Junction Stability Research Articles

From the Occipital Condyle to the Sphenoid Sinus: Extradural Extension of the Far Lateral Transcondylar Approach with Endoscopic Assistance

Surgical management of extensive skull base tumors, such as chordoma and chondrosarcoma, remains very challenging. The need for gross total removal to improve survival must be weighed against the risk of injury to neurovascular structures and the loss of stability at the craniovertebral junction. In cases of tumors that are already compromising craniovertebral junction stability, the occipital condyle can be exploited as a deep keyhole to reach the clivus, petrous apex, and sphenoid sinus. We performed an anatomic study on 7 cadaveric specimens to describe the main landmarks and boundaries of the corridor. We also provide a clinical case to demonstrate the feasibility of the approach. In all specimens, using the space provided by the condyle, it was possible to drill the petrous bone up to the posterior wall of the sphenoid sinus following the direction of the inferior petrosal sinus. To successfully complete the approach, after the hypoglossal canal was exposed, endoscopic assistance was needed to overcome the narrowing of the visual field provided by the microscope. In cases of invasive skull base tumor involving the craniovertebral junction and affecting its stability, the occipital condyle can be exploited as a deep keyhole to the homolateral and contralateral petrous apex, clivus, and sphenoid sinus.

TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum.

The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.

Skeletal muscle mTORC1 regulates neuromuscular junction stability.

BackgroundSkeletal muscle is a plastic tissue that can adapt to different stimuli. It is well established that Mammalian Target of Rapamycin Complex 1 (mTORC1) signalling is a key modulator in mediating increases in skeletal muscle mass and function. However, the role of mTORC1 signalling in adult skeletal muscle homeostasis is still not well defined.MethodsInducible, muscle‐specific Raptor and mTOR k.o. mice were generated. Muscles at 1 and 7 months after deletion were analysed to assess muscle histology and muscle force.ResultsWe found no change in muscle size or contractile properties 1 month after deletion. Prolonging deletion of Raptor to 7 months, however, leads to a very marked phenotype characterized by weakness, muscle regeneration, mitochondrial dysfunction, and autophagy impairment. Unexpectedly, reduced mTOR signalling in muscle fibres is accompanied by the appearance of markers of fibre denervation, like the increased expression of the neural cell adhesion molecule (NCAM). Both muscle‐specific deletion of mTOR or Raptor, or the use of rapamycin, was sufficient to induce 3–8% of NCAM‐positive fibres (P < 0.01), muscle fibrillation, and neuromuscular junction (NMJ) fragmentation in 24% of examined fibres (P < 0.001). Mechanistically, reactivation of autophagy with the small peptide Tat‐beclin1 is sufficient to prevent mitochondrial dysfunction and the appearance of NCAM‐positive fibres in Raptor k.o. muscles.ConclusionsOur study shows that mTOR signalling in skeletal muscle fibres is critical for maintaining proper fibre innervation, preserving the NMJ structure in both the muscle fibre and the motor neuron. In addition, considering the beneficial effects of exercise in most pathologies affecting the NMJ, our findings suggest that part of these beneficial effects of exercise are through the well‐established activation of mTORC1 in skeletal muscle during and after exercise.

Yap/Taz are required for establishing the cerebellar radial glia scaffold and proper foliation

Yap/Taz are well-established downstream effectors of the Hippo pathway, known to regulate organ size by directing proliferation and apoptosis. Although the functions of Yap/Taz have been extensively studied, little is known about their role in brain development. Here, through genetic ablation, we show that Yap/Taz are required for cerebellar morphogenesis. Yap/Taz deletion in neural progenitors causes defects in secondary fissure formation, leading to abnormal folia development. Although they seemed very likely to serve an important function in the development of cerebellar granule cell precursors, Yap/Taz are dispensable for their proliferation. Furthermore, Yap/Taz loss does not rescue the medulloblastoma phenotype caused by constitutively active Smoothened. Importantly, Yap/Taz are highly expressed in radial glia and play a crucial role in establishing the radial scaffold and cellular polarity of neural progenitors during embryogenesis. We found that Yap/Taz are necessary to establish and maintain junctional integrity of cerebellar neuroepithelium as prominent junction proteins are not maintained at the apical junction in the absence of Yap/Taz. Our study identifies a novel function of Yap/Taz in cerebellar foliation and finds that they are required to establish the radial glia scaffold and junctional stability.

