Molecular Basis of Arthritogenic Alphavirus Receptor MXRA8 Binding to Chikungunya Virus Envelope Protein.

Arthritogenic alphaviruses, such as Chikungunya virus (CHIKV), cause severe and debilitating rheumatic diseases worldwide, resulting in severe morbidity and economic costs. Recently, MXRA8 was reported as an entry receptor. Here, we present the crystal structures of the mouse MXRA8, human MXRA8 in complex with the CHIKV E protein, and the cryo-electron microscopy structure of human MXRA8 and CHIKV virus-like particle. MXRA8 has two Ig-like domains with unique structural topologies. This receptor binds in the "canyon" between two protomers of the E spike on the surface of the virion. The atomic details at the interface between the two binding entities reveal that both the two domains and the hinge region of MXRA8 are involved in interaction with CHIKV E1-E2 residues from two protomers. Notably, the stalk region of MXRA8 is critical for CHIKV virus entry. This finding provides important information regarding the development of therapeutic countermeasures against those arthritogenic alphaviruses.

Expression of the membrane tetraspanin claudin 18 on cancer cells promotes T lymphocyte infiltration and antitumor immunity in pancreatic cancer.

Tumors weakly infiltrated by T lymphocytes poorly respond to immunotherapy. We aimed to unveil malignancy-associated programs regulating T cell entrance, arrest, and activation in the tumor environment. Differential expression of cell adhesion and tissue architecture programs, particularly the presence of the membrane tetraspanin claudin (CLDN)18 as a signature gene, demarcated immune-infiltrated from immune-depleted mouse pancreatic tumors. In human pancreatic ductal adenocarcinoma (PDAC) and non-small cell lung cancer, CLDN18 expression positively correlated with more differentiated histology and favorable prognosis. CLDN18 on the cell surface promoted accrual of cytotoxic T lymphocytes (CTLs), facilitating direct CTL contacts with tumor cells by driving the mobilization of the adhesion protein ALCAM to the lipid rafts of the tumor cell membrane through actin. This process favored the formation of robust immunological synapses (ISs) between CTLs and CLDN18-positive cancer cells, resulting in increased T cell activation. Our data reveal an immune role for CLDN18 in orchestrating T cell infiltration and shaping the tumor immune contexture.

Structural and functional reorganization of inhibitory synapses by activity-dependent cleavage of neuroligin-2.

Recent evidence has demonstrated that the transsynaptic nanoscale organization of synaptic proteins plays a crucial role in regulating synaptic strength in excitatory synapses. However, the molecular mechanism underlying this transsynaptic nanostructure in inhibitory synapses still remains unclear and its impact on synapse function in physiological or pathological contexts has not been demonstrated. In this study, we utilized an engineered proteolysis technique to investigate the effects of acute cleavage of neuroligin-2 (NL2) on synaptic transmission. Our results show that the rapid cleavage of NL2 led to impaired synaptic transmission by reducing both neurotransmitter release probability and quantum size. These changes were attributed to the dispersion of RIM1/2 and GABAA receptors and a weakened spatial alignment between them at the subsynaptic scale, as observed through superresolution imaging and model simulations. Importantly, we found that endogenous NL2 undergoes rapid MMP9-dependent cleavage during epileptic activities, which further exacerbates the decrease in inhibitory transmission. Overall, our study demonstrates the significant impact of nanoscale structural reorganization on inhibitory transmission and unveils ongoing modulation of mature GABAergic synapses through active cleavage of NL2 in response to hyperactivity.

Adult expression of the cell adhesion protein Fasciclin 3 is required for the maintenance of adult olfactory interneurons.

