Cell Rep. 2020 Jul 28;32(4):107957.
doi: 10.1016/j.celrep.2020.107957.
Background
Protein tyrosine phosphatase non-receptor type 2 (PTPN2) is a ubiquitously expressed tyrosine phosphatase found at high levels in resting and activated T cells. PTPN2 has received considerable attention because reductions in its expression correlate with the development of autoimmune diseases. Moreover, its known role in negatively regulating TCR sensitivity through dephosphorylation of SRC family kinases and in attenuating JAK-STAT-mediated cytokine signaling has made it an attractive target for immunotherapy. However, how complete absence of PTPN2 impacts basic aspects of CD8 T cell effector and memory differentiation and their survival capacity has remained unknown.
Methods
●Mice: OT-I; Lck-Cre;Ptpn2fl/fl(KO) and OT-I; Ptpnfl/fl(WT) mice●AdoptiveT cell transfers●Invitro stimulation system●Proteomics analysis using the network enrichment tool KeyPathwayMiner and the Ingenuity pathway analysis tool (IPA).●Generation of bone marrow derived dendritic cells (BMDCs) to assess TCR signaling
Results
1. PTPN2 Deficiency Promotes the Long-Term Maintenance of T Cells that Lack a Typical CD127+ Memory Phenotype. To explore how PTPN2 impacts T cell differentiation, they transferred Lck-Cre; Ptpn2fl/fl OT-I (KO) and control Ptpn2fl/fl OT-I CD8 T cells (WT) into host mice and infected the mice with recombinant Listeria monocytogenes(Lm), which was modified to express the ovalbumin-derived SIINFEKL ligand (N4). The results showed that the absence of PTPN2 caused a clear shift in the ratio of CD127-KLRG1+ terminal effector versus CD127+KLRG1- memory precursor CD8 T cells upon infection with Lm-N4.2. PTPN2 Deficiency Enables the Re-expansion of KLRG1+ T Cell Populations. As a next step, they thought to determine the functional capacity of the CD127-KLRG1+ T cells that survive in the absence of PTPN2. KLRG1-specific T cells are known to arise in large numbers in many types of acute infection. They are thought to predominantly mark cells that have turned toward the final stage of differentiation and lost the ability to form memory T cells. They transferred CD127+KLRG1– and CD127-KLRG1+ WT and KO OT-I T cells at 7 days post infection with Lm-N4 into naive secondary host mice. Significantly, the transferred KLRG1+ PTPN2-deficient T cells mounted a robust secondary T cell response following pathogen challenge.3. PTPN2 Deficiency Largely Enhances the Expansion of Ex Vivo-Stimulated and Adoptively Transferred T Cells. The efficacy of adoptive T cell therapies critically depends on the number of engrafted T cells and their invivo expansion magnitude. They stimulated T cells in vitro and transferred T cells to host mice. The results showed that there were ~ 3 times more PTPN2-deficient T cells in the spleen compared with WT cells, ~ 11 times more in the blood, and ~ 7 times more in the liver. Phenotypically, the recovered KOOT-I T cells displayed again a bias toward an increased frequency of KLRG1+ T cells.4. Deletion of PTPN2 Alters Cytokine Signal Transduction in Recently Activated T Cells. They used proteomics to assess the mechanisms by which elimination of PTPN2 can enhance T cell survival and programmed expansion. The data suggested that the absence of PTPN2 predominantly increases the responsiveness to common γ-chaincytokines and consequently augments co-stimulation-independent expansion and survival of recently activated T cells.5. PTPN2 Deficiency Increases IL-2- and IL-15-Induced Signal Transduction in T Cells during Programmed Expansion. They observed that PTPN2-deficient OT-I Tcells show increased IL-2- and IL-15-induced signaling, which was reflected in enhanced phosphorylation levels of STAT5-Y694 after activation. Further experiments showed that activated PTPN2-deficient T cells did not alter TCR signal transduction capacity as occurs in naive cells.6. PTPN2 Deficiency Enhances IL-2 Sensitivity and Survival Capacity of Recently Activated T Cells. They observed that PTPN2-deficient cells showed better survival following the provision of limited IL-2 levels compared with WT cells, which suggested that this improved IL-2 sensitivity results in the increased expansion of PTPN2-deficient T cells.Conclusions
Overall, PTPN2 deficiency renders cells in vivo and in vitro less dependent on survival-promoting cytokines, such as IL-2 and IL-15. Remarkably, briefly ex vivo-activated PTPN2-deficient T cells accumulate in 3- to 11-fold higher numbers following transfer into unmanipulated, antigen-free mice. Moreover, the absence of PTPN2 augments the survival of short-lived effector T cells and allows them to robustly re-expand upon secondary challenge. Importantly, they find no evidence for impaired effector function ormemory formation. Mechanistically, PTPN2 deficiency causes broad changes in the expression and phosphorylation of T cell expansion and survival-associated proteins. Altogether, their work underlined the therapeutic potential of targeting PTPN2 in T cell-based therapies to augment the number and survival capacity of antigen-specific T cells.