Clustering of the enteropathogenic Escherichia coli (EPEC) type III secretion system (T3SS) effector translocated intimin receptor (Tir) by intimin leads to actin polymerisation and pyroptotic cell ...death in macrophages. The effect of Tir clustering on the viability of EPEC-infected intestinal epithelial cells (IECs) is unknown. We show that EPEC induces pyroptosis in IECs in a Tir-dependent but actin polymerisation-independent manner, which was enhanced by priming with interferon gamma (IFNγ). Mechanistically, Tir clustering triggers rapid Ca2+ influx, which induces lipopolysaccharide (LPS) internalisation, followed by activation of caspase-4 and pyroptosis. Knockdown of caspase-4 or gasdermin D (GSDMD), translocation of NleF, which blocks caspase-4 or chelation of extracellular Ca2+, inhibited EPEC-induced cell death. IEC lines with low endogenous abundance of GSDMD were resistant to Tir-induced cell death. Conversely, ATP-induced extracellular Ca2+ influx enhanced cell death, which confirmed the key regulatory role of Ca2+ in EPEC-induced pyroptosis. We reveal a novel mechanism through which infection with an extracellular pathogen leads to pyroptosis in IECs.
Many methods are used to manufacture bioinspired adhesive arrays such as photolithography and nanoimprinting methods, which are very high cost and time‐consuming. In this manuscript, projection ...microstereolithography 3D printing method is firstly adopted to prepare the bioinspired dry adhesive in several micrometers, which is low cost, time saving, convenient and can realize rapid, large‐scale, high‐precision, and controllable complex structure manufacture. The morphology and adhesive properties of four kinds of adhesive with flat punch, mushroom‐shaped, suction cup‐shaped, and titled micropillar structures are investigated. Scanning electron microscope (SEM) observation shows that the very regular pattern of the adhesive is generated and no collapse phenomenon is observed. The adhesion test results show the mushroom‐shaped adhesive reach the maximum adhesion of 15 KPa, which can be maintained after repeated uses. The contact angle of the adhesive is 143.7°, showing the good self‐cleaning ability. The mushroom‐shaped adhesive exhibits excellent adhesion property, high repeatability, and good self‐cleaning ability, which is further applied in grasping and transferring various surfaces such as solar panels, printed circuit board, flanges, and so on.
In this manuscript, projection microstereolithography 3D printing method is firstly adopted to prepare the bioinspired adhesive in several micrometers, which is low cost, time saving, convenient, and can realize rapid, large‐scale, high‐precision, and controllable complex structure manufacture. The mushroom‐shaped adhesive exhibits excellent adhesion property, high repeatability, and good self‐cleaning ability, which is further applied in grasping and transferring various surfaces.
Membrane fouling can cause severe flux drops and affect the quality of produced water, which is a major obstacle for membrane applications. Great efforts have been made to examine theoretical models ...and numerical simulations for fouling behavior and mechanisms in the past decades, but there is a lack of literature providing a systematic summary. This work aims to present a state-of-the-art review of the principles, applicability and advantages of fouling theoretical models (i.e., the concentration polarization, cake layer formation and blocking models), and numerical simulations (i.e., computational fluid dynamics, Monte Carlo simulation, and artificial neural networks) for fouling behavior and mechanisms. Through these models and simulations, the behaviors of foulant particles at the microscopic level are analyzed in detail from the perspective of force, energy, and particle trajectory during the fouling process. The concise summary of fouling modeling in this review gives guidelines for the selection and application of models to simulate the membrane fouling process accurately, and the optimization of the operation in membrane-based processes.
The translocated intimin receptor (Tir) is an essential type III secretion system (T3SS) effector of attaching and effacing pathogens contributing to the global foodborne disease burden. Tir acts as ...a cell-surface receptor in host cells, rewiring intracellular processes by targeting multiple host proteins. We investigated the molecular basis for Tir's binding diversity in signalling, finding that Tir is a disordered protein with host-like binding motifs. Unexpectedly, also are several other T3SS effectors. By an integrative approach, we reveal that Tir dimerises via an antiparallel OB-fold within a highly disordered N-terminal cytosolic domain. Also, it has a long disordered C-terminal cytosolic domain partially structured at host-like motifs that bind lipids. Membrane affinity depends on lipid composition and phosphorylation, highlighting a previously unrecognised host interaction impacting Tir-induced actin polymerisation and cell death. Furthermore, multi-site tyrosine phosphorylation enables Tir to engage host SH2 domains in a multivalent fuzzy complex, consistent with Tir's scaffolding role and binding promiscuity. Our findings provide insights into the intracellular Tir domains, highlighting the ability of T3SS effectors to exploit host-like protein disorder as a strategy for host evasion.
