Neural Cell Adhesion Molecule NCAM Research Articles

The dynamic TRPV2 ion channel proximity proteome reveals functional links of calcium flux with cellular adhesion factors NCAM and L1CAM in neurite outgrowth

TRPV2 voltage-insensitive, calcium-permeable ion channels play important roles in cancer progression, immune response, and neuronal development. Despite TRPV2’s physiological impact, underlying endogenous proteins mediating TRPV2 responses and affected signaling pathways remain elusive. Using quantitative peroxidase-catalyzed (APEX2) proximity proteomics we uncover dynamic changes in the TRPV2-proximal proteome and identify calcium signaling and cell adhesion factors recruited to the molecular channel neighborhood in response to activation.Quantitative TRPV2 proximity proteomics further revealed activation-induced enrichment of protein clusters with biological functions in neural and cellular projection. We demonstrate a functional connection between TRPV2 and the neural immunoglobulin cell adhesion molecules NCAM and L1CAM. NCAM and L1CAM stimulation robustly induces TRPV2 [Ca2+]I flux in neuronal PC12 cells and this TRPV2-specific [Ca2+]I flux requires activation of the protein kinase PKCα. TRPV2 expression directly impacts neurite lengths that are modulated by NCAM or L1CAM stimulation. Hence, TRPV2’s calcium signaling plays a previously undescribed, yet vital role in cell adhesion, and TRPV2 calcium flux and neurite development are intricately linked via NCAM and L1CAM cell adhesion proteins.

News and Views on Polysialic Acid: From Tumor Progression and Brain Development to Psychiatric Disorders, Neurodegeneration, Myelin Repair and Immunomodulation.

Polysialic acid (polySia) is a sugar homopolymer consisting of at least eight glycosidically linked sialic acid units. It is a posttranslational modification of a limited number of proteins with the neural cell adhesion molecule NCAM being the most prominent. As extensively reviewed before, polySia-NCAM is crucial for brain development and synaptic plasticity but also modulates tumor growth and malignancy. Functions of polySia have been attributed to its polyanionic character, its spatial expansion into the extracellular space, and its modulation of NCAM interactions. In this mini-review, we first summarize briefly, how the modulation of NCAM functions by polySia impacts tumor cell growth and leads to malformations during brain development of polySia-deficient mice, with a focus on how the latter may be linked to altered behaviors in the mouse model and to neurodevelopmental predispositions to psychiatric disorders. We then elaborate on the implications of polySia functions in hippocampal plasticity, learning and memory of mice in light of recently described polySia changes related to altered neurogenesis in the aging human brain and in neurodegenerative disease. Furthermore, we highlight recent progress that extends the range of polySia functions across diverse fields of neurobiology such as cortical interneuron development and connectivity, myelination and myelin repair, or the regulation of microglia activity. We discuss possible common and distinct mechanisms that may underlie these seemingly divergent roles of polySia, and provide prospects for new therapeutic approaches building on our improved understanding of polySia functions.

Influence of IGF-I serum concentration on muscular regeneration capacity in patients with sarcopenia

BackgroundPrevious research has described a neuroprotective effect of IGF-I, supporting neuronal survival, axon growth and proliferation of muscle cells. Therefore, the association between IGF-I concentration, muscle histology and electrophysiological markers in a cohort of patients with sarcopenia dares investigation.MethodsMeasurement of serum concentrations of IGF-I and binding partners, electromyographic measurements with the MUNIX (Motor Unit Number Index) method and muscle biopsies were performed in 31 patients with acute hip fracture older age 60 years. Molecular markers for denervation (neural cell adhesion molecule NCAM) and proliferation markers (Ki67) were assessed by immunofluorescence staining of muscle biopsy tissue. Skeletal muscle mass by bioelectrical impedance analysis and hand-grip strength were measured to assess sarcopenia status according to EWGSOP2 criteria.ResultsThirty-one patients (20 women) with a mean age of 80.6 ± 7.4 years were included. Concentrations of IGF-I and its binding partners were significantly associated with sarcopenia (ß = − 0.360; p = 0.047) and MUNIX (ß = 0.512; p = 0.005). Further, expression of NCAM (ß = 0.380; p = 0.039) and Ki67 (ß = 0.424; p = 0.022) showed significant associations to IGF-I concentrations.ConclusionsThe findings suggest a pathogenetic role of IGF-I in sarcopenia based on muscle denervation.

