SUMMARY STING is an ER-associated membrane protein that is critical for innate-immune sensing of pathogens. STING-mediated activation of the IFN-I pathway through the TBK1/IRF3 signaling axis involves both cyclic-dinucleotide binding, and its translocation from the ER to vesicles. However, how these events are coordinated, and the exact mechanism of STING activation, remain poorly understood. Here, we found that the Shigella effector protein IpaJ potently inhibits STING signaling by blocking its translocation from the ER to ERGIC, even in the context of dinucleotide binding. Reconstitution using purified components revealed STING translocation as the rate-limiting event in maximal signal transduction. Furthermore, STING mutations associated with autoimmunity in humans were found to cause constitutive ER exit, and to activate STING independent of cGAMP binding. Together, these data provide compelling evidence for an ER-retention and ERGIC/Golgi-trafficking mechanism of STING regulation that is subverted by bacterial pathogens and is deregulated in human genetic disease.

To identify tumor-derived exosomal biomarkers that are able to discriminate between adenocarcinoma and squamous cell carcinoma (SCC) as a noninvasive method in the early diagnosis of non-small cell lung cancer (NSCLC). Tumor-derived exosomes from the plasma of early-stage NSCLC patients were isolated. Exosomal miRNA profiling of 46 stage I NSCLC patients and 42 healthy individuals was performed using miRNA-seq to identify and validate adenocarcinoma- and SCC-specific miRNAs. The diagnostic accuracy of select miRNAs was tested further with an additional 60 individuals. There were 11 and 6 miRNAs expressed at remarkably higher levels, 13 and 8 miRNAs expressed at lower levels in adenocarcinoma and SCC patients, respectively, compared with healthy volunteers. Distinct adenocarcinoma- and SCC-specific exosomal miRNAs were validated. The reliability of miRNA-seq data was verified with several demonstrated diagnostic potential miRNAs for NSCLC and other carcinomas, as reported in previous studies, such as let-7, miR-21, miR-24, and miR-486. The results indicated that miR-181-5p, miR-30a-3p, miR-30e-3p, and miR-361-5p were adenocarcinoma-specific, and miR-10b-5p, miR-15b-5p, and miR-320b were SCC-specific. The diagnostic accuracy of three combination miRNA panels was evaluated using an AUC value of 0.899, 0.936, and 0.911 for detecting NSCLC, adenocarcinoma, and SCC, respectively. Tumor-derived exosomal miRNAs, adenocarcinoma-specific miR-181-5p, miR-30a-3p, miR-30e-3p and miR-361-5p, and SCC-specific miR-10b-5p, miR-15b-5p, and miR-320b were observed by next-generation sequencing, and their diagnostic accuracy were verified. These miRNAs may be promising and effective candidates in the development of highly sensitive, noninvasive biomarkers for early NSCLC diagnosis. .

The cell surface receptor CED-1 mediates apoptotic cell recognition by phagocytic cells, enabling cell corpse clearance in Caenorhabditis elegans. Here, we found that the C. elegans intracellular protein sorting complex, retromer, was required for cell corpse clearance by mediating the recycling of CED-1. Retromer was recruited to the surfaces of phagosomes containing cell corpses, and its loss of function caused defective cell corpse removal. The retromer probably acted through direct interaction with CED-1 in the cell corpse recognition pathway. In the absence of retromer function, CED-1 associated with lysosomes and failed to recycle from phagosomes and cytosol to the plasma membrane. Thus, retromer is an essential mediator of apoptotic cell clearance by regulating phagocytic receptor(s) during cell corpse engulfment.

The Linear Ubiquitin chain Assembly Complex (LUBAC) is a multimeric E3 ligase that catalyzes M1-or linear ubiquitination of activated immune receptor signaling complexes (RSCs). While mutations that disrupt linear ubiquitin assembly lead to complex disease pathologies including immunodeficiency and autoinflammation in both humans and mice, microbial toxins that target LUBAC function have not yet been discovered. Here, we report the identification of two homologous Shigella flexneri Type III Secretion System (T3SS) effector E3 ligases IpaH1.4 and IpaH2.5 that directly interact with LUBAC subunit HOIL-1L (RBCK1) and conjugate K48-linked ubiquitin chains to the catalytic RING-between-RING domain of HOIP (RNF31). Proteasomal degradation of HOIP leads to irreversible inactivation of linear ubiquitination and blunting of NF-κB nuclear translocation in response to TNF, IL-1β, and pathogen associated molecular patterns (PAMPs). Loss of function studies in mammalian cells in combination with bacterial genetics explains how Shigella evades a broad spectrum of immune surveillance systems by cooperative inhibition of receptor ubiquitination, and reveals the critical importance of LUBAC in host defense against pathogens.The Linear Ubiquitin chain Assembly Complex (LUBAC) is a multimeric E3 ligase composed of two accessory subunits HOIL-1L (RBCK1) and SHARPIN, and a catalytic subunit HOIP (RNF31). Recruitment of LUBAC to activated cytokine-or Pattern Recognition Receptors (PRRs) 1-3 results in the ligation of RIPK1 and NEMO (IKKγ) with methionine 1 (M1)-linked linear ubiquitin (Ub) chains 4 . This ubiquitination event is crucial for activation of transcription factors NF-κB and AP-1 that induce rapid gene expression in response to microbial infection 2,4-7 . Because of the ubiquitous requirement of M1-Ub in numerous cytokine signaling pathways, humans lacking functional LUBAC exhibit severe autoinflammatory diseases and are especially vulnerable to pyogenic bacterial infections including life-threatening enteroinvasive Escherichia coli 8,9 . While recent studies have Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use