Junctional Adhesion Molecules (JAMs): Cell Adhesion Receptors With Pleiotropic Functions in Cell Physiology and Development

Genetic Mutations in Cell Junction Proteins Associated with Brain Calcification

Intracerebral calcium deposition, classified into primary familial brain calcification (PFBC) and secondary brain calcification, occurs within the brain parenchyma and vasculature. PFBC manifests with progressive motor decline, dysarthria, and cognitive impairment, with limited treatment options available. Recent research has suggested a link between dysfunction of the blood-brain barrier (BBB) and PFBC, with certain genetic variants potentially affecting neurovascular unit (NVU) function, thereby contributing to BBB integrity disruption and brain calcification. Cell junctions play an indispensable role in maintaining the function of NVUs. The pathogenic mechanisms of PFBC-causative genes, such as PDGFRB, PDGFB, MYORG, and JAM2, involve NVU disruption. Cell junctions, such as tight junctions, gap junctions, adherens junctions, desmosomes, hemidesmosomes, and focal adhesions, are vital for cell-cell and cell-extracellular matrix connections, maintaining barrier function, cell adhesion, and facilitating ion and metabolite exchange. Several recent studies have highlighted the role of mutations in genes encoding cell junction proteins in the onset and progression of brain calcification and its related phenotypes. This emerging body of research offers a unique perspective for investigating the underlying mechanisms driving brain calcification. In this review, we conducted an examination of the literature reporting on genetic variants in cell junction proteins associated with brain calcification to delineate potential molecular pathways and investigate genotype-phenotype correlations. This approach not only reinforces the rationale for molecular subtyping of brain calcification but also lays the groundwork for the discovery of novel causative genes involved in pathogenesis. © 2024 International Parkinson and Movement Disorder Society.

Tight junction proteins in glial tumors development and progression

Tight junctions form a paracellular barrier in epithelial and endothelial cells, and they regulate the diffusion of fluids, molecules, and the penetration of cells across tissue compartments. Tight junctions are composed of a group of integral membrane proteins, which include the claudin family, tight junction-associated Marvel protein family, junctional adhesion molecule family, and proteins that anchor the cytoskeleton, such as zonula occludens proteins and the cingulin family. Several factors, such as neurotransmitters or cytokines, and processes like ischemia/hypoxia, inflammation, tumorigenesis, phosphorylation/dephosphorylation, ubiquitination, and palmitoylation, regulate tight junction proteins. Claudins are involved in tumorigenesis processes that lead to glioma formation. In gliomas, there is a noticeable dysregulation of claudins, occludin, and zonula occludens-1 abundance, and their dislocation has been observed. The weakening of intercellular adhesion and cell detachment is responsible for glioma infiltration into surrounding tissues. Furthermore, the paracellular permeability of the blood-brain barrier, formed with the involvement of tight junction proteins, influences the development of peritumoral edema - and, simultaneously, the rate of drug delivery to the glial tumor. Understanding the junctional and paracellular environments in brain tumors is crucial to predicting glial tumor progression and the feasibility of chemotherapeutic drug delivery. This knowledge may also illuminate differences between high and low-grade gliomas.

CCN5 suppresses injury-induced vascular restenosis by inhibiting smooth muscle cell proliferation and facilitating endothelial repair via thymosin β4 and Cd9 pathway

BACKGROUND AND AIMS

Members of the CCN matricellular protein family are crucial in various biological processes. This study aimed to characterize vascular cell-specific effects of CCN5 on neointimal formation and its role in preventing in-stent restenosis (ISR) after percutaneous coronary intervention (PCI).

METHODS

Stent-implanted porcine coronary artery RNA-seq and mouse injury-induced femoral artery neointima single-cell RNA sequencing were performed. Plasma CCN5 levels were measured by enzyme-linked immunosorbent assay. Endothelial cell (EC)- and vascular smooth muscle cell (VSMC)-specific CCN5 loss-of-function and gain-of-function mice were generated. Mass spectrometry and co-immunoprecipitation were conducted to identify CCN5 interacting proteins. Additionally, CCN5 recombinant protein (CCN5rp)-coated stents were deployed to evaluate its anti-ISR effects in a porcine model.

RESULTS

Plasma CCN5 levels were significantly reduced and correlated closely with the degree of restenosis in ISR patients. CCN5 expression was significantly decreased in VSMCs of stent-implanted porcine coronary segments and injured mouse femoral arteries, especially in synthetic VSMCs. In contrast, elevated CCN5 expression was observed in regenerating ECs of injured vessels. Endothelial cell- and VSMC-specific CCN5 deletion mice exhibited exacerbation of injury-induced neointimal hyperplasia, while CCN5 gain-of-function alleviated neointimal formation. Mechanistic studies identified thymosin β4 (Tβ4) as a CCN5 interacting protein in ECs and EC-CCN5 promoted injury repair through Tβ4 cleavage product Ac-SDKP. Also, CCN5rp promoted EC repair to suppress neointimal hyperplasia via interaction with Cd9 extracellular domain. Moreover, implantation with CCN5rp-coated stent significantly increased stent strut coverage with ECs, which suppressed neointimal formation and ultimately alleviated ISR.

CONCLUSIONS

CCN5 exerts a dual protective effect on ISR by inhibiting VSMC proliferation and facilitating EC repair. CCN5rp-coated stent might be promising in the prevention of ISR after PCI.

Integrated transcriptomics and lipidomics reveals protective effect in vascular endothelial barrier of a polysaccharide from Typhae Pollen

Endothelial cell dysfunction caused by inflammation and even vascular leakage are important manifestations of blood stasis syndrome (BSS). Reversible regulation of vascular integrity to cure BSS has attracted considerable interest. Herein, a novel acidic polysaccharide (TPP-4) was purified and characterized from Typhae Pollen, a typical traditional Chinese medicine for treating BSS, especially for bleeding caused by blood stasis. A series of structural characterization methods, including spectroscopic methods (FT-IR and UV), chromatographic methods (HPGPC, HPAEC-PDA and GC-MS) and NMR, have been used to reveal the fine structure of TPP-4. TPP-4 was a homogeneous heteropolysaccharide comprised with RG-I backbone. TPP-4 showed fantastic activities in vascular integrity regulation both in vitro (HUVECs) and in vivo (zebrafish). Transcriptomics revealed that SOX7 and lipid metabolism were the potential targets. Lipidomics showed that TPP-4 could regulate lipid metabolism disorders caused by vascular inflammation, particularly affecting LPE levels. The above regulatory effects were furtherly demonstrated to be related with VEGFA/PI3K/mTOR signaling pathway through various molecular biological experiments.

Wall of Resilience: How the Intestinal Epithelium Prevents Inflammatory Onslaught in the Gut

The intestinal epithelium forms the boundary between the intestinal immune system in the lamina propria and the outside world, the intestinal lumen, which contains a diverse array of microbial and environmental antigens. Composed of specialized cells, this epithelial monolayer has an exceptional turnover rate. Differentiated epithelial cells are released into the intestinal lumen within a few days, at the villus tip, a process that requires strict regulation. Dysfunction of the epithelial barrier increases the intestinal permeability and paves the way for luminal antigens to pass into the intestinal serosa. Stem cells at the bottom of Lieberkühn crypts provide a constant supply of mature epithelial cells. Differentiated intestinal epithelial cells exhibit a diverse array of mechanisms that enable communication with surrounding cells, fortification against microorganisms, and orchestration of nutrient absorption and hormonal balance. Furthermore, tight junctions regulate paracellular permeability properties, and their disruption can lead to an impairment of the intestinal barrier, allowing inflammation to develop or further progress. Intestinal epithelial cells provide a communication platform through which they maintain homeostasis with a spectrum of entities including immune cells, neuronal cells, and connective tissue cells. This homeostasis can be disrupted in disease, such as inflammatory bowel disease. Patients suffering from inflammatory bowel disease show an impaired gut barrier, dysregulated cellular communication, and aberrant proliferation and demise of cells. This review summarizes the individual cellular and molecular mechanisms pivotal for upholding the integrity of the intestinal epithelial barrier and shows how these can be disrupted in diseases, such as inflammatory bowel disease.

