Binding properties of the neural cell adhesion molecule to different components of the extracellular matrix

High-Coverage Whole-Exome Sequencing Identifies Candidate Genes for Suicide in Victims with Major Depressive Disorder

We carried out whole-exome ultra-high throughput sequencing in brain samples of suicide victims who had suffered from major depressive disorder and control subjects who had died from other causes. This study aimed to reveal the selective accumulation of rare variants in the coding and the UTR sequences within the genes of suicide victims. We also analysed the potential effect of STR and CNV variations, as well as the infection of the brain with neurovirulent viruses in this behavioural disorder. As a result, we have identified several candidate genes, among others three calcium channel genes that may potentially contribute to completed suicide. We also explored the potential implication of the TGF-β signalling pathway in the pathogenesis of suicidal behaviour. To our best knowledge, this is the first study that uses whole-exome sequencing for the investigation of suicide.

WITHDRAWN: NCAM and the FGF-Receptor

In this review, the structural biology of interaction between the neural cell adhesion molecule (NCAM) and the fibroblast growth factor (FGF) receptor is described and a possible mechanism of the FGF-receptor activation by NCAM is discussed. Most of the FGF-receptor molecules are thought to be constantly involved in a transient interaction with NCAM. However, the FGF-receptor becomes activated only when NCAM is involved the trans-homophilic binding (mediating cell-cell adhesion). The trans-homophilic binding between the NCAM molecules is believed to result in formation of either one- or two-dimensional 'zipper'-like arrays of the NCAM molecules, which leads to NCAM clustering and as a result to clustering of the FGF-receptor, which in turn may lead to its activation through a direct receptor-receptor dimerization (and thus activation) due to an increase in the local concentration of the receptor.

Proteolytic cleavage of the neural cell adhesion molecule by ADAM17/TACE is involved in neurite outgrowth

The transmembrane and multidomain neural cell adhesion molecule (NCAM) plays important functional roles in the developing and adult nervous system. NCAM is proteolytically processed and appears in soluble forms in the cerebrospinal fluid and in serum under normal and pathological conditions. In this report, we present evidence that the metalloprotease a disintegrin and a metalloprotease (ADAM)17/tumour necrosis factor alpha converting enzyme (TACE) cleaves the polysialylated as well as the non-polysialylated transmembrane isoforms of NCAM, whereas the glycophosphatidylinositol-linked isoform of NCAM is not proteolytically cleaved. A truncated, enzymatically inactive mutant of TACE did not result in release of the NCAM110 cleavage product. Proteolytic cleavage was enhanced by a calmodulin-specific inhibitor and the actin-destabilizing agents cytochalasin D and latrunculin B. In contrast, the microtubule-stabilizing agent colchicine or microtubule-destabilizing agent paclitaxel did not affect the release of the 110-kDa fragment of NCAM. Neurite outgrowth from cerebellar microexplants was inhibited in the presence of the metalloprotease inhibitor GM 6001 on substrate-coated NCAM, but not on poly-l-lysine. Upon transfection of hippocampal neurones with an enzymatically inactive mutant of TACE, NCAM-stimulated neurite outgrowth was inhibited without affecting neurite outgrowth on poly-l-lysine, showing that proteolytic processing of NCAM by the metalloprotease TACE is involved in NCAM-mediated neurite outgrowth.

Neural-cell adhesion molecule (NCAM) expression by immature and tumor-derived endothelial cells favors cell organization into capillary-like structures

The neural cell adhesion molecule (NCAM) is widely expressed during embryogenesis, down-regulated in the course of differentiation to be re-expressed during progression of some tumors. We here found that renal tumor-derived endothelial cells (TEC) but not normal endothelial cells (HMEC) expressed NCAM. In TEC, NCAM expression was regulated by the renal embryonic transcription factor PAX2, as transfection with PAX2 antisense abrogated NCAM expression. NCAM stimulation with an agonistic synthetic NCAM peptide enhanced apoptosis resistance and increased ability of TEC to organize in vessel-like structures. The angiogenic effect of NCAM peptide was, at least in part, mediated by the association of NCAM and FGFR1. HMEC transiently acquired NCAM when organized in vessel-like structures after VEGF stimulation or when transfected with PAX2 gene. During the process of VEGF-induced endothelial differentiation of renal stem cells and of circulating endothelial progenitors, NCAM was transiently expressed to disappear at complete endothelial maturation. Targeting NCAM with a saporin-conjugated peptide induced a cytotoxic effect on TEC but not on HMEC. In conclusion, we identified a new role of NCAM in tumor neo-angiogenesis relevant for endothelial cell organization into capillary-like structures. In addition, we found that NCAM expression was associated with an immature phenotype of endothelial cells.

The molecular pathogenetic role of cell adhesion in endocrine neoplasia

It is becoming increasingly evident that cell adhesion is an important determinant of organised growth and the maintenance of architectural integrity. Indeed, reduced adhesiveness between cells and with the extracellular matrix is a hallmark of neoplastic growth. In neuroendocrine tissues, neural cell adhesion molecule is implicated in modulating cell growth, migration, and differentiation. This review will focus on the molecular pathways involving key growth factor receptors that govern normal adhesive forces. The extent to which disruption of these adhesive forces contributes to the tumorigenic process in neuroendocrine tissues will be highlighted. Validation of the functional relevance of these adhesive pathways will be discussed in light of targeted pharmacotherapeutic studies that are unmasking novel approaches to the treatment of neuroendocrine tumours.