Vascular Endothelial Receptor Tyrosine Phosphatase: Identification of Novel Substrates Related to Junctions and a Ternary Complex with EPHB4 and TIE2*[S

Vascular endothelial protein tyrosine phosphatase (VE-PTP, PTPRB) is a receptor type phosphatase that is crucial for the regulation of endothelial junctions and blood vessel development. We and others have shown recently that VE-PTP regulates vascular integrity by dephosphorylating substrates that are key players in endothelial junction stability, such as the angiopoietin receptor TIE2, the endothelial adherens junction protein VE-cadherin and the vascular endothelial growth factor receptor VEGFR2. Here, we have systematically searched for novel substrates of VE-PTP in endothelial cells by utilizing two approaches. First, we studied changes in the endothelial phosphoproteome on exposing cells to a highly VE-PTP-specific phosphatase inhibitor followed by affinity isolation and mass-spectrometric analysis of phosphorylated proteins by phosphotyrosine-specific antibodies. Second, we used a substrate trapping mutant of VE-PTP to pull down phosphorylated substrates in combination with SILAC-based quantitative mass spectrometry measurements. We identified a set of substrate candidates of VE-PTP, of which a remarkably large fraction (29%) is related to cell junctions. Several of those were found in both screens and displayed very high connectivity in predicted functional interaction networks. The receptor protein tyrosine kinase EPHB4 was the most prominently phosphorylated protein on VE-PTP inhibition among those VE-PTP targets that were identified by both proteomic approaches. Further analysis revealed that EPHB4 forms a ternary complex with VE-PTP and TIE2 in endothelial cells. VE-PTP controls the phosphorylation of each of these two tyrosine kinase receptors. Despite their simultaneous presence in a ternary complex, stimulating each of the receptors with their own specific ligand did not cross-activate the respective partner receptor. Our systematic approach has led to the identification of novel substrates of VE-PTP, of which many are relevant for the control of cellular junctions further promoting the importance of VE-PTP as a key player of junctional signaling.

P120 Catenin Isoforms Differentially Associate with Breast Cancer Invasion and Metastasis.

Tumor metastasis is the endpoint of tumor progression and depends on the ability of tumor cells to locally invade tissue, transit through the bloodstream and ultimately to colonize secondary organs at distant sites. P120 catenin (p120) has been implicated as an important regulator of metastatic dissemination because of its roles in cell–cell junctional stability, cytoskeletal dynamics, growth and survival. However, conflicting roles for p120 in different tumor models and steps of metastasis have been reported, and the understanding of p120 functions is confounded by the differential expression of p120 isoforms, which differ in N-terminal length, tissue localization and, likely, function. Here, we used in silico exon expression analyses, in vitro invasion assays and both RT-PCR and immunofluorescence of human tumors. We show that alternative exon usage favors expression of short isoform p120-3 in 1098 breast tumors and correlates with poor prognosis. P120-3 is upregulated at the invasive front of breast cancer cells migrating as collective groups in vitro. Furthermore, we demonstrate in histological sections of 54 human breast cancer patients that p120-3 expression is maintained throughout the metastatic cascade, whereas p120-1 is differentially expressed and diminished during invasion and in metastases. These data suggest specific regulation and functions of p120-3 in breast cancer invasion and metastasis.

BIFURCATIONS OF STEADY STATES OF THE BIAXIAL CREW MODEL

Many transport systems (car, airplane, ship) have symmetry property. For such systems symmetrical deviations of some control parameter (steering wheel) from the neutral position lead to symmetry of the dynamic behaviour of the object (equivalence of left and right turns). In this case the straight-line motion of an object with constant velocity corresponds to a trivial solution of the corresponding dynamic system (symmetric solution). Conditions for dangerous-safe loss of symmetric junction stability (the case of one zero proper linear approximation system) can be obtained from the analysis of the true birth-fusion of stationary states with a stationary state corresponding to a symmetric solution. This approach makes it possible to obtain conditions of dangerous and safe loss of symmetric junction stability equivalent to the conditions of MM. Bautin [3] with the lowest possible computational cost. The proposed approach is illustrated by the example of the stability analysis of a nonlinear model of a double-axle crew with excessive rotation. It is shown that the condition of hazardous and safe loss of stability of straight-line motion (symmetric junction) is determined by the ratio between dimensionless coefficients of axle deflection and coupling coefficients on transaxle axes. However, clutch coefficients are not included in the linear system of equations of perturbed motion but refer to a substantially nonlinear characteristic of the forces of withdrawal.

