The intracellular domain of L1CAM binds to casein kinase 2α and is neuroprotective via inhibition of the tumor suppressors PTEN and p53

Effects of L1 adhesion molecule agonistic mimetics on signal transduction in neuronal functions

The L1 cell adhesion molecule plays an essential role in neural development and repair. It is not only a 'lock and key' recognition molecule, but an important signal transducer that stimulates regenerative-beneficial cellular functions such as neurite outgrowth, neuronal cell migration, survival, myelination, and synapse formation. Triggering L1 functions after neurotrauma improves functional recovery. In addition, loss-of-function mutations in the L1 gene lead to the L1 syndrome, a rare, X-linked neurodevelopmental disorder with an incidence of approximately 1:30,000 in newborn males. To use L1 for beneficial functions, we screened small compound libraries for L1 agonistic mimetics that trigger L1 functions and improve conditions in animal models of neurotrauma and the L1 syndrome. To understand the mechanisms underlying these functions, it is important to gain a better understanding of L1-dependent cellular signaling that is triggered by the L1 agonistic mimetics. We tested the cell signaling features of L1 agonistic mimetics that contribute to neurite outgrowth and neuronal migration. Our findings indicates that L1 agonistic mimetics trigger the same cell signaling pathways underlying neurite outgrowth, but only the L1 mimetics tacrine, polydatin, trimebutine and honokiol trigger neuronal migration. In contrast, the mimetics crotamiton and duloxetine did not affect neuronal migration, thus limiting their use in increasing neuronal migration, leaving open the question of whether this is a desired or not desired feature in the adult.

Duloxetine ameliorates valproic acid-induced hyperactivity, anxiety-like behavior, and social interaction deficits in zebrafish

Syndromic autism spectrum disorders (ASDs) are characterized by impaired social communication and repetitive/stereotyped behaviors. Currently available therapeutic agents against ASD have limited efficacy. Thus, searching for novel and effective drugs ameliorating core symptoms, in particular social deficits, is of utmost importance. Duloxetine (DLX), an antidepressant that has been identified as an agonist mimetic for the cell adhesion molecule L1, exhibits beneficial functions in vitro and in vivo. Therefore, in this study, we focused on the rapid and persistent neuroprotective function of DLX following valproic acid (VPA)-triggered hyperactivity, anxiety-like behavior and social deficits in zebrafish. Embryonic exposure to VPA reduced survival in a dose- and time-dependent manner, delayed hatching, and also resulted in a significant number of malformed larvae. After initial dose-response experiments in zebrafish larvae, 10 μM VPA exposure between 0.33 and 4.5 days post fertilization (dpf) was identified as an effective concentration that led to an early and persistent ASD-like phenotype in zebrafish. ASD-like elevated acetylcholine esterase (AChE) activity and reduced Akt-mTOR signaling was observed in zebrafish whole brain. Acute administration of DLX (4.5-6 dpf) reduced the VPA-induced ASD-like phenotype in zebrafish larvae. Additionally, such early-life acute DLX treatment had long-term effects in ameliorating social impairments, hyperactivity, and anxiety-like behaviors through adulthood. This was accompanied by reduced AChE activity and by normalized Akt-mTOR signaling. Overall, DLX treatment showed a long-term therapeutic effect on autistic-like behaviors, and alteration of AChE activity and Akt-mTOR signaling were identified as crucial in the VPA-induced ASD zebrafish model.

CK2 Regulation: Perspectives in 2021

The protein kinase CK2 (CK2) family encompasses a small number of acidophilic serine/threonine kinases that phosphorylate substrates involved in numerous biological processes including apoptosis, cell proliferation, and the DNA damage response. CK2 has also been implicated in many human malignancies and other disorders including Alzheimer′s and Parkinson’s diseases, and COVID-19. Interestingly, no single mechanism describes how CK2 is regulated, including activation by external proteins or domains, phosphorylation, or dimerization. Furthermore, the kinase has an elongated activation loop that locks the kinase into an active conformation, leading CK2 to be labelled a constitutively active kinase. This presents an interesting paradox that remains unanswered: how can a constitutively active kinase regulate biological processes that require careful control? Here, we highlight a selection of studies where CK2 activity is regulated at the substrate level, and discuss them based on the regulatory mechanism. Overall, this review describes numerous biological processes where CK2 activity is regulated, highlighting how a constitutively active kinase can still control numerous cellular activities. It is also evident that more research is required to fully elucidate the mechanisms that regulate CK2 and what causes aberrant CK2 signaling in disease.