Exploring Mechanical Forces Shaping Self-Organization and Morphogenesis During Early Embryo Development

Embryonic development is a dynamic process orchestrated by a delicate interplay of biochemical and biophysical factors. While the role of genetics and biochemistry in embryogenesis has been extensively studied, recent research has highlighted the significance of mechanical regulation in shaping and guiding this intricate process. Here, we provide an overview of the current understanding of the mechanical regulation of embryo development. We explore how mechanical forces generated by cells and tissues play a crucial role in driving the development of different stages. We examine key morphogenetic processes such as compaction, blastocyst formation, implantation, and egg cylinder formation, and discuss the mechanical mechanisms and cues involved. By synthesizing the current body of literature, we highlight the emerging concepts and open questions in the field of mechanical regulation. We aim to provide an overview of the field, inspiring future investigations and fostering a deeper understanding of the mechanical aspects of embryo development.

Multilayered proteomics reveals that JAM-A promotes breast cancer progression via regulation of amino acid transporter LAT1

Recent studies have shown that transmembrane-type tight junction proteins are upregulated in various cancers compared with their levels in normal tissues and are involved in cancer progression, suggesting that they are potential therapeutic targets. Here, we demonstrated the expression profile and a novel role of junctional adhesion molecule-A (JAM-A) in breast cancer. Immunohistochemistry of surgical specimens showed that JAM-A was highly expressed from carcinoma in situ lesions, as in other adenocarcinomas, with higher expression in invasive carcinomas. High expression of JAM-A contributed to malignant aspects such as lymph node metastasis and lymphatic involvement positivity. In breast cancer cells, JAM-A expression status affects malignant potentials including proliferation and migration. Multilayered proteomics revealed that JAM-A interacts with the amino acid transporter LAT1 in breast cancer cells. JAM-A regulates the expression of LAT1 and interacts with it on the whole cell membrane, leading to enhanced amino acid uptake to promote tumor growth. Double high expression of JAM-A and LAT1 predicts poor prognosis in patients with breast cancer. Of note, an antibody against an extracellular domain of JAM-A suppressed the proliferation of breast cancer cells. Our findings indicate the possibility of JAM-A-targeted therapy ideally combined with LAT1-targeted therapy as a new therapeutic strategy against breast cancer.

Single nuclei RNA-seq reveals a medium spiny neuron glutamate excitotoxicity signature prior to the onset of neuronal death in an ovine Huntington's disease model

Huntington's disease (HD) is a neurodegenerative genetic disorder caused by an expansion in the CAG repeat tract of the huntingtin (HTT) gene resulting in behavioural, cognitive, and motor defects. Current knowledge of disease pathogenesis remains incomplete, and no disease course-modifying interventions are in clinical use. We have previously reported the development and characterisation of the OVT73 transgenic sheep model of HD. The 73 polyglutamine repeat is somatically stable and therefore likely captures a prodromal phase of the disease with an absence of motor symptomatology even at 5-years of age and no detectable striatal cell loss. To better understand the disease-initiating events we have undertaken a single nuclei transcriptome study of the striatum of an extensively studied cohort of 5-year-old OVT73 HD sheep and age matched wild-type controls. We have identified transcriptional upregulation of genes encoding N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors in medium spiny neurons, the cell type preferentially lost early in HD. Further, we observed an upregulation of astrocytic glutamate uptake transporters and medium spiny neuron GABAA receptors, which may maintain glutamate homeostasis. Taken together, these observations support the glutamate excitotoxicity hypothesis as an early neurodegeneration cascade-initiating process but the threshold of toxicity may be regulated by several protective mechanisms. Addressing this biochemical defect early may prevent neuronal loss and avoid the more complex secondary consequences precipitated by cell death.

RhoGDI1 regulates cell-cell junctions in polarized epithelial cells

Cell-cell contact formation of polarized epithelial cells is a multi-step process that involves the co-ordinated activities of Rho family small GTPases. Consistent with the central role of Rho GTPases, a number of Rho guanine nucleotide exchange factors (GEFs) and Rho GTPase-activating proteins (GAPs) have been identified at cell-cell junctions at various stages of junction maturation. As opposed to RhoGEFs and RhoGAPs, the role of Rho GDP dissociation inhibitors (GDIs) during cell-cell contact formation is poorly understood. Here, we have analyzed the role of RhoGDI1/ARHGDIA, a member of the RhoGDI family, during cell-cell contact formation of polarized epithelial cells. Depletion of RhoGDI1 delays the development of linear cell-cell junctions and the formation of barrier-forming tight junctions. In addition, RhoGDI1 depletion impairs the ability of cells to stop migration in response to cell collision and increases the migration velocity of collectively migrating cells. We also find that the cell adhesion receptor JAM-A promotes the recruitment of RhoGDI1 to cell-cell contacts. Our findings implicate RhoGDI1 in various processes involving the dynamic reorganization of cell-cell junctions.

Sodium-Glucose Cotransporter Inhibitors: Cellular Mechanisms Involved in the Lipid Metabolism and the Treatment of Chronic Kidney Disease Associated with Metabolic Syndrome

Metabolic syndrome (MetS) is a multifactorial condition that significantly increases the risk of cardiovascular disease and chronic kidney disease (CKD). Recent studies have emphasized the role of lipid dysregulation in activating cellular mechanisms that contribute to CKD progression in the context of MetS. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have demonstrated efficacy in improving various components of MetS, including obesity, dyslipidemia, and insulin resistance. While SGLT2i have shown cardioprotective benefits, the underlying cellular mechanisms in MetS and CKD remain poorly studied. Therefore, this review aims to elucidate the cellular mechanisms by which SGLT2i modulate lipid metabolism and their impact on insulin resistance, mitochondrial dysfunction, oxidative stress, and CKD progression. We also explore the potential benefits of combining SGLT2i with other antidiabetic drugs. By examining the beneficial effects, molecular targets, and cytoprotective mechanisms of both natural and synthetic SGLT2i, this review provides a comprehensive understanding of their therapeutic potential in managing MetS-induced CKD. The information presented here highlights the significance of SGLT2i in addressing the complex interplay between metabolic dysregulation, lipid metabolism dysfunction, and renal impairment, offering clinicians and researchers a valuable resource for developing improved treatment strategies and personalized approaches for patients with MetS and CKD.

Identification and Validation of JAM-A as a Novel Prognostic and Immune Factor in Human Tumors

Junctional adhesion molecule-A (JAM-A), also known as F11 receptor (F11R), is a transmembrane glycoprotein that is involved in various biological processes, including cancer initiation and progression. However, the functional characteristics and significance of JAM-A in pan-cancer remain unexplored. In this study, we used multiple databases to gain a comprehensive understanding of JAM-A in human cancers. JAM-A was widely expressed in various tissues, mainly located on the microtubules and cell junctions. Aberrant expression of JAM-A was detected in multiple cancers at both mRNA and protein levels, which can be correlated with poorer prognosis and may be attributed to genetic alterations and down-regulated DNA methylation. JAM-A expression was also associated with immune infiltration and may affect immunotherapy responses in several cancers. Functional enrichment analysis indicated that JAM-A participated in tight junction and cancer-related pathways. In vitro experiments verified that JAM-A knockdown suppressed the proliferation and migration abilities of breast cancer cells and liver cancer cells. Overall, our study suggests that JAM-A is a pan-cancer regulator and a potential biomarker for predicting prognosis and immune-therapeutic responses for different tumors.

Tuning apicobasal polarity and junctional recycling in the hemogenic endothelium orchestrates the morphodynamic complexity of emerging pre-hematopoietic stem cells

Hematopoietic stem cells emerge in the embryo from an aortic-derived tissue called the hemogenic endothelium (HE). The HE appears to give birth to cells of different nature and fate but the molecular principles underlying this complexity are largely unknown. Here we show, in the zebrafish embryo, that two cell types emerge from the aortic floor with radically different morphodynamics. With the support of live imaging, we bring evidence suggesting that the mechanics underlying the two emergence types rely, or not, on apicobasal polarity establishment. While the first type is characterized by reinforcement of apicobasal polarity and maintenance of the apical/luminal membrane until release, the second type emerges via a dynamic process reminiscent of trans-endothelial migration. Interfering with Runx1 function suggests that the balance between the two emergence types depends on tuning apicobasal polarity at the level of the HE. In support of this and unexpectedly, we show that Pard3ba - one of the four Pard3 proteins expressed in the zebrafish - is sensitive to interference with Runx1 activity, in aortic endothelial cells. This supports the idea of a signaling cross talk controlling cell polarity and its associated features, between aortic and hemogenic cells. In addition, using new transgenic fish lines that express Junctional Adhesion Molecules and functional interference, we bring evidence for the essential role of ArhGEF11/PDZ-RhoGEF in controlling the HE-endothelial cell dynamic interface, including cell-cell intercalation, which is ultimately required for emergence completion. Overall, we highlight critical cellular and dynamic events of the endothelial-to-hematopoietic transition that support emergence complexity, with a potential impact on cell fate.

