Regulation of CD8 T Cell Differentiation by the RNA-Binding Protein DDX5.

The RNA-binding protein DEAD-box protein 5 (DDX5) is a polyfunctional regulator of gene expression, but its role in CD8+ T cell biology has not been extensively investigated. In this study, we demonstrate that deletion of DDX5 in murine CD8+ T cells reduced the differentiation of terminal effector, effector memory T, and terminal effector memory cells while increasing the generation of central memory T cells, whereas forced expression of DDX5 elicited the opposite phenotype. DDX5-deficient CD8+ T cells exhibited increased expression of genes that promote central memory T cell differentiation, including Tcf7 and Eomes. Taken together, these findings reveal a role for DDX5 in regulating the differentiation of effector and memory CD8+ T cell subsets in response to microbial infection.

RNA binding protein DDX5 directs tuft cell specification and function to regulate microbial repertoire and disease susceptibility in the intestine.

OBJECTIVE: Tuft cells residing in the intestinal epithelium have diverse functions. In the small intestine, they provide protection against inflammation, combat against helminth and protist infections, and serve as entry portals for enteroviruses. In the colon, they had been implicated in tumourigenesis. Commitment of intestinal progenitor cells to the tuft cell lineage requires Rho GTPase Cell Division Cycle 42 (CDC42), a Rho GTPase that acts downstream of the epidermal growth factor receptor and wingless-related integration site signalling cascades, and the master transcription factor POU class 2 homeobox 3 (POU2F3). This study investigates how this pathway is regulated by the DEAD box containing RNA binding protein DDX5 in vivo. DESIGN: We assessed the role of DDX5 in tuft cell specification and function in control and epithelial cell-specific Ddx5 knockout mice (DDX5ΔIEC) using transcriptomic approaches. RESULTS: DDX5ΔIEC mice harboured a loss of intestinal tuft cell populations, modified microbial repertoire, and altered susceptibilities to ileal inflammation and colonic tumourigenesis. Mechanistically, DDX5 promotes CDC42 protein synthesis through a post-transcriptional mechanism to license tuft cell specification. Importantly, the DDX5-CDC42 axis is parallel but distinct from the known interleukin-13 circuit implicated in tuft cell hyperplasia, and both pathways augment Pou2f3 expression in secretory lineage progenitors. In mature tuft cells, DDX5 not only promotes integrin signalling and microbial responses, it also represses gene programmes involved in membrane transport and lipid metabolism. CONCLUSION: RNA binding protein DDX5 directs tuft cell specification and function to regulate microbial repertoire and disease susceptibility in the intestine.

Noncoding RNAs in inflammation and colorectal cancer.

Despite advanced clinical treatments, mortality in patients with metastatic colorectal cancer (CRC) remains high. Three critical determinants in CRC progression include the epithelial proliferation checkpoints, epithelial-to-mesenchymal transition (EMT) and inflammatory cytokines in the tumour microenvironment. Genes involved in these three processes are regulated at the transcriptional and post-transcriptional level. Recent studies revealed previously unappreciated roles of non-coding ribonucleic acids (ncRNAs) in modulating the proliferation checkpoints, EMT, and inflammatory gene expression in CRC. In this review, we will discuss the mechanisms underlying the roles of ncRNAs in CRC as well as examine future perspectives in this field. Better understanding of ncRNA biology will provide novel targets for future therapeutic development.

Inhibition of NFAT5-Dependent Astrocyte Swelling Alleviates Neuropathic Pain.

Astrocyte swelling is implicated in various neurological disorders. However, whether astrocyte swelling contributes to neuropathic pain remains elusive. This study elucidates the pivotal role of the nuclear factor of activated T-cells 5 (NFAT5) emerges as a master regulator of astrocyte swelling in the spinal dorsal horn (SDH) during neuropathic pain. Despite the ubiquitous expression of NFAT5 protein in SDH cell types, it selectively induces swelling specifically in astrocytes, not in microglia. Mechanistically, NFAT5 directly controls the expression of the water channel aquaporin-4 (AQP4), a key regulator exclusive to astrocytes. Additionally, aurora kinase B (AURKB) orchestrates NFAT5 phosphorylation, enhancing its protein stability and nuclear translocation, thereby regulating AQP4 expression. The findings establish NFAT5 as a crucial regulator for neuropathic pain through the modulation of astrocyte swelling. The AURKB-NFAT5-AQP4 pathway in astrocytes emerges as a potential therapeutic target to combat neuropathic pain.

