Host-mediated ubiquitination of a mycobacterial protein suppresses immunity.

Mycobacterium tuberculosis is an intracellular pathogen that uses several strategies to interfere with the signalling functions of host immune molecules. Many other bacterial pathogens exploit the host ubiquitination system to promote pathogenesis1,2, but whether this same system modulates the ubiquitination of M. tuberculosis proteins is unknown. Here we report that the host E3 ubiquitin ligase ANAPC2-a core subunit of the anaphase-promoting complex/cyclosome-interacts with the mycobacterial protein Rv0222 and promotes the attachment of lysine-11-linked ubiquitin chains to lysine 76 of Rv0222 in order to suppress the expression of proinflammatory cytokines. Inhibition of ANAPC2 by specific short hairpin RNA abolishes the inhibitory effect of Rv0222 on proinflammatory responses. Moreover, mutation of the ubiquitination site on Rv0222 impairs the inhibition of proinflammatory cytokines by Rv0222 and reduces virulence during infection in mice. Mechanistically, lysine-11-linked ubiquitination of Rv0222 by ANAPC2 facilitates the recruitment of the protein tyrosine phosphatase SHP1 to the adaptor protein TRAF6, preventing the lysine-63-linked ubiquitination and activation of TRAF6. Our findings identify a previously unrecognized mechanism that M. tuberculosis uses to suppress host immunity, and provide insights relevant to the development of effective immunomodulators that target M. tuberculosis.

Nuclear cGAS suppresses DNA repair and promotes tumorigenesis.

Accurate repair of DNA double-stranded breaks by homologous recombination preserves genome integrity and inhibits tumorigenesis. Cyclic GMP-AMP synthase (cGAS) is a cytosolic DNA sensor that activates innate immunity by initiating the STING-IRF3-type I IFN signalling cascade1,2. Recognition of ruptured micronuclei by cGAS links genome instability to the innate immune response3,4, but the potential involvement of cGAS in DNA repair remains unknown. Here we demonstrate that cGAS inhibits homologous recombination in mouse and human models. DNA damage induces nuclear translocation of cGAS in a manner that is dependent on importin-α, and the phosphorylation of cGAS at tyrosine 215-mediated by B-lymphoid tyrosine kinase-facilitates the cytosolic retention of cGAS. In the nucleus, cGAS is recruited to double-stranded breaks and interacts with PARP1 via poly(ADP-ribose). The cGAS-PARP1 interaction impedes the formation of the PARP1-Timeless complex, and thereby suppresses homologous recombination. We show that knockdown of cGAS suppresses DNA damage and inhibits tumour growth both in vitro and in vivo. We conclude that nuclear cGAS suppresses homologous-recombination-mediated repair and promotes tumour growth, and that cGAS therefore represents a potential target for cancer prevention and therapy.

The value of plasma presepsin as a diagnostic and prognostic biomarker for sepsis in Southern China.

BACKGROUND: Presepsin is a soluble CD14 subtype that has been considered as a novel marker for patients with sepsis. This study explored the clinical value of presepsin for sepsis in Southern China, and further established models for diagnosis and prognosis of sepsis through using machine learning (ML), by combining presepsin and other laboratory parameters. METHODS: 269 subjects (105 infected patients, 164 sepsis and septic shock) and 198 healthy controls were enrolled. Laboratory parameters (hematological parameters, coagulation parameters, liver function indices, renal function indices, and inflammatory markers) were collected. Plasma presepsin was tested by chemiluminescence enzyme immunoassay. ML of DxAI™ Research platform was used to establish diagnostic and prognostic models. Sensitivity, specificity, and other performance indicators were used to evaluate the performance of each model. RESULTS: The level of presepsin was obviously increased in sepsis and sepsis shock, compared with that of infected and healthy group (all P < 0.0001). Presepsin concentration was positively correlated with positive blood culture and 30-day mortality in sepsis and septic shock patients. Through ROC curve analysis, Hb, UREA, APTT, CRP, PCT, and presepsin were incorporated into machine learning to construct diagnosis models. Ada Boost model had the best diagnostic efficiency (AUC: 0.94 (95% CI 0.919-0.968) in the training set and AUC: 0.86 (95% CI 0.813-0.900) in validation set). Furthermore, AST, APTT, UREA, PCT, and presepsin were included in the prognosis ML models, and the Bernoulli NB model had greater predictive ability for 30-day mortality risk of sepsis (AUC: 0.706), which was higher than that of PCT (AUC: 0.617) and presepsin (AUC: 0.634) alone. CONCLUSION: Machine-learning model based on presepsin and routinely laboratory parameters showed good performance of diagnostic and prognostic ability for sepsis patients.

