Glucokinase regulatory protein is essential for the proper subcellular localisation of liver glucokinase.
Glucokinase (GK), a key enzyme in the glucose homeostatic responses of the liver, changes its intracellular localisation depending on the metabolic status of the cell. Rat liver GK and Xenopus laevis GK, fused to the green fluorescent protein (GFP), concentrated in the nucleus of cultured rat hepatocytes at low glucose and translocated to the cytoplasm at high glucose. Three mutant forms of Xenopus GK with reduced affinity for GK regulatory protein (GKRP) did not concentrate in the hepatocyte nuclei, even at low glucose. In COS-1 and HeLa cells, a blue fluorescent protein (BFP)-tagged version of rat liver GK was only able to accumulate in the nucleus when it was co-expressed with GKRP-GFP. At low glucose, both proteins concentrated in the nuclear compartment and at high glucose, BFP-GK translocated to the cytosol while GKRP-GFP remained in the nucleus. These findings indicate that the presence of and binding to GKRP are necessary and sufficient for the proper intracellular localisation of GK and directly involve GKRP in the control of the GK subcellular distribution.
de la Iglesia
N
N
Departament de Bioquímica i Biologia Molecular, Universitat de Barcelona, Martí i Franquès, Spain.
Veiga-da-Cunha
M
M
Van Schaftingen
E
E
Guinovart
J J
JJ
Ferrer
J C
JC
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002352:Carrier Proteins; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression; D005941:Glucokinase / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; C485100:GCKR protein, human; C499484:Gckr protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C080906:glucokinase regulatory protein; C499485:liver glucokinase regulatory protein, Xenopus; D049452:Green Fluorescent Proteins; D005941:Glucokinase; D005947:Glucose