The long non-coding RNA MALAT1 regulates intestine host-microbe interactions and polyposis.

The long non-coding RNA (lncRNA) Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) maintains the integrity of the intestinal epithelial barrier and regulates local inflammation. However, its influences on intestinal microbial communities and tissue susceptibility to cancer development remain unexplored. Here, we report that MALAT1 regulates host anti-microbial response gene expression and the composition of mucosal-associated microbial communities in a region-specific manner. In the APC mutant mouse model of intestine tumorigenesis, knocking out MALAT1 results in higher polyp counts in the small intestine and colon. Interestingly, intestine polyps that developed in the absence of MALAT1 were smaller in size. These findings highlight the unexpected bivalent role of MALAT1 in restricting and promoting cancer progression at different disease stages. Among the 30 MALAT1-targets shared by both the small intestine and colon, ZNF638 and SENP8 levels are predictive of colon adenoma patient overall survival and disease-free survival. Genomic assays further revealed that MALAT1 modulates intestinal target expression and splicing through both direct and indirect mechanisms. This study expands the role of lncRNAs in regulating intestine homeostasis, microbial communities, and cancer pathogenesis.

The arginine methyltransferase PRMT5 promotes mucosal defense in the intestine.

PRMT5 is a type II arginine methyltransferase abundantly expressed in the colonic epithelium. It is up-regulated in inflammatory bowel disease and colorectal cancer. However, its role in mucosal defense against enteric infection has not been studied. Here, we report that Prmt5 in the murine colon is up-regulated in response to Citrobacter rodentium infection. Pathogen clearance in mice with haploinsufficient expression of Prmt5 is significantly delayed compared with wildtype littermate controls. Transcriptomic analyses further reveal that PRMT5 regulates the expression of canonical crypt goblet cell genes involved in mucus production, assembly, and anti-microbial responses via methyltransferase activity-dependent and -independent mechanisms. Together, these findings uncover PRMT5 as a novel regulator of mucosal defense and a potential therapeutic target for treating intestinal diseases.

RNA binding protein DDX5 restricts RORγt+ Treg suppressor function to promote intestine inflammation.

Retinoid-related orphan receptor (RAR) gamma (RORγt)-expressing regulatory T cells (RORγt+ Tregs) play pivotal roles in preventing T cell hyperactivation and maintaining tissue homeostasis, in part by secreting the anti-inflammation cytokine interleukin-10 (IL-10). Here, we report that hypoxia-induced factor 1α (HIF1α) is the master transcription factor for Il10 in RORγt+ Tregs. This critical anti-inflammatory pathway is negatively regulated by an RNA binding protein DEAD box helicase 5 (DDX5). As a transcriptional corepressor, DDX5 restricts the expression of HIF1α and its downstream target gene Il10 in RORγt+ Tregs. T cell-specific Ddx5 knockout (DDX5ΔT) mice have augmented RORγt+ Treg suppressor activities and are better protected from intestinal inflammation. Genetic ablation or pharmacologic inhibition of HIF1α restores enteropathy susceptibility in DDX5ΔT mice. The DDX5-HIF1α-IL-10 pathway is conserved in mice and humans. These findings reveal potential therapeutic targets for intestinal inflammatory diseases.

Candida albicans-specific Th17 cell-mediated response contributes to alcohol-associated liver disease.

Alcohol-associated liver disease is accompanied by intestinal mycobiome dysbiosis, yet the impacts on liver disease are unclear. We demonstrate that Candida albicans-specific T helper 17 (Th17) cells are increased in circulation and present in the liver of patients with alcohol-associated liver disease. Chronic ethanol administration in mice causes migration of Candida albicans (C. albicans)-reactive Th17 cells from the intestine to the liver. The antifungal agent nystatin decreased C. albicans-specific Th17 cells in the liver and reduced ethanol-induced liver disease in mice. Transgenic mice expressing T cell receptors (TCRs) reactive to Candida antigens developed more severe ethanol-induced liver disease than transgene-negative littermates. Adoptively transferring Candida-specific TCR transgenic T cells or polyclonal C. albicans-primed T cells exacerbated ethanol-induced liver disease in wild-type mice. Interleukin-17 (IL-17) receptor A signaling in Kupffer cells was required for the effects of polyclonal C. albicans-primed T cells. Our findings indicate that ethanol increases C. albicans-specific Th17 cells, which contribute to alcohol-associated liver disease.

