Key roles for phosphorylation and the Coiled-coil domain in TRIM56-mediated positive regulation of TLR3-TRIF-dependent innate immunity.

Tripartite-motif protein-56 (TRIM56) positively regulates the induction of type I interferon response via the TLR3 pathway by enhancing IRF3 activation and depends on its C-terminal residues 621-750 for interacting with the adaptor TRIF. However, the precise underlying mechanism and detailed TRIM56 determinants remain unclear. Herein, we show ectopic expression of murine TRIM56 also enhances TLR3-dependent interferon-ß promoter activation, suggesting functional conservation. We found that endogenous TRIM56 and TRIF formed a complex early (0.5-2 h) after poly-I:C stimulation and that TRIM56 overexpression also promoted activation of NF-κB by poly-I:C but not that by TNF-α or IL-1ß, consistent with a specific effect on TRIF prior to the bifurcation of NF-κB and IRF3. Using transient transfection and Tet-regulated cell lines expressing various TRIM56 mutants, we demonstrated the Coiled-coil domain and a segment spanning residues ∼434-610, but not the B-box or residues 355-433, were required for TRIM56 augmentation of TLR3 signaling. Moreover, alanine substitution at each putative phosphorylation site, Ser471, Ser475, and Ser710, abrogated TRIM56 function. Concordantly, mutants bearing Ser471Ala, Ser475Ala, or Ser710Ala, or lacking the Coiled-coil domain, all lost the capacity to enhance poly-I:C-induced establishment of an antiviral state. Furthermore, the Ser710Ala mutation disrupted the TRIM56-TRIF association. Using phospho-specific antibodies, we detected biphasic phosphorylation of TRIM56 at Ser471 and Ser475 following TLR3 stimulation, with the early phase occurring at ∼0.5 to 1 h, prior to IRF3 phosphorylation. Together, these data reveal novel molecular details critical for the TRIM56 augmentation of TLR3-dependent antiviral response and highlight important roles for TRIM56 scaffolding and phosphorylation.

Predicting subsolid pulmonary nodules before percutaneous needle biopsy: a comparison of artificial neural network and biopsy results.

AIM: To establish an artificial neural network (ANN) model to predict subsolid nodules (SSNs) before percutaneous core-needle biopsy (PCNB). The results of the two methods were compared to provide guidance on the treatment of SSNs. MATERIALS AND METHODS: This was a single-centre retrospective study using data from 1,459 SSNs between 2013 and 2021. The ANN was developed using data from patients who underwent surgery following computed tomography (CT) (SFC) and validated using data from patients who underwent surgery following biopsy (SFB). The prediction results of the ANN for the PCNB group and the histopathological results obtained after biopsy were compared with the histopathological results of lung nodules in the same group after surgery. Additionally, the choice of predictors for PCNB was analysed using multivariate analysis. RESULTS: There was no significant difference between the accuracies of the ANN and PCNB in the SFB group (p=0.086). The sensitivity of PCNB was lower than that of the ANN (p=0.000), but the specificity was higher (p=0.001). PCNB had better diagnostic ability than the ANN. The incidence of precursor lesions and non-neoplastic lesions in the SFB group was lower than that in the SFC group (p=0.000). A history of malignant tumours, size (2-3 cm), volume (>400 cm3) and mean CT value (≥-450 HU) are important factors for selecting PCNB. CONCLUSIONS: Both ANN and PCNB have comparable accuracy in diagnosing SSNs; however, PCNB has a slightly higher diagnostic ability than ANN. Selecting appropriate patients for PCNB is important for maximising the benefit to SSN patients.

SHIP1 is required for the formation of neutrophil extracellular traps in rheumatoid arthritis.

Aberrant neutrophil extracellular traps (NETs) are involved in the pathogenesis of rheumatoid arthritis (RA). However, the specific pathway leading to NET formation in RA is poorly understood. Therefore, therapies targeting NETs are not available in RA. In this study, we demonstrated Src homology 2 domain-containing inositol phosphatase-1 (SHIP1) function as a hub to regulate NETosis through SHIP1/ p38 MAPK/TNF-α pathway both in vitro and ex vivo and inhibiting SHIP1 expression ameliorated RA symptoms in vivo. Neutrophils from RA patients showed enhanced NETosis as well as increased SHIP1, p38 mitogen-activated protein kinase (MAPK) family expression and tumor necrosis factor-α (TNF-α) expression. Inhibiting SHIP1 in neutrophils using small molecules counteracted the above-mentioned dysregulations and resulted in decrease in NETosis, p38 expression and TNF-α concentration. Consistent with this, SHIP1 agonist led to upregulated p38MAPK and NET formation. Moreover, inhibiting SHIP1 in vivo led to decreased NETosis and showed beneficial therapeutic effects in Collagen-induced arthritis (CIA) mice. Taken together, these results indicated that activation of SHIP1/MAPK/TNF-α pathway was necessary for upregulated NETosis in RA, which provided evidence for targeting SHIP1 in RA treatment.

