Neuropsin promotes hippocampal synaptogenesis by regulating the expression and cleavage of L1CAM.

During early postnatal brain development, the formation of proper synaptic connections between neurons is crucial for the development of functional neural networks. Recent studies have established the involvement of protease-mediated modulations of extracellular components in both synapse formation and elimination. The secretory serine protease neuropsin (also known as kallikrein-8) cleaves a few transmembrane or extracellular matrix proteins in a neural activity-dependent manner and regulates neural plasticity. However, neuropsin-dependent proteolysis of extracellular components and the involvement of these components in mouse brain development are poorly understood. We have observed that during hippocampus development, expression of neuropsin and levels of full-length or cleaved fragments of the neuropsin substrate protein L1 cell adhesion molecule (L1CAM) positively correlate with synaptogenesis. Our subcellular fractionation studies show that the expression of neuropsin and its proteolytic activity on L1CAM are enriched at developing hippocampal synapses. Activation of neuropsin expression upregulates the transcription and cleavage of L1CAM. Furthermore, blocking of neuropsin activity, as well as knockdown of L1CAM expression, significantly downregulates in vitro hippocampal synaptogenesis. Taken together, these findings provide evidence for the involvement of neuropsin activity-dependent regulation of L1CAM expression and cleavage in hippocampal synaptogenesis.

N-BAR and F-BAR proteins-endophilin-A3 and PSTPIP1-control clathrin-independent endocytosis of L1CAM.

Recent advances in the field demonstrate the high diversity and complexity of endocytic pathways. In the current study, we focus on the endocytosis of L1CAM. This glycoprotein plays a major role in the development of the nervous system, and is involved in cancer development and is associated with metastases and poor prognosis. Two L1CAM isoforms are subject to endocytosis: isoform 1, described as a clathrin-mediated cargo; isoform 2, whose endocytosis has never been studied. Deciphering the molecular machinery of isoform 2 internalisation should contribute to a better understanding of its pathophysiological role. First, we demonstrated in our cellular context that both isoforms of L1CAM are mainly a clathrin-independent cargo, which was not expected for isoform 1. Second, the mechanism of L1CAM endocytosis is specifically mediated by the N-BAR domain protein endophilin-A3. Third, we discovered PSTPIP1, an F-BAR domain protein, as a novel actor in this endocytic process. Finally, we identified galectins as endocytic partners and negative regulators of L1CAM endocytosis. In summary, the interplay of the BAR proteins endophilin-A3 and PSTPIP1, and galectins fine tune the clathrin-independent endocytosis of L1CAM.

KLF12 interacts with TRIM27 to affect cisplatin resistance and cancer metastasis in esophageal squamous cell carcinoma by regulating L1CAM expression.

Krüppel-like factor 12 (KLF12) has been characterized as a transcriptional repressor, and previous studies have unveiled its roles in angiogenesis, neural tube defect, and natural killer (NK) cell proliferation. However, the contribution of KLF12 to cancer treatment remains undefined. Here, we show that KLF12 is downregulated in various cancer types, and KLF12 downregulation promotes cisplatin resistance and cancer metastasis in esophageal squamous cell carcinoma (ESCC). Mechanistically, KLF12 binds to the promoters of L1 Cell Adhesion Molecule (L1CAM) and represses its expression. Depletion of L1CAM abrogates cisplatin resistance and cancer metastasis caused by KLF12 loss. Moreover, the E3 ubiquitin ligase tripartite motif-containing 27 (TRIM27) binds to the N-terminal region of KLF12 and ubiquitinates KLF12 at K326 via K33-linked polyubiquitination. Notably, TRIM27 depletion enhances the transcriptional activity of KLF12 and consequently inhibits L1CAM expression. Overall, our study elucidated a novel regulatory mechanism involving TRIM27, KLF12 and L1CAM, which plays a substantial role in cisplatin resistance and cancer metastasis in ESCC. Targeting these genes could be a promising approach for ESCC treatment.

TFG regulates secretory and endosomal sorting pathways in neurons to promote their activity and maintenance.

