Functional Neuroligin-2-MDGA1 interactions differentially regulate synaptic GABAARs and cytosolic gephyrin aggregation.

Neuroligin-2 (Nlgn2) is a key synaptic adhesion protein at virtually all GABAergic synapses, which recruits GABAARs by promoting assembly of the postsynaptic gephyrin scaffold. Intriguingly, loss of Nlgn2 differentially affects subsets of GABAergic synapses, indicating that synapse-specific interactors and redundancies define its function, but the nature of these interactions remain poorly understood. Here we investigated how Nlgn2 function in hippocampal area CA1 is modulated by two proposed interaction partners, MDGA1 and MDGA2. We show that loss of MDGA1 expression, but not heterozygous deletion of MDGA2, ameliorates the abnormal cytosolic gephyrin aggregation, the reduction in inhibitory synaptic transmission and the exacerbated anxiety-related behaviour characterizing Nlgn2 knockout (KO) mice. Additionally, combined Nlgn2 and MDGA1 deletion causes an exacerbated layer-specific loss of gephyrin puncta. Given that both Nlgn2 and the MDGA1 have been correlated with many psychiatric disorders, our data support the notion that cytosolic gephyrin aggregation may represent an interesting target for novel therapeutic strategies.

IGLON5 Frequency in Idiopathic REM Sleep Behavior Disorder: A Multicenter Study.

BACKGROUND AND OBJECTIVES: Idiopathic/isolated REM sleep behavior disorder (iRBD) has been strongly linked to neurodegenerative synucleinopathies such as Parkinson disease, dementia with Lewy bodies, and multiple system atrophy. However, there have been increasing reports of RBD as a presenting feature of serious and treatable autoimmune syndromes, particularly IGLON5. This study's objective was to investigate the frequency of autoantibodies in a large cohort of participants with iRBD. METHODS: Participants were enrolled in the North American Prodromal Synucleinopathy cohort with polysomnography-confirmed iRBD, free of parkinsonism and dementia. Plasma samples were systematically screened for the autoantibodies IGLON5, DPPX, LGI1, and CASPR2 using plasma IgG cell-based assay. Positive or equivocal results were confirmed by repeat testing, plus tissue-based indirect immunofluorescence assay for IGLON5. RESULTS: Of 339 samples analyzed, 3 participants (0.9%) had confirmed positive IGLON5 autoantibodies in the cell-based assay, which were confirmed by the tissue-based assay. An additional participant was positive for CASPR2 with low titer by cell-based assay only (of lower clinical certainty). These cases exhibited a variety of symptoms including dream enactment, cognitive decline, autonomic dysfunction, and motor symptoms. In 1 IGLON5 case and the CASPR2 case, evolution was suggestive of typical synucleinopathy, suggesting the possibility that findings were incidental. However, 2 participants with IGLON5 died before diagnosis was clinically suspected, with a final clinical picture highly suggestive of autoimmune disease. DISCUSSION: Our finding that nearly 1% of a large iRBD cohort may have a serious but potentially treatable autoantibody syndrome has important clinical implications. In particular, it raises the question of whether autoantibody testing for IGLON-5-IgG should be widely implemented for participants with iRBD, considering the difficulty in diagnosis of autoimmune diseases, their response to treatment, and the potential for rapid disease progression. However, any routine testing protocol will also have to consider costs and potential adverse effects of false-positive findings. TRIAL REGISTRATION INFORMATION: NCT03623672.

Proximity interactome of lymphatic VE-cadherin reveals mechanisms of junctional remodeling and reelin secretion.

The adhesion receptor vascular endothelial (VE)-cadherin transduces an array of signals that modulate crucial lymphatic cell behaviors including permeability and cytoskeletal remodeling. Consequently, VE-cadherin must interact with a multitude of intracellular proteins to exert these functions. Yet, the full protein interactome of VE-cadherin in endothelial cells remains a mystery. Here, we use proximity proteomics to illuminate how the VE-cadherin interactome changes during junctional reorganization from dis-continuous to continuous junctions, triggered by the lymphangiogenic factor adrenomedullin. These analyses identified interactors that reveal roles for ADP ribosylation factor 6 (ARF6) and the exocyst complex in VE-cadherin trafficking and recycling. We also identify a requisite role for VE-cadherin in the in vitro and in vivo control of secretion of reelin-a lymphangiocrine glycoprotein with recently appreciated roles in governing heart development and injury repair. This VE-cadherin protein interactome shines light on mechanisms that control adherens junction remodeling and secretion from lymphatic endothelial cells.

