Discrimination of GLUTs by Fructose Isomers Enables Simultaneous Screening of GLUT5 and GLUT2 Activity in Live Cells.

Facilitative carbohydrate transporters (GLUTs, SLC2 gene family) are transmembrane proteins transporting hexoses and other sugars based on cellular metabolic demands. While a direct link between GLUTs and metabolic disorders has framed them as important biological and medicinal targets, targeting disease-relevant GLUTs remains challenging. In this study, we aimed to identify substrate-GLUT interactions that would discriminate between major fructose transporters. We examined the uptake distribution for conformational and configurational isomers of fructose using the corresponding conformationally locked fluorescently labeled mimetics as probes for assessing GLUT preferences in real time. Through comparative analysis of the uptake of the probes in the yeast-based single GLUT expression systems and the multi-GLUT mammalian cell environment, we established the ability of fructose transporters to discriminate between fructose conformers and epimers. We demonstrated that recreating the conformational and configurational mixture of fructose with molecular probes allows for the specific probe distribution, with fructofuranose mimetic being taken up preferentially through GLUT5 and ß-d-fructopyranose mimetic passing through GLUT2. The uptake of α-d-fructopyranose mimetic was found to be independent of GLUT5 or GLUT2. The results of this study provide a new approach to analyzing GLUT5 and GLUT2 activity in live cells, and the findings can be used as a proof-of-concept for multi-GLUT activity screening in live cells. The research also provides new knowledge on substrate-GLUT interactions and new tools for monitoring alterations in GLUT activities.

Targeting Sugar Uptake and Metabolism for Cancer Identification and Therapy: An Overview.

Metabolic deregulations have emerged as a cancer characteristic, opening a broad avenue for strategies and tools to target cancer through sugar uptake and metabolism. High expression levels of sugar transporters in cancer cells offered glycoconjugation as an approach to achieve enhanced cellular accumulation of drugs and imaging agents, with the sugar moiety anchoring the bioactive cargo to cancer cells. On the other hand, high demand for sugar nutrients in cancers provided a new avenue to target cancer cells with metabolic or sugar uptake inhibitors to induce cancer cells starvation or death. This overview summarizes recent advances in targeting cancer cells through sugar transport for cancer detection and therapy.

Metabolism-Driven High-Throughput Cancer Identification with GLUT5-Specific Molecular Probes.

Point-of-care applications rely on biomedical sensors to enable rapid detection with high sensitivity and selectivity. Despite advances in sensor development, there are challenges in cancer diagnostics. Detection of biomarkers, cell receptors, circulating tumor cells, gene identification, and fluorescent tagging are time-consuming due to the sample preparation and response time involved. Here, we present a novel approach to target the enhanced metabolism in breast cancers for rapid detection using fluorescent imaging. Fluorescent analogs of fructose target the fructose-specific transporter GLUT5 in breast cancers and have limited to no response from normal cells. These analogs demonstrate a marked difference in adenocarcinoma and premalignant cells leading to a novel detection approach. The vastly different uptake kinetics of the analogs yields two unique signatures for each cell type. We used normal breast cells MCF10A, adenocarcinoma cells MCF7, and premalignant cells MCF10AneoT, with hepatocellular carcinoma cells HepG2 as the negative control. Our data indicated that MCF10AneoT and MCF7 cells had an observable difference in response to only one of the analogs. The response, observed as fluorescence intensity, leads to a two-point assessment of the cells in any sample. Since the treatment time is 10 min, there is potential for use in rapid on-site high-throughput diagnostics.