Abstract
Human glucose transporters (GLUTs) facilitate the uptake of hexoses into cells. In cancer, the increased proliferation necessitates higher expression of GLUTs, with particular emphasis on GLUT1 and GLUT3. Thus, inhibiting GLUTs holds promise as an anticancer therapy by starving these cells of fuel. Ganoderic acid A (GAA), a triterpene found in Ganoderma lucidum, has anticancer and antidiabetic properties. Recent studies show that GAA reduces glucose uptake in cancer cells, which indicates that GAA may affect GLUT1/GLUT3 by inhibiting glucose uptake. Therefore, this study aimed to inspect whether GAA could target GLUT1/GLUT3 and play an inhibitory role in changing their endofacial and exofacial conformations. To this end, AlphaFold2 was employed to model the endofacial and exofacial conformations of GLUT3 and GLUT1, respectively. Molecular docking, molecular dynamics simulation, cell viability, cellular thermal shift assays (CETSA), glucose uptake, qPCR, and western blotting were harnessed. In comparison to the endofacial (cytochalasin B) and exofacial (phloretin) GLUT1/3 inhibitors, the computational findings unveiled GAA's capacity to bind and stabilize GLUT1/3 in their two conformational states, with a preference for binding the endofacial conformation. A low, non-cytotoxic dose of GAA thermally stabilized both transporters and inhibited glucose uptake in human lung cancer cells, similar to cytochalasin B and phloretin. In conclusion, this study has unearthed novel functionalities of GAA, suggesting its potential utility in cancer therapy by targeting glucose metabolism.