The structural features that distinguish PD-L2 from PD-L1 emerged in placental mammals

Abstract

Programmed cell death protein 1 (PD-1) is an inhibitory receptor on T lymphocytes that is critical for modulating adaptive immunity. As such, it has been successfully exploited for cancer immunotherapy. Programmed death ligand 1 (PD-L1) and PD-L2 are ligands for PD-1; the former is ubiquitously expressed in inflamed tissues, whereas the latter is restricted to antigen-presenting cells. PD-L2 binds to PD-1 with 3-fold stronger affinity compared with PD-L1. To date, this affinity discrepancy has been attributed to a tryptophan (W110PD-L2) that is unique to PD-L2 and has been assumed to fit snuggly into a pocket on the PD-1 surface. Contrary to this model, using surface plasmon resonance to monitor real-time binding of recombinantly-expressed and -purified proteins, we found that W110PD-L2 acts as an “elbow” that helps shorten PD-L2 engagement with PD-1 and therefore lower affinity. Furthermore, we identified a “latch” between the C and D β-strands of the binding face as the source of the PD-L2 affinity advantage. We show that the 3-fold affinity advantage of PD-L2 is the consequence of these two opposing features, the W110PD-L2 “elbow” and a C–D region “latch.” Interestingly, using phylogenetic analysis, we found that these features evolved simultaneously upon the emergence of placental mammals, suggesting that PD-L2–affinity tuning was part of the alterations to the adaptive immune system required for placental gestation.

Dual and Opposite Costimulatory Targeting with a Novel Human Fusion Recombinant Protein Effectively Prevents Renal Warm Ischemia Reperfusion Injury and Allograft Rejection in Murine Models

“…Consequently, these results support the protein affinity to its designed targets, appearing as an interesting option in the inflammatory animal models addressed in the present study. Despite the reported similar KD values of the CD80 and HYBRI CTLA4 interaction, the KD values of the PD-1 and HYBRI’s PD-L2 interaction are higher than the values found in the literature [ 31 , 49 , 50 , 51 , 52 ]. Similarly to the increased affinity of the modified PD-L2 described by Philips et al [ 51 ], PD-L2 molecules in the HYBRI construct may have suffered conformational changes, which might account for its increased binding to PD-1.…”

“…Despite the reported similar KD values of the CD80 and HYBRI CTLA4 interaction, the KD values of the PD-1 and HYBRI's PD-L2 interaction are higher than the values found in the literature [31,[49][50][51][52]. Similarly to the increased affinity of the modified PD-L2 described by Philips et al [51], PD-L2 molecules in the HYBRI construct may have suffered conformational changes, which might account for its increased binding to PD-1. Nevertheless, in both rat models HYBRI shows therapeutic efficacy, which suggests that the binding is high enough to exert biological effects.…”

Treatment of rheumatic immune-related adverse events due to cancer immunotherapy with immune checkpoint inhibitors—is it time for a paradigm shift?

“…In contrast, PD-L2 expression is restricted mainly to antigenpresenting cells. PD-L2 has a much stronger affinity for PD-1 than does PD-L1 [12]. There is a difference in the expression of these two ligands in different tumor types, something which might have therapeutic implications [13].…”

SPRD: a surface plasmon resonance database of common factors for better experimental planning

“…The quality of the SPR data depends on the several external factors such as buffer compositions [ 19 ], types of the sensor chip with different matrix on the gold surface [ 20 – 22 ], and coupling techniques of ligands on the sensor surface [ 23 , 24 ]. For slow dissociating analyte-ligand interactions, the chip surface has to be regenerated with proper regeneration solution without affecting the ligand activity [ 25 ].…”