Antipsychotics inhibit glucose transport: Determination of olanzapine binding site in Staphylococcus epidermidis glucose/H(+) symporter.
The antipsychotic drug olanzapine is widely prescribed to treat schizophrenia and other psychotic disorders. However, it often causes unwanted side effects, including diabetes, due to disruption of insulin-dependant glucose metabolism through a mechanism yet to be elucidated. To determine if olanzapine can affect the first step in glucose metabolism - glucose transport inside cells - we investigated the effect of this drug on the transport activity of a model glucose transporter. The glucose transporter from Staphylococcus epidermidis (GlcPSe) is specific for glucose, inhibited by various human glucose transporter (GLUT) inhibitors, has high sequence and structure homology to GLUTs, and is readily amenable to transport assay, mutagenesis, and computational modeling. We found that olanzapine inhibits glucose transport of GlcPSe with an IC50 0.9 ± 0.1 mM. Computational docking of olanzapine to the GlcPSe structure revealed potential binding sites that were further examined through mutagenesis and transport assay to identify residues important for olanzapine inhibition. These investigations suggest that olanzapine binds in a polar region of the cytosolic part of the transporter, and interacts with residues R129, strictly conserved in all GLUTs, and N136, conserved in only a few GLUTs, including the insulin-responsive GLUT4. We propose that olanzapine inhibits GlcPSe by impeding the alternating opening and closing of the substrate cavity necessary for glucose transport. It accomplishes this by disrupting a key salt bridge formed by conserved residues R129 and E362, that stabilizes the outward-facing conformation of the transporter.
Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Petr
P
Babkin
Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Alayna M
AM
George Thompson
Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Cristina V
CV
Iancu
Department of Pharmaceutical Sciences, College of Pharmacy, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA.
D Eric
DE
Walters
Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Jun-Yong
JY
Choe
Carbohydrate transporter; DMSO, dimethyl sulfoxide; DTT, dithiothreitol; Diabetes; Drug design; Drug side effect; E. coli, Escherichia coli; EDTA, ethylenediaminetetraacetate; GLUT, glucose transporter (SLC2); GLUT4; GlcPSe, Staphylococcus epidermidis glucose/H+ symporter; HRP, horseradish peroxidase; KPi, potassium phosphate buffer; MOE, Molecular Operating Environment; Membrane proteins; Molecular docking; OLZ, olanzapine; RSO vesicles, right-side-out vesicles; SLC2; Sugar transporter