Microbial community redundance in biomethanation systems lead to faster recovery of methane production rates after starvation.

The Power-to-Gas concept corresponds to the use of the electric energy surplus to produce H2 by water electrolysis, that can be further converted to methane by biomethanation. However, the fluctuant production of renewable energy sources can lead to discontinuous H2 injections into the reactors, that may interfere with the adaptation of the microbial community to high H2 partial pressures. In this study, the response of the microbial community to H2 and organic feed starvation was evaluated in in-situ and ex-situ biomethanation. The fed-batch reactors were fed with acetate or glucose and H2, and one or four weeks of starvation periods were investigated. Methane productivity was mostly affected by the four-week starvation period. However, both in-situ and ex-situ biomethanation reactors recovered their methane production rate after starvation within approximately one-week of normal operation, while the anaerobic digestion (AD) reactors did not recover their performances even after 3 weeks of normal operation. The recovery failure of the AD reactors was probably related to a slow growth of the syntrophic and methanogen microorganisms, that led to a VFA accumulation. On the contrary, the faster recovery of both biomethanation reactors was related to the replacement of Methanoculleus sp. by Methanobacterium sp., restoring the methane production in the in-situ and ex-situ biomethanation reactors. This study has shown that biomethanation processes can respond favourably to the intermittent H2 addition without compromising their CH4 production performance.

Missense Mutations of Codon 116 in the SOD1 Gene Cause Rapid Progressive Familial ALS and Predict Short Viability With PMA Phenotype.

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron disease, characterized by a great variety of both clinical presentations and genetic causes. Previous studies had identified two different missense mutations in SOD1 (p.R116C and p.R116G) causing familial ALS. In this study, we report a novel heterozygous missense mutation in the SOD1 gene (p.R116S) in a family with inherited ALS manifested as fast-deteriorating pure lower motor neuron symptoms. The patient displayed similar clinical picture and prognostic value to previous reported cases with different R116 substitution mutations. Modeling of all R116 substitutions in the resolved SOD1 protein structure revealed a shared mechanism with destroyed hydrogen bonds between R116 and other two residues, which might lead to protein unfolding and oligomer formation, ultimately conferring neurotoxicity.

Correction: Extracellular phosphorylation of a receptor tyrosine kinase controls synaptic localization of NMDA receptors and regulates pathological pain.

[This corrects the article DOI: 10.1371/journal.pbio.2002457.].

[Analysis of Injection of Xuesaitong (lyophilized) in 30097 cases in real world].

To investigate the extensive application of Injection of Xuesaitong(lyophilized) in clinical real world study, and provide basis for clinical guidance on rational drug use and improvement of drug instructions. A prospective, multi-center, large-sample hospital centralized monitoring method was adopted to collect the general information and medication information of all patients who received Injection of Xuesaitong(lyophilized) during the study period in the respective monitoring units. Data analysis was performed using SAS 9.1 software. This study included 79 hospitals, with 30 097 patients being recruited. The patients who met the indications for stroke and hemiplegia accounted for 31.18%, those who experienced indications of chest pain and heartache accounted for 23.15%, and patients with central retinal vein occlusion indication accounted for 0.53%. The minimum single dose of Injection of Xuesaitong(lyophilized) was 20 mg, the maximum single dose was 1 000 mg, and the average single dose was(383.31±78.10) mg. 69.96% of the patients used 0.9% sodium chloride as the menstruum, 28.78% of the patients used 5% glucose as the menstruum, and 0.19% of the patients used 10% glucose as the menstruum. The minimum time for Injection of Xuesaitong(lyophilized) to dissolve is 0 min, 120 min maximally, and(14.26±13.73) min on an average basis. Patients using Injection of Xuesaitong(lyophilized) by intravenous drip accounted for 99.93%, with a slowest drip rate of 10 drops per min, fastest drip rate of 80 drops per min, and an average of(43.91±10.77) drops per min. Injection of Xuesaitong(lyophilized) was used for a minimum of 1 day and a maximum of 80 days, with an average of(8.22±5.12) days. Combined use with other injections accounted for 80.67%, 47.14% of them flushed the tube and 3.31% of them replaced infusion sets. The study found 40 cases of adverse reactions in patients with Injection of Xuesaitong(lyophilized), with an overall incidence of 0.13%(0.09% to 0.17%) for adverse reactions. In the real world application, the usage of Injection of Xuesaitong(lyophilized) basically meets the requirement of drug instructions in terms of indications, dosages, and methods of administration. However, it still needs to be improved in standardizing the selection of the menstruum, drip rate, course of treatment, and the combined usage of medicine.