Role of Fibroblast Growth Factors Receptors (FGFRs) in Brain Tumors, Focus on Astrocytoma and Glioblastoma.

Simple SummaryConsidering the high mortality rate and the increasing spread of brain tumors both in adulthood and in childhood, we explore the role and involvement of fibroblast growth factors receptors (FGFRs) in two specific types of brain tumors: astrocytoma and glioblastoma. Fibroblast growth factors (FGFs) and their receptors (FGFRs) regulate pivotal cellular processes during embryonal development of the CNS, and as a survival mechanism for adult neurons and astrocytes. Moreover, interactions between the neural cell adhesion molecules NCAM and N-cadherin with FGFR are important for a number of developmental events and have also been implicated in tumor progression. Thus, this review provides an overview on the biological mechanisms of FGFRs related to oncogenesis and a new point of view for future preclinical and clinical studies to develop increasingly targeted therapies.Despite pharmacological treatments and surgical practice options, the mortality rate of astrocytomas and glioblastomas remains high, thus representing a medical emergency for which it is necessary to find new therapeutic strategies. Fibroblast growth factors (FGFs) act through their associated receptors (FGFRs), a family of tyrosine kinase receptors consisting of four members (FGFR1–4), regulators of tissue development and repair. In particular, FGFRs play an important role in cell proliferation, survival, and migration, as well as angiogenesis, thus their gene alteration is certainly related to the development of the most common diseases, including cancer. FGFRs are subjected to multiple somatic aberrations such as chromosomal amplification of FGFR1; mutations and multiple dysregulations of FGFR2; and mutations, translocations, and significant amplifications of FGFR3 and FGFR4 that correlate to oncogenesis process. Therefore, the in-depth study of these receptor systems could help to understand the etiology of both astrocytoma and glioblastoma so as to achieve notable advances in more effective target therapies. Furthermore, the discovery of FGFR inhibitors revealed how these biological compounds improve the neoplastic condition by demonstrating efficacy and safety. On this basis, this review focuses on the role and involvement of FGFRs in brain tumors such as astrocytoma and glioblastoma.

Sialic Acid Metabolic Engineering of Breast Cancer Cells Interferes with Adhesion and Migration

Breast cancer is the most frequent cancer diagnosed in women and the second most common cancer-causing death worldwide. The major problem around the management of breast cancer is its high heterogeneity and the development of therapeutic resistance. Therefore, understanding the fundamental breast cancer biology is crucial for better diagnosis and therapy. Protein sialylation is a key posttranslational modification of glycoproteins, which is also involved in tumor progression and metastasis. Increased expression of sialic acids (Sia) can interfere in receptor–ligand interactions and might protect tumor cells from the immune system. Furthermore, Sia content on the cell membrane plays a role in cancer resistance towards chemo- and radiation therapy. In this study, we glycoengineered MCF-7 breast cancer cells using a series of non-natural Sia precursors, which are prolonged in their acyl side chain. We observed a significant reduction in the natural Sia (N-Acetylneuraminic acid) expression after cultivation of MCF-7 cells with these Sia precursors. In addition, the expression of polySia, a unique glycosylation of the neural cell adhesion molecule NCAM, which interferes with cell adhesion, was decreased. We conclude that sialic acid engineering i) opens up novel opportunities to study the biological role of Sia in breast cancer and ii) provides a toolbox to examine the sialic acid-dependent complex cellular alterations in breast cancer cell biology.