Molecular pathways that intrinsically regulate neuronal maintenance are poorly understood, but rare pathogenic mutations that underlie neurodegenerative disease can offer important insights into the mechanisms that facilitate lifelong neuronal function. Here, we leverage a rat model to demonstrate directly that the TFG p.R106C variant implicated previously in complicated forms of hereditary spastic paraplegia (HSP) underlies progressive spastic paraparesis with accompanying ventriculomegaly and thinning of the corpus callosum, consistent with disease phenotypes identified in adolescent patients. Analyses of primary cortical neurons obtained from CRISPR-Cas9-edited animals reveal a kinetic delay in biosynthetic secretory protein transport from the endoplasmic reticulum (ER), in agreement with prior induced pluripotent stem cell-based studies. Moreover, we identify an unexpected role for TFG in the trafficking of Rab4A-positive recycling endosomes specifically within axons and dendrites. Impaired TFG function compromises the transport of at least a subset of endosomal cargoes, which we show results in down-regulated inhibitory receptor signaling that may contribute to excitation-inhibition imbalances. In contrast, the morphology and trafficking of other organelles, including mitochondria and lysosomes, are unaffected by the TFG p.R106C mutation. Our findings demonstrate a multifaceted role for TFG in secretory and endosomal protein sorting that is unique to cells of the central nervous system and highlight the importance of these pathways to maintenance of corticospinal tract motor neurons.

Expression of L1 Cell Adhesion Molecule, a Nephronal Principal Cell Marker, in Nephrogenic Adenoma.

Nephrogenic adenoma (NA) is a benign, reactive lesion seen predominantly in the urinary bladder and often associated with antecedent inflammation, instrumentation, or an operative history. Its histopathologic diversity can create diagnostic dilemmas and pathologists use morphologic evaluation along with available immunohistochemical (IHC) markers to navigate these challenges. IHC assays currently do not designate or specify NA's potential putative cell of origin. Leveraging single-cell RNA-sequencing technology, we nominated a principal (P) cell-collecting duct marker, L1 cell adhesion molecule (L1CAM), as a potential biomarker for NA. IHC characterization revealed L1CAM to be positive in all 35 (100%) patient samples of NA; negative expression was seen in the benign urothelium, benign prostatic glands, urothelial carcinoma (UCA) in situ, prostatic adenocarcinoma, majority of high-grade UCA, and metastatic UCA. In the study, we also used single-cell RNA sequencing to nominate a novel compendium of biomarkers specific for the proximal tubule, loop of Henle, and distal tubule (DT) (including P and intercalated cells), which can be used to perform nephronal mapping using RNA in situ hybridization and IHC technology. Employing this technique on NA we found enrichment of both the P-cell marker L1CAM and, the proximal tubule type-A and -B cell markers, PDZKI1P1 and PIGR, respectively. The cell-type markers for the intercalated cell of DTs (LINC01187 and FOXI1), and the loop of Henle (UMOD and IRX5), were found to be uniformly absent in NA. Overall, our findings show that based on cell type-specific implications of L1CAM expression, the shared expression pattern of L1CAM between DT P cells and NA. L1CAM expression will be of potential value in assisting surgical pathologists toward a diagnosis of NA in challenging patient samples.

L1 Cell Adhesion Molecule (L1CAM) Expression and Molecular Alterations Distinguish Low-Grade Oncocytic Tumor From Eosinophilic Chromophobe Renal Cell Carcinoma.

Renal low-grade oncocytic tumor (LOT) is a recently recognized renal cell neoplasm designated within the "other oncocytic tumors" category in the 2022 World Health Organization classification system. Although the clinicopathologic, immunohistochemical, and molecular features reported for LOT have been largely consistent, the data are relatively limited. The morphologic overlap between LOT and other low-grade oncocytic neoplasms, particularly eosinophilic chromophobe renal cell carcinoma (E-chRCC), remains a controversial area in renal tumor classification. To address this uncertainty, we characterized and compared large cohorts of LOT (n = 67) and E-chRCC (n = 69) and revealed notable differences between the 2 entities. Clinically, LOT predominantly affected women, whereas E-chRCC showed a male predilection. Histologically, although almost all LOTs were dominated by a small-nested pattern, E-chRCC mainly showed solid and tubular architectures. Molecular analysis revealed that 87% of LOT cases harbored mutations in the tuberous sclerosis complex (TSC)-mTOR complex 1 (mTORC1) pathway, most frequently in MTOR and RHEB genes; a subset of LOT cases had chromosomal 7 and 19q gains. In contrast, E-chRCC lacked mTORC1 mutations, and 60% of cases displayed chromosomal losses characteristic of chRCC. We also explored the cell of origin for LOT and identified L1 cell adhesion molecule (L1CAM), a collecting duct and connecting tubule principal cell marker, as a highly sensitive and specific ancillary test for differentiating LOT from E-chRCC. This distinctive L1CAM immunohistochemical labeling suggests the principal cells as the cell of origin for LOT, unlike the intercalated cell origin of E-chRCC and oncocytoma. The ultrastructural analysis of LOT showed normal-appearing mitochondria and intracytoplasmic lumina with microvilli, different from what has been described for chRCC. Our study further supports LOT as a unique entity with a benign clinical course. Based on the likely cell of origin and its clinicopathologic characteristics, we propose that changing the nomenclature of LOT to "Oncocytic Principal Cell Adenoma of the Kidney" may be a better way to define and describe this entity.