The proper functioning of the nervous system is dependent on the establishment and maintenance of intricate networks of neurons that form functional neural circuits. Once neural circuits are assembled during development, a distinct set of molecular programs is likely required to maintain their connectivity throughout the lifetime of the organism. Here, we demonstrate that Fasciclin 3 (Fas3), an axon guidance cell adhesion protein, is necessary for the maintenance of the olfactory circuit in adult Drosophila. We utilized the TARGET system to spatiotemporally knockdown Fas3 in selected populations of adult neurons. Our findings show that Fas3 knockdown results in the death of olfactory circuit neurons and reduced survival of adults. We also demonstrated that Fas3 knockdown activates caspase-3-mediated cell death in olfactory local interneurons, which can be rescued by overexpressing baculovirus p35, an anti-apoptotic protein. This work adds to the growing set of evidence indicating a crucial role for axon guidance proteins in the maintenance of neuronal circuits in adults.

Necl2/3-mediated mechanism for tripartite synapse formation.

Ramified, polarized protoplasmic astrocytes interact with synapses via perisynaptic astrocyte processes (PAPs) to form tripartite synapses. These astrocyte-synapse interactions mutually regulate their structures and functions. However, molecular mechanisms for tripartite synapse formation remain elusive. We developed an in vitro co-culture system for mouse astrocytes and neurons that induced astrocyte ramifications and PAP formation. Co-cultured neurons were required for astrocyte ramifications in a neuronal activity-dependent manner, and synaptically-released glutamate and activation of astrocytic mGluR5 metabotropic glutamate receptor were likely involved in astrocyte ramifications. Astrocytic Necl2 trans-interacted with axonal Necl3, inducing astrocyte-synapse interactions and astrocyte functional polarization by recruiting EAAT1/2 glutamate transporters and Kir4.1 K+ channel to the PAPs, without affecting astrocyte ramifications. This Necl2/3 trans-interaction increased functional synapse number. Thus, astrocytic Necl2, synaptically-released glutamate and axonal Necl3 cooperatively formed tripartite glutamatergic synapses in vitro. Studies on hippocampal mossy fiber synapses in Necl3 knockout and Necl2/3 double knockout mice confirmed these previously unreported mechanisms for astrocyte-synapse interactions and astrocyte functional polarization in vivo.

LncRNA PSMB8-AS1 Instigates Vascular Inflammation to Aggravate Atherosclerosis.

BACKGROUND: Increasing evidence suggests that long noncoding RNAs play significant roles in vascular biology and disease development. One such long noncoding RNA, PSMB8-AS1, has been implicated in the development of tumors. Nevertheless, the precise role of PSMB8-AS1 in cardiovascular diseases, particularly atherosclerosis, has not been thoroughly elucidated. Thus, the primary aim of this investigation is to assess the influence of PSMB8-AS1 on vascular inflammation and the initiation of atherosclerosis. METHODS: We generated PSMB8-AS1 knockin and Apoe (Apolipoprotein E) knockout mice (Apoe-/-PSMB8-AS1KI) and global Apoe and proteasome subunit-ß type-9 (Psmb9) double knockout mice (Apoe-/-Psmb9-/-). To explore the roles of PSMB8-AS1 and Psmb9 in atherosclerosis, we fed the mice with a Western diet for 12 weeks. RESULTS: Long noncoding RNA PSMB8-AS1 is significantly elevated in human atherosclerotic plaques. Strikingly, Apoe-/-PSMB8-AS1KI mice exhibited increased atherosclerosis development, plaque vulnerability, and vascular inflammation compared with Apoe-/- mice. Moreover, the levels of VCAM1 (vascular adhesion molecule 1) and ICAM1 (intracellular adhesion molecule 1) were significantly upregulated in atherosclerotic lesions and serum of Apoe-/-PSMB8-AS1KI mice. Consistently, in vitro gain- and loss-of-function studies demonstrated that PSMB8-AS1 induced monocyte/macrophage adhesion to endothelial cells and increased VCAM1 and ICAM1 levels in a PSMB9-dependent manner. Mechanistic studies revealed that PSMB8-AS1 induced PSMB9 transcription by recruiting the transcription factor NONO (non-POU domain-containing octamer-binding protein) and binding to the PSMB9 promoter. PSMB9 (proteasome subunit-ß type-9) elevated VCAM1 and ICAM1 expression via the upregulation of ZEB1 (zinc finger E-box-binding homeobox 1). Psmb9 deficiency decreased atherosclerotic lesion size, plaque vulnerability, and vascular inflammation in Apoe-/- mice in vivo. Importantly, endothelial overexpression of PSMB8-AS1-increased atherosclerosis and vascular inflammation were attenuated by Psmb9 knockout. CONCLUSIONS: PSMB8-AS1 promotes vascular inflammation and atherosclerosis via the NONO/PSMB9/ZEB1 axis. Our findings support the development of new long noncoding RNA-based strategies to counteract atherosclerotic cardiovascular disease.

