Regulation of PD-L1 through direct binding of cholesterol to CRAC motifs

Cholesterol, an essential molecule for cell structure, function, and viability, plays crucial roles in the development, progression, and survival of Cancer cells. Earlier studies have shown that cholesterol-lowering drugs can inhibit the high expression of programmed-death ligand 1 (PD-L1) that contributes to immunoevasion in Cancer cells. However, the regulatory mechanism of cell surface PD-L1 abundance by Cholesterol is still controversial. Here, using nuclear magnetic resonance and biochemical techniques, we demonstrated that Cholesterol can directly bind to the transmembrane domain of PD-L1 through two cholesterol-recognition amino acid consensus (CRAC) motifs, forming a sandwich-like architecture and stabilizing PD-L1 to prevent downstream degradation. Mutations at key binding residues prohibit PD-L1-cholesterol interactions, decreasing the cellular abundance of PD-L1. Our results reveal a unique regulatory mechanism that controls the stability of PD-L1 in Cancer cells, providing an alternative method to overcome PD-L1-mediated immunoevasion in cancers.