The Basic Requirement of Tight Junction Proteins in Blood-Brain Barrier Function and Their Role in Pathologies

This review addresses the role of tight junction proteins at the blood-brain barrier (BBB). Their expression is described, and their role in physiological and pathological processes at the BBB is discussed. Based on this, new approaches are depicted for paracellular drug delivery and diagnostics in the treatment of cerebral diseases. Recent data provide convincing evidence that, in addition to its impairment in the course of diseases, the BBB could be involved in the aetiology of CNS disorders. Further progress will be expected based on new insights in tight junction protein structure and in their involvement in signalling pathways.

Systematic-Narrative Hybrid Literature Review: Crosstalk between Gastrointestinal Renin-Angiotensin and Dopaminergic Systems in the Regulation of Intestinal Permeability by Tight Junctions

In the first part of this article, the role of intestinal epithelial tight junctions (TJs), together with gastrointestinal dopaminergic and renin-angiotensin systems, are narratively reviewed to provide sufficient background. In the second part, the current experimental data on the interplay between gastrointestinal (GI) dopaminergic and renin-angiotensin systems in the regulation of intestinal epithelial permeability are reviewed in a systematic manner using the PRISMA methodology. Experimental data confirmed the copresence of DOPA decarboxylase (DDC) and angiotensin converting enzyme 2 (ACE2) in human and rodent enterocytes. The intestinal barrier structure and integrity can be altered by angiotensin (1-7) and dopamine (DA). Both renin-angiotensin and dopaminergic systems influence intestinal Na+/K+-ATPase activity, thus maintaining electrolyte and nutritional homeostasis. The colocalization of B0AT1 and ACE2 indicates the direct role of the renin-angiotensin system in amino acid absorption. Yet, more studies are needed to thoroughly define the structural and functional interaction between TJ-associated proteins and GI renin-angiotensin and dopaminergic systems.

Junctional Adhesion Molecule (JAM)-C recruitment of Pard3 and drebrin to cell contacts initiates neuron-glia recognition and layer-specific cell sorting in developing cerebella

Sorting maturing neurons into distinct layers is critical for brain development, with disruptions leading to neurological disorders and pediatric cancers. Lamination coordinates where, when, and how cells interact, facilitating events that direct migrating neurons to their destined positions within emerging neural networks and control the wiring of connections in functional circuits. While the role of adhesion molecule expression and presentation in driving adhesive recognition during neuronal migration along glial fibers is recognized, the mechanisms by which the spatial arrangement of these molecules on the cell surface dictates adhesive specificity and translates contact-based external cues into intracellular responses like polarization and cytoskeletal organization remain largely unexplored. We used the cerebellar granule neuron (CGN) system to demonstrate that JAM-C receptor cis-binding on the same cell and trans-binding to neighboring cells controls the recruitment of the Pard3 polarity protein and drebrin microtubule-actin crosslinker at CGN to glial adhesion sites, complementing previous studies that showed Pard3 controls JAM-C exocytic surface presentation. Leveraging advanced imaging techniques, specific probes for cell recognition, and analytical methods to dissect adhesion dynamics, our findings reveal: 1) JAM-C cis or trans mutants result in reduced adhesion formation between CGNs and cerebellar glia, 2) these mutants exhibit delayed recruitment of Pard3 at the adhesion sites, and 3) CGNs with JAM-C mutations experience postponed sorting and entry into the cerebellar molecular layer (ML). By developing a conditional system to image adhesion components from two different cells simultaneously, we made it possible to investigate the dynamics of cell recognition on both sides of neuron-glial contacts and the subsequent recruitment of proteins required for CGN migration. This system and an approach that calculates local correlation based on convolution kernels at the cell adhesions site revealed that CGN to CGN JAM recognition preferentially recruits higher levels of Pard3 and drebrin than CGN to glia JAM recognition. The long latency time of CGNs in the inner external germinal layer (EGL) can be attributed to the combined strength of CGN-CGN contacts and the less efficient Pard3 recruitment by CGN-BG contacts, acting as gatekeepers to ML entry. As CGNs eventually transition to glia binding for radial migration, our research demonstrates that establishing permissive JAM-recognition sites on glia via cis and trans interactions of CGN JAM-C serves as a critical temporal checkpoint for sorting at the EGL to ML boundary. This mechanism integrates intrinsic and extrinsic cellular signals, facilitating heterotypic cell sorting into the ML and dictating the precise spatial organization within the cerebellar architecture.

ITF2357 regulates NF-κB signaling pathway to protect barrier integrity in retinal pigment epithelial cells

The robust integrity of the retinal pigment epithelium (RPE), which contributes to the outer brain retina barrier (oBRB), is compromised in several retinal degenerative and vascular disorders, including diabetic macular edema (DME). This study evaluates the role of a new generation of histone deacetylase inhibitor (HDACi), ITF2357, in regulating outer blood-retinal barrier function and investigates the underlying mechanism of action in inhibiting TNFα-induced damage to RPE integrity. Using the immortalized RPE cell line (ARPE-19), ITF2357 was found to be non-toxic between 50 nM and 5 μM concentrations. When applied as a pre-treatment in conjunction with an inflammatory cytokine, TNFα, the HDACi was safe and effective in preventing epithelial permeability by fortifying tight junction (ZO-1, -2, -3, occludin, claudin-1, -2, -3, -5, -19) and adherens junction (E-cadherin, Nectin-1) protein expression post-TNFα stress. Mechanistically, ITF2357 depicted a late action at 24 h via attenuating IKK, IκBα, and p65 phosphorylation and ameliorated the expression of IL-1β, IL-6, and MCP-1. Also, ITF2357 delayed IκBα synthesis and turnover. The use of Bay 11-7082 and MG132 further uncovered a possible role for ITF2357 in non-canonical NF-κB activation. Overall, this study revealed the protection effects of ITF2357 by regulating the turnover of tight and adherens junction proteins and modulating NF-κB signaling pathway in the presence of an inflammatory stressor, making it a potential therapeutic application for retinal vascular diseases such as DME with compromised outer blood-retinal barrier.

Aiming the magic bullet: targeted delivery of imaging and therapeutic agents to solid tumors by pHLIP peptides

The family of pH (Low) Insertion Peptides (pHLIP) comprises a tumor-agnostic technology that uses the low pH (or high acidity) at the surfaces of cells within the tumor microenvironment (TME) as a targeted biomarker. pHLIPs can be used for extracellular and intracellular delivery of a variety of imaging and therapeutic payloads. Unlike therapeutic delivery targeted to specific receptors on the surfaces of particular cells, pHLIP targets cancer, stromal and some immune cells all at once. Since the TME exhibits complex cellular crosstalk interactions, simultaneous targeting and delivery to different cell types leads to a significant synergistic effect for many agents. pHLIPs can also be positioned on the surfaces of various nanoparticles (NPs) for the targeted intracellular delivery of encapsulated payloads. The pHLIP technology is currently advancing in pre-clinical and clinical applications for tumor imaging and treatment.

TMEM25 is a Par3-binding protein that attenuates claudin assembly during tight junction development

The tight junction (TJ) in epithelial cells is formed by integral membrane proteins and cytoplasmic scaffolding proteins. The former contains the claudin family proteins with four transmembrane segments, while the latter includes Par3, a PDZ domain-containing adaptor that organizes TJ formation. Here we show the single membrane-spanning protein TMEM25 localizes to TJs in epithelial cells and binds to Par3 via a PDZ-mediated interaction with its C-terminal cytoplasmic tail. TJ development during epithelial cell polarization is accelerated by depletion of TMEM25, and delayed by overexpression of TMEM25 but not by that of a C-terminally deleted protein, indicating a regulatory role of TMEM25. TMEM25 associates via its N-terminal extracellular domain with claudin-1 and claudin-2 to suppress their cis- and trans-oligomerizations, both of which participate in TJ strand formation. Furthermore, Par3 attenuates TMEM25-claudin association via binding to TMEM25, implying its ability to affect claudin oligomerization. Thus, the TJ protein TMEM25 appears to negatively regulate claudin assembly in TJ formation, which regulation is modulated by its interaction with Par3.