Developmental Regulation of Basket Interneuron Synapses and Behavior through NCAM in Mouse Prefrontal Cortex.

Parvalbumin (PV)-expressing basket interneurons in the prefrontal cortex (PFC) regulate pyramidal cell firing, synchrony, and network oscillations. Yet, it is unclear how their perisomatic inputs to pyramidal neurons are integrated into neural circuitry and adjusted postnatally. Neural cell adhesion molecule NCAM is expressed in a variety of cells in the PFC and cooperates with EphrinA/EphAs to regulate inhibitory synapse density. Here, analysis of a novel parvalbumin (PV)-Cre: NCAM F/F mouse mutant revealed that NCAM functions presynaptically in PV+ basket interneurons to regulate postnatal elimination of perisomatic synapses. Mutant mice exhibited an increased density of PV+ perisomatic puncta in PFC layer 2/3, while live imaging in mutant brain slices revealed fewer puncta that were dynamically eliminated. Furthermore, EphrinA5-induced growth cone collapse in PV+ interneurons in culture depended on NCAM expression. Electrophysiological recording from layer 2/3 pyramidal cells in mutant PFC slices showed a slower rise time of inhibitory synaptic currents. PV-Cre: NCAM F/F mice exhibited impairments in working memory and social behavior that may be impacted by altered PFC circuitry. These findings suggest that the density of perisomatic synapses of PV+ basket interneurons is regulated postnatally by NCAM, likely through EphrinA-dependent elimination, which is important for appropriate PFC network function and behavior.

Patient-derived organoids (PDOs) as a novel in vitro model for neuroblastoma tumours

BackgroundNeuroblastoma (NB) is a paediatric tumour of the sympathetic nervous system. Half of all cases are defined high-risk with an overall survival less than 40% at 5 years from diagnosis. The lack of in vitro models able to recapitulate the intrinsic heterogeneity of primary NB tumours has hindered progress in understanding disease pathogenesis and therapy response.MethodsHere we describe the establishment of 6 patient-derived organoids (PDOs) from cells of NB tumour biopsies capable of self-organising in a structure resembling the tissue of origin.ResultsPDOs recapitulate the histological architecture typical of the NB tumour. Moreover, PDOs expressed NB specific markers such as neural cell adhesion molecules, NB84 antigen, synaptophysin (SYP), chromogranin A (CHGA) and neural cell adhesion molecule NCAM (CD56). Analyses of whole genome genotyping array revealed that PDOs maintained patient-specific chromosomal aberrations such as MYCN amplification, deletion of 1p and gain of chromosome 17q. Furthermore, the PDOs showed stemness features and retained cellular heterogeneity reflecting the high heterogeneity of NB tumours.ConclusionsWe were able to create a novel preclinical model for NB exhibiting self-renewal property and allowing to obtain a reservoir of NB patients’ biological material useful for the study of NB molecular pathogenesis and to test drugs for personalised treatments.

Plasma neuronal exosomes serve as biomarkers of cognitive impairment in HIV infection and Alzheimer's disease.

Plasma neuronal exosomes serve as biomarkers of cognitive impairment in HIV infection and Alzheimer's disease.

Generation and intracellular trafficking of a polysialic acid-carrying fragment of the neural cell adhesion molecule NCAM to the cell nucleus

Polysialic acid (PSA) and its major protein carrier, the neural cell adhesion molecule NCAM, play important roles in many nervous system functions during development and in adulthood. Here, we show that a PSA-carrying NCAM fragment is generated at the plasma membrane by matrix metalloproteases and transferred to the cell nucleus via endosomes and the cytoplasm. Generation and nuclear import of this fragment in cultured cerebellar neurons is induced by a function-triggering NCAM antibody and a peptide comprising the effector domain (ED) of myristoylated alanine-rich C kinase substrate (MARCKS) which interacts with PSA within the plane of the plasma membrane. These treatments lead to activation of the fibroblast growth factor (FGF) receptor, phospholipase C (PLC), protein kinase C (PKC) and phosphoinositide-3-kinase (PI3K), and subsequently to phosphorylation of MARCKS. Moreover, the NCAM antibody triggers calmodulin-dependent activation of nitric oxide synthase, nitric oxide (NO) production, NO-dependent S-nitrosylation of matrix metalloprotease 9 (MMP9) as well as activation of matrix metalloprotease 2 (MMP2) and MMP9, whereas the ED peptide activates phospholipase D (PLD) and MMP2, but not MMP9. These results indicate that the nuclear PSA-carrying NCAM fragment is generated by distinct and functionally defined signal transducing mechanisms.