Protocol to assess cell-intrinsic regulatory mechanisms using an ex vivo murine T cell polarization and co-culture system.

This protocol describes an ex vivo cell culture system for simultaneously generating a mixture of CD4+ T helper lineages, including T helper 17 (Th17), RORγt+ Treg, and conventional Treg (cTreg), in proportions representative of those found in mucosal tissues in vivo. When combined with a co-culture approach, this system allows a more rapid assessment of a candidate molecule's T cell-intrinsic and -extrinsic functions over the traditional bone marrow chimera and co-transfer approaches. For complete details on the use and execution of this protocol, please refer to Ma et al. (2022).

RORγt phosphorylation protects against T cell-mediated inflammation.

RAR-related orphan receptor-γ (RORγt) is an essential transcription factor for thymic T cell development, secondary lymphoid tissue organogenesis, and peripheral immune cell differentiation. Serine 182 phosphorylation is a major post-translational modification (PTM) on RORγt. However, the in vivo contribution of this PTM in health and disease settings is unclear. We report that this PTM is not involved in thymic T cell development and effector T cell differentiation. Instead, it is a critical regulator of inflammation downstream of IL-1ß signaling and extracellular signal regulated kinases (ERKs) activation. ERKs phosphorylation of serine 182 on RORγt serves to simultaneously restrict Th17 hyperactivation and promote anti-inflammatory cytokine IL-10 production in RORγt+ Treg cells. Phospho-null RORγtS182A knockin mice experience exacerbated inflammation in models of colitis and experimental autoimmune encephalomyelitis (EAE). In summary, the IL-1ß-ERK-RORγtS182 circuit protects against T cell-mediated inflammation and provides potential therapeutic targets to combat autoimmune diseases.

The DNA Glycosylase NEIL2 Suppresses Fusobacterium-Infection-Induced Inflammation and DNA Damage in Colonic Epithelial Cells.

Colorectal cancer (CRC) is the third most prevalent cancer, while the majority (80-85%) of CRCs are sporadic and are microsatellite stable (MSS), and approximately 15-20% of them display microsatellite instability (MSI). Infection and chronic inflammation are known to induce DNA damage in host tissues and can lead to oncogenic transformation of cells, but the role of DNA repair proteins in microbe-associated CRCs remains unknown. Using CRC-associated microbes such as Fusobacterium nucleatum (Fn) in a coculture with murine and human enteroid-derived monolayers (EDMs), here, we show that, among all the key DNA repair proteins, NEIL2, an oxidized base-specific DNA glycosylase, is significantly downregulated after Fn infection. Fn infection of NEIL2-null mouse-derived EDMs showed a significantly higher level of DNA damage, including double-strand breaks and inflammatory cytokines. Several CRC-associated microbes, but not the commensal bacteria, induced the accumulation of DNA damage in EDMs derived from a murine CRC model, and Fn had the most pronounced effect. An analysis of publicly available transcriptomic datasets showed that the downregulation of NEIL2 is often encountered in MSS compared to MSI CRCs. We conclude that the CRC-associated microbe Fn induced the downregulation of NEIL2 and consequent accumulation of DNA damage and played critical roles in the progression of CRCs.

DDX5 promotes oncogene C3 and FABP1 expressions and drives intestinal inflammation and tumorigenesis.

Tumorigenesis in different segments of the intestinal tract involves tissue-specific oncogenic drivers. In the colon, complement component 3 (C3) activation is a major contributor to inflammation and malignancies. By contrast, tumorigenesis in the small intestine involves fatty acid-binding protein 1 (FABP1). However, little is known of the upstream mechanisms driving their expressions in different segments of the intestinal tract. Here, we report that the RNA-binding protein DDX5 binds to the mRNA transcripts of C3 and Fabp1 to augment their expressions posttranscriptionally. Knocking out DDX5 in epithelial cells protected mice from intestinal tumorigenesis and dextran sodium sulfate (DSS)-induced colitis. Identification of DDX5 as a common upstream regulator of tissue-specific oncogenic molecules provides an excellent therapeutic target for intestinal diseases.