Comparison of the redox potential in the endocytic pathway of different cell types by imaging live cells via FRET

Abstract

Sub‐cellular compartments have different redox environments and these electrochemical differences play a vital role in their distinct functions. Although much research has been conducted on the mitrochondria, nuclei, secretory pathway, and extracellular space, much remains to be elucidated regarding the redox potential in the endocytic pathway. Additionally, although some cells have been studied in this regard such as macrophages and dendritic cells, there exists no real comparison across different cell as to whether there is any variance in the redox potential across the endocytic pathway. We used fluorescence resonance energy transfer (FRET)‐ based redox‐sensitive fusion protein probes to compare FRET signals across cancer cells (PC3 and BT549 cell line), fibroblasts, and bone marrow‐derived dendritic cells in order to draw conclusions about the redox potential in the endocytic pathways. We found that the redox‐sensitive reporter encapsulated inside pHsensitive liposomes could be taken up by the different cells and tracked live by using FRET. Our results show that all the endosomes have a reducing environment although to a different degree depending upon the cell tested. In comparing the redox data with previously obtained Bone Marrow Macrophage (BMMO) data, our preliminary results show that all the cells tested were less reducing than the BMMOs but further study is needed to determine any statistical differences in comparison to each other. These findings may have implications for drug delivery via the endocytic pathway across different types of cells.