The enteropathogenic Escherichia coli (EPEC) type III secretion system effector Tir, which mediates intimate bacterial attachment to epithelial cells, also triggers Ca2+ influx followed by LPS entry ...and caspase‐4‐dependent pyroptosis, which could be antagonized by the effector NleF. Here we reveal the mechanism by which EPEC induces Ca2+ influx. We show that in the intestinal epithelial cell line SNU‐C5, Tir activates the mechano/osmosensitive cation channel TRPV2 which triggers extracellular Ca2+ influx. Tir‐induced Ca2+ influx could be blocked by siRNA silencing of TRPV2, pre‐treatment with the TRPV2 inhibitor SET2 or by growing cells in low osmolality medium. Pharmacological activation of TRPV2 in the absence of Tir failed to initiate caspase‐4‐dependent cell death, confirming the necessity of Tir. Consistent with the model implicating activation on translocation of TRPV2 from the ER to plasma membrane, inhibition of protein trafficking by either brefeldin A or the effector NleA prevented TRPV2 activation and cell death. While infection with EPECΔnleA triggered pyroptotic cell death, this could be prevented by NleF. Taken together this study shows that while integration of Tir into the plasma membrane activates TRPV2, EPEC uses NleA to inhibit TRPV2 trafficking and NleF to inhibit caspase‐4 and pyroptosis.
During EPEC infection, translocated Tir is clustered by intimin. This leads to induction of membrane curvature and trafficking of the mechanosensitive ion channel TRPV2 from the ER to the plasma membrane and Ca2+ influx from the extracellular space into the cytosol. This is followed by influx of LPS, activation of caspase‐4 and pyroptosis. Counteracting this pathway are NleA which blocks trafficking of TRPV2 from the ER upstream of caspase‐4 and NleF which inhibits caspase‐4.
Cyclic di-adenosine monophosphate (c-di-AMP) is a recently discovered signaling molecule important for the survival of Firmicutes, a large bacterial group that includes notable pathogens such as ...Staphylococcus aureus. However, the exact role of this molecule has not been identified. dacA, the S. aureus gene encoding the diadenylate cyclase enzyme required for c-di-AMP production, cannot be deleted when bacterial cells are grown in rich medium, indicating that c-di-AMP is required for growth in this condition. Here, we report that an S. aureus dacA mutant can be generated in chemically defined medium. Consistent with previous findings, this mutant had a severe growth defect when cultured in rich medium. Using this growth defect in rich medium, we selected for suppressor strains with improved growth to identify c-di-AMP–requiring pathways. Mutations bypassing the essentiality of dacA were identified in alsT and opuD, encoding a predicted amino acid and osmolyte transporter, the latter of which we show here to be the main glycine betaine–uptake system in S. aureus. Inactivation of these transporters likely prevents the excessive osmolyte and amino acid accumulation in the cell, providing further evidence for a key role of c-di-AMP in osmotic regulation. Suppressor mutations were also obtained in hepS, hemB, ctaA, and qoxB, coding proteins required for respiration. Furthermore, we show that dacA is dispensable for growth in anaerobic conditions. Together, these findings reveal an essential role for the c-di-AMP signaling network in aerobic, but not anaerobic, respiration in S. aureus.
The enteropathogenic Escherichia coli (EPEC) type III secretion system effector Tir, which mediates intimate bacterial attachment to epithelial cells, also triggers Ca
influx followed by LPS entry ...and caspase-4-dependent pyroptosis, which could be antagonized by the effector NleF. Here we reveal the mechanism by which EPEC induces Ca
influx. We show that in the intestinal epithelial cell line SNU-C5, Tir activates the mechano/osmosensitive cation channel TRPV2 which triggers extracellular Ca
influx. Tir-induced Ca
influx could be blocked by siRNA silencing of TRPV2, pre-treatment with the TRPV2 inhibitor SET2 or by growing cells in low osmolality medium. Pharmacological activation of TRPV2 in the absence of Tir failed to initiate caspase-4-dependent cell death, confirming the necessity of Tir. Consistent with the model implicating activation on translocation of TRPV2 from the ER to plasma membrane, inhibition of protein trafficking by either brefeldin A or the effector NleA prevented TRPV2 activation and cell death. While infection with EPECΔnleA triggered pyroptotic cell death, this could be prevented by NleF. Taken together this study shows that while integration of Tir into the plasma membrane activates TRPV2, EPEC uses NleA to inhibit TRPV2 trafficking and NleF to inhibit caspase-4 and pyroptosis.
