The deubiquitinase OTUD1 inhibits colonic inflammation by suppressing RIPK1-mediated NF-κB signaling

The E3 ubiquitin ligase(E3)-mediated ubiquitination and deubiquitinase(DUB)-mediated deubiquitination processes are closely associated with the occurrence and development of colonic inflammation.Ovarian tumor deubiquitinase 1(OTUD1)is involved in immunoregulatory functions linked to infectious diseases.However,the effect of OTUD1 on intestinal immune responses during colonic inflammatory disorders such as inflammatory bowel disease(IBD)remains unclear.Here,we show that loss of OTUD1 in mice contributes to the pathogenesis of dextran sulfate sodium(DSS)-induced colitis via excessive release of proinflammatory cytokines.In addition,bone marrow transplantation experiments revealed that OTUD1 in hematopoietic cells plays a dominant role in protection against colitis.Mechanistically,OTUD1 physically interacts with receptor-interacting serine/threonine-protein kinase 1(RIPK1)and selectively cleaves K63-linked polyubiquitin chains from RIPK1 to inhibit the recruitment of NF-κB essential modulator(NEMO).Moreover,the expression of OTUD1 in mucosa samples from ulcerative colitis(UC)patients was lower than that in mucosa samples from healthy controls.Furthermore,we demonstrate that the UC-associated OTUD1 G430V mutation abolishes the ability of OTUD1 to inhibit RIPK1-mediated NF-κB activation and intestinal inflammation.Taken together,our study unveils a previously unexplored role of OTUD1 in moderating intestinal inflammation by inhibiting RIPK1-mediated NF-κB activation,suggesting that the OTUD1-RIPK1 axis could be a potential target for the treatment of IBD.

Mycobacterium tuberculosis Mce2E suppresses the macrophage innate immune response and promotes epithelial cell proliferation

The intracellular pathogen Mycobacterium tuberculosis(Mtb)can survive in the host and cause disease by interfering with a variety of cellular functions.The mammalian cell entry 2(mce2)operon of Mtb has been shown to contribute to tuberculosis pathogenicity.However,little is known about the regulatory roles of Mtb Mce2 family proteins towards host cellular functions.Here we show that the Mce2 family protein Mce2E suppressed the macrophage innate immune response and promoted epithelial cell proliferation.Mce2E inhibited activation of the extracellular signal-regulated kinase(ERK)and Jun N-terminal kinase(JNK)mitogen-activated protein kinase(MAPK)signaling pathways in a non-canonical D motif(a MAPK-docking motif)-dependent manner,leading to reduced expression of TNF and IL-6 in macrophages.Furthermore,Mce2E promoted proliferation of human lung epithelium-derived lung adenoma A549 cells by inhibiting K48-linked polyubiquitination of eEF1A1 in aβstrand region-dependent manner.In summary,Mce2E is a novel multifunctional Mtb virulence factor that regulates host cellular functions in a niche-dependent manner.Our data suggest a potential novel target for TB therapy.

TRIM27 maintains gut homeostasis by promoting intestinal stem cell self-renewal

Dysregulation of gut homeostasis is associated with irritable bowel syndrome(IBS),a chronic functional gastrointestinal disorder affecting approximately 11.2%of the global population.The poorly understood pathogenesis of IBS has impeded its treatment.Here,we report that the E3 ubiquitin ligase tripartite motif-containing 27(TRIM27)is weakly expressed in IBS but highly expressed in inflammatory bowel disease(IBD),a frequent chronic organic gastrointestinal disorder.Accordingly,knockout of Trim27 in mice causes spontaneously occurring IBS-like symptoms,including increased visceral hyperalgesia and abnormal stool features,as observed in IBS patients.Mechanistically,TRIM27 stabilizesβ-catenin and thus activates Wnt/β-catenin signaling to promote intestinal stem cell(ISC)self-renewal.Consistent with these findings,Trim27 deficiency disrupts organoid formation,which is rescued by reintroducing TRIM27 orβ-catenin.Furthermore,Wnt/β-catenin signaling activator treatment ameliorates IBS symptoms by promoting ISC self-renewal.Taken together,these data indicate that TRIM27 is critical for maintaining gut homeostasis,suggesting that targeting the TRIM27/Wnt/β-catenin axis could be a potential treatment strategy for IBS.Our study also indicates that TRIM27 might serve as a potential biomarker for differentiating IBS from IBD.

Mycobacterium tuberculosis effector proteins: functional multiplicity and regulatory diversity

Tuberculosis(TB),which is caused by Mycobacterium tuberculosis(Mtb),remains the leading cause of death from a single infectious agent.Moreover,TB is responsible for approximately one-quarter of all deaths related to antimicrobial resistance upon the emergence of drug-resistant TB.1 Mtb infection is also associated with multiple other human diseases,such as lung cancer,autoimmune diseases,and metabolic syndromes.Because Mtb lacks classical bacterial toxins(including endotoxins and exotoxins),its pathogenesis mainly involves intricate pathogen-host interplay,which is mediated by a variety of pathogenic factors,including surface-associated and secreted effector proteins.Therefore,a better understanding of the molecular details of the Mtb–host interaction is invaluable for the development of new therapeutic strategies against TB.