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Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
SGK1 kinase upregulates GLUT1 activity and plasma membrane expression
Monica Palmada1, Christoph Boehmer, Ahmad Akel
1Institute of Physiology I, University of Tübingen, Germany.
Serum- and glucocorticoid-inducible kinase 1 (SGK1) enhances glucose transporter 1 (GLUT1) activity by increasing its presence in the cell membrane. This SGK1-mediated regulation of GLUT1 is independent of protein kinase B (PKB).
Area of Science:
- Molecular biology
- Cellular physiology
- Biochemistry
Background:
- Phosphatidylinositol 3-kinase (PI3K) pathway is crucial for insulin-stimulated glucose uptake.
- Insulin signaling affects glucose transporter 1 (GLUT1) and GLUT4 translocation.
- Protein kinase B (PKB) mediates insulin's effect on GLUT4, but not GLUT1.
Purpose of the Study:
- To investigate the role of serum- and glucocorticoid-inducible kinase 1 (SGK1) in regulating glucose transporter 1 (GLUT1).
- To determine if SGK1 directly modulates GLUT1 activity and membrane abundance.
Main Methods:
- Tracer-flux assays in Xenopus oocytes and HEK-293 cells.
- Utilized constitutively active (S422D)SGK1 and inactive (K127N)SGK1 mutants.
- Kinetic analysis of GLUT1 transport rates and substrate affinity.
Main Results:
- Constitutively active SGK1 significantly enhanced GLUT1-mediated glucose transport.
- SGK1's effect on GLUT1 requires its catalytic activity.
- SGK1 increases GLUT1 abundance at the plasma membrane, not via protein synthesis.
- SGK1 enhances maximal transport rate without altering GLUT1 substrate affinity.
Conclusions:
- SGK1 directly regulates GLUT1 activity and plasma membrane localization.
- SGK1-mediated GLUT1 regulation is independent of PKB.
- SGK1 may account for the PI3K-dependent, PKB-independent insulin stimulation of GLUT1.
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