CAND1 regulates lunapark for the proper tubular network of the endoplasmic reticulum

Endoplasmic reticulum (ER) tubules connect each other by three-way junctions, resulting in a tubular ER network. Oligomerization of three-way junction protein lunapark (Lnp) is important for its localization and the three-way junction stability. On the other hand, Lnp has an N-terminal ubiquitin ligase activity domain, which is also important for the three-way junction localization. To understand the mode of action of Lnp, we isolated Cullin-associated and neddylation-dissociated 1 (CAND1), a regulator of Skp1-Cul1-F-box (SCF) ubiquitin ligase, as a Lnp-binding protein by affinity chromatography. CAND1 and Lnp form a higher-molecular-weight complex in vitro, while they do not co-localize at the three-way junctions. CAND1 reduces the auto-ubiquitination activity of Lnp. CAND1 knockdown enhances proteasomal degradation of Lnp and reduces the tubular ER network in mammalian cells. These results suggest that CAND1 has the potency to promote the formation of the higher-molecular-weight complex with Lnp and reduce the auto-ubiquitination activity of Lnp, thereby regulating the three-way junction stability of the tubular ER network.

A variable-temperature scanning tunneling microscope operated in a continuous flow cryostat.

We present a continuous flow cryostat scanning tunneling microscope (STM) which can be operated at temperatures between 4.9 K and 300 K. A variable temperature insert with 20 mm aperture is installed in the cryostat. A base temperature of 4.9 K at the STM head was achieved with helium exchange gas cooling. By using a novel design of zirconia structure, the size of the STM head was minimized to 9.2 mm in outer diameter. The high compactness and rigidity of the STM head make it less sensitive to vibrations, contributing to the high stability of the tip-sample junction. The drifting rates of the STM at 4.9 K in the X-Y plane and Z direction are 1.96 and 3.05 pm/min, respectively. The performance of the STM was demonstrated by atomically resolved imaging of graphite and NbSe2 without using external vibrational isolation. Furthermore, the dI/dV spectra of NbSe2 were resolved near its critical temperature, illustrating the formation process of the superconducting gap as a function of temperature. This STM is ultrahigh vacuum and strong magnetic field compatible, making it promising for direct application in the extreme conditions involving water-cooled magnets and hybrid magnets.

Bipolar Membrane Development for Reversible Fuel Cells

Bipolar membranes (BPMs) are composed of a cation exchange layer (CEL), an anion exchange layer (AEL), and a nanometer scale bipolar junction (Fig 1). At reverse bias polarization (electrolysis mode) the potential drop within both the AEL and CEL are almost negligible when compared to the potential drop within the junction. This large potential drop within the bipolar junction results in a high electric field, which, in combination with water dissociation catalyst, allow BPMs to facilitate water dissociation (into H+ and OH- ions) at a rate seven orders of magnitude greater than the rate in bulk water [1]. At forward bias polarization (fuel cell mode), H+ and OH- produced on the electrodes transport through the membrane and meet at bipolar junction forming H2O. BPMs have been studied at the laboratory and pilot scale for a wide variety of applications, including: electrodialysis for water treatment [2], CO2 reduction [3], solar water splitting [4], and fuel cells [5]. Despite the commercial availability of BPMs, significant hurdles exist both in the fundamental understanding of limiting processes and their subsequent incorporation into electrochemical devices. This is particularly true for BPM reversible fuel cell applications where the requirements for an optimized bipolar junction are specialized for each case. The main technological challenges to enable BPM reversible fuel cell operation include: i)Optimizing bipolar junction to perform in both fuel cell mode and electrolysis mode; ii)Achieving high bipolar junction stability at high current densities; iii)Achieving high membrane durability when cycling between each mode; IV)Optimizing ion exchange layers to decrease membrane resistance Here we will discuss the optimization of BPM junctions to enable reversible fuel cells. Both 2-D and 3-D approaches with and without water dissociation promoters will be applied to fabricate BPM junctions. An example of the improved interfacial charge transfer for BPMs fabricated using 3-D electrospun junctions is shown in Fig 2. Both membranes show high enough water transport into bipolar junction at current densities up to 500 mA/cm2. BPM#2 with 3-D junction shows lower activation overpotential and 0.8 V less at 500 mA/cm2 than BPM#1 with 2-D junction. Different junction designs are preferred for fuel cell mode and electrolysis mode. Therefore, it is important to find a balance in between that could work in both modes and achieve reversible operation. BPM stability of recycling between fuel cell mode and electrolysis mode will also be shown. Reference [1] Strathmann, H., Krol, J. J., Rapp, H. J., & Eigenberger, G. (1997). Limiting current density and water dissociation in bipolar membranes. Journal of Membrane Science, 125(1), 123-142. [2] Reig, M., Valderrama, C., Gibert, O., & Cortina, J. L. (2016). Selectrodialysis and bipolar membrane electrodialysis combination for industrial process brines treatment: Monovalent-divalent ions separation and acid and base production. Desalination, 399, 88-95. [3] Li, Y. C., Zhou, D., Yan, Z., Gonçalves, R. H., Salvatore, D. A., Berlinguette, C. P., & Mallouk, T. E. (2016). Electrolysis of CO2 to syngas in bipolar membrane-based electrochemical cells. ACS Energy Letters, 1(6), 1149-1153. [4] Luo, J., Vermaas, D. A., Bi, D., Hagfeldt, A., Smith, W. A., & Grätzel, M. (2016). Bipolar Membrane‐Assisted Solar Water Splitting in Optimal pH. Advanced Energy Materials, 6(13), 1600100. [5] Peng, S., Xu, X., Lu, S., Sui, P. C., Djilali, N., & Xiang, Y. (2015). A self-humidifying acidic–alkaline bipolar membrane fuel cell. Journal of Power Sources, 299, 273-279. Figure 1