Further insights into anti-IgLON5 disease: a case with complex clinical presentation.

BACKGROUND: Anti-IgLON5 disease is an autoimmune encephalitis overlapping with neurodegenerative disorders due to pathological accumulation of hyperphosphorylated tau. It is characterized by several clinical manifestations determined by involvement of different brain areas, and mild response to first-line immunotherapies. We report a case of anti-IgLON5 disease with a multifaceted semiology and an unusually good response to glucocorticoid monotherapy. CASE PRESENTATION: A 68-year-old man with type 2 diabetes was evaluated for an 8-month history of progressive gait disorder causing frequent falls. He also suffered from obstructive sleep apneas and complained of dysphonia, dysarthria, occasional dysphagia, urinary incontinence, and upper limb action tremor. Neurological examination demonstrated bilateral eyelid ptosis, limitation of ocular horizontal smooth pursuit movements, slow horizontal saccades, and lack of inhibition of the vestibulo-ocular reflex during rapid horizontal head torsions. The patient also displayed involuntary, slow, rhythmic movements of the left periorbital and perioral muscles, spreading to the ipsilateral hemipalate and hemitongue, along with bilateral negative upper limb myoclonus. There were proximal muscle wasting in the upper limbs, proximal weakness of the four limbs, and diffuse fasciculations. Ataxia of stance and gait and of the four limbs was noted. MRI of the brain and spine was unremarkable; nerve conduction studies revealed a chronic, predominantly demyelinating, sensory-motor polyneuropathy, probably due to diabetes. Routine CSF examination was unrevealing and serum GFAP level was 89.6 pg/mL; however, the autoimmunity tests revealed a high-titer positivity for anti-IgLON5 autoantibodies in both CSF and serum, leading to the diagnosis of anti-IgLON5 disease. Symptoms improved significantly after intravenous methylprednisolone. CONCLUSIONS: Hemifacial and hemiorolingual myorhythmia along with peculiar oculomotor abnormalities characterizes the multifaceted clinical picture of our case. The complex semiology of our patient may reflect multifocal targeting of the autoimmune process or sequential spreading of tau inclusions in different brain areas. Our patient's optimal response to glucocorticoid monotherapy could be underpinned by a slightly different phenotype in which autoimmunity plays a greater pathogenic role than tauopathy, with a lower burden of tau deposition. In such patients, neurodegeneration and tau accumulation could be merely secondary to immune-mediated neuronal dysfunction, supporting the existence of a group of glucocorticoid-responsive patients.

Effects of Human Neural Stem Cells Overexpressing Neuroligin and Neurexin in a Spinal Cord Injury Model.

Recent studies have highlighted the therapeutic potential of stem cells for various diseases. However, unlike other tissues, brain tissue has a specific structure, consisting of synapses. These synapses not only transmit but also process and refine information. Therefore, synaptic regeneration plays a key role in therapy of neurodegenerative disorders. Neurexins (NRXNs) and neuroligins (NLGNs) are synaptic cell adhesion molecules that connect pre- and postsynaptic neurons at synapses, mediate trans-synaptic signaling, and shape neural network properties by specifying synaptic functions. In this study, we investigated the synaptic regeneration effect of human neural stem cells (NSCs) overexpressing NRXNs (F3.NRXN) and NLGNs (F3.NLGN) in a spinal cord injury model. Overexpression of NRXNs and NLGNs in the neural stem cells upregulated the expression of synaptophysin, PSD95, VAMP2, and synapsin, which are synaptic markers. The BMS scores indicated that the transplantation of F3.NRXN and F3.NLGN enhanced the recovery of locomotor function in adult rodents following spinal cord injury. Transplanted F3.NRXN and F3.NLGN differentiated into neurons and formed a synapse with the host cells in the spinal cord injury mouse model. In addition, F3.NRXN and F3.NLGN cells restored growth factors (GFs) and neurotrophic factors (NFs) and induced the proliferation of host cells. This study suggested that NSCs overexpressing NRXNs and NLGNs could be candidates for cell therapy in spinal cord injuries by facilitating synaptic regeneration.

