NPTX2 in Cerebrospinal Fluid Predicts the Progression From Normal Cognition to Mild Cognitive Impairment.

OBJECTIVE: This study examined whether cerebrospinal fluid (CSF) baseline levels of the synaptic protein NPTX2 predict time to onset of symptoms of mild cognitive impairment (MCI), both alone and when accounting for traditional CSF Alzheimer's disease (AD) biomarker levels. Longitudinal NPTX2 levels were also examined. METHODS: CSF was collected longitudinally from 269 cognitively normal BIOCARD Study participants (mean baseline age = 57.7 years; mean follow-up = 16.3 years; n = 77 progressed to MCI/dementia). NPTX2 levels were measured from 3 correlated peptides using quantitative parallel reaction monitoring mass spectrometry. Levels of Aß42 /Aß40 , p-tau181 , and t-tau were measured from the same CSF specimens using Lumipulse automated electrochemiluminescence assays. RESULTS: In Cox regression models, lower baseline NPTX2 levels were associated with an earlier time to MCI symptom onset (hazard ratio [HR] = 0.76, SE = 0.09, p = 0.023). This association was significant for progression within 7 years (p = 0.036) and after 7 years from baseline (p = 0.001). Baseline NPTX2 levels improved prediction of time to MCI symptom onset after accounting for baseline AD biomarker levels (p < 0.01), and NPTX2 did not interact with the CSF AD biomarkers or APOE-ε4 genetic status. In linear mixed effects models, higher baseline p-tau181 and t-tau levels were associated with higher baseline levels of NPTX2 (both p < 0.001) and greater rates of NPTX2 declines over time. INTERPRETATION: NPTX2 may be a valuable prognostic biomarker during preclinical AD that provides additive and independent prediction of MCI onset among individuals who are cognitively normal. We hypothesize that NPTX2-mediated circuit homeostasis confers resilience during the early phase of AD. ANN NEUROL 2023;94:620-631.

Middle-aged and older people's preference for medical-elderly care integrated institutions in China: a discrete choice experiment study.

BACKGROUND: With the continuing impact of the aging population, medical-elderly care integrated institutions, as a way to bear the pressure of medical and elderly care, effectively ensure the quality of life of the elderly in their later years. OBJECTIVES: To explore the preferences of medical-elderly care integrated institutions among Chinese middle-aged and older people and to provide a reference for establishing elderly-oriented development of medical-elderly care integrated institutions. METHODS: In this study, a discrete choice experiment (DCE) was used to investigate the preferences of people aged 45 years and older in medical-elderly care integrated institutions in China from October 20, 2022, to November 10, 2022. A mixed logit regression model was used to analyze the DCE data. Participants' willingness to pay for each attribute was also calculated. RESULTS: Data from 420 participants who provided valid responses were included in the analysis. In terms of the choice preference, moderate service quality (vs. poor service quality: ß = 1.707, p < 0.001, 95% CI 1.343 ~ 2.071) and high medical technology level (vs. low medical technology level: ß = 1.535, p < 0.001, 95% CI 1.240 ~ 1.830) were the most important attributes to middle-aged and older people, followed by monthly cost, environmental facilities, the convenience of transportation, and entertainment activities. Regarding the willingness to pay, participants were more willing to pay for service quality and medical technology level than for other attributes. They were willing to pay $3156 and $2838 more for "poor service quality" and "low medical technology level," respectively, to receive "moderate service quality " (p = 0.007, 95% CI 963 ~ 5349) and "high medical technology level" (p = 0.005, 95% CI 852 ~ 4824). CONCLUSIONS: The state should attach great importance to the development of medical-elderly care integrated services industry, actively optimize the model of the medical-elderly care integrated service, improve the facilities, and create a healthy environment. At the same time, give full play to the role of medical insurance, long-term care insurance, and commercial insurance, so as to improve the comprehensive quality of life of the elderly. PUBLIC CONTRIBUTION: The design of the experimental selection was guided by 10 experts in the field, 5 Chinese government officials, and interviews and focus group discussions, without whose participation this study would not have been possible.

Neuronal pentraxin 2 correlates with neurodegeneration but not cognition in idiopathic normal pressure hydrocephalus (iNPH).