JAM-C Is Important for Lens Epithelial Cell Proliferation and Lens Fiber Maturation in Murine Lens Development

Purpose

The underlying mechanism of congenital cataracts caused by deficiency or mutation of junctional adhesion molecule C (JAM-C) gene remains unclear. Our study aims to elucidate the abnormal developmental process in Jamc-/- lenses and reveal the genes related to lens development that JAM-C may regulate.

Methods

Jamc knockout (Jamc-/-) mouse embryos and pups were generated for in vivo studies. Four key developmental stages from embryonic day (E) 12.5 to postnatal day (P) 0.5 were selected for the following experiments. Hematoxylin and eosin staining was used for histological analysis. The 5-bromo-2'-deoxyuridine (BrdU) incorporation assay and TUNEL staining were performed to label lens epithelial cell (LEC) proliferation and apoptosis, respectively. Immunofluorescence and Western blot were used to analyze the markers of lens epithelium, cell cycle exit, and lens fiber differentiation.

Results

JAM-C was expressed throughout the process of lens development. Deletion of Jamc resulted in decreased lens size and disorganized lens fibers, which arose from E16.5 and aggravated gradually. The LECs of Jamc-/- lenses showed decreased quantity and proliferation, accompanied with reduction of key transcription factor, FOXE3. The fibers in Jamc-/- lenses were disorganized. Moreover, Jamc-deficient lens fibers showed significantly altered distribution patterns of Cx46 and Cx50. The marker of fiber homeostasis, γ-crystallin, was also decreased in the inner cortex and core fibers of Jamc-/- lenses.

Conclusions

Deletion of JAM-C exhibits malfunction of LEC proliferation and fiber maturation during murine lens development, which may be related to the downregulation of FOXE3 expression and abnormal localization patterns of Cx46 and Cx50.

Cell Adhesion at the Tight Junctions: New Aspects and New Functions

Tight junctions (TJ) are cell-cell adhesive structures that define the permeability of barrier-forming epithelia and endothelia. In contrast to this seemingly static function, TJs display a surprisingly high molecular complexity and unexpected dynamic regulation, which allows the TJs to maintain a barrier in the presence of physiological forces and in response to perturbations. Cell-cell adhesion receptors play key roles during the dynamic regulation of TJs. They connect individual cells within cellular sheets and link sites of cell-cell contacts to the underlying actin cytoskeleton. Recent findings support the roles of adhesion receptors in transmitting mechanical forces and promoting phase separation. In this review, we discuss the newly discovered functions of cell adhesion receptors localized at the TJs and their role in the regulation of the barrier function.

Transcriptomic profiling of tissue environments critical for post-embryonic patterning and morphogenesis of zebrafish skin

Pigment patterns and skin appendages are prominent features of vertebrate skin. In zebrafish, regularly patterned pigment stripes and an array of calcified scales form simultaneously in the skin during post-embryonic development. Understanding the mechanisms that regulate stripe patterning and scale morphogenesis may lead to the discovery of fundamental mechanisms that govern the development of animal form. To learn about cell types and signaling interactions that govern skin patterning and morphogenesis, we generated and analyzed single-cell transcriptomes of skin from wild-type fish as well as fish having genetic or transgenically induced defects in squamation or pigmentation. These data reveal a previously undescribed population of epidermal cells that express transcripts encoding enamel matrix proteins, suggest hormonal control of epithelial-mesenchymal signaling, clarify the signaling network that governs scale papillae development, and identify a critical role for the hypodermis in supporting pigment cell development. Additionally, these comprehensive single-cell transcriptomic data representing skin phenotypes of biomedical relevance should provide a useful resource for accelerating the discovery of mechanisms that govern skin development and homeostasis.

Tight junction proteins related to blood-brain barrier and their regulatory signaling pathways in ischemic stroke

Tight junctions (TJs) are crucial for intercellular connections. The abnormal expression of proteins related to TJs can result in TJ destruction, structural damage, and endothelial and epithelial cell dysfunction. These factors are associated with the occurrence and progression of several diseases. Studies have shown that blood-brain barrier (BBB) damage and dysfunction are the prominent pathological features of stroke. TJs are directly associated with the BBB integrity. In this article, we first discuss the structure and function of BBB TJ-related proteins before focusing on the crucial events that cause TJ dysfunction and BBB damage, as well as the regulatory mechanisms that affect the qualitative and quantitative expression of TJ proteins during ischemic stroke. Multiple regulatory mechanisms, including phosphorylation, matrix metalloproteinases (MMPs), and microRNAs, regulate TJ-related proteins and affect BBB permeability. Some signaling pathways and mechanisms have been demonstrated to have dual functions. Hopefully, our understanding of the regulation of BBB TJs in ischemic stroke will be applied to the development of targeted medications and therapeutic therapies.

Spatial Transcriptomic Analysis of Focal and Normal Areas of Myocyte Disarray in Human Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM) is a common inherited disorder that can lead to heart failure and sudden cardiac death, characterized at the histological level by focal areas of myocyte disarray, hypertrophy and fibrosis, and only a few disease-targeted therapies exist. To identify the focal and spatially restricted alterations in the transcriptional pathways and reveal novel therapeutic targets, we performed a spatial transcriptomic analysis of the areas of focal myocyte disarray compared to areas of normal tissue using a commercially available platform (GeoMx, nanoString). We analyzed surgical myectomy tissue from four patients with HCM and the control interventricular septum tissue from two unused organ donor hearts that were free of cardiovascular disease. Histological sections were reviewed by an expert pathologist, and 72 focal areas with varying degrees of myocyte disarray (normal, mild, moderate, severe) were chosen for analysis. Areas of interest were interrogated with the Human Cancer Transcriptome Atlas designed to profile 1800 transcripts. Differential expression analysis revealed significant changes in gene expression between HCM and the control tissue, and functional enrichment analysis indicated that these genes were primarily involved in interferon production and mitochondrial energetics. Within the HCM tissue, differentially expressed genes between areas of normal and severe disarray were enriched for genes related to mitochondrial energetics and the extracellular matrix in severe disarray. An analysis of the gene expression of the ligand-receptor pair revealed that the HCM tissue exhibited downregulation of platelet-derived growth factor (PDGF), NOTCH, junctional adhesion molecule, and CD46 signaling while showing upregulation of fibronectin, CD99, cadherin, and amyloid precursor protein signaling. A deconvolution analysis utilizing the matched single nuclei RNA-sequencing (snRNA-seq) data to determine cell type composition in areas of interest revealed significant differences in fibroblast and vascular cell composition in areas of severe disarray when compared to normal areas in HCM samples. Cell composition in the normal areas of the control tissue was also divergent from the normal areas in HCM samples, which was consistent with the differential expression results. Overall, our data identify novel and potential disease-modifying targets for therapy in HCM.

JAM-A Overexpression in Human Umbilical Cord-Derived Mesenchymal Stem Cells Accelerated the Angiogenesis of Diabetic Wound By Enhancing Both Paracrine Function and Survival of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) is promising in promoting wound healing mainly due to their paracrine function. Nonetheless, the transplanted MSCs presented poor survival with cell dysfunction and paracrine problem in diabetic environment, thus limiting their therapeutic efficacy and clinical application. JAM-A, an adhesion molecule, has been reported to play multi-functional roles in diverse cells. We therefore investigated the potential effect of JAM-A on MSCs under diabetic environment and explored the underlying mechanism. Indeed, high-glucose condition inhibited MSCs viability and JAM-A expression. However, JAM-A abnormality was rescued by lentivirus transfection and JAM-A overexpression promoted MSCs proliferation, migration and adhesion under hyperglycemia. Moreover, JAM-A overexpression attenuated high-glucose-induced ROS production and MSCs apoptosis. The bio-effects of JAM-A on MSCs under hyperglycemia were confirmed by RNA-seq with enrichment analyses. Moreover, Luminex chip results showed JAM-A overexpression dramatically upregulated PDGF-BB and VEGF in the supernatant of MSCs, which was verified by RT-qPCR and western blotting. The supernatant was further found to facilitate HUVECs proliferation, migration and angiogenesis under hyperglycemia. In vivo experiments revealed JAM-A overexpression significantly enhanced MSCs survival, promoted wound angiogenesis, and thus accelerated diabetic wound closure, partially by enhancing PDGF-BB and VEGF expression. This study firstly demonstrated that JAM-A expression of MSCs was inhibited upon high-glucose stimulation. JAM-A overexpression alleviated high-glucose-induced MSCs dysfunction, enhanced their anti-oxidative capability, protected MSCs from hyperglycemia-induced apoptosis and improved their survival, thus strengthening MSCs paracrine function to promote angiogenesis and significantly accelerating diabetic wound healing, which offers a promising strategy to maximize MSCs-based therapy in diabetic wound.

