Diacylglycerol kinase ζ limits IL-2-dependent control of PD-1 expression in tumor-infiltrating T lymphocytes

Abstract

BackgroundThe inhibitory functions triggered by the programmed cell death-1 (PD-1) receptor following binding to its ligand (PD-L1) protect healthy organs from cytotoxic T cells, and neutralize antitumor T cell attack. Antibody-based therapies to block PD-1/PD-L1 interaction have yielded notable results, but most patients eventually develop resistance. This failure is attributed to CD8+ T cells achieving hyporesponsive states from which recovery is hardly feasible. Dysfunctional T cell phenotypes are favored by a sustained imbalance in the diacylglycerol (DAG)- and Ca2+-regulated transcriptional programs. In mice, DAG kinase ζ (DGKζ) facilitates DAG consumption, limiting T cell activation and cytotoxic T cell responses. DGKζ deficiency facilitates tumor rejection in mice without apparent adverse autoimmune effects. Despite its therapeutic potential, little is known about DGKζ function in human T cells, and no known inhibitors target this isoform.MethodsWe used a human triple parameter reporter cell line to examine the consequences of DGKζ depletion on the transcriptional restriction imposed by PD-1 ligation. We studied the effect of DGKζ deficiency on PD-1 expression dynamics, as well as the impact of DGKζ absence on the in vivo growth of MC38 adenocarcinoma cells.ResultsWe demonstrate that DGKζ depletion enhances DAG-regulated transcriptional programs, promoting interleukin-2 production and partially counteracting PD-1 inhibitory functions. DGKζ loss results in limited PD-1 expression and enhanced expansion of cytotoxic CD8+ T cell populations. This is observed even in immunosuppressive milieus, and correlates with the reduced ability of MC38 adenocarcinoma cells to form tumors in DGKζ-deficient mice.ConclusionsOur results, which define a role for DGKζ in the control of PD-1 expression, confirm DGKζ potential as a therapeutic target as well as a biomarker of CD8+ T cell dysfunctional states.

Sorting Nexin 27 Enables MTOC and Secretory Machinery Translocation to the Immune Synapse

“…( 34 ). In agreement with previously reported data for DGKζ-silenced TPR cells ( 73 ), TCS-CD86 engagement of SNX27-silenced TPR cells promoted a more robust NF-κB and AP-1 induction but diminished that of NFAT compared to control cells ( Figure 8A ) . The inhibitory effect of SNX27 silencing on NFAT activation resembles that described when silencing other polarity regulators, suggesting common mechanisms leading to it, such as defective microtubule organization ( 70 ).…”

“…In the current study, we further investigated the transcriptional regulation by SNX27 in IS-forming TPR cells. SNX27-silenced T cells stimulated with TCS-CD86 display increased AP-1 and NF-κB-dependent transcription, as well as augmented IL-2 secretion compared to control cells, an effect similar to that described for DGKζ-silenced TPR cells ( 73 ). The use of this model confirms previous luciferase studies in CD3/CD28-stimulated Jurkat T cells and demonstrates the strict regulation of NF-κB transcription by SNX27.…”

Immune Checkpoint Receptors Signaling in T Cells

“…Recent studies suggest the possibility of a signaling connection between DGKα/DGKζ and immune checkpoint receptors. Indeed, both isoforms are involved in PD-1-promoted downregulation of the DAG-driven Ras/MAPK/AP1 pathway, contributing to the establishment of T cell exhaustion and PD-1 expression [ 130 , 131 ]. In line with this, DGKα is upregulated in tumor-infiltrating lymphocytes but also when resistance to PD-1-targeted therapies arises, and its inhibition counteracts such resistance, with the added value of directly hitting DGK-addicted cancer cells [ 132 , 133 ].…”

Wiskott-Aldrich syndrome protein interacts and inhibits diacylglycerol kinase alpha promoting IL-2 induction

“…Quantitative studies indicate that DGKz is responsible for the metabolism of most of the DAG generated by phosphatidylinositol 4,5-bisphosphate (PIP 2 ) hydrolysis and controls the activation of DAG-effectors such as protein kinase C theta (PKCq) and RasGRP1 (6,7). Conversely, DGKa activity is rapidly recruited in a phosphatidylinositol (3)(4)(5)-trisphosphate (PIP 3 )-dependent manner to phosphorylate a minor pool of DAG at the periphery of the immune synapse, playing a key function in shaping the immune synapse and cell polarization (8).…”

“…The activity of both isoforms promotes T cell anergy, a tolerance condition characterized by the uncoupling of ligand-induced TCR activation from downstream signalling, while their inhibition potentiates T cell activation and IL-2 synthesis ( 2 , 3 ). In addition, DGKα and DGKζ contribute to tumour cell immune escape, and their inhibition rescues defective anti-tumour killing activity in tumour-specific exhausted T cells ( 4 , 5 ). Quantitative studies indicate that DGKζ is responsible for the metabolism of most of the DAG generated by phosphatidylinositol 4,5-bisphosphate (PIP 2 ) hydrolysis and controls the activation of DAG-effectors such as protein kinase C theta (PKCθ) and RasGRP1 ( 6 , 7 ).…”