[Post-marketing intensive safety monitoring of Injection of Xuesaitong (lyophilized) in 30097 cases].

To investigate the safety of Injection of Xuesaitong(lyophilized) in clinical "real world" application, including the types, incidence, as well as the severity and treatment measures of adverse reactions/adverse events. This will serve as a basis for hospitals and enterprises to develop risk control measures. A prospective, multi-center, and large-sample hospital centralized monitoring method was used to conduct post-marketing safety monitoring of Injection of Xuesaitong(lyophilized) in medical institutions nationwide. Paper case report forms were adopted to collect general information, medication and adverse reaction information of patients using Injection of Xuesaitong(lyophilized). Data analysis was performed by using SAS 9.1 software. The study included 79 hospitals with 30 097 patients. 199 cases of adverse events were found in patients administered with Injection of Xuesaitong(lyophilized), a total of 206 times. Among 199 cases, 40 of them showed adverse reactions, accounting for an overall incidence of 0.13% and 95%CI[0.09%,0.17%], which was an occasional grade. There were 38 cases of mild adverse reactions, accounting for 95.0%, 2 cases of moderate adverse reactions, accounting for 5.0%. Adverse reaction symptoms were relieved in six patients, accounting for 15.0% of the total number of adverse reactions, adverse reaction symptoms disappeared in 34 cases, with an overall percentage of 85.0%. The results of the study showed the adverse reactions in patients using Injection of Xuesaitong(lyophilized) were rare and mild, with a good prognosis. Therefore, clinical administration of Injection of Xuesaitong(lyophilized) is relatively safe.

Positive surface charge of GluN1 N-terminus mediates the direct interaction with EphB2 and NMDAR mobility.

Localization of the N-methyl-D-aspartate type glutamate receptor (NMDAR) to dendritic spines is essential for excitatory synaptic transmission and plasticity. Rather than remaining trapped at synaptic sites, NMDA receptors undergo constant cycling into and out of the postsynaptic density. Receptor movement is constrained by protein-protein interactions with both the intracellular and extracellular domains of the NMDAR. The role of extracellular interactions on the mobility of the NMDAR is poorly understood. Here we demonstrate that the positive surface charge of the hinge region of the N-terminal domain in the GluN1 subunit of the NMDAR is required to maintain NMDARs at dendritic spine synapses and mediates the direct extracellular interaction with a negatively charged phospho-tyrosine on the receptor tyrosine kinase EphB2. Loss of the EphB-NMDAR interaction by either mutating GluN1 or knocking down endogenous EphB2 increases NMDAR mobility. These findings begin to define a mechanism for extracellular interactions mediated by charged domains.

The E3 ligase TRIM56 is a host restriction factor of Zika virus and depends on its RNA-binding activity but not miRNA regulation, for antiviral function.

Infection by Zika virus (ZIKV) is linked to microcephaly and other neurological disorders, posing a significant health threat. Innate immunity is the first line of defense against invading pathogens, but relatively little is understood regarding host intrinsic mechanisms that guard against ZIKV. Here, we show that host tripartite motif-containing protein 56 (TRIM56) poses a barrier to ZIKV infection in cells of neural, epithelial and fibroblast origins. Overexpression of TRIM56, but not an E3 ligase-dead mutant or one lacking a short C-terminal portion, inhibited ZIKV RNA replication. Conversely, depletion of TRIM56 increased viral RNA levels. Although the C-terminal region of TRIM56 bears sequence homology to NHL repeat of TRIM-NHL proteins that regulate miRNA activity, knockout of Dicer, which abolishes production of miRNAs, had no demonstrable effect on ZIKV restriction imposed by TRIM56. Rather, we found that TRIM56 is an RNA-binding protein that associates with ZIKV RNA in infected cells. Moreover, a recombinant TRIM56 fragment comprising the C-terminal 392 residues captured ZIKV RNA in cell-free reactions, indicative of direct interaction. Remarkably, deletion of a short C-terminal tail portion abrogated the TRIM56-ZIKV RNA interaction, concomitant with a loss in antiviral activity. Altogether, our study reveals TRIM56 is an RNA binding protein that acts as a ZIKV restriction factor and provides new insights into the antiviral mechanism by which this E3 ligase tackles flavivirus infections.

