PD-L1 degradation is regulated by electrostatic membrane association of its cytoplasmic domain

• Published in: Nature communications 2021-08, Vol.12 (1), p.5106-13, Article 5106
• Main Authors: Wen, Maorong, Cao, Yunlei, Wu, Bin, Xiao, Taoran, Cao, Ruiyu, Wang, Qian, Liu, Xiwei, Xue, Hongjuan, Yu, Yang, Lin, Jialing, Xu, Chenqi, Xu, Jie, OuYang, Bo
• Format: Article
• Language: English
• Subjects: 101/6; 13/31; 14/19; 38/70; 631/250/580/1884; 631/45/287/1192; 631/45/612/1237; 631/535/878/1263; 82/16; 82/29; 82/80; 82/83; 96/33; B7-H1 Antigen - chemistry; B7-H1 Antigen - genetics; B7-H1 Antigen - metabolism; Biochemistry; Cancer; Cell Membrane - metabolism; Degradation; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2; Domains; Electrostatic properties; HEK293 Cells; Humanities and Social Sciences; Humans; Immunotherapy; Lipids; Lymphocytes; Membranes; Membranes - metabolism; Metformin; Molecular biology; multidisciplinary; Mutation; NMR; Nuclear magnetic resonance; PD-L1 protein; Phospholipids; Plasma; Proteins; Regulatory mechanisms (biology); Residues; Science; Science (multidisciplinary); Spectrum analysis; Stability; Static Electricity; Tumor cells; Tumors
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-25416-7

The cytoplasmic domain of PD-L1 (PD-L1-CD) regulates PD-L1 degradation and stability through various mechanism, making it an attractive target for blocking PD-L1-related cancer signaling. Here, by using NMR and biochemical techniques we find that the membrane association of PD-L1-CD is mediated by electrostatic interactions between acidic phospholipids and basic residues in the N-terminal region. The absence of the acidic phospholipids and replacement of the basic residues with acidic residues abolish the membrane association. Moreover, the basic-to-acidic mutations also decrease the cellular abundance of PD-L1, implicating that the electrostatic interaction with the plasma membrane mediates the cellular levels of PD-L1. Interestingly, distinct from its reported function as an activator of AMPK in tumor cells, the type 2 diabetes drug metformin enhances the membrane dissociation of PD-L1-CD by disrupting the electrostatic interaction, thereby decreasing the cellular abundance of PD-L1. Collectively, our study reveals an unusual regulatory mechanism that controls the PD-L1 level in tumor cells, suggesting an alternative strategy to improve the efficacy of PD-L1-related immunotherapies. The cytoplasmic domain of PD-L1 (PD-L1-CD) is involved in regulating PD-L1 stability and degradation. Here the authors show that membrane binding of PD-L1-CD mediates the cellular levels of PD-L1, while metformin can disrupt the interaction between PD-L1-CD and the membrane to reduce PD-L1 levels.