MICU1 controls cristae junction and spatially anchors mitochondrial Ca2+ uniporter complex

Recently identified core proteins (MICU1, MCU, EMRE) forming the mitochondrial Ca2+ uniporter complex propelled investigations into its physiological workings. Here, we apply structured illumination microscopy to visualize and localize these proteins in living cells. Our data show that MICU1 localizes at the inner boundary membrane (IBM) due to electrostatic interaction of its polybasic domain. Moreover, this exclusive localization of MICU1 is important for the stability of cristae junctions (CJ), cytochrome c release and mitochondrial membrane potential. In contrast to MICU1, MCU and EMRE are homogeneously distributed at the inner mitochondrial membrane under resting conditions. However, upon Ca2+ elevation MCU and EMRE dynamically accumulate at the IBM in a MICU1-dependent manner. Eventually, our findings unveil an essential function of MICU1 in CJ stabilization and provide mechanistic insights of how sophistically MICU1 controls the MCU-Complex while maintaining the structural mitochondrial membrane framework.

SUN-LB665: Stability of the Neuromuscular Junction in Cancer Cachexia

SUN-LB665: Stability of the Neuromuscular Junction in Cancer Cachexia

Efficient heating of single-molecule junctions for thermoelectric studies at cryogenic temperatures

The energy dependent thermoelectric response of a single molecule contains valuable information about its transmission function and its excited states. However, measuring it requires devices that can efficiently heat up one side of the molecule while being able to tune its electrochemical potential over a wide energy range. Furthermore, to increase junction stability, devices need to operate at cryogenic temperatures. In this work, we report on a device architecture to study the thermoelectric properties and the conductance of single molecules simultaneously over a wide energy range. We employ a sample heater in direct contact with the metallic electrodes contacting the single molecule which allows us to apply temperature biases up to ΔT = 60 K with minimal heating of the molecular junction. This makes these devices compatible with base temperatures Tbath &amp;lt; 2 K and enables studies in the linear (ΔT≪Tmolecule) and nonlinear (ΔT≫Tmolecule) thermoelectric transport regimes.