Expression of NCAM in activated portal fibroblasts during regeneration of the rat liver after partial hepatectomy

In the portal tract of the regenerating liver after partial hepatectomy, vascular and bile ductular remodeling takes place in response to the portal hyperdynamic state and parenchymal hyperplasia. In order to reveal phenotypical changes in the portal fibroblasts, we immunohistochemically investigated neural cell adhesion molecules (NCAM) and alpha smooth muscle actin (alphaSMA) expression and the ultrastructural changes in them during liver regeneration. In the control rat liver, portal fibroblasts were negative for both NCAM and alphaSMA. They became positive for both markers two days after partial hepatectomy, increased in staining intensity, reached a maximum at three to four days, then decreased, being still clearly positive at 14 days. Under an electron microscope, portal fibroblasts from the regenerating liver had larger amounts of cytoplasm and rough endoplasmic reticulum than those from the control liver; thus they might be activated. Additionally, periportal hepatic stellate cells in the regenerating liver were activated with alphaSMA, but without NCAM. The present study has demonstrated that portal fibroblasts express NCAM and alphaSMA in the regenerating liver after partial hepatectomy via transformation into myofibroblasts following reconstruction of the portal tracts.

Structural biology of NCAM homophilic binding and activation of FGFR

In this review, we analyse the structural basis of the homophilic interactions of the neural cell adhesion molecule (NCAM) and the NCAM-mediated activation of the fibroblast growth factor receptor (FGFR). Recent structural evidence suggests that NCAM molecules form cis-dimers in the cell membrane through a high affinity interaction. These cis-dimers, in turn, mediate low affinity trans-interactions between cells via formation of either one- or two-dimensional 'zippers'. We provide evidence that FGFR is probably activated by NCAM very differently from the way by which it is activated by FGFs, reflecting the different conditions for NCAM-FGFR and FGF-FGFR interactions. The affinity of FGF for FGFR is approximately 10(6) times higher than that of NCAM for FGFR. Moreover, in the brain NCAM is constantly present on the cell surface in a concentration of about 50 microm, whereas FGFs only appear transiently in the extracellular environment and in concentrations in the nanomolar range. We discuss the structural basis for the regulation of NCAM-FGFR interactions by two molecular 'switches', polysialic acid (PSA) and adenosine triphosphate (ATP), which determine whether NCAM acts as a signalling or an adhesion molecule.

Tyrosine 734 of NCAM180 interferes with FGF receptor-dependent signaling implicated in neurite growth

The cytoplasmic domain of the neural cell adhesion molecule (NCAM) contains multiple phosphorylation sites. We report here that in addition to serine and threonine residues a tyrosine of the NCAM180 isoform is phosphorylated as shown by phosphoamino acid analysis. Exchange of the only cytoplasmic tyrosine at position 734 of human NCAM180 (NCAM180-Y734F) to phenylalanine resulted in increased neurite outgrowth of NCAM180-Y734F transfected B35 neuroblastoma cells compared to NCAM180-wt transfectants on poly-L-lysine as substrate. As demonstrated by inhibitor studies the increased neurite outgrowth was due to higher FGF receptor 1 and ERK1 activity in NCAM180-Y734F cells, indicating that tyrosine residue 734 plays a role in signal transduction mediated by the FGF receptor. On an NCAM expressing monolayer of COS-7 cells the Y734F mutation also influences FGF receptor 1 dependent neurite outgrowth, but under these conditions additional mechanisms seem to be responsible for the increased neurite length observed for NCAM180-Y734F transfected cells.

The brain angiotensin system and extracellular matrix molecules in neural plasticity, learning, and memory

The brain renin-angiotensin system (RAS) has long been known to regulate several classic physiologies including blood pressure, sodium and water balance, cyclicity of reproductive hormones and sexual behaviors, and pituitary gland hormones. These physiologies are thought to be under the control of the angiotensin II (AngII)/AT1 receptor subtype system. The AT2 receptor subtype is expressed during fetal development and is less abundant in the adult. This receptor appears to oppose growth responses facilitated by the AT1 receptor, as well as growth factor receptors. Recent evidence points to an important contribution by the brain RAS to non-classic physiologies mediated by the newly discovered angiotensin IV (AngIV)/AT4 receptor subtype system. These physiologies include the regulation of blood flow, modulation of exploratory behavior, and a facilitory role in learning and memory acquisition. This system appears to interact with brain matrix metalloproteinases in order to modify extracellular matrix molecules thus permitting the synaptic remodeling critical to the neural plasticity presumed to underlie memory consolidation, reconsolidation, and retrieval. There is support for an inhibitory influence by AngII activation of the AT1 subtype, and a facilitory role by AngIV activation of the AT4 subtype, on neuronal firing rate, long-term potentiation, associative and spatial learning. The discovery of the AT4 receptor subtype, and its facilitory influence upon learning and memory, suggest an important role for the brain RAS in normal cognitive processing and perhaps in the treatment of dysfunctional memory disease states.