X-ray structure and function of fibronectin domains two and three of the neural cell adhesion molecule L1.

The cell adhesion molecule L1 (L1CAM, L1 in short) plays crucial roles during neural development, regeneration after injury, synapse formation, synaptic plasticity and tumor cell migration. L1 belongs to the immunoglobulin superfamily and comprises in its extracellular part six immunoglobulin (Ig)-like domains and five fibronectin type III homologous repeats (FNs). The second Ig-like domain has been validated for self- (so-called homophilic) binding between cells. Antibodies against this domain inhibit neuronal migration in vitro and in vivo. The fibronectin type III homologous repeats FN2 and FN3 bind small molecule agonistic L1 mimetics and contribute to signal transduction. FN3 has a stretch of 25 amino acids that can be triggered with a monoclonal antibody, or the L1 mimetics, to enhance neurite outgrowth and neuronal cell migration in vitro and in vivo. To correlate the structural features of these FNs with function, we determined a high-resolution crystal structure of a FN2FN3 fragment, which is functionally active in cerebellar granule cells and binds several mimetics. The structure illustrates that both domains are connected by a short linker sequence allowing a flexible and largely independent organization of both domains. This becomes further evident by comparing the X-ray crystal structure with models derived from Small-Angle X-ray Scattering (SAXS) data for FN2FN3 in solution. Based on the X-ray crystal structure, we identified five glycosylation sites which we believe are crucial for folding and stability of these domains. Our study signifies an advance in the understanding of structure-functional relationships of L1.

Evaluation of prognostic potential of ß-catenin and L1CAM expression according to endometrial cancer risk group.

OBJECTIVE: We investigate the prognostic role of ß-catenin and L1 neuronal cell-adhesion molecule (L1CAM) according to risk groups in endometrial carcinomas (EC). METHODS: A total of 335 EC patients were classified according to the Proactive Molecular Risk Classifier for Endometrial Cancer. We evaluated the expression of ß-catenin and L1CAM using immunohistochemistry, and their association with clinicopathological characteristics and survival. RESULTS: The expressions of ß-catenin and L1CAM were observed in 10.4% of all patients, respectively, and showed mutually exclusive pattern. While ß-catenin expression was associated with endometrioid histology (p = 0.035) and low tumor grade (p = 0.045), L1CAM expression was associated with non-endometrioid histology (p < 0.001), high tumor grade (p < 0.001), lymphovascular space invasion (p = 0.006), and advanced International Federation of Gynecology and Obstetrics (FIGO) stage (p = 0.001). ß-catenin expression was most frequent in the no specific molecular (NSMP) group (26/35, 74.3%), followed by the DNA polymerase-ε-mutated (POLE-mut) (6/35, 17.1%), and mismatch repair-deficiency (dMMR) (3/35, 8.6%). L1CAM expression was most frequent in the p53-abnormal group (22/35, 62.9%), followed by the NSMP (6/35, 17.1%), dMMR (4/35, 11.4%), and POLE-mut (3/35, 8.6%). Although both markers did not show statistical significance in multivariate analysis for both progression-free survival (PFS) and overall survival in entire cohort, ß-catenin positivity was identified as the sole factor associated with worse PFS in the high-intermediate risk subgroup (p = 0.001). CONCLUSION: The expression of nuclear ß-catenin may serve as a potential biomarker for predicting recurrence and guiding therapeutic strategies in high-intermediate risk EC patients.

The impact of estrogen receptor and L1 cell adhesion molecule expression on endometrial cancer outcome correlates with clinicopathological risk group and molecular subgroup.