AIM OF THE STUDY: Neuronal pentraxin-2 (NPTX2) is a synaptic protein responsible for modulating plasticity at excitatory synapses. While the role of NPTX2 as a novel synaptic biomarker in cognitive disorders has been elucidated recently, its role in idiopathic normal pressure hydrocephalus (iNPH) is not yet understood. CLINICAL RATIONALE FOR STUDY: To determine if NPTX2 predicts cognition in patients with iNPH, and whether it could serve as a predictive marker for shunt outcomes. MATERIAL AND METHODS: 354 iNPH patients underwent cerebrospinal fluid drainage (CSF) as part of the tap test or extended lumbar drainage. Demographic and clinical measures including age, Evans Index (EI), Montreal Cognitive Assessment (MoCA) score, Functional Activities Questionnaire (FAQ) score, and baseline and post-shunt surgery Timed Up and Go (TUG) test scores were ascertained. CSF NPTX2 concentrations were measured using an ELISA. CSF ß-amyloid 1-40 (Aß1-40), ß-amyloid 1-42 (Aß1-42), and phosphorylated tau-181 (pTau-181) were measured by chemiluminescent assays. Spearman's correlation was used to determine the correlation between CSF NPTX2 concentrations and age, EI, MoCA and FAQ, TUG, Aß1-40/Aß1-42 ratio, and pTau-181 concentrations. Logistic regression was used to determine if CSF NPTX2 values were a predictor of short-term improvement post-CSF drainage or long-term improvement post-shunt surgery. RESULTS: There were 225 males and 129 females with a mean age of 77.7 years (± 7.06). Average CSF NPTX2 level in all iNPH patients was 559.97 pg/mL (± 432.87). CSF NPTX2 level in those selected for shunt surgery was 505.61 pg/mL (± 322.38). NPTX2 showed modest correlations with pTau-181 (r = 0.44, p < 0.001) with a trend for Aß42/Aß40 ratio (r = -0.1, p = 0.053). NPTX2 concentrations did not correlate with age (r = -0.012, p = 0.83) or MoCA score (r = 0.001, p = 0.87), but correlated negatively with FAQ (r = -0.15, p = 0.019). CONCLUSIONS: While CSF NPTX2 values correlate with neurodegeneration, they do not correlate with cognitive or functional measures in iNPH. CSF NPTX2 cannot serve as a predictor of either short-term or long-term improvement after CSF drainage. CLINICAL IMPLICATIONS: These results suggest that synaptic degeneration is not a core feature of iNPH pathophysiology.

Applications of nanomaterials in COVID-19 pandemic.

The novel coronavirus 2019 (COVID-19) pandemic represents one of the biggest global health threats in the last two decades, so researchers around the world are searching for solutions and treatments for COVID-19. At the time of writing, there are no specific drugs that have demonstrated suitable effectiveness in treating COVID-19. The current challenge involves designing tools for the prevention, rapid and accurate diagnosis, drug delivery, and effective treatment of this novel coronavirus. In this short review, we discuss how nanotechnology offers new ways to combat COVID-19, and how nanomaterials can be applied to control the COVID-19 outbreak. We also summarize relevant studies regarding the use of nanomaterials for preventing viral spread, preparing vaccines, and diagnosing coronavirus, as well as studies that show how nanoparticles can be used as drug delivery systems for the treatment of viral infections. Research on nanotechnology-based diagnosis, drug delivery, and antiviral therapy is currently in the early stages. However, the unique chemical properties of some nanomaterials highlight the broad prospect of nanomaterials in the future, and we propose that they will play an important role in the fight against COVID-19.

Liquid biopsy for ALK-positive early non-small-cell lung cancer predicts disease relapse.

Background: We aimed to determine whether circulating tumor cells (CTCs) and cell-free DNA (cfDNA) aids in prognosis of relapse-free survival (RFS). Methods: Non-small cell lung cancer patients with ALK mutations were recruited prospectively. CTCs and cfDNA were quantified at different time points. RFS was estimated and correlated. Results: Baseline median CTCs and cfDNA were 16 cells and 57 ng/mL and declined to nine cells and 30 ng/mL, respectively, postsurgery in 150 patients. Interestingly, patients without detectable CTCs postsurgery fared better for RFS. cfDNA monitoring showed deviations within 7 months of surgery that were significant predictors for RFS. Conclusion: Short-term monitoring of CTCs and cfDNA variations shows promise for early risk detection and may aid in better disease control.