The blood-brain barrier: structure, regulation, and drug delivery

Blood-brain barrier (BBB) is a natural protective membrane that prevents central nervous system (CNS) from toxins and pathogens in blood. However, the presence of BBB complicates the pharmacotherapy for CNS disorders as the most chemical drugs and biopharmaceuticals have been impeded to enter the brain. Insufficient drug delivery into the brain leads to low therapeutic efficacy as well as aggravated side effects due to the accumulation in other organs and tissues. Recent breakthrough in materials science and nanotechnology provides a library of advanced materials with customized structure and property serving as a powerful toolkit for targeted drug delivery. In-depth research in the field of anatomical and pathological study on brain and BBB further facilitates the development of brain-targeted strategies for enhanced BBB crossing. In this review, the physiological structure and different cells contributing to this barrier are summarized. Various emerging strategies for permeability regulation and BBB crossing including passive transcytosis, intranasal administration, ligands conjugation, membrane coating, stimuli-triggered BBB disruption, and other strategies to overcome BBB obstacle are highlighted. Versatile drug delivery systems ranging from organic, inorganic, and biologics-derived materials with their synthesis procedures and unique physio-chemical properties are summarized and analyzed. This review aims to provide an up-to-date and comprehensive guideline for researchers in diverse fields, offering perspectives on further development of brain-targeted drug delivery system.

The activation of EP300 by F11R leads to EMT and acts as a prognostic factor in triple-negative breast cancers

Cancer progression is influenced by junctional adhesion molecule (JAM) family members. The relationship between JAM family members and different types of cancer was examined using The Cancer Genome Atlas dataset. mRNA levels of the F11R (F11 receptor) in tumours were inversely correlated to the expression of JAM-2 and JAM-3. This relationship was unique to breast cancer (BCa) and was associated with poor prognosis (p = 0.024, hazard ratio = 1.44 [1.05-1.99]). A 50-gene molecular signature (prediction analysis of microarray 50) was used to subtype BCa. F11R mRNA expression significantly increased in human epidermal growth factor receptor 2 (HER2)-enriched (p = 0.0035) and basal-like BCa tumours (p = 0.0005). We evaluated F11R protein levels in two different compositions of BCa subtype patient tissue array cohorts to determine the relationship between BCa subtype and prognosis. Immunohistochemistry staining revealed that a high F11R protein level was associated with poor overall survival (p < 0.001; Taipei Medical University [TMU] cohort, p < 0.001; Kaohsiung Veterans General Hospital [KVGH] cohort) or disease-free survival (p < 0.001 [TMU cohort], p = 0.034 [KVGH cohort]) in patients with BCa. Comparison of F11R levels in different subtypes revealed the association of poor prognosis with high levels of F11R among luminal (p < 0.001 [TMU cohort], p = 0.027 [KVGH cohort]), HER2 positive (p = 0.018 [TMU cohort], p = 0.037 [KVGH cohort]), and triple-negative (p = 0.013 [TMU cohort], p = 0.037 [KVGH cohort]) BCa. F11R-based RNA microarray analysis and Ingenuity Pathway Analysis were successful in profiling the detailed gene ontology of triple-negative BCa cells regulated by F11R. The EP300 transcription factor was highly correlated with F11R in BCa (R = 0.51, p < 0.001). By analysing these F11R-affected molecules with the L1000CDs datasets, we were able to predict some repurposing drugs for potential application in F11R-positive BCa treatment.

Junctional adhesion molecule-A is dispensable for myeloid cell recruitment and diversification in the tumor microenvironment

Junctional adhesion molecule-A (JAM-A), expressed on the surface of myeloid cells, is required for extravasation at sites of inflammation and may also modulate myeloid cell activation. Infiltration of myeloid cells is a common feature of tumors that drives disease progression, but the function of JAM-A in this phenomenon and its impact on tumor-infiltrating myeloid cells is little understood. Here we show that systemic cancer-associated inflammation in mice enhanced JAM-A expression selectively on circulating monocytes in an IL1β-dependent manner. Using myeloid-specific JAM-A-deficient mice, we found that JAM-A was dispensable for recruitment of monocytes and other myeloid cells to tumors, in contrast to its reported role in inflammation. Single-cell RNA sequencing revealed that loss of JAM-A did not influence the transcriptional reprogramming of myeloid cells in the tumor microenvironment. Overall, our results support the notion that cancer-associated inflammation can modulate the phenotype of circulating immune cells, and we demonstrate that tumors can bypass the requirement of JAM-A for myeloid cell recruitment and reprogramming.

Deciphering the Genetic Crosstalk between Microglia and Oligodendrocyte Precursor Cells during Demyelination and Remyelination Using Transcriptomic Data

Demyelinating disorders show impaired remyelination due to failure in the differentiation of oligodendrocyte progenitor cells (OPCs) into mature myelin-forming oligodendrocytes, a process driven by microglia-OPC crosstalk. Through conducting a transcriptomic analysis of microarray studies on the demyelination-remyelination cuprizone model and using human samples of multiple sclerosis (MS), we identified molecules involved in this crosstalk. Differentially expressed genes (DEGs) of specific regions/cell types were detected in GEO transcriptomic raw data after cuprizone treatment and in MS samples, followed by functional analysis with GO terms and WikiPathways. Additionally, microglia-OPC crosstalk between microglia ligands, OPC receptors and target genes was examined with the NicheNet model. We identified 108 and 166 DEGs in the demyelinated corpus callosum (CC) at 2 and 4 weeks of cuprizone treatment; 427 and 355 DEGs in the remyelinated (4 weeks of cuprizone treatment + 14 days of normal diet) compared to 2- and 4-week demyelinated CC; 252 DEGs in MS samples and 2730 and 12 DEGs in OPC and microglia of 4-week demyelinated CC. At this time point, we found 95 common DEGs in the CC and OPCs, and one common DEG in microglia and OPCs, mostly associated with myelin and lipid metabolism. Crosstalk analysis identified 47 microglia ligands, 43 OPC receptors and 115 OPC target genes, all differentially expressed in cuprizone-treated samples and associated with myelination. Our differential expression pipeline identified demyelination/remyelination transcriptomic biomarkers in studies using diverse platforms and cell types/tissues. Cellular crosstalk analysis yielded novel markers of microglia ligands, OPC receptors and target genes.