OBJECTIVE: To assess the risk stratification of clinicopathologically and molecularly classified endometrial cancer based on estrogen receptor (ER) and L1 cell adhesion molecule (L1CAM) expression. METHODS: This was a retrospective study of patients who underwent primary treatment at a single tertiary center. Carcinomas were classified into 5 clinicopathological risk groups, as per European guidelines. Immunohistochemistry and polymerase-ϵ sequencing were conducted for molecular classification and determination of ER and L1CAM expression. RESULTS: Data from 1044 patients were analyzed. The median follow-up was 67.5 months. In univariable analyses, ER expression correlated with improved disease-specific survival (DSS) in the "no specific molecular profile" (NSMP) (P < 0.001) and mismatch repair deficient (MMRd) (P = 0.002) subgroups. Negative L1CAM expression was associated with enhanced DSS in the NSMP subgroup alone (P < 0.001). ER (hazard ratio [HR] 0.18), but not L1CAM, exhibited prognostic significance within NSMP when controlling for parameters available at the time of diagnosis (tumor histotype, grade, age). ER and L1CAM were not independently associated with DSS within NSMP when controlling for parameters available after surgery (clinicopathological risk groups, age, adjuvant therapy). However, in high-risk-advanced-metastatic cases, both ER (HR 0.26) and L1CAM (HR 3.9) independently correlated with DSS. Similarly, within MMRd, ER was associated with improved DSS in high-risk-advanced-metastatic carcinomas (HR 0.42). CONCLUSION: The prognostic significance of ER and L1CAM varies across clinicopathological risk groups and molecular subgroups of endometrial cancer. Notably, risk assessment for high-risk-advanced-metastatic NSMP and MMRd subtype carcinomas can be refined by ER status.

"Floppy brain" in congenital hydrocephalus.

Hydrocephalus is classically considered to be a disorder of altered cerebrospinal fluid (CSF) circulation, leading to the dilation of cerebral ventricles. Here, we report a clinical case of a patient who presented with fetal-onset hydrocephalus with diffusely reduced cortical and white matter volumes resulting from a genetic mutation in L1CAM, a well-known hydrocephalus disease gene involved in neuronal cell adhesion and axon development. After CSF was drained from the ventricle intraoperatively, the patient's cortical mantle collapsed and exhibited a "floppy" appearance on neuroimaging, suggesting an inability of the hydrocephalic brain to maintain its structural integrity. The case provides clinical support for altered brain biomechanical properties in human hydrocephalus and adds to the emerging hypothesis that altered brain development with secondary impact on brain structural stability may contribute to ventricular enlargement in some subsets of hydrocephalus.

The Conundrum of Mechanics Versus Genetics in Congenital Hydrocephalus and Its Implications for Fetal Therapy Approaches: A Scoping Review.

Recent advances in gene therapy, particularly for single-gene disorders (SGDs), have led to significant progress in developing innovative precision medicine approaches that hold promise for treating conditions such as primary hydrocephalus (CH), which is characterized by increased cerebrospinal fluid (CSF) volumes and cerebral ventricular dilation as a result of impaired brain development, often due to genetic causes. CH is a significant contributor to childhood morbidity and mortality and a driver of healthcare costs. In many cases, prenatal ultrasound can readily identify ventriculomegaly as early as 14-20 weeks of gestation, with severe cases showing poor neurodevelopmental outcomes. Postnatal surgical approaches, such as ventriculoperitoneal shunts, do not address the underlying genetic causes, have high complication rates, and result in a marginal improvement of neurocognitive deficits. Prenatal somatic cell gene therapy (PSCGT) promises a novel approach to conditions such as CH by targeting genetic mutations in utero, potentially improving long-term outcomes. To better understand the pathophysiology, genetic basis, and molecular pathomechanisms of CH, we conducted a scoping review of the literature that identified over 160 published genes linked to CH. Mutations in L1CAM, TRIM71, MPDZ, and CCDC88C play a critical role in neural stem cell development, subventricular zone architecture, and the maintenance of the neural stem cell niche, driving the development of CH. Early prenatal interventions targeting these genes could curb the development of the expected CH phenotype, improve neurodevelopmental outcomes, and possibly limit the need for surgical approaches. However, further research is needed to establish robust genotype-phenotype correlations and develop safe and effective PSCGT strategies for CH.