Pivotal role for the ESCRT-II complex subunit EAP30/SNF8 in IRF3-dependent innate antiviral defense.

The activation of interferon (IFN)-regulatory factor-3 (IRF3), characterized by phosphorylation and nuclear translocation of the latent transcription factor, is central to initiating innate antiviral responses. Whereas much has been learned about the upstream pathways and signaling mechanisms leading to IRF3 activation, how activated IRF3 operates in the nucleus to control transcription of IFNs remains obscure. Here we identify EAP30 (a.k.a, SNF8/VPS22), an endosomal sorting complex required for transport (ESCRT)-II subunit, as an essential factor controlling IRF3-dependent antiviral defense. Depletion of EAP30, but not other ESCRT-II subunits, compromised IRF3-dependent induction of type I and III IFNs, IFN-stimulated genes (ISGs) and chemokines by double-stranded RNA or viruses. EAP30, however, was dispensable for the induction of inflammatory mediators of strict NF-κB target. Significantly, knockdown of EAP30 also impaired the establishment of an antiviral state against vesicular stomatitis virus and hepatitis C virus, which are of distinct viral families. Mechanistically, EAP30 was not required for IRF3 activation but rather acted at a downstream step. Specifically, a fraction of EAP30 localized within the nucleus, where it formed a complex with IRF3 and its transcriptional co-activator, CREB-binding protein (CBP), in a virus-inducible manner. These interactions promoted IRF3 binding to target gene promoters such as IFN-ß, IFN-λ1 and ISG56. Together, our data describe an unappreciated role for EAP30 in IRF3-dependent innate antiviral response in the nucleus.

Does stimulating various coping strategies alleviate loneliness? Results from an online friendship enrichment program.

Loneliness stems from a mismatch between the social relationships one has and those one desires. Loneliness often has severe consequences for individuals and society. Recently, an online adaptation of the friendship enrichment program (FEP) was developed and tested to gain insight in its contribution to the alleviation of loneliness. Three loneliness coping strategies are introduced during the program: network development, adapting relationship standards, and reducing the importance of the discrepancy between actual and desired relationships. Data were collected among 239 participants aged 50-86. Loneliness was measured four times using a multi-item scale, and on various days with a single, direct question. Loneliness assessed with the scale declined during and after the program. Scores on loneliness assessed for a specific day, however, are more ambiguous. Despite the immediate positive effect of conducting assignments, we did not observe a decline in the single loneliness item score over the course of the program. The online FEP seems to reduce loneliness in general, but these effects are not visible on today's loneliness. Nevertheless, the online intervention to reduce loneliness is a valuable new contribution to the collection of loneliness interventions.

Extracellular phosphorylation of a receptor tyrosine kinase controls synaptic localization of NMDA receptors and regulates pathological pain.

Extracellular phosphorylation of proteins was suggested in the late 1800s when it was demonstrated that casein contains phosphate. More recently, extracellular kinases that phosphorylate extracellular serine, threonine, and tyrosine residues of numerous proteins have been identified. However, the functional significance of extracellular phosphorylation of specific residues in the nervous system is poorly understood. Here we show that synaptic accumulation of GluN2B-containing N-methyl-D-aspartate receptors (NMDARs) and pathological pain are controlled by ephrin-B-induced extracellular phosphorylation of a single tyrosine (p*Y504) in a highly conserved region of the fibronectin type III (FN3) domain of the receptor tyrosine kinase EphB2. Ligand-dependent Y504 phosphorylation modulates the EphB-NMDAR interaction in cortical and spinal cord neurons. Furthermore, Y504 phosphorylation enhances NMDAR localization and injury-induced pain behavior. By mediating inducible extracellular interactions that are capable of modulating animal behavior, extracellular tyrosine phosphorylation of EphBs may represent a previously unknown class of mechanism mediating protein interaction and function.

De-ubiquitinating enzyme, USP11, promotes transforming growth factor ß-1 signaling through stabilization of transforming growth factor ß receptor II.