[Effect of polyphyllin D on proliferation and apoptosis of human pancreatic cancer cells].

Polyphyllin D is a steroid saponin monomer in Polyphyllin, with antibacterial, analgesic, sedative, anti-tumor and other pharmacological effects, but is rarely reported in pancreatic cancer. This study detected apoptosis-relevant indicators, in order to explore the effect of polyphyllin D on the proliferation and apoptosis of human pancreatic cancer Panc-1 cells and relevant mechanisms of action. After pancreatic cancer Panc-1 cells were treated with polyphyllin D(0, 1, 2, 3, 4, 5 µg·µL~(-1)) for 24, 48 and 72 hours, CCK-8 method was used to detect the effect of polyphyllin D on the proliferation of pancreatic cancer Panc-1 cells. Flow cytometry was used to detect cell cycle and changes in mitochondrial membrane potential(MMP). The apoptosis was detected by Annexin V-FITC/PI staining, and Western blot was used to detect the protein expressions of cytochrome C(Cyto C), Bax, Bcl-2, cleaved caspase-3 and cleaved caspase-9. The results indicated that compared with the control group, polyphyllin D could inhibit the proliferative activity of Panc-1 cells in a time and concentration-dependent manner. Flow cytometry results showed that polyphyllin D could block the cells in S and G_2/M phase in a concentration manner, the MMP of the cells was significantly reduced, and the apoptosis rate increased with the concentration of polyphyllin D. Western blot results showed that polyphyllin D could concentration-dependently up-regulate the protein expression levels of Bax, Cyto C, cleaved caspase-3 and cleaved caspase-9, and down-regulate the protein expression level of Bcl-2. The above findings suggested that polyphyllin D could effectively inhibit the proliferation of Panc-1 cells, and its mechanism may be related to the blocking of cell growth cycle and the apoptosis induced by mitochondrial pathway.

The potent mechanism-based inactivation of CYP2D6 and CYP3A4 with fusidic acid in in vivo bioaccumulation.

1. The accumulation of fusidic acid (FA) after multiple doses of FA has been reported on in previous studies but the related mechanisms have not been clarified fully. In the present study, we explain the mechanisms related to the mechanism-based inactivation of CYP2D6 and CYP3A4. 2. The irreversible inhibitory effects of FA on CYP2D6 and CYP3A4 were examined via a series of experiments, including: (a) time-, concentration- and NADPH-dependent inactivation, (b) substrate protection in enzyme inactivation and (c) partition ratio with recombinant human CYP enzymes. Metoprolol α-hydroxylation and midazolam 1'-hydroxylation were used as marker reactions for CYP2D6 and CYP3A4 activities, and HPLC-MS/MS measurement was also utilised. 3. FA caused to the time- and concentration-dependent inactivation of CYP2D6 and CYP3A4. About 55.8% of the activity of CYP2D6 and 75.8% of the activity of CYP3A4 were suppressed after incubation with 10 µM FA for 15 min. KI and kinact were found to be 2.87 µM and 0.033 min-1, respectively, for CYP2D6, while they were 1.95 µM and 0.029 min-1, respectively, for CYP3A4. Inhibition of CYP2D6 and CYP3A4 activity was found to require the presence of NADPH. Substrates of CYP2D6 and CYP3A4 showed that the enzymes were protected against the inactivation induced by FA. The estimated partition ratio for the inactivation was 7 for CYP2D6 and 12 for CYP3A4. 4. FA is a potent mechanism-based inhibitor of CYP2D6 and CYP3A4, which may explain the accumulation of FA in vivo.

The extracellular matrix glycoprotein tenascin-R regulates neurogenesis during development and in the adult dentate gyrus of mice.