Integrating digital pathology with transcriptomic and epigenomic tools for predicting metastatic uterine tumor aggressiveness

The incidence of new cancer cases is expected to increase significantly in the future, posing a worldwide problem. In this regard, precision oncology and its diagnostic tools are essential for developing personalized cancer treatments. Digital pathology (DP) is a particularly key strategy to study the interactions of tumor cells and the tumor microenvironment (TME), which play a crucial role in tumor initiation, progression and metastasis. The purpose of this study was to integrate data on the digital patterns of reticulin fiber scaffolding and the immune cell infiltrate, transcriptomic and epigenetic profiles in aggressive uterine adenocarcinoma (uADC), uterine leiomyosarcoma (uLMS) and their respective lung metastases, with the aim of obtaining key TME biomarkers that can help improve metastatic prediction and shed light on potential therapeutic targets. Automatized algorithms were used to analyze reticulin fiber architecture and immune infiltration in colocalized regions of interest (ROIs) of 133 invasive tumor front (ITF), 89 tumor niches and 70 target tissues in a total of six paired samples of uADC and nine of uLMS. Microdissected tissue from the ITF was employed for transcriptomic and epigenetic studies in primary and metastatic tumors. Reticulin fiber scaffolding was characterized by a large and loose reticular fiber network in uADC, while dense bundles were found in uLMS. Notably, more similarities between reticulin fibers were observed in paired uLMS then paired uADCs. Transcriptomic and multiplex immunofluorescence-based immune profiling showed a higher abundance of T and B cells in primary tumor and in metastatic uADC than uLMS. Moreover, the epigenetic signature of paired samples in uADCs showed more differences than paired samples in uLMS. Some epigenetic variation was also found between the ITF of metastatic uADC and uLMS. Altogether, our data suggest a correlation between morphological and molecular changes at the ITF and the degree of aggressiveness. The use of DP tools for characterizing reticulin scaffolding and immune cell infiltration at the ITF in paired samples together with information provided by omics analyses in a large cohort will hopefully help validate novel biomarkers of tumor aggressiveness, develop new drugs and improve patient quality of life in a much more efficient way.

A Functional Network Driven by MicroRNA-125a Regulates Monocyte Trafficking in Acute Inflammation

During the onset of acute inflammation, rapid trafficking of leukocytes is essential to mount appropriate immune responses towards an inflammatory insult. Monocytes are especially indispensable for counteracting the inflammatory stimulus, neutralising the noxa and reconstituting tissue homeostasis. Thus, monocyte trafficking to the inflammatory sites needs to be precisely orchestrated. In this study, we identify a regulatory network driven by miR-125a that affects monocyte adhesion and chemotaxis by the direct targeting of two adhesion molecules, i.e., junction adhesion molecule A (JAM-A), junction adhesion molecule-like (JAM-L) and the chemotaxis-mediating chemokine receptor CCR2. By investigating monocytes isolated from patients undergoing cardiac surgery, we found that acute yet sterile inflammation reduces miR-125a levels, concomitantly enhancing the expression of JAM-A, JAM-L and CCR2. In contrast, TLR-4-specific stimulation with the pathogen-associated molecular pattern (PAMP) LPS, usually present within the perivascular inflamed area, resulted in dramatically induced levels of miR-125a with concomitant repression of JAM-A, JAM-L and CCR2 as early as 3.5 h. Our study identifies miR-125a as an important regulator of monocyte trafficking and shows that the phenotype of human monocytes is strongly influenced by this miRNA, depending on the type of inflammatory stimulus.

Intestinal brush border formation requires a TMIGD1-based intermicrovillar adhesion complex

Intestinal epithelial cells absorb nutrients through the brush border, composed of dense arrays of highly ordered microvilli at their apical membranes. A protocadherin-based intermicrovillar adhesion complex localized at microvilli tips mediates microvilli packing and organization. Here, we identified a second adhesion complex localized at the proximal base region of microvilli. This complex contained the immunoglobulin superfamily member TMIGD1, which directly interacted with the microvillar scaffolding proteins EBP50 and E3KARP. Complex formation with EBP50 required the activation of EBP50 by the actin-binding protein ezrin and was enhanced by the dephosphorylation of Ser¹⁶² in the PDZ2 domain of EBP50 by the phosphatase PP1α. Binding of the EBP50-ezrin complex to TMIGD1 enhanced the dynamic turnover of EBP50 at microvilli. Enterocyte-specific inactivation of Tmigd1 in mice resulted in microvillar blebbing, loss of intermicrovillar adhesion, and perturbed brush border formation. Thus, we identified a second adhesion complex in microvilli and propose a mechanism that promotes microvillar formation and dynamics.

Deficiency of Jamc Leads to Congenital Nuclear Cataract and Activates the Unfolded Protein Response in Mouse Lenses

Purpose

The malfunction of junctional adhesion molecule C (JAM-C) has been reported to induce congenital cataract in humans and mice; however, specific characters and the mechanism of this cataract are still unclear. This study aimed to characterize abnormal lens development in Jamc knockout mice and clarify the underlying mechanism.

Methods

Jamc knockout mice backcrossed onto the C57BL/6 genetic background were used for this research. Slit-lamp and darkfield images showed the cataract phenotype of Jamc^−/− mice. Hematoxylin and eosin staining was performed to visualize the morphological and histological features. RNA sequencing was applied to detect differentially expressed genes. Quantitative RT-PCR, western blot, and immunofluorescence were used to determine the level of unfolded protein response (UPR)-related genes. TUNEL staining was utilized to label cell death.

Results

Jamc knockout mice exhibited nuclear cataract with abnormal lens morphology and defective degradation of nuclei and organelles in lens fiber cells. Compared with wild-type control mice, the expression level of BiP, CHOP, TRIB3, and CHAC1, genes involved in endoplasmic reticulum stress and the UPR, were highly upregulated in Jamc^−/− lenses, suggesting that abnormal lens development was accompanied by UPR activation. Moreover, increased cell death was also found in Jamc^−/− lenses.

Conclusions

Congenital nuclear cataract caused by Jamc deficiency is accompanied by defective degradation of nuclei and organelles in lens fiber cells, lens structure disorder, and UPR activation, suggesting that JAM-C is required for maintaining normal lens development and that UPR activation is involved in cataract formation in Jamc-deficient lenses.

Effect of iodoacetic acid on the reproductive system of male mice

Iodoacetic acid (IAA) is one of the most common water disinfection byproducts (DBPs). Humans and animals are widely and continuously exposed to it. Many species of water DBPs are harmful to the reproductive system of organisms. Nevertheless, the potential effects of IAA exposure on testosterone and spermatogenesis in vivo remain ambiguous. Spermatogenous cells are the site of spermatogenesis, Leydig cells are the site of testosterone synthesis, and Sertoli cells build the blood–testis barrier (BTB), providing a stable environment for the aforementioned important physiological functions in testicular tissue. Therefore, we observed the effects of IAA on spermatogenic cells, Leydig cells, and Sertoli cells in the testis. In this study, we found that oral administration of IAA (35 mg/kg body weight per day for 28 days) in male mice increased serum LH levels and reduced sperm motility, affecting average path velocity and straight line velocity of sperm. In addition, IAA promoted the expression of γH2AX, a marker for DNA double-strand breaks. Moreover, IAA downregulated the protein expression of the scavenger receptor class B type 1 (SRB1), and decreased lipid droplet transport into Leydig cells, which reduced the storage of testosterone synthesis raw materials and might cause a drop in testosterone production. Furthermore, IAA did not affect the function of BTB. Thus, our results indicated that IAA exposure affected spermatogenesis and testosterone synthesis by inducing DNA damage and reducing lipid droplet transport.

JAM-A facilitates hair follicle regeneration in Alopecia Areata through functioning as ceRNA to protect VCAN expression in dermal papilla cells

The dermal papilla cells in hair follicles function as critical regulators of hair growth. In particular, alopecia areata (AA) is closely related to the malfunctioning of the human dermal papilla cells (hDPCs). Thus, identifying the regulatory mechanism of hDPCs is important in inducing hair follicle (HF) regeneration in AA patients. Recently, growing evidence has indicated that 3′ untranslated regions (3′ UTR) of key genes may participate in the regulatory circuitry underlying cell differentiation and diseases through a so-called competing endogenous mechanism, but none have been reported in HF regeneration. Here, we demonstrate that the 3′ UTR of junctional adhesion molecule A (JAM-A) could act as an essential competing endogenous RNA to maintain hDPCs function and promote HF regeneration in AA. We showed that the 3′ UTR of JAM-A shares many microRNA (miRNA) response elements, especially miR-221–3p, with versican (VCAN) mRNA, and JAM-A 3′ UTR could directly modulate the miRNA-mediated suppression of VCAN in self-renewing hDPCs. Furthermore, upregulated VCAN can in turn promote the expression level of JAM-A. Overall, we propose that JAM-A 3′ UTR forms a feedback loop with VCAN and miR-221–3p to regulate hDPC maintenance, proliferation, and differentiation, which may lead to developing new therapies for hair loss.