The transforming growth factor ß-1 (TGFß-1) signaling pathway plays a central role in the pathogenesis of pulmonary fibrosis. Two TGFß-1 receptors, TßRI and TßRII, mediate this pathway. TßRI protein stability, as mediated by the ubiquitin/de-ubiquitination system, has been well studied; however, the molecular regulation of TßRII still remains unclear. Here we reveal that a de-ubiquitinating enzyme, USP11, promotes TGFß-1 signaling through de-ubiquitination and stabilization of TßRII. We elucidate the role that mitoxantrone (MTX), an USP11 inhibitor, has in the attenuation of TGFß-1 signaling. Inhibition or downregulation of USP11 results in increases in TßRII ubiquitination and reduction of TßRII stability. Subsequently, TGFß-1 signaling is greatly attenuated, as shown by the decreases in phosphorylation of SMAD2/3 levels as well as that of fibronectin (FN) and smooth muscle actin (SMA). Overexpression of USP11 reduces TßRII ubiquitination and increases TßRII stabilization, thereby elevating phosphorylation of SMAD2/3 and the ultimate expression of FN and SMA. Further, elevated expression of USP11 and TßRII were detected in lung tissues from bleomycin-challenged mice and IPF patients. Therefore, USP11 may contribute to the pathogenesis of pulmonary fibrosis by stabilization of TßRII and promotion of TGFß-1 signaling. This study provides mechanistic evidence for development of USP11 inhibitors as potential antifibrotic drugs for pulmonary fibrosis.

The Molecular Chaperone GRP78 Contributes to Toll-like Receptor 3-mediated Innate Immune Response to Hepatitis C Virus in Hepatocytes.

Toll-like receptor-3 (TLR3) senses double-stranded RNA intermediates produced during hepatitis C virus (HCV) replication, leading to activation of interferon regulatory factor-3 (IRF3) and NF-κB and subsequent antiviral and proinflammatory responses. Yet, how this TLR3-dependent pathway operates in hepatocytes is unclear. Upon fractionating cultured hepatocytes into various cellular organelles, we observed that TLR3 predominantly resides in endolysosomes of hepatocytes. To determine the critical regulators of TLR3 signaling in response to HCV infection in human hepatocytes, we isolated endolysosome fractions from mock-infected and HCV-infected hepatoma Huh7.5 cells that had been reconstituted for TLR3 expression, separated these fractions on two-dimensional gels, and identified up-regulated/down-regulated proteins by mass spectrometry. Approximately a dozen of cellular proteins were found to be differentially expressed in endolysosome fractions following HCV infection. Of these, expression of several molecular chaperone proteins was elevated. Knockdown of one of these chaperones, glucose-regulated protein 78 kDa (GRP78), compromised TLR3-dependent induction of interferon-stimulated genes and chemokines following HCV infection or poly(I:C) stimulation in cultured hepatocytes. Consistent with this finding, GRP78 depletion impaired TLR3-mediated establishment of an antiviral state. Mechanistically, although TLR3 trafficking to endolysosomes was not affected, phosphorylated IRF3 diminished faster following GRP78 knockdown. Remarkably, GRP78 transcript was significantly up-regulated in liver biopsies of chronic hepatitis C patients as compared with normal liver tissues. Moreover, the GRP78 expression level correlated with that of RANTES (regulated upon activation, normal T-cell expressed and secreted) and CXCL10, two inflammatory chemokines most frequently elevated in HCV-infected liver. Altogether, our data suggest that GRP78 contributes to TLR3-mediated, IRF3-dependent innate immune response to HCV in hepatocytes.

The C-Terminal Tail of TRIM56 Dictates Antiviral Restriction of Influenza A and B Viruses by Impeding Viral RNA Synthesis.