NINJ1: A new player in multiple sclerosis pathogenesis and potential therapeutic target.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by demyelination. Current treatment options for MS focus on immunosuppression, but their efficacy can be limited. Recent studies suggest a potential role for nerve injury-induced protein 1 (NINJ1) in MS pathogenesis. NINJ1, a protein involved in cell death and inflammation, may contribute to the infiltration and activation of inflammatory cells in the CNS, potentially through enhanced blood-brain barrier crossing; enhancing plasma membrane rupture during cell death, leading to the release of inflammatory mediators and further tissue damage. This review explores the emerging evidence for NINJ1's involvement in MS. It discusses how NINJ1 might mediate the migration of immune cells across the blood-brain barrier, exacerbate neuroinflammation, and participate in plasma membrane rupture-related damage. Finally, the review examines potential therapeutic strategies targeting NINJ1 for improved MS management. Abbreviations: MS, Multiple sclerosis; CNS, Central nervous system; BBB, Blood-brain barrier; GSDMD, Gasdermin-D; EAE, Experimental autoimmune encephalitis; HMGB-1, High mobility group box-1 protein; LDH, Lactate dehydrogenase; PMR, Plasma membrane rupture; DMF, Dimethyl fumarate; DUSP1, Dual-specificity phosphatase 1; PAMPs, Pathogen-associated molecular patterns; DAMPs, Danger-associated molecular patterns; PRRs, Pattern recognition receptors; GM-CSF, Granulocyte-macrophage colony stimulating factor; IFN-γ, Interferon gamma; TNF, Tumor necrosis factor; APCs, Antigen-presenting cells; ECs, Endothelial cells; TGF-ß, Transforming growth factor-ß; PBMCs, Peripheral blood mononuclear cells; FACS, Fluorescence-activated cell sorting; MCP-1, Monocyte chemoattractant protein-1; NLRP3, Pyrin domain-containing 3; TCR, T cell receptor; ROS, Reactive oxygen species; AP-1, Activator protein-1; ANG1, Angiopoietin 1; BMDMs, Bone marrow-derived macrophages; Arp2/3, actin-related protein 2/3; EMT, epithelial-mesenchymal transition; FAK, focal adhesion kinase; LIMK1, LIM domain kinase 1; PAK1, p21-activated kinases 1; Rac1, Ras-related C3 botulinum toxin substrate 1; ß-cat, ß-caten; MyD88, myeloid differentiation primary response gene 88; TIRAP, Toll/interleukin-1 receptor domain-containing adapter protein; TLR4, Toll-like receptor 4; IRAKs, interleukin-1 receptor-associated kinases; TRAF6, TNF receptor associated factor 6; TAB2/3, TAK1 binding protein 2/3; TAK1, transforming growth factor-ß-activated kinase 1; JNK, c-Jun N-terminal kinase; ERK1/2, Extracellular Signal Regulated Kinase 1/2; IKK, inhibitor of kappa B kinase; IκB, inhibitor of NF-κB; NF-κB, nuclear factor kappa-B; AP-1, activator protein-1; ASC, Apoptosis-associated Speck-like protein containing a CARD; NEK7, NIMA-related kinase 7; NLRP3, Pyrin domain-containing 3; CREB, cAMP response element-binding protein.

Neurexin-3 in the paraventricular nucleus of the hypothalamus regulates body weight and glucose homeostasis independently of food intake.