Engineered adhesion molecules drive synapse organization.

In multicellular organisms, cell-adhesion molecules connect cells into tissues and mediate intercellular signaling between these cells. In vertebrate brains, synaptic cell-adhesion molecules (SAMs) guide the formation, specification, and plasticity of synapses. Some SAMs, when overexpressed in cultured neurons or in heterologous cells co-cultured with neurons, drive formation of synaptic specializations onto the overexpressing cells. However, genetic deletion of the same SAMs from neurons often has no effect on synapse numbers, but frequently severely impairs synaptic transmission, suggesting that most SAMs control the function and plasticity of synapses (i.e., organize synapses) instead of driving their initial establishment (i.e., make synapses). Since few SAMs were identified that mediate initial synapse formation, it is difficult to develop methods that enable experimental control of synaptic connections by targeted expression of these SAMs. To overcome this difficulty, we engineered novel SAMs from bacterial proteins with no eukaryotic homologues that drive synapse formation. We named these engineered adhesion proteins "Barnoligin" and "Starexin" because they were assembled from parts of Barnase and Neuroligin-1 or of Barstar and Neurexin3ß, respectively. Barnoligin and Starexin robustly induce the formation of synaptic specializations in a specific and directional manner in cultured neurons. Synapse formation by Barnoligin and Starexin requires both their extracellular Barnase- and Barstar-derived interaction domains and their Neuroligin- and Neurexin-derived intracellular signaling domains. Our findings support a model of synapse formation whereby trans-synaptic interactions by SAMs drive synapse organization via adhesive interactions that activate signaling cascades.

ICAM-1 Deletion Using CRISPR/Cas9 Protects the Brain from Traumatic Brain Injury-Induced Inflammatory Leukocyte Adhesion and Transmigration Cascades by Attenuating the Paxillin/FAK-Dependent Rho GTPase Pathway.

Intercellular adhesion molecule-1 (ICAM-1) is identified as an initiator of neuroinflammatory responses that lead to neurodegeneration and cognitive and sensory-motor deficits in several pathophysiological conditions including traumatic brain injury (TBI). However, the underlying mechanisms of ICAM-1-mediated leukocyte adhesion and transmigration and its link with neuroinflammation and functional deficits following TBI remain elusive. Here, we hypothesize that blocking of ICAM-1 attenuates the transmigration of leukocytes to the brain and promotes functional recovery after TBI. The experimental TBI was induced in vivo by fluid percussion injury (25 psi) in male and female wild-type and ICAM-1-/- mice and in vitro by stretch injury (3 psi) in human brain microvascular endothelial cells (hBMVECs). We treated hBMVECs and animals with ICAM-1 CRISPR/Cas9 and conducted several biochemical analyses and demonstrated that CRISPR/Cas9-mediated ICAM-1 deletion mitigates blood-brain barrier (BBB) damage and leukocyte transmigration to the brain by attenuating the paxillin/focal adhesion kinase (FAK)-dependent Rho GTPase pathway. For analyzing functional outcomes, we used a cohort of behavioral tests that included sensorimotor functions, psychological stress analyses, and spatial memory and learning following TBI. In conclusion, this study could establish the significance of deletion or blocking of ICAM-1 in transforming into a novel preventive approach against the pathophysiology of TBI.

