IL-15 and PIM kinases direct the metabolic programming of intestinal intraepithelial lymphocytes

Intraepithelial lymphocytes (IEL) respond to IL-15 complexed with IL-15Ra but how this intrinsically affects IEL is unclear. Here the authors use proteomics analyses of the main mouse IEL subsets and identify PIM kinases as essential for IEL proliferation, metabolism and effector function downstream of IL-15

Tissue environment, not ontogeny, defines murine intestinal intraepithelial T lymphocytes

Tissue-resident intestinal intraepithelial T lymphocytes (T-IEL) patrol the gut and have important roles in regulating intestinal homeostasis. T-IEL include both induced T-IEL, derived from systemic antigen-experienced lymphocytes, and natural T-IEL, which are developmentally targeted to the intestine. While the processes driving T-IEL development have been elucidated, the precise roles of the different subsets and the processes driving activation and regulation of these cells remain unclear. To gain functional insights into these enigmatic cells, we used high-resolution, quantitative mass spectrometry to compare the proteomes of induced T-IEL and natural T-IEL subsets, with naive CD8(+) T cells from lymph nodes. This data exposes the dominant effect of the gut environment over ontogeny on T-IEL phenotypes. Analyses of protein copy numbers of >7000 proteins in T-IEL reveal skewing of the cell surface repertoire towards epithelial interactions and checkpoint receptors; strong suppression of the metabolic machinery indicating a high energy barrier to functional activation; upregulated cholesterol and lipid metabolic pathways, leading to high cholesterol levels in T-IEL; suppression of T cell antigen receptor signalling and expression of the transcription factor TOX, reminiscent of chronically activated T cells. These novel findings illustrate how T-IEL integrate multiple tissue-specific signals to maintain their homeostasis and potentially function

Loss of Adenomatous polyposis coli function renders intestinal epithelial cells resistant to the cytokine IL-22

Interleukin-22 (IL-22) is a critical immune defence cytokine that maintains intestinal homeostasis and promotes wound healing and tissue regeneration, which can support the growth of colorectal tumours. Mutations in the adenomatous polyposis coli gene (Apc) are a major driver of familial colorectal cancers (CRCs). How IL-22 contributes to APC-mediated tumorigenesis is poorly understood. To investigate IL-22 signalling in wild-type (WT) and APC-mutant cells, we performed RNA sequencing (RNAseq) of IL-22-treated murine small intestinal epithelial organoids. In WT epithelia, antimicrobial defence and cellular stress response pathways were most strongly induced by IL-22. Surprisingly, although IL-22 activates signal transducer and activator of transcription 3 (STAT3) in APC-mutant cells, STAT3 target genes were not induced. Our analyses revealed that ApcMin/Min cells are resistant to IL-22 due to reduced expression of the IL-22 receptor, and increased expression of inhibitors of STAT3, particularly histone deacetylases (HDACs). We further show that IL-22 increases DNA damage and genomic instability, which can accelerate cellular transition from heterozygosity (ApcMin/+) to homozygosity (ApcMin/Min) to drive tumour formation. Our data reveal an unexpected role for IL-22 in promoting early tumorigenesis while excluding a function for IL-22 in transformed epithelial cells

The prosurvival IKK-related kinase IKKϵ integrates LPS and IL17A signaling cascades to promote Wnt-dependent tumor development in the intestine

Constitutive Wnt signaling promotes intestinal cell proliferation, but signals from the tumor microenvironment are also required to support cancer development. The role that signaling proteins play to establish a tumor microenvironment has not been extensively studied. Therefore, we assessed the role of the proinflammatory Ikk-related kinase Ikkϵ in Wnt-driven tumor development. We found that Ikkϵ was activated in intestinal tumors forming upon loss of the tumor suppressor Apc. Genetic ablation of Ikkϵ in b-catenin-driven models of intestinal cancer reduced tumor incidence and consequently extended survival. Mechanistically, we attributed the tumor-promoting effects of Ikkϵ to limited TNF-dependent apoptosis in transformed intestinal epithelial cells. In addition, Ikkϵ was also required for lipopolysaccharide (LPS) and IL17A-induced activation of Akt, Mek1/2, Erk1/2, and Msk1. Accordingly, genes encoding proinflammatory cytokines, chemokines, and anti-microbial peptides were downregulated in Ikkϵ-deficient tissues, subsequently affecting the recruitment of tumor-associated macrophages and IL17A synthesis. Further studies revealed that IL17A synergized with commensal bacteria to trigger Ikkϵ phosphorylation in transformed intestinal epithelial cells, establishing a positive feedback loop to support tumor development. Therefore, TNF, LPS, and IL17A-dependent signaling pathways converge on Ikkϵ to promote cell survival and to establish an inflammatory tumor microenvironment in the intestine upon constitutive Wnt activation. � 2016 American Association for Cancer Research

The Arabidopsis thaliana LSU peptides: An interactomics-based approach to unravel their role in the plant stress response

Plants defend themselves against pathogens and abiotic stresses using a wide arsenal of defence mechanisms. The model plant Arabidopsis thaliana has four members of the LSU (Low Sulfur Upregulated) gene family (LSU1-4) encoding small proteins with 59-89% sequence similarity and homologues in several other plants and major crops. Originally, the LSU peptides were characterized as induced during sulfur deficiencies, but recent studies suggest an important regulatory role in various plant processes, including development and stress responses. Large scale interactome studies based on yeast two-hybrid (Y2H) analyses show that the LSU peptides interact with a large number of other A. thaliana proteins with different functions. In addition, LSU peptides were identified as targets of virulence effectors of different (hemi)biotrophic plant pathogens. There are also descriptions of several phenotypes of A. thaliana mutants with an altered expression of the LSU peptides, such as an altered sensitivity to both (hemi)biotrophic and necrotrophic pathogens, certain abiotic stresses and distortions in flower development. Currently, these studies suggest that the LSU peptides would function as important hub proteins in the integration and regulation of environmental signals. However, the precise molecular function of the LSU peptides still remains unknown. The goal of this project is to better understand the in planta interaction potential of the LSU peptides and to unravel their precise role in the plant stress response. For this purpose, different complimentary in planta protein interaction analyses will be combined with protein localisation studies, gene expression analyses and a thorough functional analysis of the LSU peptides and confirmed interactors. This will be done mainly through phenotyping of mutant A. thaliana lines using a wide range of pathogen and abiotic stress tests.status: publishe