Neurexin-3 (Nrxn3) has been genetically associated with obesity, but the underlying neural mechanisms remain poorly understood. This study aimed to investigate the role of Nrxn3 in the paraventricular nucleus of the hypothalamus (PVN) in regulating energy balance and glucose homeostasis. We found that Nrxn3 expression in the PVN was upregulated in response to metabolic stressors, including cold exposure and fasting. Using Cre-loxP technology, we selectively ablated Nrxn3 in CaMKIIα-expressing neurons of the PVN in male mice. This genetic manipulation resulted in marked weight gain attributable to increased adiposity and impaired glucose tolerance, without affecting food intake. Our findings identify PVN CaMKIIα-expressing neurons as a critical locus where Nrxn3 modulates energy balance by regulating adipogenesis and glucose metabolism, independently of appetite. These results reveal a novel neural mechanism potentially linking Nrxn3 dysfunction to obesity pathogenesis, suggesting that targeting PVN Nrxn3-dependent neural pathways may inform new therapeutic approaches for obesity prevention and treatment.

Septins promote macrophage pyroptosis by regulating gasdermin D cleavage and ninjurin-1-mediated plasma membrane rupture.

The septin cytoskeleton is primarily known for roles in cell division and host defense against bacterial infection. Despite recent insights, the full breadth of roles for septins in host defense is poorly understood. In macrophages, Shigella induces pyroptosis, a pro-inflammatory form of cell death dependent upon gasdermin D (GSDMD) pores at the plasma membrane and cell surface protein ninjurin-1 (NINJ1) for membrane rupture. Here, we discover that septins promote macrophage pyroptosis induced by lipopolysaccharide (LPS)/nigericin and Shigella infection, but do not affect cytokine expression or release. We observe that septin filaments assemble at the plasma membrane, and cleavage of GSDMD is impaired in septin-depleted cells. We found that septins regulate mitochondrial dynamics and the expression of NINJ1. Using a Shigella-zebrafish infection model, we show that septin-mediated pyroptosis is an in vivo mechanism of infection control. The discovery of septins as a mediator of pyroptosis may inspire innovative anti-bacterial and anti-inflammatory treatments.

The Inflammation-Induced Dysregulation of Reelin Homeostasis Hypothesis of Alzheimer's Disease.

Alzheimer's disease (AD) accounts for most dementia cases, but we lack a complete understanding of the mechanisms responsible for the core pathology associated with the disease (e.g., amyloid plaque and neurofibrillary tangles). Inflammation has been identified as a key contributor of AD pathology, with recent evidence pointing towards Reelin dysregulation as being associated with inflammation. Here we describe Reelin signaling and outline existing research involving Reelin signaling in AD and inflammation. Research is described pertaining to the inflammatory and immunological functions of Reelin before we propose a mechanism through which inflammation renders Reelin susceptible to dysregulation resulting in the induction and exacerbation of AD pathology. Based on this hypothesis, it is predicted that disorders of both inflammation (including peripheral inflammation and neuroinflammation) and Reelin dysregulation (including disorders associated with upregulated Reelin expression and disorders of Reelin downregulation) have elevated risk of developing AD. We conclude with a description of AD risk in various disorders involving Reelin dysregulation and inflammation.

IgLON5-IgG: Innocent Bystander or Perpetrator?

Anti-IgLON5 (IgLON5-IgG)-associated disease is a newly defined clinical entity. This literature review aims to evaluate its pathogenesis, which remains a pivotal question. Features that favour a primary neurodegenerative mechanism include the non-inflammatory tauopathy neuropathological signature and overrepresentation of microtubule-associated protein tau (MAPT) H1/H1 genotype as seen in other sporadic tauopathies. In contrast, the cell-surface localisation of IgLON5, capability of anti-IgLON5 antibodies to exert direct in vitro pathogenicity and disrupt IgLON5 interactions with its binding partners, human leukocyte antigen (HLA)-DRB1*10:01 and HLA-DQB1*05:01 allele preponderance with high affinity binding of IgLON5 peptides, and responsiveness to immunotherapy favour a primary autoimmune process. The presentation and course of anti-IgLON5-associated disease is heterogenous; hence, we hypothesise that a multitude of immune mechanisms are likely simultaneously operational in this disease cohort.

De novo monoallelic Reelin missense variants cause dominant neuronal migration disorders via a dominant-negative mechanism.

