TIM-3 Suppresses Anti-CD3/CD28-Induced TCR Activation and IL-2 Expression through the NFAT Signaling Pathway

Abstract

TIM-3 (T cell immunoglobulin and mucin-domain containing protein 3) is a member of the TIM family of proteins that is preferentially expressed on Th1 polarized CD4+ and CD8+ T cells. Recent studies indicate that TIM-3 serves as a negative regulator of T cell function (i.e. T cell dependent immune responses, proliferation, tolerance, and exhaustion). Despite having no recognizable inhibitory signaling motifs, the intracellular tail of TIM-3 is apparently indispensable for function. Specifically, the conserved residues Y265/Y272 and surrounding amino acids appear to be critical for function. Mechanistically, several studies suggest that TIM-3 can associate with interleukin inducible T cell kinase (ITK), the Src kinases Fyn and Lck, and the p85 phosphatidylinositol 3-kinase (PI3K) adaptor protein to positively or negatively regulate IL-2 production via NF-κB/NFAT signaling pathways. To begin to address this discrepancy, we examined the effect of TIM-3 in two model systems. First, we generated several Jurkat T cell lines stably expressing human TIM-3 or murine CD28-ECD/human TIM-3 intracellular tail chimeras and examined the effects that TIM-3 exerts on T cell Receptor (TCR)-mediated activation, cytokine secretion, promoter activity, and protein kinase association. In this model, our results demonstrate that TIM-3 inhibits several TCR-mediated phenotypes: i) NF-kB/NFAT activation, ii) CD69 expression, and iii) suppression of IL-2 secretion. To confirm our Jurkat cell observations we developed a primary human CD8+ cell system that expresses endogenous levels of TIM-3. Upon TCR ligation, we observed the loss of NFAT reporter activity and IL-2 secretion, and identified the association of Src kinase Lck, and PLC-γ with TIM-3. Taken together, our results support the conclusion that TIM-3 is a negative regulator of TCR-function by attenuating activation signals mediated by CD3/CD28 co-stimulation.

Inhibitory Receptors Induced by VSV Viroimmunotherapy Are Not Necessarily Targets for Improving Treatment Efficacy

“…Though it is has been demonstrated that signaling through both PD-1 and TIM-3 diminish T cell responses by regulating transcription factor activity, it remains to been seen how this signaling is qualitatively different than the inhibitory signaling that occurs with T cells possessing a chronically dysfunctional phenotype. 26,27 We hope these results will stimulate further investigation into the differences between infection and tumor-induced expression of inhibitory receptors and serve as a potentially cautionary result for use of immune checkpoint inhibitors in contexts which may not reflect clinically analogous situations. Therefore, it will be important to appreciate these differences in future studies of combinations of oncolytic virotherapy with checkpoint inhibitor blockade.…”

Angiotensin II Regulates Th1 T Cell Differentiation Through Angiotensin II Type 1 Receptor-PKA-Mediated Activation of Proteasome

“…Many factors are known to regulate Th1 and Th2 differentiation, especially renin-angiotensin system (RAS). A growing body of evidence suggests that anti-CD3/CD28 treatment also induces Th1 differentiation reflected by upregulation of IL-2, IFN-α and NF-kB activity in Jurkat cells or in human CD4 + T cells [19, 20]. Many factors are known to regulate Th1 and Th2 differentiation, including renin-angiotensin system (RAS).Ang II, a major effector of RAS, plays a critical role in this process.…”

TIM-3 as a Target for Cancer Immunotherapy and Mechanisms of Action

“…The phosphorylated tyrosines within the cytoplasmic domain of TIM-3 can then recruit p85 adaptor protein, leading to the activation of PI3 kinases. TIM-3 has also been shown to inhibit TCR proximal signaling [47,48]. In TIM-3 + CD8 + effector T cells, Gal-9 is shown to induce co-localization of TIM-3 with receptor phosphatases CD45 and CD148, and thereby inhibits TCR signaling [49].…”