Mutation of a putative MAP kinase consensus site regulates NCAM endocytosis and NCAM-dependent neurite outgrowth

The cytoplasmic domain of the neural cell adhesion molecule NCAM contains several putative serine/threonine phosphorylation sites whose functions are largely unknown. Human NCAM140 (NCAM140) possesses a potential MAP kinase phosphorylation site at threonine (T) 803. The aim of this study was to analyze a possible phosphorylation of NCAM140 by MAP kinases and to identify the functional role of T803. We found that NCAM140 is phosphorylated by the MAP kinase ERK2 in vitro. Exchange of T803 to aspartic acid (D) which mimics constitutive phosphorylation at the respective position resulted in increased endocytosis compared to NCAM140 in neuroblastoma cells and primary neurons. Consistently, NCAM140 endocytosis was inhibited by the MEK inhibitor U0126 in contrast to NCAM140-T803D or NCAM140-T803A endocytosis supporting a role of a potential ERK2 mediated phosphorylation at this site in endocytosis. Furthermore, cells expressing NCAM140-T803D developed significantly shorter neurites than NCAM140 expressing cells indicating that a potential phosphorylation of NCAM by ERK2 also regulates NCAM-dependent neurite outgrowth.

GFRα1 Regulates Purkinje Cell Migration by Counteracting NCAM Function

SummaryDuring embryonic development of the cerebellum, Purkinje cells (PCs) migrate away from the ventricular zone to form the PC plate. The mechanisms that regulate PC migration are incompletely understood. Here, we report that the neurotrophic receptor GFRα1 is transiently expressed in developing PCs and loss of GFRα1 delays PC migration. Neither GDNF nor RET, the canonical GFRα1 ligand and co-receptor, respectively, contribute to this process. Instead, we found that the neural cell adhesion molecule NCAM is co-expressed and directly interacts with GFRα1 in embryonic PCs. Genetic reduction of NCAM expression enhances wild-type PC migration and restores migration in Gfra1 mutants, indicating that NCAM restricts PC migration in the embryonic cerebellum. In vitro experiments indicated that GFRα1 can function both in cis and trans to counteract NCAM and promote PC migration. Collectively, our studies show that GFRα1 contributes to PC migration by limiting NCAM function.

T/NK-Cell Immunophenotype with Coexpression of CD56 Predicts Poor Outcome in Childhood T-ALL. Results of the ALL-BFM 2000 Trial