Abnormal generation of inhibitory neurons that synthesize γ-aminobutyric acid (GABAergic) is characteristic of neuropsychological disorders. We provide evidence that the extracellular matrix molecule tenascin-R (TNR) - which is predominantly expressed by a subpopulation of interneurons - plays a role in the generation of GABAergic and granule neurons in the murine dentate gyrus by regulating fate determination of neural stem or progenitor cells (NSCs). During development, absence of TNR in constitutively TNR-deficient (TNR(-/-)) mice results in increased numbers of dentate gyrus GABAergic neurons, decreased expression of its receptor ß1 integrin, increased activation of p38 MAPK and increased expression of the GABAergic specification gene Ascl1. Postnatally, increased GABAergic input to adult hippocampal NSCs in TNR(-/-) mice is associated not only with increased numbers of GABAergic and, particularly, parvalbumin-immunoreactive neurons, as seen during development, but also with increased numbers of granule neurons, thus contributing to the increased differentiation of NSCs into granule cells. These findings indicate the importance of TNR in the regulation of hippocampal neurogenesis and suggest that TNR acts through distinct direct and indirect mechanisms during development and in the adult.

The role of HMGB1-RAGE axis in migration and invasion of hepatocellular carcinoma cell lines.

High mobility group protein box1 (HMGB1) and its receptor-receptor for advanced glycation end products (RAGE) are pivotal factors in the development and progression of many types of tumor, but the role of HMGB1-RAGE axis in hepatocellular carcinoma (HCC) especially its effects on metastasis and recurrence remains obscure. Here, we report the role of HMGB1-RAGE axis in the biological behaviors of HCC cell lines and the underlying molecular mechanism. We show that the expressions of HMGB1, RAGE, and extracellular HMGB1 increase consistently according to cell metastasis potentials, while the concentration of soluble form of RAGE (sRAGE) is inversely related to metastasis potential of HCC cells. Furthermore, our data show that rhHMGB1 promotes cellular proliferation, migration, and invasion, and increases the level of nuclear factor kappa B (NF-κB), while administrations of HMGB1-siRNA, RAGE-siRNA, anti-HMGB1 neutralizing antibody, anti-RAGE neutralizing antibody, and sRAGE inhibit cellular proliferation, migration, and invasion. Moreover, we also demonstrate that the expression of NF-кB is inhibited by knockdown of HMGB1 or RAGE. Collectively, these data demonstrate that HMGB1 activates RAGE signaling pathways and induces NF-кB activation to promote cellular proliferation, invasion, and metastasis, in HCC cell lines. Taken together, HMGB1-RAGE axis may become a potential target in HCC therapy.

The neuronal pentraxin Nptx2 regulates complement activity and restrains microglia-mediated synapse loss in neurodegeneration.

Complement overactivation mediates microglial synapse elimination in neurological diseases such as Alzheimer's disease (AD) and frontotemporal dementia (FTD), but how complement activity is regulated in the brain remains largely unknown. We identified that the secreted neuronal pentraxin Nptx2 binds complement C1q and thereby regulates its activity in the brain. Nptx2-deficient mice show increased complement activity, C1q-dependent microglial synapse engulfment, and loss of excitatory synapses. In a neuroinflammation culture model and in aged TauP301S mice, adeno-associated virus (AAV)-mediated neuronal overexpression of Nptx2 was sufficient to restrain complement activity and ameliorate microglia-mediated synapse loss. Analysis of human cerebrospinal fluid (CSF) samples from a genetic FTD cohort revealed reduced concentrations of Nptx2 and Nptx2-C1q protein complexes in symptomatic patients, which correlated with elevated C1q and activated C3. Together, these results show that Nptx2 regulates complement activity and microglial synapse elimination in the brain and that diminished Nptx2 concentrations might exacerbate complement-mediated neurodegeneration in patients with FTD.

High mobility group box chromosomal protein 1 in acute-on-chronic liver failure patients and mice with ConA-induced acute liver injury.

High mobility group box chromosomal protein 1 (HMGB1) is an important proinflammatory molecule in many inflammatory disorders, but little is known about its role in acute-on-chronic liver failure (ACLF). Here, we investigated the relationship between the expression of HMGB1 and the disease onset and severity of ACLF patients and mice with acute liver injury/failure induced by concanavalin A (ConA). Peripheral blood mononuclear cells (PBMCs) and serum from ACLF patients were collected, and a mouse model of acute liver injury/failure was induced by ConA. HMGB1 mRNA expression in patient PBMCs or in murine livers and serum HMGB1 protein in ACLF patients and mice were assayed by RT-PCR and Western blotting, respectively. HMGB1 translocation in hepatocytes of ConA-treated mice was assessed by immunohistochemical staining. Up-regulated HMGB1 mRNA levels in PBMCs and accumulated protein in serum were both correlated with disease severity in ACLF patients. In the animal model, HMGB1 levels increased at 4 h and reached its peak value at 8-12 h after challenge with ConA, which suggests that HMGB1 is a relatively late proinflammatory cytokine compared with TNF-α. Translocation of HMGB1 from the nucleus to the cytoplasm in hepatocytes was correlated with the severity of liver injury in mice. While specific anti-HMGB1 antibodies and nicotine protected mice from acute liver injury/failure by reducing mortality and improving liver tissue injury, treatment with recombinant HMGB1 led to an increased mortality due to ConA challenge. Thus, the data from the present study suggest that HMGB1 plays a critical role in the systemic inflammation of ACLF and could be a potential therapeutic target in the treatment of ACLF.