UNLABELLED: Accumulating data suggest that tripartite-motif-containing (TRIM) proteins participate in host responses to viral infections, either by acting as direct antiviral restriction factors or through regulating innate immune signaling of the host. Of >70 TRIMs, TRIM56 is a restriction factor of several positive-strand RNA viruses, including three members of the family Flaviviridae(yellow fever virus, dengue virus, and bovine viral diarrhea virus) and a human coronavirus (OC43), and this ability invariably depends upon the E3 ligase activity of TRIM56. However, the impact of TRIM56 on negative-strand RNA viruses remains unclear. Here, we show that TRIM56 puts a check on replication of influenza A and B viruses in cell culture but does not inhibit Sendai virus or human metapneumovirus, two paramyxoviruses. Interestingly, the anti-influenza virus activity was independent of the E3 ligase activity, B-box, or coiled-coil domain. Rather, deletion of a 63-residue-long C-terminal-tail portion of TRIM56 abrogated the antiviral function. Moreover, expression of this short C-terminal segment curtailed the replication of influenza viruses as effectively as that of full-length TRIM56. Mechanistically, TRIM56 was found to specifically impede intracellular influenza virus RNA synthesis. Together, these data reveal a novel antiviral activity of TRIM56 against influenza A and B viruses and provide insights into the mechanism by which TRIM56 restricts these medically important orthomyxoviruses. IMPORTANCE: Options to treat influenza are limited, and drug-resistant influenza virus strains can emerge through minor genetic changes. Understanding novel virus-host interactions that alter influenza virus fitness may reveal new targets/approaches for therapeutic interventions. We show here that TRIM56, a tripartite-motif protein, is an intrinsic host restriction factor of influenza A and B viruses. Unlike its antiviral actions against positive-strand RNA viruses, the anti-influenza virus activity of TRIM56 was independent of the E3 ligase activity. Rather, expression of a short segment within the very C-terminal tail of TRIM56 inhibited the replication of influenza viruses as effectively as that of full-length TRIM56 by specifically targeting viral RNA synthesis. These data reveal the remarkable multifaceted activity of TRIM56, which has developed multiple domains to inhibit multiple viral families. They also raise the possibility of developing a broad-spectrum, TRIM56-based antiviral approach for addition to influenza prophylaxis and/or control strategies.

Geographical variations of risk factors associated with HCV infection in drug users in southwestern China.

Hepatitis C virus (HCV) has become a global public health problem. Many studies have been conducted to identify risk factors for HCV infection. However, some of these studies reported inconsistent results. Using data collected from 11 methadone clinics, we fit both a non-spatial logistical regression and a geographically weighted logistic regression to analyse the association between HCV infection and some factors at the individual level. This study enrolled 5401 patients with 30·0% HCV infection prevalence. The non-spatial logistical regression found that injection history, drug rehabilitation history and senior high-school education or above were related to HCV infection; and being married was negatively associated with HCV infection. Using the spatial model, we found that Yi ethnicity was negatively related to HCV infection in 62·0% of townships, and being married was negatively associated with HCV infection in 81·0% of townships. Senior high-school education or above was positively associated with HCV infection in 55·2% of townships of the Yi Autonomous Prefecture. The spatial model offers better understanding of the geographical variations of the risk factors associated with HCV infection. The geographical variations may be useful for customizing intervention strategies for local regions for more efficient allocation of limited resources to control transmission of HCV.

Understanding the Probability of a Disability Resulting From Work-Related Injuries.

OBJECTIVES: To assess the conditions under which the measured risk of a workplace injury resulting in a disability changes. METHODS: Multivariate regression analysis and administrative claims data build an understanding of the factors that underlie the probability that a workplace injury results in a disability (disability probability). RESULTS: First, jointly examining injury incidence rates and disability probabilities challenges some conclusions suggested by examining the two separately. Second, some characteristics identified as risk factors for disability when studied in isolation are not risk factors. Third, risk factors are qualitatively consistent across groups of workers but quantitatively different. CONCLUSIONS: Policymakers might draw incorrect conclusions about the risk of a workplace injury becoming a disability unless the research provides a joint assessment of incidence rates and disability probabilities and a comprehensive analysis of risk factors across worker groups.

Anchoring and synaptic stability of PSD-95 is driven by ephrin-B3.

Organization of signaling complexes at excitatory synapses by membrane-associated guanylate kinase (MAGUK) proteins regulates synapse development, plasticity, senescence and disease. Post-translational modification of MAGUK family proteins can drive their membrane localization, yet it is unclear how these intracellular proteins are targeted to sites of synaptic contact. Here we show using super-resolution imaging, biochemical approaches and in vivo models that the trans-synaptic organizing protein ephrin-B3 controls the synaptic localization and stability of PSD-95 and links these events to changes in neuronal activity via negative regulation of a newly identified mitogen-associated protein kinase (MAPK)-dependent phosphorylation site on ephrin-B3, Ser332. Unphosphorylated ephrin-B3 was enriched at synapses, and interacted directly with and stabilized PSD-95 at synapses. Activity-induced phosphorylation of Ser332 dispersed ephrin-B3 from synapses, prevented the interaction with PSD-95 and enhanced the turnover of PSD-95. Thus, ephrin-B3 specifies the synaptic localization of PSD-95 and likely links the synaptic stability of PSD-95 to changes in neuronal activity.