Reelin (RELN) is a secreted glycoprotein essential for cerebral cortex development. In humans, recessive RELN variants cause cortical and cerebellar malformations, while heterozygous variants were associated with epilepsy, autism, and mild cortical abnormalities. However, the functional effects of RELN variants remain unknown. We identified inherited and de novo RELN missense variants in heterozygous patients with neuronal migration disorders (NMDs) as diverse as pachygyria and polymicrogyria. We investigated in culture and in the developing mouse cerebral cortex how different variants impacted RELN function. Polymicrogyria-associated variants behaved as gain-of-function, showing an enhanced ability to induce neuronal aggregation, while those linked to pachygyria behaved as loss-of-function, leading to defective neuronal aggregation/migration. The pachygyria-associated de novo heterozygous RELN variants acted as dominant-negative by preventing WT RELN secretion in culture, animal models, and patients, thereby causing dominant NMDs. We demonstrated how mutant RELN proteins in vitro and in vivo predict cortical malformation phenotypes, providing valuable insights into the pathogenesis of such disorders.

Anti-contactin-associated protein 1 antibody-positive nodopathy presenting with central nervous system symptoms.

Contactin-associated protein 1 (Caspr1) is widespread in both the peripheral and central nervous systems (CNS). However, anti-Caspr1 antibody-positive nodopathy associated with CNS symptoms has not previously been reported. In this case, a 69-year-old man presented with polyneuropathy and memory loss. The patient had negative myoclonus, positive myoclonus, and pseudoathetosis in the upper limbs, and we detected anti-Caspr1 antibodies in the serum and cerebrospinal fluid. Therefore, anti-Caspr1 nodopathy was diagnosed. After rituximab treatment, all symptoms of polyneuropathy, involuntary movements, and memory impairment improved. In conclusion, anti-Caspr1 antibodies might also affect the CNS; therefore, CNS symptoms of anti-Caspr1 nodopathy require attention.

OCRL1 Deficiency Affects the Intracellular Traffic of ApoER2 and Impairs Reelin-Induced Responses.

Lowe Syndrome (LS) is a rare X-linked disorder characterized by renal dysfunction, cataracts, and several central nervous system (CNS) anomalies. The mechanisms underlying the neurological dysfunction in LS remain unclear, albeit they share some phenotypic characteristics similar to the deficiency or dysfunction of the Reelin signaling, a relevant pathway with roles in CNS development and neuronal functions. In this study, we investigated the role of OCRL1, an inositol polyphosphate 5-phosphatase encoded by the OCRL gene, mutated in LS, focusing on its impact on endosomal trafficking and receptor recycling in human neuronal cells. Specifically, we tested the effects of OCRL1 deficiency in the trafficking and signaling of ApoER2/LRP8, a receptor for the ligand Reelin. We found that loss of OCRL1 impairs ApoER2 intracellular trafficking, leading to reduced receptor expression and decreased levels at the plasma membrane. Additionally, human neurons deficient in OCRL1 showed impairments in ApoER2/Reelin-induced responses. Our findings highlight the critical role of OCRL1 in regulating ApoER2 endosomal recycling and its impact on the ApoER2/Reelin signaling pathway, providing insights into potential mechanisms underlying the neurological manifestations of LS.

Versatile nanobody-based approach to image, track and reconstitute functional Neurexin-1 in vivo.

Neurexins are key adhesion proteins that coordinate extracellular and intracellular synaptic components. Nonetheless, the low abundance of these multidomain proteins has complicated any localization and structure-function studies. Here we combine an ALFA tag (AT)/nanobody (NbALFA) tool with classic genetics, cell biology and electrophysiology to examine the distribution and function of the Drosophila Nrx-1 in vivo. We generate full-length and ΔPDZ ALFA-tagged Nrx-1 variants and find that the PDZ binding motif is key to Nrx-1 surface expression. A PDZ binding motif provided in trans, via genetically encoded cytosolic NbALFA-PDZ chimera, fully restores the synaptic localization and function of NrxΔPDZ-AT. Using cytosolic NbALFA-mScarlet intrabody, we achieve compartment-specific detection of endogenous Nrx-1, track live Nrx-1 transport along the motor neuron axons, and demonstrate that Nrx-1 co-migrates with Rab2-positive vesicles. Our findings illustrate the versatility of the ALFA system and pave the way towards dissecting functional domains of complex proteins in vivo.