Adhesion molecule L1 inhibition increases infarct size in cerebral ischemia-reperfusion without change in blood-brain barrier disruption

OBJECTIVE

Neural cell adhesion molecule L1CAM (L1) is involved in neuroprotection. To investigate a possible neuroprotective effect of L1 during ischemia, we determined whether blocking L1 with an antagonistic antibody would worsen the outcome of focal cerebral ischemia-reperfusion and increase blood-brain barrier (BBB) disruption.

METHODS

Transient middle cerebral artery occlusion (MCAO) was performed in anesthetized rats. Five µg of antagonistic mouse IgG monoclonal L1 antibody 324 or non-immune control mouse IgG was applied on the ischemic-reperfused cortex during one hour of MCAO and two hours of reperfusion. At two hours of reperfusion, BBB permeability, size of infarct using tetrazolium staining, number of TUNEL-labeled apoptotic cells, and immunohistochemistry for expression of PTEN and p53 were studied.

RESULTS

The antagonistic L1 antibody 324 increased the percentage of cortical infarct area (+36%), but did not affect BBB permeability in the ischemic-reperfused cortex. The antagonistic L1 antibody increased number of apoptotic neurons and p53 expression, but decreased PTEN expression.

CONCLUSION

Functional antagonism of L1 increases infarct size by increasing numbers of apoptotic neurons without affecting BBB permeability during the early stage of cerebral ischemia-reperfusion. Our data suggest that L1 affects primarily the brain parenchyma rather than BBB during early stages of cerebral ischemia-reperfusion and that endogenous brain L1 may be neuroprotective.

Cell Adhesion Molecules in Normal Skin and Melanoma

Cell adhesion molecules (CAMs) of the cadherin, integrin, immunoglobulin, and selectin protein families are indispensable for the formation and maintenance of multicellular tissues, especially epithelia. In the epidermis, they are involved in cell–cell contacts and in cellular interactions with the extracellular matrix (ECM), thereby contributing to the structural integrity and barrier formation of the skin. Bulk and single cell RNA sequencing data show that >170 CAMs are expressed in the healthy human skin, with high expression levels in melanocytes, keratinocytes, endothelial, and smooth muscle cells. Alterations in expression levels of CAMs are involved in melanoma propagation, interaction with the microenvironment, and metastasis. Recent mechanistic analyses together with protein and gene expression data provide a better picture of the role of CAMs in the context of skin physiology and melanoma. Here, we review progress in the field and discuss molecular mechanisms in light of gene expression profiles, including recent single cell RNA expression information. We highlight key adhesion molecules in melanoma, which can guide the identification of pathways and strategies for novel anti-melanoma therapies.

The L1 cell adhesion molecule affects protein kinase D1 activity in the cerebral cortex in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by deposition of β-amyloid protein (Aβ), neurofibrillary tangles and cognitive deficits resulting from neuronal cell death. In search for the molecular underpinnings of the disease, we were interested in the relationship between Aβ, L1 cell adhesion molecule and protein kinase D1 (PKD1), which are not only implicated in neural development and functional maintenance in the adult, but are also neuroprotective under pathological conditions. Based on our observations that L1 and phosphorylated, i.e. activated, protein kinase PKD1 (pPKD1) co-localize in cultured neurons, we investigated the functional relationship between L1 and pPKD1 in the frontal lobe of an AD human cortical tissue microarray, and found increased and positively correlating levels of both molecules when compared to a non-affected human brain. Also in the APP_SWE mouse model of AD, L1 and pPKD1 levels were increased in the frontal lobe. To investigate whether L1 influences PKD1-based functions in AD, cultured cortical neurons were stressed with either H₂O₂ or oligomeric Aβ_1-42, in the presence or absence of recombinant L1 extracellular domain, and PKD1 phosphorylation was measured. As indicated by the cell viability assay, L1 maintained neuronal survival under oxidative stress and under application of oligomeric Aβ_1-42, when PKD1 activity was inhibited, suggesting that L1 ameliorates some aspects of Aβ_1-42 pathology in parallel with reducing PKD1 function.