Serum aspartate aminotransferase is an adverse prognostic indicator for patients with resectable pancreatic ductal adenocarcinoma.

OBJECTIVE: In this study, the association between preoperative levels of serum liver enzymes and overall survival (OS) was evaluated in patients with resectable pancreatic cancer. METHODS: Preoperative serum levels of alanine aminotransferase (ALT), aspartate aminotransferases (AST), γ-glutamyltransferase, alkaline phosphatase, and lactate dehydrogenase of 101 patients with pancreatic ductal adenocarcinoma (PDAC) were collected. Univariate and multivariate Cox hazard models were used to identify independent variables associated with OS in this cohort. RESULTS: Patients with elevated AST levels had significantly worse OS than patients with lower AST levels. A nomogram was created using TNM staging and AST levels and was shown to be more accurate in prediction than the American Joint Committee on Cancer 8th edition standard method. CONCLUSION: Preoperative AST levels could be a novel independent prognostic biomarker for patients with PDAC. The incorporation of AST levels into a nomogram with TNM staging can be an accurate predictive model for OS in patients with resectable PDAC.

Diagnostic and Prognostic Value of Monocyte Distribution Width in Sepsis.

Monocyte distribution width (MDW) is a blood monocyte morphological parameter that can be easily detected by an automated hemocyte analyzer and can provide clinicians with important information about cell volume variability in peripheral blood monocyte populations. The United States' Food and Drug Administration and Conformite Europeenne have both been cleared for their clinical application in the detection of sepsis and developing sepsis in adult patients in the emergency department (ED). Recently, MDW has been found to have an early diagnosis and predictive value for sepsis in neonates and COVID-19 patients. Here, we summarize the findings of the studies investigating the clinical application of MDW in sepsis. Under different stimuli, especially in infectious diseases, the activation of innate immunity is the host's first defense mechanism, and the change in monocyte volume is considered an early indicator reflecting the state of activation of innate immunity. Pivotal study data from a large multicenter patient cohort showed that abnormal MDW at presentation increases the odds of sepsis, considering the combination of MDW and White Blood Cell Count (WBC) as part of a standard sepsis assessment protocol for ED, which may increase the sensitivity and specificity of sepsis diagnosis. Meanwhile, MDW shares a diagnostic performance comparable to that of conventional biomarkers (C-reactive protein and procalcitonin) in sepsis. In addition, some evidence suggests that increased MDW, both in adults and neonates, may be associated with unfavorable short- and long-term outcomes, which indicates its prognostic value in sepsis. Taken together, MDW is a parameter of increased morphological variability of monocytes in response to infection, and numerous studies have shown that MDW could be used as a valuable diagnostic and prognostic index in patients with sepsis or suspected sepsis.

Novel biomarker panel for the diagnosis and prognosis assessment of sepsis based on machine learning.

Background: The authors investigated a panel of novel biomarkers for diagnosis and prognosis assessment of sepsis using machine learning (ML) methods. Methods: Hematological parameters, liver function indices and inflammatory marker levels of 332 subjects were retrospectively analyzed. Results: The authors constructed sepsis diagnosis models and identified the random forest (RF) model to be the most optimal. Compared with PCT (procalcitonin) and CRP (C-reactive protein), the RF model identified sepsis patients at an earlier stage. The sepsis group had a mortality rate of 36.3%, and the RF model had greater predictive ability for the 30-day mortality risk of sepsis patients. Conclusion: The RF model facilitated the identification of sepsis patients and showed greater accuracy in predicting the 30-day mortality risk of sepsis patients.

CGAS is a micronucleophagy receptor for the clearance of micronuclei.