Abstract 505: Adenovirus Targets Connexin43 Gap Junction Expression and Function During Infection

Introduction: Myocarditis leads to pathologic remodeling of the myocardium and arrhythmia. A leading etiological agent of viral myocarditis is human Adenovirus type 5 (Ad5). Individuals affected are at a higher risk of arrhythmogenesis which can lead to sudden cardiac death. Gap junctions, comprised of connexin proteins, provide direct intercellular communication between cardiomyocytes to facilitate electrical coupling. Connexin43 (Cx43) is the predominant connexin expressed in the working myocardium and is tightly regulated by post-translational modifications. Gap junctions are also known to propagate the innate antiviral immune response but the impact of Ad5 infection on Cx43 expression and function is essentially unexplored. Hypothesis: During Ad5 infection Cx43 gap junctions are directly targeted to limit intercellular communication thus precipitating an arrhythmogenic substrate. Methods: Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), keratinocytes (HaCaT), and lentivirus-transduced HaCaTs stably overexpressing Cx43 were infected with Ad5. Biochemical fractionation and pulse chase assays were implemented to determine gap junction and Cx43 stability. Cx43 protein levels and phosphorylation status were determined by western blotting and immunoprecipitation experiments. Confocal immunofluorescence microscopy was employed determine localization and functional of Cx43 during Ad5 infection. Results: Cx43 expression is targeted early in infection with remaining protein localized at the cell-cell boarder during infection. Phosphorylation of Cx43-Ser368 was detected during early Ad5 infection implicating reduced gap junction conductance. In contrast phosphorylation of Cx43-Ser262 is reduced during Ad5 infection with a concomitant increase in protein half-life despite losses in functional gap junction intercellular communication. Conclusion: Cx43 gap junction structures are stabilized during Ad5 infection but directly targeted by specific phosphorylation events to effect channel closure. Insight provided into mechanisms by which Ad5 manipulates Cx43 regulation will provide novel therapeutic avenues to target gap junction function in a broad spectrum of heart disease states.

Unilateral Alar Ligament Injury: Diagnostic, Clinical, and Biomechanical Features

Isolated unilateral alar ligament injury (ALI) is a very rarely diagnosed condition, with only 9 cases reported in the literature. The purpose of this study is to determine clinical, diagnostic, and biomechanical features of unilateral ALI. A total of 6 patients diagnosed with ALI were included in this series. The hospital records and radiologic imaging of admission and follow-ups were investigated retrospectively. Rotation of the neck and/or hyperflexion was always present as a mechanism of injury. The patients were neurologically intact. All patients presented with mild neck pain aggravated by head rotation. On computed tomography (CT) scans, the dens was observed to be displaced to the opposite side. Magnetic resonance imaging (MRI) showed a widened lateral dens-atlas space with high signal intensity. All patients underwent lateral flexion-extension CTs for the confirmation of craniovertebral junction (CVJ) stability. The patients were treated with hard collars. The follow-up MRI of 3 patients obtained at the third month showed normal lateral dens-atlas interval and recovered ligaments. All patients were pain free after 6 months. Unilateral ALI appears to be more common but misdiagnosed than previously thought. Trauma mechanism consists of hyperflexion and contralateral rotation. Neck pain aggravated with rotation is the most significant clinical finding. Dens lateralization is the most important finding in CT scans. An MRI focusing on the CVJ is essential for the diagnosis. The stability of CVJ must be checked with a flexion-extension CT scan. Unilateral ALI is a stable condition and responds to conservative treatment.

Cx43 phosphorylation–mediated effects on ERK and Akt protect against ischemia reperfusion injury and alter the stability of the stress-inducible protein NDRG1

Gap junctions contain intercellular channels that enable intercellular communication of small molecules while also serving as a signaling scaffold. Connexins, the proteins that form gap junctions in vertebrates, are highly regulated and typically have short (<2 h) half-lives. Connexin43 (Cx43), the predominate connexin in the myocardium and epithelial tissues, is phosphorylated on more than a dozen serine residues and interacts with a variety of protein kinases. These interactions regulate Cx43 and gap junction formation and stability. Casein kinase 1 (CK1)-mediated phosphorylation of Cx43 promotes gap junction assembly. Using murine knock-in technology and quantitative PCR, immunoblotting, and immunoprecipitation assays, we show here that mutation of the CK1 phosphorylation sites in Cx43 reduces the levels of total Cx43 in the myocardium and increases Cx43 phosphorylation on sites phosphorylated by extracellular signal-regulated kinase (ERK). In aged myocardium, we found that, compared with WT Cx43, mutant Cx43 expression increases ERK activation, phosphorylation of Akt substrates, and protection from ischemia-induced injury. Our findings also uncovered that Cx43 interacts with the hypoxia-inducible protein N-Myc downstream-regulated gene 1 protein (NDRG1) and that Cx43 phosphorylation status controls this interaction and dramatically affects NDRG1 stability. We propose that, in addition to altering gap junction stability, Cx43 phosphorylation directly and dynamically regulates cellular signaling through ERK and Akt in response to ischemic injury. We conclude that gap junction-dependent NDRG1 regulation might explain some cellular responses to hypoxia.