The Role of receptor for Advanced Glycation End Products (RAGE) in the proliferation of hepatocellular carcinoma.

The receptor for advanced glycation end products (RAGE) is oncogenic and overexpressed in human cancers, but its role in hepatocellular carcinoma remains unclear. Here we demonstrated that RAGE is overexpressed in primary hepatocellular carcinoma (PHC) compared to adjacent para-neoplastic liver samples. Serum endogenous secretory RAGE levels were also increased in PHC patients (p < 0.01). Moreover, we demonstrated that RAGE regulates cellular proliferation in Hepatocellular carcinoma (HCC). Knockdown of RAGE by specific siRNA inhibited cellular growth in the hepatocellular carcinoma cell line, Huh7, whereas the RAGE ligand, high mobility group box 1 protein (HMGB1) increased cellular proliferation. In addition, knockdown of RAGE by siRNA arrested cells in the G1 phase and inhibited DNA synthesis (p < 0.01), while HMGB1 protein decreased the number of cells in the G1 phase and increased the number in the S phase (p < 0.05). Furthermore, quantitative real time RT-PCR (qRT-PCR) and Western Blot results demonstrated that RAGE and HMGB1 positively regulate NF-κB p65 expression in Huh7 cells. These studies suggest that RAGE and RAGE ligands are important targets for therapeutic intervention in hepatocellular carcinoma.

Long Noncoding RNA LOC554202 Predicts a Poor Prognosis and Correlates with Immune Infiltration in Thyroid Cancer.

Thyroid cancer (TC) is one of the widely diagnosed carcinomas in women before the age of 30. Nevertheless, there is currently a lack of specific biomarkers for predicting the prognosis of TC. Long noncoding RNAs (lncRNAs) were important regulators in human cancer progression as previously described. Unfortunately, there is little known on these lncRNAs' functions and molecular mechanisms in TC. In our literature, we found that LOC554202 (MIR31HG) was upregulated in TC samples and correlated with clinicopathological features, including M stage, N stage, and lymph nodes examined status in TC. In addition, we found that LOC554202 overexpression was evidently correlated with high immune infiltrate levels of CD8+ T cells, macrophage, neutrophil, myeloid dendritic cells, and B cells in TC. Knockdown of LOC554202 impeded TC cell proliferation and cycle progression. We found that LOC554202 had an association with metabolic pathways, vesicle-mediated transport, tricarboxylic acid cycle, Hedgehog signaling pathway, and Hippo signaling pathway in TC. Reducing LOC554202 hindered TC cell proliferation and cycle progression. Finally, we found that LOC554202 participated in modulating the expression of the regulators of Hippo signaling and TCA pathway, such as CCND2, CCND3, SDHC, SDHD, SUCLA2, and SUCLG1. We thought that this study would largely enhance our understanding of LOC554202's functional roles in human TC progression and immune response.

Neuronal pentraxin 2 is required for facilitating excitatory synaptic inputs onto spinal neurons involved in pruriceptive transmission in a model of chronic itch.