Purpose: To investigate the prognostic impact of the coexpression of the natural killer cell marker CD56 / neural-cell adhesion molecule NCAM and to compare it to the immunophenotype subgroups according to the EGIL/WHO 2008 classification and to the early T-cell precursor (ETP) subtype for patients with T-ALL treated in the ALL-BFM 2000 protocol.Patients and Methods: The immunophenotype of 493 children with T-ALL was analyzed centrally at diagnosis with a four-color antibody panel consisting of 28 different antibodies for the detection of antigen expression in the cytoplasm and on the surface of the blast cell population. The frequency of immunophenotypic subtypes and their correlation with event-free survival (EFS) and cumulative incidence of relapse (CIR) were investigated.Results: The frequencies of T-ALL subtypes according to the EGIL/WHO classification were 0.4% for pro-T-ALL, 19.9% for pre-T-ALL, 64.7% for cortical T-ALL and 15% for mature T-ALL. The frequency of the ETP subtype according to the ETP-Score published by Inukai T. et al. (Br J Haematol. 2012) was 6.7% (surface CD3 negative) or 7.5% (with surface CD3 positivity) of all the patients with T-ALL. This is a lower frequency compared to the findings in the St. Jude and AIEOP patients published by Coustan-Smith E. et al. (Lancet Oncology 2009), but similar to what has been reported for the Tokyo Children's Cancer Study Group Study L99-15 by Inukai T. et al. (Br J Haematol. 2012). Coexpression of CD56 was detected in 7.2% of all T-ALL patients. The percentage of ETP in the CD56+ T-ALL cohort was 4-fold increased (30%) as compared to all T-ALL patients (7.2%).The 5-year EFS rates for the EGIL/WHO subgroups pre-T-ALL (n=57), cortical-T-ALL (n=310), and mature T-ALL (n=66) were not statistically different (0.72, SE=0.06, 0.83, SE=0.02, and 0.74, SE=0.06, respectively, Fig. 1). Also the 5-year EFS for the ETP (n=23) did not statistically differ from the non-ETP T-ALL cohort (Fig.1). By contrast, patients with CD56 coexpression (n=35) had a significantly lower 5-year EFS and a higher CIR at 5 years than patients without CD56-expression (EFS: 0.56, SE=0.09 vs. 0.80, SE=0.02, log-rank p = 0.001; CIR: 0.25, SE=0.8 vs. 0.14, SE=0.02, p(Gray) = 0.08), (Fig. 2). In the multivariate analysis, considering other risk parameters like age older than 10 years, WBC greater than 100,000 and prednisone response, CD56 coexpression was an independent prognostic marker for 5-year-EFS with a hazard ratio (HR) of 2.50 (p = 0.002). CD56 coexpression lost significant prognostic impact with the addition of the MRD risk groups to the multivariate model (HR=1.45, n.s.).Conclusion: In the ALL-BFM 2000 trial the prognostic significance of the ETP-phenotype, which has been previously demonstrated as being prognostically unfavorable in several ALL clinical trials, could not be confirmed. The CD56-coexpression, although not superior to the MRD risk assignment, warrants further investigation as an additional independent prognostic indicator at diagnosis for unfavorable clinical outcome in childhood T-ALL. [Display omitted] [Display omitted] DisclosuresMoricke:JazzPharma: Honoraria, Other: financial support of travel costs.

Polysialic acid enters the cell nucleus attached to a fragment of the neural cell adhesion molecule NCAM to regulate the circadian rhythm in mouse brain.

In the mammalian nervous system, the neural cell adhesion molecule NCAM is the major carrier of the glycan polymer polysialic acid (PSA) which confers important functions to NCAM's protein backbone. PSA attached to NCAM contributes not only to cell migration, neuritogenesis, synaptic plasticity, and behavior, but also to regulation of the circadian rhythm by yet unknown molecular mechanisms. Here, we show that a PSA-carrying transmembrane NCAM fragment enters the nucleus after stimulation of cultured neurons with surrogate NCAM ligands, a phenomenon that depends on the circadian rhythm. Enhanced nuclear import of the PSA-carrying NCAM fragment is associated with altered expression of clock-related genes, as shown by analysis of cultured neuronal cells deprived of PSA by specific enzymatic removal. In vivo, levels of nuclear PSA in different mouse brain regions depend on the circadian rhythm and clock-related gene expression in suprachiasmatic nucleus and cerebellum is affected by the presence of PSA-carrying NCAM in the cell nucleus. Our conceptually novel observations reveal that PSA attached to a transmembrane proteolytic NCAM fragment containing part of the extracellular domain enters the cell nucleus, where PSA-carrying NCAM contributes to the regulation of clock-related gene expression and of the circadian rhythm.

