Figure 4.

Identification of secretory protein VSTM2A as a novel ligand of PD-L1

(A) Experimental strategy for identification of the potential cell membrane receptor of VSTM2A by Ni-NTA purification and LC-MS/MS. MS/MS spectra of the peptides matched with human PD-L1 are shown on the right. (B) Predicted 3D structure of human VSTM2A and PD-1. (C) Detection of the interaction between human PD-L1 and VSTM2A using overexpression followed by coIP. (D) Detection of human PD-L1/VSTM2A interaction by reciprocal coIP using VSTM2A conditioned medium and endogenous PD-L1. (E) Detection of the interaction between human VSTM2A and mouse Pd-l1 by coIP. (F) Domain mapping of PD-L1 for VSTM2A binding. (G) Domain mapping of VSTM2A for PD-L1 binding. (H) Detection of the interaction between human PD-L2 and VSTM2A by coIP. (I) Summary of the interaction properties of VSTM2A with PD-L1/L2. CM, conditioned medium; Hm, human; Ms, mouse.