Glioma malignancy is linked to interdependent and inverse AMOG and L1 adhesion molecule expression

BACKGROUND

Gliomas account for the majority of primary human brain tumors and remain a challenging neoplasm for cure due to limited therapeutic options. Cell adhesion molecules play pivotal roles in the growth and progression of glial tumors. Roles of the adhesion molecules on glia (AMOG) and L1CAM (L1) in glioma cells have been shown to correlate with tumorigenesis: Increased expression of L1 and decreased expression of AMOG correlate with degree of malignancy.

METHODS

We evaluated the interdependence in expression of these molecules by investigating the role of AMOG in vitro via modulation of L1 expression and analyzing apoptosis and cell senescence of glioma cells.

RESULTS

Immunohistochemical staining of normal human cortical and glioma tissue microarrays demonstrated that AMOG expression was lower in human gliomas compared to normal tissue and is inversely correlated with the degree of malignancy. Moreover, reduction of AMOG expression in human glioblastoma cells elevated L1 expression, which is accompanied by decreased cell apoptosis as well as senescence.

CONCLUSION

AMOG and L1 interdependently regulate their expression levels not only in U-87 MG cells but also in U251 and SHG44 human glioma cell lines. The capacity of AMOG to reduce L1 expression suggests that methods for increasing AMOG expression may provide a therapeutic choice for the management of glial tumors with high expression of L1.

Enhanced Neuronal Survival and Neurite Outgrowth Triggered by Novel Small Organic Compounds Mimicking the LewisX Glycan

Glycosylation fine-tunes signal transduction of adhesion molecules during neural development and supports synaptic plasticity and repair after injury in the adult nervous system. One abundantly expressed neural glycan is LewisX (LeX). Although it is known that its expression starts at the formation of the neural tube during the second embryonic week in the mouse and peaks during the first postnatal week, its functional relevance is only rudimentarily understood. To gain better insights into the functions of this glycan, we identified small organic compounds that mimic structurally and functionally this glycan glycosidically linked to several neural adhesion molecules. Mimetic compounds were identified by competitive enzyme-linked immunosorbent assay (ELISA) using the LeX-specific monoclonal antibodies L5 and SSEA-1 for screening a library of small organic molecules. In this assay, antibody binding to substrate-coated LeX glycomimetic peptide is measured in the presence of compounds, allowing identification of molecules that inhibit antibody binding and thereby mimic LeX. Gossypol, orlistat, ursolic acid, folic acid, and tosufloxacin inhibited antibody binding in a concentration-dependent manner. With the aim to functionally characterize the molecular consequences of the compounds' actions, we here present evidence that, at nM concentrations, the mimetic compounds enhance neurite outgrowth and promote neuronal survival of cultured mouse cerebellar granule cells via, notably, distinct signal transduction pathways. These findings raise hopes that these LeX mimetics will be powerful tools for further studying the functions of LeX and its effects in acute and chronic nervous system disease models. It is worth mentioning in this context that the LeX compounds investigated in the present study have been clinically approved for different therapies.

Phenelzine, a cell adhesion molecule L1 mimetic small organic compound, promotes functional recovery and axonal regrowth in spinal cord-injured zebrafish

Injury to the spinal cord initiates a cascade of cellular and molecular events that contribute to the tissue environment that is non-permissive for cell survival and axonal regrowth/sprouting in the adult mammalian central nervous system. The endogenous repair response is impaired in this generally inhibitory environment. Previous studies indicate that homophilic interactions of the neural cell adhesion molecule L1 (L1CAM) promote recovery after spinal cord injury and ameliorate neurodegenerative processes in experimental rodent and zebrafish models. In light of reports that phenelzine, a small organic compound that mimics L1, stimulates neuronal survival, neuronal migration, neurite outgrowth, and Schwann cell proliferation in vitro in a L1-dependent manner, we examined the restorative potential of phenelzine in a zebrafish model of spinal cord injury. Addition of phenelzine into the aquarium water immediately after spinal cord injury accelerated locomotor recovery and promoted axonal regrowth and remyelination in larval and adult zebrafish. Phenelzine treatment up-regulated the expression and proteolysis of L1.1 (a homolog of the mammalian recognition molecule L1) and phosphorylation of Erk in the spinal cord caudal to lesion site. By combining the results of the present study with those of other studies, we propose that phenelzine bears hopes for therapy of nervous system injuries.