EphA4 Induces the Phosphorylation of an Intracellular Adaptor Protein Dab1 via Src Family Kinases.

Dab1 is an intracellular adaptor protein essential for brain formation during development. Tyrosine phosphorylation in Dab1 plays important roles in neuronal migration, dendrite development, and synapse formation by affecting several downstream pathways. Reelin is the best-known extracellular protein that induces Dab1 phosphorylation. However, whether other upstream molecule(s) contribute to Dab1 phosphorylation remains largely unknown. Here, we found that EphA4, a member of the Eph family of receptor-type tyrosine kinases, induced Dab1 phosphorylation when co-expressed in cultured cells. Tyrosine residues phosphorylated by EphA4 were the same as those phosphorylated by Reelin in neurons. The autophosphorylation of EphA4 was necessary for Dab1 phosphorylation. We also found that EphA4-induced Dab1 phosphorylation was mediated by the activation of the Src family tyrosine kinases. Interestingly, Dab1 phosphorylation was not observed when EphA4 was activated by ephrin-A5 in cultured cortical neurons, suggesting that Dab1 is localized in a different compartment in them. EphA4-induced Dab1 phosphorylation may occur under limited and/or pathological conditions in the brain.

The Association between Obesity Susceptibility and Polymorphisms of MC4R, SH2B1, and NEGR1 in Tibetans.

Background: A high-altitude environment has inhibitory effects on obesity. Tibetans are not a high-risk population for obesity, but there are still obese individuals within that population. Obesity has become a worldwide health problem, and previous studies have found that obesity is closely associated with hereditary factors. Few studies have investigated obesity in Tibetans, and the association between gene polymorphisms and obesity in Tibetans remains unclear. Methods: Our study investigated the fat mass of 140 native Tibetan individuals (70 men and 70 women) from Lhasa and analyzed the associations between polymorphisms of melanocortin 4 receptor (MC4R), Src homology 2B adapter protein 1 (SH2B1), and neuronal growth regulator 1 (NEGR1) and obesity. Result: Among Tibetan individuals, there were differences in genotype and allele frequencies between those in the obesity group and those in the healthy group at MC4R (rs17782313) and SH2B1 (rs7359397). The polymorphisms of MC4R (rs17782313) were associated with fat mass and obesity in Tibetan men and women, and there was an association between SH2B1 (rs7359397) polymorphisms and fat mass and obesity in Tibetan men. However, polymorphisms of NEGR1 (rs3101336) were not associated with fat mass or obesity in Tibetan individuals. Conclusion: Among Tibetan individuals, polymorphisms of MC4R (rs17782313) and SH2B1 (rs7359397) were associated with obesity, but NEGR1 (rs3101336) polymorphisms were not associated with obesity.

Programmed cell death: NINJ1 and mechanisms of plasma membrane rupture.

Lytic cell death culminates in cell swelling and plasma membrane rupture (PMR). The cellular contents released, including proteins, metabolites, and nucleic acids, can act as danger signals and induce inflammation. During regulated cell death (RCD), lysis is actively initiated and can be preceded by an initial loss of membrane integrity caused by pore-forming proteins, allowing small molecules and cytokines to exit the cell. A recent seminal discovery showed that ninjurin1 (NINJ1) is the common executioner of PMR downstream of RCD, resulting in the release of large proinflammatory molecules and representing a novel target of cell death-associated lysis. We summarize recent developments in understanding membrane integrity and rupture of the plasma membrane with a focus on NINJ1.

Bnip3 expression is strongly associated with reelin-positive entorhinal cortex layer II neurons.