Expression of polysialyltransferases (STX and PST) in adult rat olfactory bulb after an olfactory associative discrimination task

Neuronal plasticity and neurogenesis occur in the adult hippocampus and in other brain structures such as the olfactory bulb and often involve the neural cell adhesion molecule NCAM. During an olfactory associative discrimination learning task, NCAM polysialylation triggers neuronal plasticity in the adult hippocampus. The PST enzyme likely modulates this polysialylation, but not STX, a second sialyltransferase. How the two polysialyltransferases are involved in the adult olfactory bulb remains unknown. We addressed this question by investigating the effect of olfactory associative learning on plasticity and neurogenesis. After a hippocampo-dependent olfactory associative task learning, we measured the expression of both PST and STX polysialyltransferases in the olfactory bulbs of adult rats using quantitative PCR. In parallel, immunohistochemistry was used to evaluate both NCAM polysialylation level and newly-born cells, with or without learning. After learning, no changes were observed neither in the expression level of PST and NCAM polysialylation, nor in STX gene expression level and newly-born cells number in the olfactory bulb.

S.04.01 Alterations in structure and neurotransmission of cortical inhibitory networks in animal models and schizophrenic patients: role of the polysialylated form of the neural cell adhesion molecule NCAM

S.04.01 Alterations in structure and neurotransmission of cortical inhibitory networks in animal models and schizophrenic patients: role of the polysialylated form of the neural cell adhesion molecule NCAM

OMIP-028: activation panel for Rhesus macaque NK cell subsets.

OMIP-028: activation panel for Rhesus macaque NK cell subsets.

Deficits of olfactory interneurons in polysialyltransferase- and NCAM-deficient mice.

The neurogenic niche of the anterior subventricular zone (SVZ) persistently generates neuroblasts, which migrate along the rostral migratory stream (RMS) into the olfactory bulb (OB), where they differentiate into granule and periglomerular cells. Loss of the neural cell adhesion molecule NCAM or its post-translational modification polysialic acid (polySia) impairs migration causing accumulations of cells in the proximal RMS and decreased OB volume. Polysialylation of NCAM is implemented by two polysialyltransferases, ST8SIA2 and ST8SIA4, with overlapping functions. Here, we used mice with Ncam1 and polysialyltransferase deletions to analyze how partial or complete loss of polySia synthesis or a combined loss of polySia and NCAM affects the RMS and the interneuron composition in the OB. Numerous calretinin (CR)-positive cells were detected dispersed around the RMS in Ncam1 knockout, St8sia2, St8sia4 double-knockout, and St8sia2, St8sia4, Ncam1 triple-knockout mice, as well as in St8sia2(-/-) but not in St8sia4(-/-) mice. These changes were not reflected by reductions of CR-positive cells in the granule or glomerular layer of the OB. Instead, calbindin-positive periglomerular interneurons were strongly reduced in all polySia-NCAM negative mice and slightly attenuated in St8sia2(-/-) as well as in the St8sia4(-/-) mice, which were devoid of ectopic CR-positive cells along the RMS. Consistent with the early developmental generation of calbindin- as compared with CR-positive OB interneurons, this phenotype was fully developed at postnatal day 5. Together, these results demonstrate that the early development of calbindin-positive periglomerular interneurons depends on the presentation of polySia on NCAM and requires the activity of both polysialyltransferases.

A complementary density gradient of zwitterionic polymer brushes and NCAM peptides for selectively controlling directional migration of Schwann cells