Apelin-13 attenuates ER stress-mediated neuronal apoptosis by activating Gαi/Gαq-CK2 signaling in ischemic stroke

Cerebral ischemia/reperfusion (I/R) injury-induced neuronal apoptosis contributes to the death and disability in patients with ischemic stroke. However, underlying mechanisms remain elusive and it lacks effective treatment. Here we reported that the expression of casein kinase 2 (CK2) was significantly reduced in brains of middle cerebral artery occlusion/reperfusion (MACO/R) model rats and oxygen-glucose deprivation/reperfusion (OGD/R) model neurons, which was associated with the activation of eIF2-ATF4-CHOP signaling pathway, leading to neuronal apoptosis. Moreover, we found that apelin-13 significantly upregulated CK2 expression and inhibited eIF2-ATF4-CHOP activation, attenuating cerebral I/R injury-induced infarct and neuronal apoptosis in MACO/R model rats and OGD/R model neurons. Furthermore, we demonstrated that the rescue effect of apelin-13 on I/R injury-induced neuronal apoptosis was mediated by Gα_i/Gα_q-CK2-dependent inhibition of eIF2-ATF4-CHOP activation. These data indicated cerebral I/R injury reduced CK2 expression and activated eIF2-ATF4-CHOP signaling contributing to neuronal apoptosis, and apelin-13 can activate Gα_i/Gα_q-CK2 signaling attenuating eIF2-ATF4-CHOP-mediated neuronal apoptosis. It provides a novel insight that not only apelin-13 but also CK2 agonists may have therapeutic potential for protecting neurons from I/R injury-induced apoptosis, facilitating post-stroke recovery.

Tumorigenic proteins upregulated in the MYCN-amplified IMR-32 human neuroblastoma cells promote proliferation and migration

Childhood neuroblastoma is one of the most common types of extra-cranial cancer affecting children with a clinical spectrum ranging from spontaneous regression to malignant and fatal progression. In order to improve the clinical outcomes of children with high-risk neuroblastoma, it is crucial to understand the tumorigenic mechanisms that govern its malignant behaviors. MYCN proto-oncogene, bHLH transcription factor (MYCN) amplification has been implicated in the malignant, treatment-evasive nature of aggressive, high-risk neuroblastoma. In this study, we used a SILAC approach to compare the proteomic signatures of MYCN-amplified IMR-32 and non-MYCN-amplified SK-N-SH human neuroblastoma cells. Tumorigenic proteins, including fatty-acid binding protein 5 (FABP5), L1-cell adhesion molecule (L1-CAM), baculoviral IAP repeat containing 5 [BIRC5 (survivin)] and high mobility group protein A1 (HMGA1) were found to be significantly upregulated in the IMR-32 compared to the SK-N-SH cells and mapped to highly tumorigenic pathways including, MYC, MYCN, microtubule associated protein Tau (MAPT), E2F transcription factor 1 (E2F1), sterol regulatory element binding transcription factor 1 or 2 (SREBF1/2), hypoxia-inducible factor 1α (HIF-1α), Sp1 transcription factor (SP1) and amyloid precursor protein (APP). The transcriptional knockdown (KD) of MYCN, HMGA1, FABP5 and L1-CAM significantly abrogated the proliferation of the IMR-32 cells at 48 h post transfection. The early apoptotic rates were significantly higher in the IMR-32 cells in which FABP5 and MYCN were knocked down, whereas cellular migration was significantly abrogated with FABP5 and HMGA1 KD compared to the controls. Of note, L1-CAM, HMGA1 and FABP5 KD concomitantly downregulated MYCN protein expression and MYCN KD concomitantly downregulated L1-CAM, HMGA1 and FABP5 protein expression, while survivin protein expression was significantly downregulated by MYCN, HMGA1 and FABP5 KD. In addition, combined L1-CAM and FABP5 KD led to the concomitant downregulation of HMGA1 protein expression. On the whole, our data indicate that this inter-play between MYCN and the highly tumorigenic proteins which are upregulated in the malignant IMR-32 cells may be fueling their aggressive behavior, thereby signifying the importance of combination, multi-modality targeted therapy to eradicate this deadly childhood cancer.

