PD-L2 suppresses T cell signaling via coinhibitory microcluster formation and SHP2 phosphatase recruitment

Abstract

The coinhibitory receptor, PD-1, is of major importance for the suppression of T cell activation in various types of immune responses. A high-resolution imaging study showed that PD-1 forms a coinhibitory signalosome, “PD-1 microcluster”, with the phosphatase, SHP2, to dephosphorylate the TCR/CD3 complex and its downstream signaling molecules. Such a consecutive reaction entirely depended on PD-1–PD-L1/2 binding. PD-L2 is expressed on professional antigen-presenting cells and also on some tumor cells, which possibly explains the discrepant efficacy of immune checkpoint therapy for PD-L1-negative tumors. Here, we performed precise imaging analysis of PD-L2 forming PD-1–PD-L2 clusters associating with SHP2. PD-L2 could compete with PD-L1 for binding to PD-1, occupying the same space at TCR microclusters. The PD-1 microcluster formation was inhibited by certain mAbs with functional consequences. Thus, PD-1 microcluster formation provides a visible index for the effectiveness of anti-PD-1- or anti-PD-L1/2-mediated T cell suppression. PD-L2 may exert immune suppressive responses cooperatively with PD-L1 on the microcluster scale.

Cutaneous manifestations associated with immune checkpoint inhibitors

“…This signalosome suppresses T-cell responses. Similar to the effect of anti-PD-L1 agents, PD-L2 blockade may exert anti-tumor effects, although no therapeutic agents target PD-L2 ( 10 ). In the future, anti-PD-L2 agents are expected to be used to treat all types of cancer.…”

Evaluation of therapeutic PD-1 antibodies by an advanced single-molecule imaging system for human PD-1 microclusters

“…Recent clinical reports have described malignant tumors with high expression of human (h) PD-L2 or with dual expression of hPD-L1 and hPD-L2 as a ligand for hPD-1 4 . As such, in our previous report, we con rmed the endogenous expression of hPD-L1 and hPD-L2 by different cell lines of human lung cancers before or after in vitro culture with interferon γ (IFNγ) and found various patterns of hPD-1 ligand expression depending on each line 5 . Many types of ICIs have been developed and approved for therapies of these types of cancers all over the world.…”

“…Previous reports have shown that the recruitment of SHP2 to PD-1 microclusters occurs transiently and quickly after mPD-1 is crosslinked by mPD-L1 or mPD-L2. The clustering of SHP2 would take just tens of seconds 5,11 . In contrast, other reports have biochemically demonstrated that human SHP2 was immediately recruited to the cytoplasmic tail of hPD-1, while the colocalization of hSHP2 at hPD-1 tends to be more prolonged than mPD-1 with mSHP2 14 .…”

“…In our previous report, using a supported lipid bilayer (SLB) expressing MHC molecules and murine (m) PD-L1, we described that TCR microclusters are colocalized by PD-1 after PD-1-PD-L1 binding. PD-1 could recruit the phosphatase, SHP2, at the TCR microclusters and attenuate the dephosphorylation status of a TCR/CD3 complex, CD28, and almost all of the signaling molecules downstream of TCRs through forming PD-1-mediated "inhibitory microclusters" 5,11 .…”

Tumor microenvironment signaling and therapeutics in cancer progression

“…Programmed cell death protein 1 (PD-1) signaling Some tumors express PD-L1, which contributes to immune evasion by inhibiting cytotoxic responses. Thus, anti-PD-1/PD-L1 antibodies can promote T cell activation and enhance anti-tumor immunity by blocking the interaction between PD-1 and PD-L1/PD-L2 [270,271]. Typically, PD-L1 or PD-L2 are expressed on the surface of cancer cells or antigen-presenting cells and transduce a signal for cooperation with PD-1 expression on the cell surface of T lymphocytes to stimulate restraint signaling [272,273].…”