Inhibitor Discovery for the Human GLUT1 from Homology Modeling and Virtual Screening

The human Glucose Transporter 1 (hGLUT1
or SLC2A1) is a facilitative
membrane transporter found in the liver, intestines, kidney, and brain,
where it transports sugars such as d-glucose and d-galactose. Genetic variations in hGLUT1 are associated with a broad
range of diseases and metabolic disorders. For example, hGLUT1 is
upregulated in various cancer types (e.g., breast carcinoma) to support
the increased anaerobic glycolysis and the Warburg effect. Thus, hGLUT1
is an emerging therapeutic target, which also transports commonly
used cancer biomarkers (e.g., 18F-DG). In this study, we
use computational prediction followed by experimental testing, to
characterize hGLUT1. We construct homology models of hGLUT1 in a partially
occluded outward open (“occluded”) conformation based
on the X-ray structure of the E. coli xylose transporter,
XylE. Comparison of the binding site of the occluded models to experimentally
determined hGLUT structures revealed a hydrophobic pocket adjacent
to the sugar-binding site, which was tested experimentally via site-directed mutagenesis. Virtual screening of various
libraries of purchasable compounds against the occluded models, followed
by experimental testing with cellular assays revealed seven previously
unknown hGLUT1 ligands with IC50 values ranging from 0.45
μM to 59 μM. These ligands represent three unique chemotypes
that are chemically different from any other known hGLUT1 ligands.
The newly characterized hydrophobic pocket can potentially be utilized
by the new ligands for increased affinity. Furthermore, the previously
unknown hGLUT1 ligands can serve as chemical tools to further characterize
hGLUT1 function or lead molecules for future drug development.