An excitatory neuron subset in the spinal dorsal horn (SDH) that expresses gastrin-releasing peptide receptors (GRPR) is critical for pruriceptive transmission. Here, we show that glutamatergic excitatory inputs onto GRPR+ neurons are facilitated in mouse models of chronic itch. In these models, neuronal pentraxin 2 (NPTX2), an activity-dependent immediate early gene product, is upregulated in the dorsal root ganglion (DRG) neurons. Electron microscopy reveals that NPTX2 is present at presynaptic terminals connected onto postsynaptic GRPR+ neurons. NPTX2-knockout prevents the facilitation of synaptic inputs to GRPR+ neurons, and repetitive scratching behavior. DRG-specific NPTX2 expression rescues the impaired behavioral phenotype in NPTX2-knockout mice. Moreover, ectopic expression of a dominant-negative form of NPTX2 in DRG neurons reduces chronic itch-like behavior in mice. Our findings indicate that the upregulation of NPTX2 expression in DRG neurons contributes to the facilitation of glutamatergic inputs onto GRPR+ neurons under chronic itch-like conditions, providing a potential therapeutic target.

Correction: Boiten et al. Pathologically Decreased CSF Levels of Synaptic Marker NPTX2 in DLB Are Correlated with Levels of Alpha-Synuclein and VGF. Cells 2021, 10, 38.

The authors want to notify that they have made the following changes to the author list of the paper [...].

Comparison of methods of isolating extracellular vesicle microRNA from HepG2 cells for High-throughput sequencing.

Background: Extracellular vesicles (EVs) were reported to participate in various cellular processes based on the biomolecules, particularly microRNAs. Numerous commercial EVs isolation reagents are available. However, whether these reagents are suitable for separating EVs from the culture medium supernatant supernatant of model cell lines, such as HepG2, and whether the isolated products are suitable for High-throughput sequencing remains unclear. Methods: We examined three commonly used EVs isolation kits: the ExoQuick-TC exosome precipitation solution (EQ), Total Exosome Isolation from cell culture medium (EI), and exoEasy Maxi Kit (EM), to isolate EVs from HepG2 cell culture medium supernatants. EVs were identified based on marker proteins, particle size measurements, and electron microscopy analysis. The total amounts of microRNA and microRNA High-throughput sequencing data quality from EVs isolated by each kit were compared. Results: The total amount of EVs' microRNA isolated from the EI and EM groups were higher than that obtained from the EQ group (EQ/EI: p = 0.036, EI/EM: p = 0.024). High-throughput sequencing data quality evaluation showed that the EI group possessed higher quality than those in the EM group. Conclusion: For the cell culture medium from HepG2, EVs' microRNA isolated by EI reagents might be more suitable for High-throughput sequencing applications.

NCAM-induced neurite outgrowth depends on binding of calmodulin to NCAM and on nuclear import of NCAM and fak fragments.

The neural cell adhesion molecule NCAM plays important functional roles not only during nervous system development, but also in the adult after injury and in synaptic plasticity. Homophilic binding of NCAM triggers intracellular signaling events resulting in cellular responses such as neurite outgrowth that require NCAM palmitoylation-dependent raft localization and activation of the nonreceptor tyrosine kinases fyn and fak. In this study, we show that stimulation of NCAM by a function-triggering NCAM antibody results in proteolytic processing of NCAM and fak. The C-terminal fragment of NCAM, consisting of the intracellular domain, the transmembrane domain, and a stub of the extracellular domain, and the N-terminal fragment of fak are imported into the nucleus. NCAM-stimulated fak activation, generation, and nuclear import of NCAM and fak fragments as well as neurite outgrowth are abolished by mutation of the calmodulin binding motif in the intracellular domain of NCAM that is responsible for the calcium-dependent binding of calmodulin to NCAM. This mutation interferes neither with NCAM cell surface expression, palmitoylation, and raft localization nor with fyn activation. The way by which the transmembrane NCAM fragment reaches the nucleus in a calmodulin- and calcium-dependent manner is by endocytotic transport via the endoplasmic reticulum and the cytoplasm. The generation and nuclear import of NCAM and phosphorylated fak fragments resulting from NCAM stimulation may represent a signal pathway activating cellular responses in parallel or in association with classical kinase- and phosphorylation-dependent signaling cascades.

Neural cell adhesion molecule-associated polysialic acid regulates synaptic plasticity and learning by restraining the signaling through GluN2B-containing NMDA receptors.