Following the Evolutionary Paths of Dscam1 Proteins toward Highly Specific Homophilic Interactions.

Many adhesion proteins, evolutionarily related through gene duplication, exhibit distinct and precise interaction preferences and affinities crucial for cell patterning. Yet, the evolutionary paths by which these proteins acquire new specificities and prevent cross-interactions within their family members remain unknown. To bridge this gap, this study focuses on Drosophila Down syndrome cell adhesion molecule-1 (Dscam1) proteins, which are cell adhesion proteins that have undergone extensive gene duplication. Dscam1 evolved under strong selective pressure to achieve strict homophilic recognition, essential for neuronal self-avoidance and patterning. Through a combination of phylogenetic analyses, ancestral sequence reconstruction, and cell aggregation assays, we studied the evolutionary trajectory of Dscam1 exon 4 across various insect lineages. We demonstrated that recent Dscam1 duplications in the mosquito lineage bind with strict homophilic specificities without any cross-interactions. We found that ancestral and intermediate Dscam1 isoforms maintained their homophilic binding capabilities, with some intermediate isoforms also engaging in promiscuous interactions with other paralogs. Our results highlight the robust selective pressure for homophilic specificity integral to the Dscam1 function within the process of neuronal self-avoidance. Importantly, our study suggests that the path to achieving such selective specificity does not introduce disruptive mutations that prevent self-binding but includes evolutionary intermediates that demonstrate promiscuous heterophilic interactions. Overall, these results offer insights into evolutionary strategies that underlie adhesion protein interaction specificities.

Bi-allelic variants in neuronal cell adhesion molecule cause a neurodevelopmental disorder characterized by developmental delay, hypotonia, neuropathy/spasticity.

Cell adhesion molecules are membrane-bound proteins predominantly expressed in the central nervous system along principal axonal pathways with key roles in nervous system development, neural cell differentiation and migration, axonal growth and guidance, myelination, and synapse formation. Here, we describe ten affected individuals with bi-allelic variants in the neuronal cell adhesion molecule NRCAM that lead to a neurodevelopmental syndrome of varying severity; the individuals are from eight families. This syndrome is characterized by developmental delay/intellectual disability, hypotonia, peripheral neuropathy, and/or spasticity. Computational analyses of NRCAM variants, many of which cluster in the third fibronectin type III (Fn-III) domain, strongly suggest a deleterious effect on NRCAM structure and function, including possible disruption of its interactions with other proteins. These findings are corroborated by previous in vitro studies of murine Nrcam-deficient cells, revealing abnormal neurite outgrowth, synaptogenesis, and formation of nodes of Ranvier on myelinated axons. Our studies on zebrafish nrcamaΔ mutants lacking the third Fn-III domain revealed that mutant larvae displayed significantly altered swimming behavior compared to wild-type larvae (p < 0.03). Moreover, nrcamaΔ mutants displayed a trend toward increased amounts of α-tubulin fibers in the dorsal telencephalon, demonstrating an alteration in white matter tracts and projections. Taken together, our study provides evidence that NRCAM disruption causes a variable form of a neurodevelopmental disorder and broadens the knowledge on the growing role of the cell adhesion molecule family in the nervous system.

Junctional adhesion molecule-A deficient mice are protected from severe experimental autoimmune encephalomyelitis.

In multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), early pathological features include immune cell infiltration into the central nervous system (CNS) and blood-brain barrier (BBB) disruption. We investigated the role of junctional adhesion molecule-A (JAM-A), a tight junction protein, in active EAE (aEAE) pathogenesis. Our study confirms JAM-A expression at the blood-brain barrier and its luminal redistribution during aEAE. JAM-A deficient (JAM-A-/-) C57BL/6J mice exhibited milder aEAE, unrelated to myelin oligodendrocyte glycoprotein-specific CD4+ T-cell priming. While JAM-A absence influenced macrophage behavior on primary mouse brain microvascular endothelial cells (pMBMECs) under flow in vitro, it did not impact T-cell extravasation across primary mouse brain microvascular endothelial cells. At aEAE onset, we observed reduced lymphocyte and CCR2+ macrophage infiltration into the spinal cord of JAM-A-/- mice compared to control littermates. This correlated with increased CD3+ T-cell accumulation in spinal cord perivascular spaces and brain leptomeninges, suggesting JAM-A absence leads to T-cell trapping in central nervous system border compartments. In summary, JAM-A plays a role in immune cell infiltration and clinical disease progression in aEAE.

Cell trajectory modeling identifies a primitive trophoblast state defined by BCAM enrichment.

In early placental development, progenitor cytotrophoblasts (CTB) differentiate along one of two cellular trajectories: the villous or extravillous pathways. CTB committed to the villous pathway fuse with neighboring CTB to form the outer multinucleated syncytiotrophoblast (SCT), whereas CTB committed to the extravillous pathway differentiate into invasive extravillous trophoblasts (EVT). Unfortunately, little is known about the processes controlling human CTB progenitor maintenance and differentiation. To address this, we established a single cell RNA sequencing (scRNA-seq) dataset from first trimester placentas to identify cell states important in trophoblast progenitor establishment, renewal and differentiation. Multiple distinct trophoblast states were identified, representing progenitor CTB, column CTB, SCT precursors and EVT. Lineage trajectory analysis identified a progenitor origin that was reproduced in human trophoblast stem cell organoids. Heightened expression of basal cell adhesion molecule (BCAM) defined this primitive state, where BCAM enrichment or gene silencing resulted in enhanced or diminished organoid growth, respectively. Together, this work describes at high-resolution trophoblast heterogeneity within the first trimester, resolves gene networks within human CTB progenitors and identifies BCAM as a primitive progenitor marker and possible regulator.

Systematic pan-cancer analysis insights into ICAM1 as an immunological and prognostic biomarker.

Intercellular adhesion molecule 1 (ICAM1) is a cell surface adhesion glycoprotein in the immunoglobulin supergene family. It is associated with several epithelial tumorigenesis processes, as well as with inflammation. However, the function of ICAM1 in the prognosis of tumor immunity is still unclear. This study aimed to examine the immune function of ICAM1 in 33 tumor types and to investigate the prognostic value of tumors. Using datasets from the Cancer Genome Atlas (TCGA), Genotype Tissue Expression (GTEx), Cancer Cell Lines Encyclopedia (CCLE), Human Protein Atlas (HPA), and cBioPortal, we investigated the role of ICAM1 in tumors. We explored the potential correlation between ICAM1 expression and tumor prognosis, gene mutations, microsatellite instability, and tumor immune cell levels in various cancers. We observed that ICAM1 is highly expressed in multiple malignant tumors. Furthermore, ICAM1 is negatively or positively associated with different malignant tumor prognoses. The expression levels of ICAM1 were correlated with the tumor mutation burden (TMB) in 11 tumors and with MSI in eight tumors. ICAM1 is a gene associated with immune infiltrating cells, such as M1 macrophages and CD8+ T cells in gastric and colon cancer. Meanwhile, the expression of ICAM1 is associated with several immune-related functions and immune-regulation-related signaling pathways, such as the chemokine signaling pathway. Our study shows that ICAM1 can be used as a prognostic biomarker in many cancer types because of its function in tumorigenesis and malignant tumor immunity.

In vivo tracking of mesenchymal stem cell dynamics and therapeutics in LPS-induced acute lung injury models.

