Regulation of PD-L1 Trafficking from Synthesis to Degradation.

Programmed death-ligand 1 (PD-L1) is a transmembrane ligand for the programmed cell death protein 1 (PD-1), a receptor that inhibits T-cell activity. The PD-L1/PD-1 immune checkpoint axis has been successfully targeted to enhance antitumor immune responses. Tethering PD-L1 to the membrane spatially restricts its ability to inhibit immune responses, and it provides for the acute and reversible modulation of PD-L1 plasma membrane density by regulation of its trafficking. PD-L1 has functions that are independent of its role as a ligand for PD-1, and control of PD-L1 residence in different intracellular compartments might contribute to the regulation of those activities. Thus, control of PD-L1 trafficking is emerging as a key feature of its biology. Herein, we focus on current understating of PD-L1 trafficking and review current attempts to therapeutically target this process in cancer cells to enhance antitumor immunity.