Intracellular Transport of PD-L1 by Rab10-Positive Tubular Endosomes Originated from Macropinocytic Cups in RAW264 Macrophage-Like Cells.

In our recent study, we identified Rab10-positive long tubular endosomes, which originate from macropinocytic cups, as a novel endocytic pathway in RAW264 cells. This pathway is unique because it bypasses the lysosomal degradation route and proceeds toward the Golgi region, distinguishing it from previously known endocytic routes. However, its function remains entirely unknown. Upon exploring the cargo transported by Rab10-positive tubular endosomes, we discovered that PD-L1, a cancer immune checkpoint molecule expressed on cancer cells and macrophage surfaces, was abundantly localized in Rab10-positive tubular structures in RAW264 cells. This suggests that PD-L1 may be a significant cargo for these endosomes in macrophages. These findings offer new insights into the role of Rab10-positive tubular endosomes in the intracellular transport of PD-L1, potentially influencing its expression on the cell surface.