Functional study of a rare L1CAM gene c.1759G>C variant prove its pathogenicity.

L1 syndrome, a neurological disorder with an X-linked inheritance pattern, mainly results from mutations occurring in the L1 cell adhesion molecule (L1CAM) gene. The L1CAM molecule, belonging to the immunoglobulin (Ig) superfamily of neurocyte adhesion molecules, plays a pivotal role in facilitating intercellular signal transmission across membranes and is indispensable for proper neuronal development and function. This study identified a rare missense variant (c.1759G>C; p.G587R) in the L1CAM gene within a male fetus presenting with hydrocephalus. Due to a lack of functional analysis, the significance of the L1CAM mutation c.1759G>C (p.G587R) remains unknown. We aimed to perform further verification for its pathogenicity. Blood samples were obtained from the proband and his parents for trio clinical exome sequencing and mutation analysis. Expression level analysis was conducted using western blot techniques. Immunofluorescence was employed to investigate L1CAM subcellular localization, while cell aggregation and cell scratch assays were utilized to assess protein function. The study showed that the mutation (c.1759G>C; p.G587R) affected posttranslational glycosylation modification and induced alterations in the subcellular localization of L1-G587R in the cells. It resulted in the diminished expression of L1CAM on the cell surface and accumulation in the endoplasmic reticulum. The p.G587R altered the function of L1CAM protein and reduced homophilic adhesion capacity of proteins, leading to impaired adhesion and migration of proteins between cells. Our findings provide first biological evidence for the association between the missense mutation (c.1759G>c; p.G587R) in the L1CAM gene and L1 syndrome, confirming the pathogenicity of this missense mutation.

Increased plasmin-mediated proteolysis of L1CAM in a mouse model of idiopathic normal pressure hydrocephalus.

Idiopathic normal pressure hydrocephalus (iNPH) is a common neurological disorder that is characterized by enlarged cerebral ventricles, gait difficulty, incontinence, and dementia. iNPH usually develops after the sixth decade of life in previously asymptomatic individuals. We recently reported that loss-of-function deletions in CWH43 lead to the development of iNPH in a subgroup of patients, but how this occurs is poorly understood. Here, we show that deletions in CWH43 decrease expression of the cell adhesion molecule, L1CAM, in the brains of CWH43 mutant mice and in human HeLa cells harboring a CWH43 deletion. Loss-of-function mutations in L1CAM are a common cause of severe neurodevelopmental defects that include congenital X-linked hydrocephalus. Mechanistically, we find that CWH43 deletion leads to decreased N-glycosylation of L1CAM, decreased association of L1CAM with cell membrane lipid microdomains, increased L1CAM cleavage by plasmin, and increased shedding of cleaved L1CAM in the cerebrospinal fluid. CWH43 deletion also decreased L1CAM nuclear translocation, suggesting decreased L1CAM intracellular signaling. Importantly, the increase in L1CAM cleavage occurred primarily in the ventricular and subventricular zones where brain CWH43 is most highly expressed. Thus, CWH43 deletions may contribute to adult-onset iNPH by selectively downregulating L1CAM in the ventricular and subventricular zone.

The role of L1CAM as predictor of poor prognosis in stage I endometrial cancer: a systematic review and meta-analysis.

INTRODUCTION: Molecular and genomic profiling in endometrial cancer is increasing popularity. L1 cell adhesion molecule (L1CAM) is frequently mutated in endometrial cancer. In this paper, we aim to evaluate the prognostic role of L1CAM in patients with stage I endometrial cancer. METHODS: We performed a systematic review and meta-analysis searching in PubMed (MEDLINE), EMBASE, and Web of Science database to identify studies reporting the expression of L1CAM in endometrial cancer. The primary endpoint measure was to assess and evaluate the impact of L1CAM on survival outcomes. This study was performed according to the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) statement. RESULTS: Five studies were included. The pooled results suggested that L1CAM expression influences survival outcomes in stage I endometrial cancer. High L1CAM expression correlated with worse disease-free survival (HR 4.11, 95% CI 1.02-16.59, p = 0.047) and overall survival (HR 3.62, 95% CI 1.32-9.31, p = 0.012). High L1CAM level was also associated with a more aggressive FIGO grade and with older age. CONCLUSION: This systematic review supported that L1CAM have a prognostic role in stage I endometrial cancer, thus providing a potential useful tool for tailoring the need of adjuvant therapy.