Electroacupuncture Restores Locomotor Functions After Mouse Spinal Cord Injury in Correlation With Reduction of PTEN and p53 Expression

Background: We previously showed that electroacupuncture (EA) at Jiaji points promotes expression of adhesion molecule L1 in spinal cord tissue after mouse spinal cord injury (SCI) and contributes to recovery of neural functions. Objective: We investigated the effects of EA on downstream signaling molecules of L1 and molecules relevant to apoptosis with the aim to understand the underlying molecular mechanisms. Methods: Female C57BL/6 mice were divided into a sham group, injury group, injury+acupuncture (AP) group and injury+EA group. We investigated the changes in cognate L1-triggered signaling molecules after SCI by immunofluorescence staining and immunoblot analysis. Results: Protein levels of phosphatase and tensin homolog (PTEN) and p53 were decreased by EA at different time points after injury, whereas the levels of phosphorylated mammalian target of rapamycin (pmTOR), p-Akt and phosphorylated extracellular signal-regulatedkinase (p-Erk) were increased. Also, levels of myelin basic protein (MBP) were increased by EA. AP alone showed less pronounced changes in expression of the investigated molecules, when compared to EA. Conclusion: We propose that EA contributes to neuroprotection by inhibiting PTEN and p53 expression and by increasing the levels of pmTOR/Akt/Erk and of MBP after SCI. These observations allow novel insights into the beneficial effects of EA via L1-triggered signaling molecules after injury.

A Small Organic Compound Mimicking the L1 Cell Adhesion Molecule Promotes Functional Recovery after Spinal Cord Injury in Zebrafish

Tacrine is a small organic compound that was discovered to mimic the functions of the neural cell adhesion molecule L1 by promoting the cognate functions of L1 in vitro, such as neuronal survival, neuronal migration, neurite outgrowth, and myelination. Based on studies indicating that L1 enhances functional recovery in different central and peripheral nervous system disease paradigms of rodents, it deemed interesting to investigate the beneficial role of tacrine in the attractive zebrafish animal model, by evaluating functional recovery after spinal cord injury. To this aim, larval and adult zebrafish were exposed to tacrine treatment after spinal cord injury and monitored for locomotor recovery and axonal regrowth. Tacrine promoted the rapid recovery of locomotor activities in both larval and adult zebrafish, enhanced regrowth of severed axons and myelination, and reduced astrogliosis in the spinal cords. Tacrine treatment upregulated the expression of L1.1 (a homolog of the mammalian recognition molecule L1) and enhanced the L1.1-mediated intracellular signaling cascades in the injured spinal cords. These observations lead to the hope that, in combination with other therapeutic approaches, this old drug may become a useful reagent to ameliorate the deficits resulting from acute and chronic injuries of the mammalian nervous system.

Phenelzine, a small organic compound mimicking the functions of cell adhesion molecule L1, promotes functional recovery after mouse spinal cord injury

BACKGROUND

Neural cell adhesion molecule L1 contributes to nervous system development and maintenance by promoting neuronal survival, neuritogenesis, axonal regrowth/sprouting, myelination, and synapse formation and plasticity. L1 also enhances recovery after spinal cord injury and ameliorates neurodegenerative processes in experimental rodent models. Aiming for clinical translation of L1 into therapy we screened for and functionally characterized in vitro the small organic molecule phenelzine, which mimics characteristic L1 functions.

OBJECTIVE

The present study was designed to evaluate the potential of this compound in vivo in a mouse model of spinal cord injury.

METHODS AND RESULTS

In mice, intraperitoneal injection of phenelzine immediately after severe thoracic compression, and thereafter once daily for 6 weeks, improved hind limb function, reduced astrogliosis and promoted axonal regrowth/sprouting at 4 and 5 weeks after spinal cord injury compared to vehicle control-treated mice. Phenelzine application upregulated L1 expression in the spinal cord and stimulated the cognate L1-mediated intracellular signaling cascades in the spinal cord tissue. Phenelzine-treated mice showed decreased levels of pro-inflammatory cytokines, such as interleukin-1β, interleukin-6, and tumor necrosis factor-α in the injured spinal cord during the acute phase of inflammation.

CONCLUSIONS

This study provides new insights into the role of phenelzine in L1-mediated neural functions and modulation of inflammation. The combined results raise hopes that phenelzine may develop into a therapeutic agent for nervous system injuries.