Micronuclei are constantly considered as a marker of genome instability and very recently found to be a trigger of innate immune responses. An increased frequency of micronuclei is associated with many diseases, but the mechanism underlying the regulation of micronuclei homeostasis remains largely unknown. Here, we report that CGAS (cyclic GMP-AMP synthase), a known regulator of DNA sensing and DNA repair, reduces the abundance of micronuclei under genotoxic stress in an autophagy-dependent manner. CGAS accumulates in the autophagic machinery and directly interacts with MAP1LC3B/LC3B in a manner dependent upon its MAP1LC3-interacting region (LIR). Importantly, the interaction is essential for MAP1LC3 recruitment to micronuclei and subsequent clearance of micronuclei via autophagy (micronucleophagy) in response to genotoxic stress. Moreover, in contrast to its DNA sensing function to activate micronuclei-driven inflammation, CGAS-mediated micronucleophagy blunts the production of cyclic GMP-AMP (cGAMP) induced by genotoxic stress. We therefore conclude that CGAS is a receptor for the selective autophagic clearance of micronuclei and uncovered an unprecedented role of CGAS in micronuclei homeostasis to dampen innate immune surveillance.Abbreviations: ATG: autophagy-related; CGAS: cyclic GMP-AMP synthase; CQ: chloroquine; GABARAP: GABA type A receptor-associated protein; GFP: green fluorescent protein; LAMP1: lysosomal associated membrane protein 1; LAMP2: lysosomal associated membrane protein 2; LIR, MAP1LC3-interacting region; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; NDZ: nocodazole; STING1: stimulator of interferon response cGAMP interactor 1.

PLCß2 negatively regulates the inflammatory response to virus infection by inhibiting phosphoinositide-mediated activation of TAK1.

Excessive or uncontrolled release of proinflammatory cytokines caused by severe viral infections often results in host tissue injury or even death. Phospholipase C (PLC)s degrade phosphatidylinositol-4, 5-bisphosphate (PI(4,5)P2) lipids and regulate multiple cellular events. Here, we report that PLCß2 inhibits the virus-induced expression of pro-inflammatory cytokines by interacting with and inhibiting transforming growth factor-ß-activated kinase 1 (TAK1) activation. Mechanistically, PI(4,5)P2 lipids directly interact with TAK1 at W241 and N245, and promote its activation. Impairing of PI(4,5)P2's binding affinity or mutation of PIP2-binding sites on TAK1 abolish its activation and the subsequent production of pro-inflammatory cytokines. Moreover, PLCß2-deficient mice exhibit increased expression of proinflammatory cytokines and a higher frequency of death in response to virus infection, while the PLCß2 activator, m-3M3FBS, protects mice from severe Coxsackie virus A 16 (CVA16) infection. Thus, our findings suggest that PLCß2 negatively regulates virus-induced pro-inflammatory responses by inhibiting phosphoinositide-mediated activation of TAK1.

Oxidization of TGFß-activated kinase by MPT53 is required for immunity to Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb)-derived components are usually recognized by pattern recognition receptors to initiate a cascade of innate immune responses. One striking characteristic of Mtb is their utilization of different type VII secretion systems to secrete numerous proteins across their hydrophobic and highly impermeable cell walls, but whether and how these Mtb-secreted proteins are sensed by host immune system remains largely unknown. Here, we report that MPT53 (Rv2878c), a secreted disulfide-bond-forming-like protein of Mtb, directly interacts with TGF-ß-activated kinase 1 (TAK1) and activates TAK1 in a TLR2- or MyD88-independent manner. MPT53 induces disulfide bond formation at C210 on TAK1 to facilitate its interaction with TRAFs and TAB1, thus activating TAK1 to induce the expression of pro-inflammatory cytokines. Furthermore, MPT53 and its disulfide oxidoreductase activity is required for Mtb to induce the host inflammatory responses via TAK1. Our findings provide an alternative pathway for host signalling proteins to sense Mtb infection and may favour the improvement of current vaccination strategies.

Genome-wide association study identifies two risk loci for tuberculosis in Han Chinese.

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb), and remains a leading public health problem. Previous studies have identified host genetic factors that contribute to Mtb infection outcomes. However, much of the heritability in TB remains unaccounted for and additional susceptibility loci most likely exist. We perform a multistage genome-wide association study on 2949 pulmonary TB patients and 5090 healthy controls (833 cases and 1220 controls were genome-wide genotyped) from Han Chinese population. We discover two risk loci: 14q24.3 (rs12437118, Pcombined = 1.72 × 10-11, OR = 1.277, ESRRB) and 20p13 (rs6114027, Pcombined = 2.37 × 10-11, OR = 1.339, TGM6). Moreover, we determine that the rs6114027 risk allele is related to decreased TGM6 transcripts in PBMCs from pulmonary TB patients and severer pulmonary TB disease. Furthermore, we find that tgm6-deficient mice are more susceptible to Mtb infection. Our results provide new insights into the genetic etiology of TB.