Homodimerized cytoplasmic domain of PD-L1 regulates its complex glycosylation in living cells

Abstract

Whether membrane-anchored PD-L1 homodimerizes in living cells is controversial. The biological significance of the homodimer waits to be expeditiously explored. However, characterization of the membrane-anchored full-length PD-L1 homodimer is challenging, and unconventional approaches are needed. By using genetically incorporated crosslinkers, we showed that full length PD-L1 forms homodimers and tetramers in living cells. Importantly, the homodimerized intracellular domains of PD-L1 play critical roles in its complex glycosylation. Further analysis identified three key arginine residues in the intracellular domain of PD-L1 as the regulating unit. In the PD-L1/PD-L1-3RE homodimer, mutations result in a decrease in the membrane abundance and an increase in the Golgi of wild-type PD-L1. Notably, PD-1 binding to abnormally glycosylated PD-L1 on cancer cells was attenuated, and subsequent T-cell induced toxicity increased. Collectively, our study demonstrated that PD-L1 indeed forms homodimers in cells, and the homodimers play important roles in PD-L1 complex glycosylation and T-cell mediated toxicity.

Emerging therapeutic frontiers in cancer: insights into posttranslational modifications of PD-1/PD-L1 and regulatory pathways

“…PD-L1 can form homodimers and tetramers, and its complex glycosylation is linked to the homodimeric structure of its intracellular domain [ 190 ]. Natural compounds such as capsaicin, 6-gingerol, and curcumin may block the PD-1/PD-L1 interaction by targeting PD-L1 dimerization, enhancing anticancer immunity [ 191 ].…”

Genetically encoded crosslinkers to address protein–protein interactions

“…Further, BrEtY‐Cys pairwise crosslinking revealed that NleE interacts with the N‐terminus of PSMD10, possibly hampering its functional dimerization. In another study, a combination of Azi‐mediated photo‐crosslinking with BrEtY‐ and BrC7K‐ ( 12b ) mediated chemical crosslinking was applied to characterize dimers and tetramers of programmed death‐1 ligand (PD‐L1) on the surface of mammalian cells (Zhou et al, 2022 ).…”

B7 family protein glycosylation: Promising novel targets in tumor treatment

“…Resveratrol regulates the N-glycosylation modification of PD-L1 by inhibiting α-glucosidase/α-mannosidase, a mannose-rich abnormal glycosylated form of PD-L1 that inhibits binding to PD-1 ( 120 ). In addition, resveratrol promotes PD-L1 dimerization by interacting with the inner surface of PD-L1 ( 111 ), but dimerized PD-L1 can also bind to PD-1 and regulate T-cell toxicity ( 121 , 122 ). Poor pharmacokinetics and low potency seem to be the two main bottlenecks of resveratrol ( 123 ).…”