Junctional adhesion molecule-A deletion increases phagocytosis and improves survival in a murine model of sepsis

Expression of the tight junction–associated protein junctional adhesion molecule-A (JAM-A) is increased in sepsis, although the significance of this is unknown. Here, we show that septic JAM-A ^–/– mice have increased gut permeability, yet paradoxically have decreased bacteremia and systemic TNF and IL-1β expression. Survival is improved in JAM-A^–/– mice. However, intestine-specific JAM-A^–/– deletion does not alter mortality, suggesting that the mortality benefit conferred in mice lacking JAM-A is independent of the intestine. Septic JAM-A^–/– mice have increased numbers of splenic CD44^hiCD4⁺ T cells, decreased frequency of TNF⁺CD4⁺ cells, and elevated frequency of IL-2⁺CD4⁺ cells. Septic JAM-A^–/– mice have increased numbers of B cells in mesenteric lymph nodes with elevated serum IgA and intraepithelial lymphocyte IgA production. JAM-A^–/– × RAG^–/– mice have improved survival compared with RAG^–/– mice and identical mortality as WT mice. Gut neutrophil infiltration and neutrophil phagocytosis are increased in JAM-A^–/– mice, while septic JAM-A^–/– mice depleted of neutrophils lose their survival advantage. Therefore, increased bacterial clearance via neutrophils and an altered systemic inflammatory response with increased opsonizing IgA produced through the adaptive immune system results in improved survival in septic JAM-A^–/– mice. JAM-A may be a therapeutic target in sepsis via immune mechanisms not related to its role in permeability.

Dual Function of Par3 in Tumorigenesis

Cell maintenance and the establishment of cell polarity involve complicated interactions among multiple protein complexes as well as the regulation of different signaling pathways. As an important cell polarity protein, Par3 is evolutionarily conserved and involved in tight junction formation as well as tumorigenesis. In this review, we aimed to explore the function of Par3 in tumorigenesis. Research has shown that Par3 exhibits dual functions in human cancers, both tumor-promoting and tumor-suppressive. Here, we focus on the activities of Par3 in different stages and types of tumors, aiming to offer a new perspective on the molecular mechanisms that regulate the functions of Par3 in tumor development. Tumor origin, tumor microenvironment, tumor type, cell density, cell–cell contact, and the synergistic effect of Par3 and other tumor-associated signaling pathways may be important reasons for the dual function of Par3. The important role of Par3 in mammalian tumorigenesis and potential signaling pathways is context dependent.

Junctional Adhesion Molecules: Potential Proteins in Atherosclerosis

Junctional adhesion molecules (JAMs) are cell-cell adhesion molecules of the immunoglobulin superfamily and are involved in the regulation of diverse atherosclerosis-related processes such as endothelial barrier maintenance, leucocytes transendothelial migration, and angiogenesis. To combine and further broaden related results, this review concluded the recent progress in the roles of JAMs and predicted future studies of JAMs in the development of atherosclerosis.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Roles of the ACE/Ang II/AT1R pathway, cytokine release, and alteration of tight junctions in COVID-19 pathogenesis

This paper shows how SARS-CoV-2 alters tight junctions (TJs) in human organs. The effect of SARS-CoV-2 on the ACE/Ang II/AT1R pathway and immune cells culminates in the release of numerous pro-inflammatory mediators, leading to the presence of certain symptoms in COVID-19, such as acute lung injury (ALI), pulmonary hypertension, and pulmonary fibrosis. Furthermore, the cytokines released alter different TJs components. The study shows how the irregular release of pro-inflammatory cytokines leads to claudin disruption in various tissues of the body, resulting in different symptoms, such as alveolar fibrosis, pulmonary edema, conjunctivitis, altered fertility in males, gastrointestinal symptoms, Covid toes, and others. SARS-CoV-2 also alters occludin expression in the endothelial and blood-testis barriers (BTB) resulting in edema and altered fertility. Viral disruption of JAM-A leads to activation of the RhoA GTPase, which leads to ALI. Taken together, these results define ACE/Ang II/AT1R pathway receptors and tight junctional components as potential therapeutic targets in COVID-19.

JAML promotes acute kidney injury mainly through a macrophage-dependent mechanism

Although macrophages are undoubtedly attractive therapeutic targets for acute kidney injury (AKI) because of their critical roles in renal inflammation and repair, the underlying mechanisms of macrophage phenotype switching and efferocytosis in the regulation of inflammatory responses during AKI are still largely unclear. The present study elucidated the role of junctional adhesion molecule–like protein (JAML) in the pathogenesis of AKI. We found that JAML was significantly upregulated in kidneys from 2 different murine AKI models including renal ischemia/reperfusion injury (IRI) and cisplatin-induced AKI. By generation of bone marrow chimeric mice, macrophage-specific and tubular cell–specific Jaml conditional knockout mice, we demonstrated JAML promoted AKI mainly via a macrophage-dependent mechanism and found that JAML-mediated macrophage phenotype polarization and efferocytosis is one of the critical signal transduction pathways linking inflammatory responses to AKI. Mechanistically, the effects of JAML on the regulation of macrophages were, at least in part, associated with a macrophage-inducible C-type lectin–dependent mechanism. Collectively, our studies explore for the first time to our knowledge new biological functions of JAML in macrophages and conclude that JAML is an important mediator and biomarker of AKI. Pharmacological targeting of JAML-mediated signaling pathways at multiple levels may provide a novel therapeutic strategy for patients with AKI.

Claudin-12 deficiency inhibits tumor growth by impairing transendothelial migration of myeloid-derived suppressor cells

Migration of myeloid-derived suppressor cells (MDSCs) out of the circulation, across vascular walls, and into tumor is crucial for their immunosuppressive activity. A deeper understanding of critical junctional molecules and the regulatory mechanisms that mediate the extravasation of MDSCs could identify approaches to overcome cancer immunosuppression. In this study we used mice deficient in tight-junction protein Claudin-12 (Cldn12) compared to wild-type mice and found that loss of host Cldn12 inhibited the growth of transplanted tumors, reduced intratumoral accumulation of MDSCs, increased anti-tumor immune responses, and decreased tumor vescular density. Further studies revealed that Cldn12 expression on the cell surface of both MDSCs and endothelial cells is required for MDSCs transit across tumor vascular endothelial cells (ECs). Importantly, expression of Cldn12 in MDSCs was modulated by granulocyte-macrophage colony-stimulating factor (GM-CSF) in an AKT-dependent manner. Therefore, our results indicate that Cldn12 could serve as a promising target for restoring the anti-tumor response by interfering with MDSCs transendothelial migration.

Lentivirus-mediated subcutaneous JAM-A modification promotes skin wound healing in a mouse model by strengthening the secretory function and proliferation of fibroblasts

A better understanding of the molecular regulation of wound healing may provide novel therapeutic targets. A previous study revealed that junctional adhesion molecule A (JAM-A)-modified mesenchymal stem cells promoted wound healing. However, whether direct JAM-A modification in the skin wound edge area accelerates the wound repair process is not clear. We determined whether JAM-A modification at the skin wound edge accelerated the wound healing process. We established JAM-A modification mouse wound models and mouse primary fibroblast cell models. Wound pictures were taken to compare the wound size. H&E staining was performed to monitor the morphology of the wound and quality of the newborn skin. CCK-8 assays and immunofluorescence (IF) for Ki67 were used to measure the cell proliferation of mouse primary fibroblasts. Quantitative real-time PCR, immunohistochemistry, IF, and Western blot analysis were used to detect bFGF and EGF expression in vivo and in vitro. The JAM-A-overexpressing group exhibited a smaller residual wound size than the control group at Day 7. Thicker epidermal layers and more hair follicle-like structures were found in the JAM-A-overexpressing group at Day 21. Cell proliferation capacity was higher in JAM-A-modified mouse fibroblasts. Elevated levels of bFGF and EGF were found in the JAM-A-modified group in vivo and in vitro. JAM-A modification significantly promoted fibroblast proliferation and wound healing. Increased levels of bFGF and EGF growth factors may be part of the mechanism.

miRNA-guided reprogramming of glucose and glutamine metabolism and its impact on cell adhesion/migration during solid tumor progression

MicroRNAs (miRNAs) are small, non-coding RNAs about 22 nucleotides in length that regulate the expression of target genes post-transcriptionally, and are highly involved in cancer progression. They are able to impact a variety of cell processes such as proliferation, apoptosis and differentiation and can consequently control tumor initiation, tumor progression and metastasis formation. miRNAs can regulate, at the same time, metabolic gene expression which, in turn, influences relevant traits of malignancy such as cell adhesion, migration and invasion. Since the interaction between metabolism and adhesion or cell movement has not, to date, been well understood, in this review, we will specifically focus on miRNA alterations that can interfere with some metabolic processes leading to the modulation of cancer cell movement. In addition, we will analyze the signaling pathways connecting metabolism and adhesion/migration, alterations that often affect cancer cell dissemination and metastasis formation.