Conventional hydrogels are prone to water loss and instability, while non-hydrogel materials can be designed with high stability and repeatability. Therefore, a flexible sensing material was ...developed to meet the requirements of high elasticity, good stability, and high repeatability using a simple physical blending method. The developed ionogel comprised polyvinyl chloride (PVC) gel as the elastomer matrix, ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate as the dielectric, and dibutyl adipate (DBA) as the plasticizer. The PVC organic-ionogel exhibited good physicochemical stability without any phase change in the range of − 30 to 127 °C, and it had a maximum tensile strain of 424 %. Its shape and dimensions remained unchanged in air for 60 days, and the sensing performance was maintained following exposure to air for over a year. Moreover, the PVC organic-ionogel with moderate DBA and IL contents (DBA 7, IL 3 %) showed the best performance, which exhibited the best linearity with a relative error of only 0.96 %, sensitivity of 1.90, modulus of 17.71 kPa, response time of 161 ms, and continuous and stable operation for 35,000 cycles. This excellent performance enabled the PVC organic-ionogel to detect a range of human movements, namely finger flexion, throat vibration, muscle contraction, daily movements, and special limb movements, such as Tai Chi, with high accuracy and sensitivity. This work provides a new approach for the design of flexible sensing materials with variable parameters, in addition to a new solution for the development of wearable devices, sports-related risk monitoring, and boxing action optimization.
The introduction of ionic liquids was demonstrated can effectively increase the conductivity of PVC organic-ionogels and improve their sensing performance. PVC organic-ionogels showed excellent performance, exhibiting ultra-stable cycling performance, and were successfully applied to the monitoring of human motion. The strategy demonstrated in this study facilitates the development of high-performance flexible stretchable sensors. Display omitted
•Ionic liquid is introduced as a dielectric, which can effectively improve the sensing properties of PVC organic-ionogel.•PVC organic-ionogel exhibits excellent extensibility, repeatability and fast response, and can run 35000 times continuously.•PVC organic-ionogel can accurately detect small movements such as the limb movements of playing TaiChi.
Controlled and switchable adhesion is commonly observed in biological systems. In recent years, many scholars have focused on making switchable bio-inspired adhesives. However, making a bio-inspired ...adhesive with high adhesion performance and excellent dynamic switching properties is still a challenge. A Shape Memory Polymer Bio-inspired Adhesive (SMPBA) was successfully developed, well realizing high adhesion (about 337 kPa), relatively low preload (about 90 kPa), high adhesion-to-preload ratio (about 3.74), high switching ratio (about 6.74), and easy detachment, which are attributed to the controlled modulus and contact area by regulating temperature and the Shape Memory Effect (SME). Furthermore, SMPBA exhibits adhesion strength of 80–337 kPa on various surfaces (silicon, iron, and aluminum) with different roughness (Ra = 0.021–10.280) because of the conformal contact, reflecting outstanding surface adaptability. The finite element analysis verifies the bending ability under different temperatures, while the adhesion model analyzes the influence of preload on contact area and adhesion. Furthermore, an Unmanned Aerial Vehicle (UAV) landing device with SMPBA was designed and manufactured to achieve UAV landing on and detaching from various surfaces. This study provides a novel switchable bio-inspired adhesive and UAV landing method.
STING （also known as MITA） mediates the innate antiviral signaling and ubiquitination of STING is key to its function. However, the deubiquitination process of STING is unclear. Here we report that ...USP18 recruits USP20 to deconjugate K48-1inked ubiquitination chains from STING and promotes the stability of STING and the expression of type I IFNs and proinflammatory cytokines after DNA virus infection. USP18 deficiency or knockdown of USP20 resulted in enhanced K48-1inked ubiquitination and accelerated degradation of STING, and impaired activation of IRF3 and NF-κB as well as induction of downstream genes after infection with DNA virus HSV-1 or transfeetion of various DNA ligands. In addition, Uspl8-/- mice were more susceptible to HSV-1 infection compared with the wildtype littermates. USP18 did not deubiquitinate STING in vitro but facilitated USP20 to catalyze deubiquitination of STING in a manner independent of the enzymatic activity of USP18. In addition, reconstitution of STING into Uspl8-/- MEFs restored HSV-1-induced expression of downstream genes and cellular antiviral responses. Our findings thus uncover previously uncharacterized roles of USPI8 and USP20 in mediating virus-triggered signaling and contribute to the understanding of the complicated regulatory system of the innate antiviral responses.
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