ITPK1 Sensitizes Tumor Cells to IgA-dependent Neutrophil Killing In Vivo.

Neutrophils can efficiently trigger cytotoxicity toward tumor cells and other target cells upon engagement of the IgA receptor CD89. However, the cell-intrinsic factors that influence the induction of cell death upon exposure to neutrophil effector mechanisms in vivo remain largely unknown. To uncover genetic regulators that influence target cell sensitivity to IgA-induced neutrophil-mediated killing, we used a human CD89 (hCD89) transgenic mouse model in which IgA-mediated killing of Her2-positive CD47-deficient murine target cells is mediated by neutrophils. Using a genome-wide in vivo screening approach, we demonstrate that deletion of the gene encoding inositol-tetrakisphosphate 1 kinase (ITPK1) increases survival of target cells in anti-Her2 IgA-treated mice. Moreover, we show that this effect depends on neutrophil activity and on the ITPK1 kinase domain. Notably, ITPK1 deficiency did not measurably impact survival of IgA-opsonized target cells in in vitro systems, underscoring the importance of in vivo screening systems to uncover physiologically relevant regulators of neutrophil killing.

Time-dependent regulation of cytokine production by RNA binding proteins defines T cell effector function.

Potent T cell responses against infections and malignancies require a rapid yet tightly regulated production of toxic effector molecules. Their production level is defined by post-transcriptional events at 3' untranslated regions (3' UTRs). RNA binding proteins (RBPs) are key regulators in this process. With an RNA aptamer-based capture assay, we identify >130 RBPs interacting with IFNG, TNF, and IL2 3' UTRs in human T cells. RBP-RNA interactions show plasticity upon T cell activation. Furthermore, we uncover the intricate and time-dependent regulation of cytokine production by RBPs: whereas HuR supports early cytokine production, ZFP36L1, ATXN2L, and ZC3HAV1 dampen and shorten the production duration, each at different time points. Strikingly, even though ZFP36L1 deletion does not rescue the dysfunctional phenotype, tumor-infiltrating T cells produce more cytokines and cytotoxic molecules, resulting in superior anti-tumoral T cell responses. Our findings thus show that identifying RBP-RNA interactions reveals key modulators of T cell responses in health and disease.

T cells at work: How post-transcriptional mechanisms control T cell homeostasis and activation.

T cells are central players of the adaptive immune system by protecting us from recurring infections and by killing malignant cells. Protective T cell responses rely on the concerted production of effector molecules such as cytolytic mediators, granzymes, and perforins, as well as pro-inflammatory cytokines and chemokines. Once activated, T cells drastically change their gene expression and rapidly respond to insults by producing ample amounts of effector molecules. In the absence of antigen, T cells remain in a quiescent state and survey our body for possible pathogenic insults. Resting T cells are, however, not inert, but continuously regulate their protein production to survive and to be prepared for possible re-infections. Here, we review our current knowledge on the regulation of gene expression in activated and quiescent T cells. We specifically focus on post-transcriptional mechanisms that define the protein output and that allow dormant cells to undergo active signaling and selective translation, keeping them poised for activation. Finally, we discuss which signals drive T cell survival and their preparedness to respond to insults and which mechanisms are involved in these processes.