Mesenchymal stem cells (MSCs) have been widely used to treat various inflammatory and immune-related diseases in preclinical and clinical settings. Intravital microscopy (IVM) is considered the gold standard for investigating pathophysiological conditions in living animals. However, the potential for real-time monitoring of MSCs in the pulmonary microenvironment remains underexplored. In this study, we first constructed a lung window and captured changes in the lung at the cellular level under both inflammatory and noninflammatory conditions with a microscope. We further investigated the dynamics and effects of MSCs under two different conditions. Meanwhile, we assessed the alterations in the adhesive capacity of vascular endothelial cells in vitro to investigate the underlying mechanisms of MSC retention in an inflammatory environment. This study emphasizes the importance of the "lung window" for live imaging of the cellular behavior of MSCs by vein injection. Moreover, our results revealed that the upregulation of vascular cell adhesion molecule 1 (VCAM1) in endothelial cells post-inflammatory injury could enhance MSC retention in the lung, further ameliorating acute lung injury. In summary, intravital microscopy imaging provides a practical method to investigate the therapeutic effects of MSCs in acute lung injury.

Intermittent hypoxia increased the expression of ESM1 and ICAM-1 in vascular endothelial cells via the downregulation of microRNA-181a1.

Sleep apnea syndrome (SAS) exposes cells throughout the body to intermittent hypoxia (IH). Intermittent hypoxia is a risk factor not only for hypertension and insulin resistance but also for vascular dysfunction. We have reported correlations between IH, insulin resistance and hypertension. However, the details of why IH leads to vascular dysfunction remain unclear. In this study, we investigated inflammation-related transcripts in vascular endothelial cells (human HUEhT-1 and mouse UV2) exposed to IH by real-time RT-PCR and found that intercellular adhesion molecule-1 (ICAM-1) and endothelial cell-specific molecule-1 (ESM1) mRNAs were significantly increased. ELISA confirmed that, in the UV2 cell medium, ICAM-1 and ESM1 were significantly increased by IH. However, the promoter activities of ICAM-1 and ESM1 were not upregulated. On the other hand, IH treatment significantly decreased microRNA (miR)-181a1 in IH-treated cells. The introduction of miR-181a1 mimic but not miR-181a1 mimic NC abolished the IH-induced upregulation of Ican-1 and ESM1. These results indicated that ICAM-1 and ESM1 were upregulated by IH via the IH-induced downregulation of miR-181a1 in vascular endothelial cells and suggested that SAS patients developed atherosclerosis via the IH-induced upregulation of ICAM-1 and ESM1.

Organizing the synaptic junctions.

Synaptic adhesion molecules (SAMs) are essential for driving the formation, maturation, and plasticity of synaptic connections for neural networks. MAM domain-containing glycosylphosphatidylinositol anchors (MDGAs) are a type of SAM that regulates the formation of trans-synaptic bridges, which are critical for neurotransmission and synaptic differentiation. In a recent issue of the JBC, Lee et al. uncovered that MDGA1 can control protein-protein interactions and synaptic cleft activity by adopting different global 3D conformations. This novel molecular mechanism may be applicable to other SAMs that regulate protein-protein interactions and nanoscale organization in the synaptic cleft.

Synaptic adhesion molecule protocadherin-γC5 mediates ß-amyloid-induced neuronal hyperactivity and cognitive deficits in Alzheimer's disease.

Neuronal hyperactivity induced by ß-amyloid (Aß) is an early pathological feature in Alzheimer's disease (AD) and contributes to cognitive decline in AD progression. However, the underlying mechanisms are still unclear. Here, we revealed that Aß increased the expression level of synaptic adhesion molecule protocadherin-γC5 (Pcdh-γC5) in a Ca2+-dependent manner, associated with aberrant elevation of synapses in both Aß-treated neurons in vitro and the cortex of APP/PS1 mice in vivo. By using Pcdhgc5 gene knockout mice, we demonstrated the critical function of Pcdh-γC5 in regulating neuronal synapse formation, synaptic transmission, and cognition. To further investigate the role of Pcdh-γC5 in AD pathogenesis, the aberrantly enhanced expression of Pcdh-γC5 in the brain of APP/PS1 mice was knocked down by shRNA. Downregulation of Pcdh-γC5 efficiently rescued neuronal hyperactivity and impaired cognition in APP/PS1 mice. Our findings revealed the pathophysiological role of Pcdh-γC5 in mediating Aß-induced neuronal hyperactivity and cognitive deficits in AD and identified a novel mechanism underlying AD pathogenesis.

