Summary Many functions of the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) have been defined, but relatively little is known about the biology of an alternative mTOR complex, mTORC2. We showed that conditional deletion of rictor, an essential subunit of mTORC2, impaired differentiation into T helper 1 (Th1) and Th2 cells without diversion into FoxP3+ status or substantial effect on Th17 cell differentiation. mTORC2 promoted phosphorylation of protein kinase B (PKB, or Akt) and PKC, Akt activity, and nuclear NF-κB transcription factors in response to T cell activation. Complementation with active Akt restored only T-bet transcription factor expression and Th1 cell differentiation, whereas activated PKC-θ reverted only GATA3 transcription factor and the Th2 cell defect of mTORC2 mutant cells. Collectively, the data uncover vital mTOR – PKC and mTOR–Akt connections in T cell differentiation, and reveal distinct pathways by which mTORC2 regulates development of Th1 and Th2 cell subsets.

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The results show that a functional form of sFasL was generated by the action of the metalloproteinase matrilysin, and suggest that matrilysin cleavage of FasL is an important mediator of epithelial cell apoptosis.

Members of the nuclear factor (NF)-κB/Rel family transcription factors are induced during thymic selection and in mature T lymphocytes after ligation of the T cell antigen receptor (TCR). Despite these findings, disruption of individual NF-κB/Rel genes has revealed no intrinsic defect in the development of mature T cells, perhaps reflecting functional redundancy. To circumvent this possibility, the T cell lineage was targeted to express a trans-dominant form of IκBα that constitutively represses the activity of multiple NF-κB/Rel proteins. Transgenic cells expressing this inhibitor exhibit a significant proliferative defect, which is not reversed by the addition of exogenous interleukin-2. Moreover, mitogenic stimulation of splenocytes leads to increased apoptosis of transgenic T cells as compared with controls. In addition to deregulated T cell growth and survival, transgene expression impairs the development of normal T cell populations as evidenced by diminished numbers of TCRhi CD8 single-positive thymocytes. This defect was significantly amplified in the periphery and was accompanied by a decrease in CD4+ T cells. Taken together, these in vivo findings indicate that the NF-κB/Rel signaling pathway contains compensatory components that are essential for the establishment of normal T cell subsets.

Cytokines are inflammatory mediators important in responding to pathogens and other foreign challenges. Interleukin-4 (IL-4) and IL-13 are two cytokines produced by T helper type 2 cells, mast cells, and basophils. In addition to their physiological roles, these cytokines are also implicated in pathological conditions such as asthma and allergy. IL-4 can stimulate two receptors, type I and type II, whereas IL-13 signaling is mediated only by the type II receptor (see the STKE Connections Maps). These cytokines activate the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling cascades, which may contribute to allergic responses. In addition, stimulation of the phosphatidylinositol 3-kinase (PI3K) pathway through recruitment of members of the insulin receptor substrate family may contribute to survival and proliferation.

Despite the global impact of macrophage activation in vascular disease, the underlying mechanisms remain obscure. Here we show, with global proteomic analysis of macrophage cell lines treated with either IFNγ or IL-4, that PARP9 and PARP14 regulate macrophage activation. In primary macrophages, PARP9 and PARP14 have opposing roles in macrophage activation. PARP14 silencing induces pro-inflammatory genes and STAT1 phosphorylation in M(IFNγ) cells, whereas it suppresses anti-inflammatory gene expression and STAT6 phosphorylation in M(IL-4) cells. PARP9 silencing suppresses pro-inflammatory genes and STAT1 phosphorylation in M(IFNγ) cells. PARP14 induces ADP-ribosylation of STAT1, which is suppressed by PARP9. Mutations at these ADP-ribosylation sites lead to increased phosphorylation. Network analysis links PARP9–PARP14 with human coronary artery disease. PARP14 deficiency in haematopoietic cells accelerates the development and inflammatory burden of acute and chronic arterial lesions in mice. These findings suggest that PARP9 and PARP14 cross-regulate macrophage activation.

The majority of the genome is noncoding and was believed to be nonfunctional. However, it is now appreciated that transcriptional control of protein coding genes resides within these noncoding regions. Thousands of genes encoding long intergenic noncoding RNAs (lincRNAs) have been recently identified throughout the genome, which positively or negatively regulate transcription of neighboring target genes. Both TMEVPG1 and its mouse orthologue encode lincRNAs and are positioned near the interferon gamma gene (IFNG). Here we show that transcription of both mouse and human TMEVPG1 genes is Th1 selective and dependent upon Stat4 and T-bet, transcription factors that drive the Th1 differentiation program. Ifng expression is partially restored in Stat4−/−Tbx21−/− cells through co-expression of T-bet and Tmevpg1 and Tmevpg1 expression contributes to but alone is not sufficient to drive Th1-dependent Ifng expression. Our results suggest that TMEVPG1 belongs to the general class of lincRNAs that positively regulate gene transcription.