The neural cell adhesion molecule (NCAM) is the predominant carrier of alpha2,8 polysialic acid (PSA) in the mammalian brain. Abnormalities in PSA and NCAM expression are associated with schizophrenia in humans and cause deficits in hippocampal synaptic plasticity and contextual fear conditioning in mice. Here, we show that PSA inhibits opening of recombinant NMDA receptors composed of GluN1/2B (NR1/NR2B) or GluN1/2A/2B (NR1/NR2A/NR2B) but not of GluN1/2A (NR1/NR2A) subunits. Deficits in NCAM/PSA increase GluN2B-mediated transmission and Ca(2+) transients in the CA1 region of the hippocampus. In line with elevation of GluN2B-mediated transmission, defects in long-term potentiation in the CA1 region and contextual fear memory in NCAM/PSA-deficient mice are abrogated by application of a GluN2B-selective antagonist. Furthermore, treatment with the glutamate scavenger glutamic-pyruvic transaminase, ablation of Ras-GRF1 (a mediator of GluN2B signaling to p38 MAPK), or direct inhibition of hyperactive p38 MAPK can restore impaired synaptic plasticity in brain slices lacking PSA/NCAM. Thus, PSA carried by NCAM regulates plasticity and learning by inhibition of the GluN2B-Ras-GRF1-p38 MAPK signaling pathway. These findings implicate carbohydrates carried by adhesion molecules in modulating NMDA receptor signaling in the brain and demonstrate reversibility of cognitive deficits associated with ablation of a schizophrenia-related adhesion molecule.

Binding of the receptor tyrosine kinase TrkB to the neural cell adhesion molecule (NCAM) regulates phosphorylation of NCAM and NCAM-dependent neurite outgrowth.

Recognition molecules and neurotrophins play important roles during development and maintenance of nervous system functions. In this study, we provide evidence that the neural cell adhesion molecule (NCAM) and the neurotrophin receptor TrkB directly interact via sequences in their intracellular domains. Stimulation of TrkB by brain-derived neurotrophic factor leads to tyrosine phosphorylation of NCAM at position 734. Mutation of this tyrosine to phenylalanine completely abolishes tyrosine phosphorylation of NCAM by TrkB. Moreover, the knockdown of TrkB in hippocampal neurons leads to a reduction of NCAM-induced neurite outgrowth. Transfection of NCAM-deficient hippocampal neurons with mutated NCAM carrying an exchange of tyrosine by phenylalanine at position 734 leads to promotion of NCAM-induced neurite outgrowth in comparison with that observed after transfection with wild-type NCAM, whereas a reduction of neurite outgrowth was observed after transfection with mutated NCAM, which carries an exchange of tyrosine by glutamate that mimics the phosphorylated tyrosine. Our observations indicate a functional relationship between TrkB and NCAM.

Functional consequences of the interactions among the neural cell adhesion molecule NCAM, the receptor tyrosine kinase TrkB, and the inwardly rectifying K+ channel KIR3.3.

Cell adhesion molecules and neurotrophin receptors are crucial for the development and the function of the nervous system. Among downstream effectors of neurotrophin receptors and recognition molecules are ion channels. Here, we provide evidence that G protein-coupled inwardly rectifying K(+) channel Kir3.3 directly binds to the neural cell adhesion molecule (NCAM) and neurotrophin receptor TrkB. We identified the binding sites for NCAM and TrkB at the C-terminal intracellular domain of Kir3.3. The interaction between NCAM, TrkB, and Kir3.3 was supported by immunocytochemical co-localization of Kir3.3, NCAM, and/or TrkB at the surface of hippocampal neurons. Co-expression of TrkB and Kir3.1/3.3 in Xenopus oocytes increased the K(+) currents evoked by Kir3.1/3.3 channels. This current enhancement was reduced by the concomitant co-expression with NCAM. Both surface fluorescence measurements of microinjected oocytes and cell surface biotinylation of transfected CHO cells indicated that the cell membrane localization of Kir3.3 is regulated by TrkB and NCAM. Furthermore, the level of Kir3.3, but not of Kir3.2, at the plasma membranes was reduced in TrkB-deficient mice, supporting the notion that TrkB regulates the cell surface expression of Kir3.3. The premature expression of developmentally late appearing Kir3.1/3.3 in hippocampal neurons led to a reduction of NCAM-induced neurite outgrowth. Our observations indicate a decisive role for the neuronal K(+) channel in regulating NCAM-dependent neurite outgrowth and attribute a physiologically meaningful role to the functional interplay of Kir3.3, NCAM, and TrkB in ontogeny.