Microfluidic Isolation of Neuronal-Enriched Extracellular Vesicles Shows Distinct and Common Neurological Proteins in Long COVID, HIV Infection and Alzheimer's Disease.

Long COVID (LongC) is associated with a myriad of symptoms including cognitive impairment. We reported at the beginning of the COVID-19 pandemic that neuronal-enriched or L1CAM+ extracellular vesicles (nEVs) from people with LongC contained proteins associated with Alzheimer's disease (AD). Since that time, a subset of people with prior COVID infection continue to report neurological problems more than three months after infection. Blood markers to better characterize LongC are elusive. To further identify neuronal proteins associated with LongC, we maximized the number of nEVs isolated from plasma by developing a hybrid EV Microfluidic Affinity Purification (EV-MAP) technique. We isolated nEVs from people with LongC and neurological complaints, AD, and HIV infection with mild cognitive impairment. Using the OLINK platform that assesses 384 neurological proteins, we identified 11 significant proteins increased in LongC and 2 decreased (BST1, GGT1). Fourteen proteins were increased in AD and forty proteins associated with HIV cognitive impairment were elevated with one decreased (IVD). One common protein (BST1) was decreased in LongC and increased in HIV. Six proteins (MIF, ENO1, MESD, NUDT5, TNFSF14 and FYB1) were expressed in both LongC and AD and no proteins were common to HIV and AD. This study begins to identify differences and similarities in the neuronal response to LongC versus AD and HIV infection.

Chicoric Acid Ameliorated Beta-Amyloid Pathology and Enhanced Expression of Synaptic-Function-Related Markers via L1CAM in Alzheimer's Disease Models.

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease. The accumulation of amyloid-beta (Aß) plaques is a distinctive pathological feature of AD patients. The aims of this study were to evaluate the therapeutic effect of chicoric acid (CA) on AD models and to explore its underlying mechanisms. APPswe/Ind SH-SY5Y cells and 5xFAD mice were treated with CA. Soluble Aß1-42 and Aß plaque levels were analyzed by ELISA and immunohistochemistry, respectively. Transcriptome sequencing was used to compare the changes in hippocampal gene expression profiles among the 5xFAD mouse groups. The specific gene expression levels were quantified by qRT-PCR and Western blot analysis. It was found that CA treatment reduced the Aß1-42 levels in the APPswe/Ind cells and 5xFAD mice. It also reduced the Aß plaque levels as well as the APP and BACE1 levels. Transcriptome analysis showed that CA affected the synaptic-plasticity-related genes in the 5xFAD mice. The levels of L1CAM, PSD-95 and synaptophysin were increased in the APPswe/Ind SH-SY5Y cells and 5xFAD mice treated with CA, which could be inhibited by administering siRNA-L1CAM to the CA-treated APPswe/Ind SH-SY5Y cells. In summary, CA reduced Aß levels and increased the expression levels of synaptic-function-related markers via L1CAM in AD models.

Single Nucleotide Polymorphism in Cell Adhesion Molecule L1 Affects Learning and Memory in a Mouse Model of Traumatic Brain Injury.

The L1 cell adhesion molecule (L1) has demonstrated a range of beneficial effects in animal models of spinal cord injury, neurodegenerative disease, and ischemia; however, the role of L1 in TBI has not been fully examined. Mutations in the L1 gene affecting the extracellular domain of this type 1 transmembrane glycoprotein have been identified in patients with L1 syndrome. These patients suffer from hydrocephalus, MASA (mental retardation, adducted thumbs, shuffling gait, aphasia) symptoms, and corpus callosum agenesis. Clinicians have observed that recovery post-traumatic brain injury (TBI) varies among the population. This variability may be explained by the genetic differences present in the general population. In this study, we utilized a novel mouse model of L1 syndrome with a mutation at aspartic acid position 201 in the extracellular domain of L1 (L1-201). We assessed the impact of this specific single nucleotide polymorphism (SNP) localized to the X-chromosome L1 gene on recovery outcomes following TBI by comparing the L1-201 mouse mutants with their wild-type littermates. We demonstrate that male L1-201 mice exhibit significantly worse learning and memory outcomes in the Morris water maze after lateral fluid percussion (LFP) injury compared to male wild-type mice and a trend to worse motor function on the rotarod. However, no significant changes were observed in markers for inflammatory responses or apoptosis after TBI.