A JAM-A-tetraspanin-αvβ5 integrin complex regulates contact inhibition of locomotion

Contact inhibition of locomotion (CIL) is a process that regulates cell motility upon collision with other cells. Improper regulation of CIL has been implicated in cancer cell dissemination. Here, we identify the cell adhesion molecule JAM-A as a central regulator of CIL in tumor cells. JAM-A is part of a multimolecular signaling complex in which tetraspanins CD9 and CD81 link JAM-A to αvβ5 integrin. JAM-A binds Csk and inhibits the activity of αvβ5 integrin-associated Src. Loss of JAM-A results in increased activities of downstream effectors of Src, including Erk1/2, Abi1, and paxillin, as well as increased activity of Rac1 at cell-cell contact sites. As a consequence, JAM-A-depleted cells show increased motility, have a higher cell-matrix turnover, and fail to halt migration when colliding with other cells. We also find that proper regulation of CIL depends on αvβ5 integrin engagement. Our findings identify a molecular mechanism that regulates CIL in tumor cells and have implications on tumor cell dissemination.

The Roles of Junctional Adhesion Molecules (JAMs) in Cell Migration

The review briefly summarizes the role of the family of adhesion molecules, JAMs (junctional adhesion molecules), in various cell migration, covering germ cells, epithelial cells, endothelial cells, several leukocytes, and different cancer cells. These functions affect multiple diseases, including reproductive diseases, inflammation-related diseases, cardiovascular diseases, and cancers. JAMs bind to both similar and dissimilar proteins and take both similar and dissimilar effects on different cells. Concluding relevant results provides a reference to further research.

Functional Antagonism of Junctional Adhesion Molecule-A (JAM-A), Overexpressed in Breast Ductal Carcinoma In Situ (DCIS), Reduces HER2-Positive Tumor Progression

Simple Summary

Specific drug targets for breast ductal carcinoma in situ (DCIS) remain elusive, despite increasing disease prevalence and burden to healthcare services. Estrogen receptor (ER)-negative HER2-positive DCIS, associated with the poorest patient prognosis, is in particular need of novel therapeutic avenues. This report provides the first evidence that a cell surface protein called JAM-A is upregulated on human DCIS patient tissues and can be readily targeted by a novel JAM-A-binding peptide inhibitor in separate in vivo models of DCIS. The anti-tumor efficacy and lack of systemic toxicity of this lead inhibitor, coupled with early indications of potential signaling pathways implicated, support the value of future studies investigating JAM-A as a novel drug target in DCIS patients.

Abstract

Breast ductal carcinoma in situ (DCIS) is clinically challenging, featuring high diagnosis rates and few targeted therapies. Expression/signaling from junctional adhesion molecule-A (JAM-A) has been linked to poor prognosis in invasive breast cancers, but its role in DCIS is unknown. Since progression from DCIS to invasive cancer has been linked with overexpression of the human epidermal growth factor receptor-2 (HER2), and JAM-A regulates HER2 expression, we evaluated JAM-A as a therapeutic target in DCIS. JAM-A expression was immunohistochemically assessed in patient DCIS tissues. A novel JAM-A antagonist (JBS2) was designed and tested alone/in combination with the HER2 kinase inhibitor lapatinib, using SUM-225 cells in vitro and in vivo as validated DCIS models. Murine tumors were proteomically analyzed. JAM-A expression was moderate/high in 96% of DCIS patient tissues, versus 23% of normal adjacent tissues. JBS2 bound to recombinant JAM-A, inhibiting cell viability in SUM-225 cells and a primary DCIS culture in vitro and in a chick embryo xenograft model. JBS2 reduced tumor progression in in vivo models of SUM-225 cells engrafted into mammary fat pads or directly injected into the mammary ducts of NOD-SCID mice. Preliminary proteomic analysis revealed alterations in angiogenic and apoptotic pathways. High JAM-A expression in aggressive DCIS lesions and their sensitivity to treatment by a novel JAM-A antagonist support the viability of testing JAM-A as a novel therapeutic target in DCIS.

Using the Power of Junctional Adhesion Molecules Combined with the Target of CAR-T to Inhibit Cancer Proliferation, Metastasis and Eradicate Tumors

Decades of evidence suggest that alterations in the adhesion properties of neoplastic cells endow them with an invasive and migratory phenotype. Tight junctions (TJs) are present in endothelial and epithelial cells. Tumors arise from such tissues, thus, the role of TJ proteins in the tumor microenvironment is highly relevant. In the TJ, junctional adhesion molecules (JAM) play a key role in assembly of the TJ and control of cell–cell adhesion. Reprogramming of immune cells using chimeric antigen receptors (CAR) to allow for target recognition and eradication of tumors is an FDA approved therapy. The best-studied CAR-T cells recognize CD19, a B-cell surface molecule. CD19 is not a unique marker for tumors, liquid or solid. To address this limitation, we developed a biologic containing three domains: (1) pH-low-insertion peptide (pHLIP), which recognizes the low pH of the cancer cells, leading to the insertion of the peptide into the plasma membrane. (2) An extracellular domain of JAM proteins that fosters cell–cell interactions. (3) CD19 to be targeted by CAR-T cells. Our modular design only targets cancer cells and when coupled with anti-CD19 CAR-T cells, it decreases proliferation and metastasis in at least two cancer cell lines.

Aging-induced impaired endothelial wall shear stress mechanosensing causes arterial remodeling via JAM-A/F11R shedding by ADAM17

Physiological and pathological vascular remodeling is uniquely driven by mechanical forces from blood flow in which wall shear stress (WSS) mechanosensing by the vascular endothelium plays a pivotal role. This study aimed to determine the novel role for a disintegrin and metalloproteinase 17 (ADAM17) in impaired WSS mechanosensing, which was hypothesized to contribute to aging-associated abnormal vascular remodeling. Without changes in arterial blood pressure and blood flow rate, skeletal muscle resistance arteries of aged mice (30-month-old vs. 12-week-old) exhibited impaired WSS mechanosensing and displayed inward hypertrophic arterial remodeling. These vascular changes were recapitulated by in vivo confined, AAV9-mediated overexpression of ADAM17 in the resistance arteries of young mice. An aging-related increase in ADAM17 expression reduced the endothelial junction level of its cleavage substrate, junctional adhesion molecule-A/F11 receptor (JAM-A/F11R). In cultured endothelial cells subjected to steady WSS ADAM17 activation or JAM-A/F11R knockdown inhibited WSS mechanosensing. The ADAM17-activation induced, impaired WSS mechanosensing was normalized by overexpression of ADAM17 cleavage resistant, mutated JAM-AV232Y both in cultured endothelial cells and in resistance arteries of aged mice, in vivo. These data demonstrate a novel role for ADAM17 in JAM-A/F11R cleavage-mediated impaired endothelial WSS mechanosensing and subsequently developed abnormal arterial remodeling in aging. ADAM17 could prove to be a key regulator of WSS mechanosensing, whereby it can also play a role in pathological vascular remodeling in diseases.

DICAM promotes TH17 lymphocyte trafficking across the blood-brain barrier during autoimmune neuroinflammation

[Figure: see text].

Tight Junctions of the Neurovascular Unit

The homeostatic balance of the brain and retina is maintained by the presence of the blood-brain and inner blood-retinal barrier (BBB/iBRB, respectively) which are highly specialized barriers. Endothelial cells forming the lining of these blood vessels are interconnected by the presence of tight junctions which form the BBB and iBRB. These tight junctions, formed of numerous interacting proteins, enable the entry of molecules into neural tissues while restricting the entry of harmful material such as anaphylatoxins, bacteria and viruses. If the tight junction complex becomes dysregulated due to changes in expression levels of one or more of the components, this can have detrimental effects leading to brain and retinal pathology.