NMR Studies of the Interactions between Sialyllactoses and the Polysialytransferase Domain for Polysialylation Inhibition.

It is known that sialyllactose (SL) in mammalians is a major source of sialic acid (Sia), which can further form cytidine monophosphate sialic acid (CMP-Sia), and the final product is polysialic acid (polySia) using polysialyltransferases (polySTs) on the neural cell adhesion molecule (NCAM). This process is called NCAM polysialylation. The overexpression of polysialylation is strongly related to cancer cell migration, invasion, and metastasis. In order to inhibit the overexpression of polysialylation, in this study, SL was selected as an inhibitor to test whether polysialylation could be inhibited. Our results suggest that the interactions between the polysialyltransferase domain (PSTD) in polyST and CMP-Siaand the PSTD and polySia could be inhibited when the 3'-sialyllactose (3'-SL) or 6'-sialyllactose (6'-SL) concentration is about 0.5 mM or 6'-SL and 3 mM, respectively. The results also show that SLs (particularly for 3'-SL) are the ideal inhibitors compared with another two inhibitors, low-molecular-weight heparin (LMWH) and cytidine monophosphate (CMP), because 3'-SL can not only be used to inhibit NCAM polysialylation, but is also one of the best supplements for infant formula and the gut health system.

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.

JAM2 is a prognostic biomarker and inhibits proliferation, metastasis and epithelial-mesenchymal transition in lung adenocarcinoma.

BACKGROUND: Junctional adhesion molecule 2 (JAM2) plays a pivotal role in various biological processes, including proliferation, metastasis and angiogenesis, contributing to tumor progression. While previous studies have highlighted the polarizing functions of JAM2 in different cancer types, its specific role in lung adenocarcinoma (LUAD) remains unclear. METHODS: In this study, we harnessed multiple public databases to analyze the expression and prognostic significance of JAM2 in LUAD. Using the Linkedomics database, Matescape database and R package, we explored the associated genes, the potential biological functions and the impact of JAM2 on the tumor microenvironment. Our findings from public databases were further validated using real-time quantitative PCR, western blot and immunohistochemistry. Additionally, in vitro experiments were conducted to assess the influence of JAM2 on LUAD cell proliferation, invasion, migration, apoptosis and epithelial-mesenchymal transition. Furthermore, we established a xenograft model to investigate the in vivo effects of JAM2 on tumorigenesis. RESULTS: Our results revealed a significant downregulation of JAM2 in LUAD, and patients with low JAM2 expression exhibited unfavorable overall survival outcomes. Functional enrichment analysis indicated that JAM2 may be associated with processes such as cell adhesion, extracellular matrix, cell junctions and regulation of proliferation. Notably, increased JAM2 expression correlated with higher tumor microenvironment scores and reduced immune cell abundance. Furthermore, overexpression of JAM2 induced apoptosis, suppressed tumor proliferation and exhibited potential inhibitory effects on tumor invasion and migration through the modulation of epithelial-mesenchymal transition. Additionally, in vivo experiments confirmed that JAM2 overexpression led to a reduction in tumor growth. CONCLUSION: Overall, our study highlights the clinical significance of low JAM2 expression as a predictor of poor prognosis in LUAD patients. Moreover, JAM2 was found to exert inhibitory effects on various aspects of tumor progression. Consequently, JAM2 emerges as a promising prognostic biomarker and a potential therapeutic target for LUAD patients.