In layer II of the entorhinal cortex, the principal neurons that project to the dentate gyrus and the CA3/2 hippocampal fields markedly express the large glycoprotein reelin (Re + ECLII neurons). In rodents, neurons located at the dorsal extreme of the EC, which border the rhinal fissure, express the highest levels, and the expression gradually decreases at levels successively further away from the rhinal fissure. Here, we test two predictions deducible from the hypothesis that reelin expression is strongly correlated with neuronal metabolic rate. Since the mitochondrial turnover rate serves as a proxy for energy expenditure, the mitophagy rate arguably also qualifies as such. Because messenger RNA of the canonical promitophagic BCL2 and adenovirus E1B 19-kDa-interacting protein 3 (Bnip3) is known to be highly expressed in the EC, we predicted that Bnip3 would be upregulated in Re + ECLII neurons, and that the degree of upregulation would strongly correlate with the expression level of reelin in these neurons. We confirm both predictions, supporting that the energy requirement of Re + ECLII neurons is generally high and that there is a systematic increase in metabolic rate as one moves successively closer to the rhinal fissure. Intriguingly, the systematic variation in energy requirement of the neurons that manifest the observed reelin gradient appears to be consonant with the level of spatial and temporal detail by which they encode information about the external environment.

NINJ1 Facilitates Abdominal Aortic Aneurysm Formation via Blocking TLR4-ANXA2 Interaction and Enhancing Macrophage Infiltration.

Abdominal aortic aneurysm (AAA) is a common and potentially life-threatening condition. Chronic aortic inflammation is closely associated with the pathogenesis of AAA. Nerve injury-induced protein 1 (NINJ1) is increasingly acknowledged as a significant regulator of the inflammatory process. However, the precise involvement of NINJ1 in AAA formation remains largely unexplored. The present study finds that the expression level of NINJ1 is elevated, along with the specific expression level in macrophages within human and angiotensin II (Ang II)-induced murine AAA lesions. Furthermore, Ninj1flox/flox and Ninj1flox/floxLyz2-Cre mice on an ApoE-/- background are generated, and macrophage NINJ1 deficiency inhibits AAA formation and reduces macrophage infiltration in mice infused with Ang II. Consistently, in vitro suppressing the expression level of NINJ1 in macrophages significantly restricts macrophage adhesion and migration, while attenuating macrophage pro-inflammatory responses. Bulk RNA-sequencing and pathway analysis uncover that NINJ1 can modulate macrophage infiltration through the TLR4/NF-κB/CCR2 signaling pathway. Protein-protein interaction analysis indicates that NINJ1 can activate TLR4 by competitively binding with ANXA2, an inhibitory interacting protein of TLR4. These findings reveal that NINJ1 can modulate AAA formation by promoting macrophage infiltration and pro-inflammatory responses, highlighting the potential of NINJ1 as a therapeutic target for AAA.

Late stage melanoma is hallmarked by low NLGN4X expression leading to HIF1A accumulation.

BACKGROUND: Despite ongoing research and recent advances in therapy, metastatic melanoma remains one of the cancers with the worst prognosis. Here we studied the postsynaptic cell adhesion molecule Neuroligin 4X (NLGN4X) and investigated its role in melanoma progression. METHODS: We analysed histologic samples to assess the expression and predictive value of NLGN4X in human melanoma. The oncogenic role of NLGN4X was determined by loss or gain-of-function experiments in vitro as well as by analysis of tumorspheres, which were grafted to human skin organoids derived from pluripotent stem cells. Whole genome expression analysis and validation experiments were performed to clarify the molecular mechanism. RESULTS: We identified that suppression of NLGN4X down regulated the prefoldin member Von Hippel-Lindau binding protein 1 (VBP1). Moreover, loss of VBP1 was sufficient for accumulation of HIF1A and HIF1A signalling was further shown to be essential for the acquisition of migratory properties in melanoma. We re-established NLGN4X expression in late stage melanoma lines and observed decreased tumour growth after transplantation to human skin organoids generated from pluripotent stem cells. In line, we showed that high amounts of NLGN4X and its target VBP1 in human patient samples had a beneficial prognostic effect on patient survival. CONCLUSION: In view of these findings, we propose that decreased amounts of NLGN4X are indicative of a metastatic melanoma phenotype and that loss of NLGN4X provides a novel mechanism for HIF induction.