L1CAM drives oncogenicity in esophageal squamous cell carcinoma by stimulation of ezrin transcription

L1 cell adhesion molecule (L1CAM) is highly expressed in various types of human cancers, displaying yet unknown molecular mechanisms underlying their oncogenic potential. Here, we found that L1CAM expression was significantly increased in esophageal squamous cell carcinoma (ESCC; n = 157) lesions compared with non-cancerous tissues. High tumorous L1CAM expression significantly correlated with reduced overall survival. Experimentally, L1CAM knockdown led to decreased cell growth, migration, and invasiveness in vitro, whereas overexpression of L1CAM showed the opposite effect. In nude mice, L1CAM depletion attenuated tumorigenesis and ability to penetrate the tissues surrounding ESCC cells. Gene set enrichment analysis (GSEA) and SubpathwayMiner analysis on gene expression profiles (microarray data on ESCC tissues, GSE53625; cDNA microarray data on L1CAM-knockdown ESCC cell line, GSE86268) suggested that L1CAM-co-expression genes were related to cell motility, cell proliferation, and regulation of actin cytoskeleton, validating the above experimental findings. Further mechanistical analysis showed that L1CAM upregulated the expression of the cytoskeletal protein ezrin via activating integrin β1/MAPK/ERK/AP1 signaling and thus led to the malignant phenotypes of ESCC cells. Together, our findings suggest that L1CAM may be employed as a valuable prognosis marker and a therapeutic target for ESCC patients and that L1CAM promotes ESCC tumorigenicity by upregulating ezrin expression.

KEY MESSAGES

L1CAM promotes growth and invasiveness of ESCC cells in vitro and in vivo. L1CAM upregulates the expression of ezrin by integrin α5β1/MAPK/ERK/AP1 pathway. Ezrin is a key downstream effector in the L1CAM-promoted malignant phenotypes. High expression levels of both L1CAM and ezrin significantly correlated with reduced overall survival. Nuclear L1CAM is an independent prognosis marker for esophageal squamous cell carcinoma.

Trimebutine, a small molecule mimetic agonist of adhesion molecule L1, contributes to functional recovery after spinal cord injury in mice

Curing spinal cord injury (SCI) in mammals is a daunting task because of the lack of permissive mechanisms and strong inhibitory responses at and around the lesion. The neural cell adhesion molecule L1CAM (L1) has been shown to favor axonal regrowth and enhance neuronal survival and synaptic plasticity but delivery of full-length L1 or its extracellular domain could encounter difficulties in translation to therapy in humans. We have, therefore, identified several small organic compounds that bind to L1 and stimulate neuronal survival, neuronal migration and neurite outgrowth in an L1-dependent manner. Here, we assessed the functions of two L1 mimetics, trimebutine and honokiol, in regeneration following SCI in young adult mice. Using the Basso Mouse Scale (BMS) score, we found that ground locomotion in trimebutine-treated mice recovered better than honokiol-treated or vehicle-receiving mice. Enhanced hindlimb locomotor functions in the trimebutine group were observed at 6 weeks after SCI. Immunohistology of the spinal cords rostral and caudal to the lesion site showed reduced areas and intensities of glial fibrillary acidic protein immunoreactivity in both trimebutine and honokiol groups, whereas increased regrowth of axons was observed only in the trimebutine-treated group. Both L1- and L1 mimetic-mediated intracellular signaling cascades in the spinal cord lesion sites were activated by trimebutine and honokiol, with trimebutine being more effective than honokiol. These observations suggest that trimebutine and, to a lesser extent under the present experimental conditions, honokiol have a potential for therapy in regeneration of mammalian spinal cord injuries.

The polysialic acid mimetics idarubicin and irinotecan stimulate neuronal survival and neurite outgrowth and signal via protein kinase C

Polysialic acid (PSA) is a large, negatively charged, linear homopolymer of alpha2-8-linked sialic acid residues. It is generated by two polysialyltransferases and attached to N- and/or O-linked glycans, and its main carrier is the neural cell adhesion molecule (NCAM). PSA controls the development and regeneration of the nervous system by enhancing cell migration, axon pathfinding, synaptic targeting, synaptic plasticity, by regulating the differentiation of progenitor cells and by modulating cell-cell and cell-matrix adhesions. In the adult, PSA plays a role in the immune system, and PSA mimetics promote functional recovery after nervous system injury. In search for novel small molecule mimetics of PSA that are applicable for therapy, we identified idarubicin, an antineoplastic anthracycline, and irinotecan, an antineoplastic agent of the topoisomerase I inhibitor class, as PSA mimetics using a competition enzyme-linked immunosorbent assay. Idarubicin and irinotecan compete with the PSA-mimicking peptide and colominic acid, the bacterial analog of PSA, for binding to the PSA-specific monoclonal antibody 735. Idarubicin and irinotecan stimulate neurite outgrowth and survival of cultured cerebellar neurons after oxidative stress via protein kinase C and Erk1/2 in a similar manner as colominic acid, whereas Fyn, casein kinase II and the phosphatase and tensin homolog are only involved in idarubicin and irinotecan-stimulated neurite outgrowth. These novel results show that the structure and function of PSA can be mimicked by the small organic compounds irinotecan and idarubicin which trigger the same signaling cascades as PSA, thus introducing the possibility of retargeting these drugs to treat nervous system injuries.