First person – Anna Bajur

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Anna Bajur is first author on ‘Cytocortex-dependent dynamics of Drosophila Crumbs controls junctional stability and tension during germ band retraction’, published in JCS. Anna conducted the research described in this article while a PhD student in Prof. Elisabeth Knust's lab at Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany. She is now a Research associate/Postdoc in the lab of Dr Katelyn Spillane at King's College London, Department of Physics, UK, investigating the interplay between mechanical forces and the plasma membrane, especially in the context of signalling and modulation of cellular behaviour.

Cytocortex-dependent dynamics of Drosophila Crumbs controls junctional stability and tension during germ band retraction.

During morphogenesis, epithelia undergo dynamic rearrangements, which requires continuous remodelling of junctions and cell shape, but at the same time mechanisms preserving cell polarity and tissue integrity. Apico-basal polarity is key for the localisation of the machinery that enables cell shape changes. The evolutionarily conserved Drosophila Crumbs protein is critical for maintaining apico-basal polarity and epithelial integrity. How Crumbs is maintained in a dynamically developing embryo remains largely unknown. Here, we applied quantitative fluorescence techniques to show that, during germ band retraction, Crumbs dynamics correlates with the morphogenetic activity of the epithelium. Genetic and pharmacological perturbations revealed that the mobile pool of Crumbs is fine-tuned by the actomyosin cortex in a stage-dependent manner. Stabilisation of Crumbs at the plasma membrane depends on a proper link to the actomyosin cortex via an intact FERM-domain-binding site in its intracellular domain, loss of which leads to increased junctional tension and higher DE-cadherin (also known as Shotgun) turnover, resulting in impaired junctional rearrangements. These data define Crumbs as a mediator between polarity and junctional regulation to orchestrate epithelial remodelling in response to changes in actomyosin activity.This article has an associated First Person interview with the first author of the paper.

MAGI1 mediates tumor metastasis through c-Myb/miR-520h/MAGI1 signaling pathway in renal cell carcinoma

Renal cell carcinoma (RCC) is the third most common urological cancer with highly metastatic potential. MAGI1 plays an important role in stabilization of the adherens junctions and has been confirmed to suppress invasiveness and metastasis in multiple cancers in clinic. However, its expression and anti-metastatic ability in RCC are still unclear. In this study, we demonstrated that MAGI1 was markedly decreased in the RCC and indicated poor survival. Furthermore, we found that MAGI1 suppressed the invasion and migration of human RCC cells. Mechanistic investigations revealed that MAGI1 stabilized the PTEN/MAGI1/β-catenin complex to inhibit β-catenin signaling pathway. Moreover, MAGI1 was targeted by miR-520h which was transcriptionally activated by c-Myb. Collectively, our findings suggested that MAGI1mediated tumor metastasis through c-Myb/miR-520h/MAGI1 signaling pathway in RCC.

IL-22-binding protein exacerbates influenza, bacterial super-infection.

Secondary bacterial pneumonia is a significant complication of severe influenza infection and Staphylococcus aureus and Streptococcus pneumoniae are the primary pathogens of interest. IL-22 promotes S. aureus and S. pneumoniae host defense in the lung through epithelial integrity and induction of antimicrobial peptides and is inhibited by the soluble decoy receptor IL-22 binding protein (IL-22BP). Little is known about the effect of the IL-22/IL-22BP regulatory pathway on lung infection, and it has not been studied in the setting of super-infection. We exposed wild-type and IL-22BP−/− mice to influenza A/PR/8/34 for six days prior to infection with S. aureus (USA300) S. pneumoniae. Super-infected IL-22BP−/− mice had decreased bacterial burden and improved survival compared to controls. IL-22BP−/− mice exhibited decreased inflammation, increased lipocalin 2 expression, and deletion of IL-22BP was associated with preserved epithelial barrier function with evidence of improved tight junction stability. Human bronchial epithelial cells treated with IL-22Fc showed evidence of improved tight junctions compared to untreated cells. This study revealed that IL-22BP−/− mice are protected during influenza, bacterial super-infection, suggesting that IL-22BP has a pro-inflammatory role and impairs epithelial barrier function likely through interaction with IL-22