Selective enhancement of directional migration of Schwann cells (SCs) over fibroblasts (FIBs) plays a significant role in peripheral nerve regeneration, because this behavior facilitates neuron repair and avoids fibrosis. Herein a complementary density gradient of poly(3-dimethyl-methacryloyloxyethyl ammonium propane sulfonate) (PDMAPS, a zwitterionic polymer with antifouling property) and KHIFSDDSSE peptide (KHI, derived from neural cell adhesion molecule NCAM which mediates cell–cell adhesion) was fabricated. The gradient was visualized by fluorescent labeling, and further characterized by X-ray photoelectron spectrometry (XPS) and quartz crystal microbalance with dissipation (QCM-d). The SCs exhibited preferential orientation and enhanced directional migration on the gradient surface toward the region of lower PDMAPS density and higher KHI peptide density, while FIBs showed random migration. Moreover, the migration rate of the SCs was significantly enhanced to 2 folds, whereas that of the FIBs was reduced to 60% compared to their natural state on glass, leading to a faster migration rate of SCs than FIBs. The success of the complementary gradient relies on the appropriate interplay between the PDMAPS brushes and the cell-specific ligands, enabling the selective guidance of SCs migration.

Polysialic acid modification of the synaptic cell adhesion molecule SynCAM 1 in human embryonic stem cell-derived oligodendrocyte precursor cells

Oligodendrocyte precursor cells (OPCs) are the progenitors of myelinating oligodendrocytes in brain development and repair. Successful myelination depends on the control of adhesiveness during OPC migration and axon contact formation. The decoration of cell surface proteins with the glycan polysialic acid (polySia) is a key regulatory element of OPC interactions during development and under pathological conditions. By far the major protein carrier of polySia is the neural cell adhesion molecule NCAM, but recently, polysialylation of the synaptic cell adhesion molecule SynCAM 1 has been detected in the developing mouse brain. In mice, polySia-SynCAM 1 is associated with cells expressing NG2, a marker of a heterogeneous precursor cell population, which is the primary source for oligodendrocytes in development and myelin repair but can also give rise to astrocytes and possibly neurons. It is not yet clear if polySia-SynCAM 1 is expressed by OPCs and its occurrence in humans is elusive. By generating uniform human embryonic stem cell-derived OPC cultures, we demonstrate that polySia is present on human OPCs but down-regulated during differentiation into myelin basic protein-positive oligodendrocytes. PolySia on NCAM resides on the isoforms NCAM-180 and NCAM-140, and SynCAM 1 is identified as a novel polySia acceptor in human OPCs.

Polysialic acid on SynCAM 1 in NG2 cells and on neuropilin-2 in microglia is confined to intracellular pools that are rapidly depleted upon stimulation.

NG2 cells comprise a heterogeneous precursor population but molecular markers distinguishing between the assumed NG2 cell subpopulations are lacking. Previously, we described that a subfraction of the synaptic cell adhesion molecule SynCAM 1 is modified with the glycan polysialic acid (polySia) in NG2 cells. As for its major carrier, the neural cell adhesion molecule NCAM, polySia attenuates SynCAM 1 adhesion. Functions, as well as cellular and subcellular distribution of polySia-SynCAM 1 are elusive. Using murine glial cultures we now demonstrate that polySia-SynCAM 1 is confined to the Golgi compartment of a subset of NG2 cells and transiently recruited to the cell surface in response to depolarization. NG2 cells with Golgi-confined polySia were NCAM-negative, but positive for markers of oligodendrocyte precursor cells (OPCs). Consistent with previous data on polySia-SynCAM 1, polySia in Ncam(-/-) NG2 cells was exclusively attached to N-glycans and synthesized by ST8SIA2, one out of two mammalian polysialyltransferases. Unexpectedly, Golgi-confined polySia was also detected in Ncam(-/-) microglia, but this fraction resided on O-glycans and was produced by the second polysialyltransferase, ST8SIA4, indicating the presence of yet another polySia carrier in microglia. Searching for this carrier, we identified polysialylated neuropilin-2, so far only known from dendritic cells and exudate macrophages. Microglia activation by LPS, but not interleukin-4, caused a transient translocation of Golgi-localized polySia to the cell surface, resulting in complete depletion. Finally, NO-production of LPS-stimulated microglia was attenuated by addition of polySia suggesting that the observed loss of polySia-neuropilin-2 is involved in negative feedback regulation of pro-inflammatory microglia polarization.