Electro-Acupuncture Modulates L1 Adhesion Molecule Expression After Mouse Spinal Cord Injury

Spinal cord injury is a devastating neurological disease in desperate need of a cure. We have previously shown that overexpression of the adhesion molecule L1 contributes to locomotor recovery after injury and were therefore interested in how electro-acupuncture would influence the expression of this molecule. Here, we investigated the effects of electro-acupuncture at "Jiaji" points (EX-B2), newly established by us, in young adult mice to determine whether improved recovery via electro-acupuncture could be due to enhanced L1 expression. Locomotor function, as evaluated by the Basso Mouse Scale score and by catwalk gait parameters, was improved by electro-acupuncture at different time points after injury in parallel with enhanced levels of L1 expression. Interestingly, the levels of the astrocytic marker glial fibrillary acidic protein (GFAP) were also increased, but only in the early phase after injury, being reduced at later stages during recovery. Acupuncture alone showed less pronounced changes in expression of these molecules. We propose that electro-acupuncture improves regeneration in part by promoting the L1 expression and beneficial activation of stem cells, and by differentially modulating the expression of GFAP by promoting regeneration-conductive astrocytic responses at initial stages and reducing regeneration-adversive activation in the secondary stages. Expression of the stem cell marker nestin was upregulated by electro-acupuncture in the acute stage. The combined observations show for the first time in mice the beneficial functions of electro-acupuncture at Jiaji points in the spinal cord injury mouse model and provide novel insights into some molecular mechanisms underlying electro-acupuncture in spinal cord injury.

L1-CAM knock-down radiosensitizes neuroblastoma IMR-32 cells by simultaneously decreasing MycN, but increasing PTEN protein expression

Childhood neuroblastoma is one of the most malignant types of cancers leading to a high mortality rate. These cancerous cells can be highly metastatic and malignant giving rise to disease recurrence and poor prognosis. The proto-oncogene myelocytomatosis neuroblastoma (MycN) is known to be amplified in this type of cancer, thus, promoting high malignancy and resistance. The L1 cell adhesion molecule (L1-CAM) cleavage has been found upregulated in many types of malignant cancers. In the present study, we explored the interplay between L1-CAM, MycN and PTEN as well as the role played by PDGFR and VEGFR on tumorigenicity in neuroblastoma cells. We investigated the effect of L1-CAM knock-down (KD) and PDGFR/VEGFR inhibition with sunitinib malate (Sutent®) treatment on subsequent tumorsphere formation and cellular proliferation and migration in the MycN-amplified IMR-32 neuroblastoma cells. We further examined the effect of combined L1-CAM KD with Sutent treatment or radiotherapy on these cellular functions in our cells. Tumorsphere formation is one of the indicators of aggressiveness in malignant cancers, which was significantly inhibited in IMR-32 cells after L1-CAM KD or Sutent treatment, however, no synergistic effect was observed with dual treatments, rather L1-CAM KD alone showed a greater inhibition on tumorsphere formation compared to Sutent treatment alone. In addition, cellular proliferation and migration were significantly inhibited after L1-CAM KD in the IMR-32 cells with no synergistic effect observed on the rate of cell proliferation when combined with Sutent treatment. Again, L1-CAM KD alone exhibited greater inhibitory effect than Sutent treatment on cell proliferation. L1-CAM KD led to the simultaneous downregulation of MycN, but the upregulation of PTEN protein expression. Notably, radiotherapy (2 Gy) of the IMR-32 cells led to significant upregulation of both L1-CAM and MycN, which was abrogated with L1-CAM KD in our cells. In addition, L1-CAM KD radiosensitized the cells as exhibited by the synergistic effect on the reduction in cell proliferation compared to radiotherapy alone. Taken together, our data show the importance of L1-CAM interplay with MycN and PTEN on the MycN amplified neuroblastoma cell radioresistance, proliferation and motility.