In Vitro and In Vivo Studies of Melanoma Cell Migration by Antagonistic Mimetics of Adhesion Molecule L1CAM.

Melanoma, the deadliest type of skin cancer, has a high propensity to metastasize to other organs, including the brain, lymph nodes, lungs, and bones. While progress has been made in managing melanoma with targeted and immune therapies, many patients do not benefit from these current treatment modalities. Tumor cell migration is the initial step for invasion and metastasis. A better understanding of the molecular mechanisms underlying metastasis is crucial for developing therapeutic strategies for metastatic diseases, including melanoma. The cell adhesion molecule L1CAM (CD171, in short L1) is upregulated in many human cancers, enhancing tumor cell migration. Earlier studies showed that the small-molecule antagonistic mimetics of L1 suppress glioblastoma cell migration in vitro. This study aims to evaluate if L1 mimetic antagonists can inhibit melanoma cell migration in vitro and in vivo. We showed that two antagonistic mimetics of L1, anagrelide and 2-hydroxy-5-fluoropyrimidine (2H5F), reduced melanoma cell migration in vitro. In in vivo allograft studies, only 2H5F-treated female mice showed a decrease in tumor volume.

A Newly Developed Anti-L1CAM Monoclonal Antibody Targets Small Cell Lung Carcinoma Cells.

Few effective treatments are available for small cell lung cancer (SCLC), indicating the need to explore new therapeutic options. Here, we focus on an antibody-drug conjugate (ADC) targeting the L1 cell adhesion molecule (L1CAM). Several publicly available databases reveal that (1) L1CAM is expressed at higher levels in SCLC cell lines and tissues than in those of lung adenocarcinoma and (2) the expression levels of L1CAM are slightly higher in SCLC tissues than in adjacent normal tissues. We conducted a series of in vitro experiments using an anti-L1CAM monoclonal antibody (termed HSL175, developed in-house) and the recombinant protein DT3C, which consists of diphtheria toxin lacking the receptor-binding domain but containing the C1, C2, and C3 domains of streptococcal protein G. Our HSL175-DT3C conjugates theoretically kill cells only when the conjugates are internalized by the target (L1CAM-positive) cells through antigen-antibody interaction. The conjugates (an ADC analog) were effective against two SCLC-N (NEUROD1 dominant) cell lines, Lu-135 and STC-1, resulting in decreased viability. In addition, L1CAM silencing rendered the two cell lines resistant to HSL175-DT3C conjugates. These findings suggest that an ADC consisting of a humanized monoclonal antibody based on HSL175 and a potent anticancer drug would be effective against SCLC-N cells.

Crystal structure of Ankyrin-G in complex with a fragment of Neurofascin reveals binding mechanisms required for integrity of the axon initial segment.

The axon initial segment (AIS) has characteristically dense clustering of voltage-gated sodium channels (Nav), cell adhesion molecule Neurofascin 186 (Nfasc), and neuronal scaffold protein Ankyrin-G (AnkG) in neurons, which facilitates generation of an action potential and maintenance of axonal polarity. However, the mechanisms underlying AIS assembly, maintenance, and plasticity remain poorly understood. Here, we report the high-resolution crystal structure of the AnkG ankyrin repeat (ANK repeat) domain in complex with its binding site in the Nfasc cytoplasmic tail that shows, in conjunction with binding affinity assays with serial truncation variants, the molecular basis of AnkG-Nfasc binding. We confirm AnkG interacts with the FIGQY motif in Nfasc, and we identify another region required for their high affinity binding. Our structural analysis revealed that ANK repeats form 4 hydrophobic or hydrophilic layers in the AnkG inner groove that coordinate interactions with essential Nfasc residues, including F1202, E1204, and Y1212. Moreover, we show disruption of the AnkG-Nfasc complex abolishes Nfasc enrichment at the AIS in cultured mouse hippocampal neurons. Finally, our structural and biochemical analysis indicated that L1 syndrome-associated mutations in L1CAM, a member of the L1 immunoglobulin family proteins including Nfasc, L1CAM, NrCAM, and CHL1, compromise binding with ankyrins. Taken together, these results define the mechanisms underlying AnkG-Nfasc complex formation and show that AnkG-dependent clustering of Nfasc is required for AIS integrity.