotting, Southern; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins; D011232:Chemical Precipitation; D005941:Glucokinase / Q000502:physiology*; D006651:Histocytochemistry; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C485100:GCKR protein, human; C499484:Gckr protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012333:RNA, Messenger; C080906:glucokinase regulatory protein; D005941:Glucokinase