Structure and interactions of NCAM Ig1-2-3 suggest a novel zipper mechanism for homophilic adhesion

The neural cell adhesion molecule, NCAM, mediates Ca(2+)-independent cell-cell and cell-substratum adhesion via homophilic (NCAM-NCAM) and heterophilic (NCAM-non-NCAM molecules) binding. NCAM plays a key role in neural development, regeneration, and synaptic plasticity, including learning and memory consolidation. The crystal structure of a fragment comprising the three N-terminal Ig modules of rat NCAM has been determined to 2.0 A resolution. Based on crystallographic data and biological experiments we present a novel model for NCAM homophilic binding. The Ig1 and Ig2 modules mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), whereas the Ig3 module mediates interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through simultaneous binding to the Ig1 and Ig2 modules. This arrangement results in two perpendicular zippers forming a double zipper-like NCAM adhesion complex.

N-CAM expression and localization in PC12 cells modulated by extracellular peptides

The neural cell adhesion molecules (N-CAMs) play an important role in mediating cell-cell interactions in the nervous system. Different isoforms of these membrane proteins are involved in the formation of the neuronal network and in the dynamic phases of neuronal plasticity. We studied the early stages of the pseudo neuronal differentiation of PC12 cells induced by a class of small acidic peptides capable of modulating gene expression in these cells. The data presented here indicate that peptides with specific sequences induce an increase in N-CAM mRNA expression and protein translocation to the plasma membrane to a comparable degree as NGF.

Expression of neural cell-adhesion molecule mRNA during mouse molar tooth development

This study employed in situ hybridisation using a probe recognising all isoforms of the molecule. Expression of the molecule in tooth germs started at embryonic day 13, when they were at the bud stage. Both inner cells of the epithelial bud and peripheral cells of the dental mesenchyme were positive. At the cap stage, positive cells were found in the inner part of the enamel organ but only in a limited area near the outer enamel epithelium. In the mesenchyme at the cap stage, expression was weak in the dental papilla and strong in the follicle. From the bell stage onward, epithelial cells in the enamel organ were negative except for the cells of the stratum intermedium, which were transiently positive at early and late bell stages. In the dental papilla, expression had mostly ceased during and after the bell stage, although transient expression was found in cuspal areas at the early bell stage. The dental follicle strongly expressed neural cell-adhesion molecule (NCAM) to the end of the experimental period, at post-natal day 4. In contrast to the first molar at its earliest stage of appearance, in which both the thickened epithelium and surrounding mesenchyme were negative for the expression of the molecule, the second molar appeared as a combination of extending epithelial thickenings and mesenchymal cells strongly positive for its expression. This study newly identifies the dental papilla and the stratum intermedium as NCAM-expressing sites.

Neural plasticity and the brain renin-angiotensin system

The brain renin-angiotensin system mediates several classic physiologies including body water balance, maintenance of blood pressure, cyclicity of reproductive hormones and sexual behaviors, and regulation of pituitary gland hormones. In addition, angiotensin peptides have been implicated in neural plasticity and memory. The present review initially describes the extracellular matrix (ECM) and the roles of cell adhesion molecules (CAMs), matrix metalloproteinases, and tissue inhibitors of metalloproteinases in the maintenance and degradation of the ECM. It is the ECM that appears to permit synaptic remodeling and thus is critical to the plasticity that is presumed to underlie mechanisms of memory consolidation and retrieval. The interrelationship among long-term potentiation (LTP), CAMs, and synaptic strengthening is described, followed by the influence of angiotensins on LTP. There is strong support for an inhibitory influence by angiotensin II (AngII) and a facilitory role by angiotensin IV (AngIV), on LTP. Next, the influences of AngII and IV on associative and spatial memories are summarized. Finally, the impact of sleep deprivation on matrix metalloproteinases and memory function is described. Recent findings indicate that sleep deprivation-induced memory impairment is accompanied by a lack of appropriate changes in matrix metalloproteinases within the hippocampus and neocortex as compared with non-sleep deprived animals. These findings generally support an important contribution by angiotensin peptides to neural plasticity and memory consolidation.

Cosignaling of NCAM via lipid rafts and the FGF receptor is required for neuritogenesis

The neural cell adhesion molecule (NCAM) has been reported to stimulate neuritogenesis either via nonreceptor tyrosine kinases or fibroblast growth factor (FGF) receptor. Here we show that lipid raft association of NCAM is crucial for activation of the nonreceptor tyrosine kinase pathway and induction of neurite outgrowth. Transfection of hippocampal neurons of NCAM-deficient mice revealed that of the three major NCAM isoforms only NCAM140 can act as a homophilic receptor that induces neurite outgrowth. Disruption of NCAM140 raft association either by mutation of NCAM140 palmitoylation sites or by lipid raft destruction attenuates activation of the tyrosine focal adhesion kinase and extracellular signal-regulated kinase 1/2, completely blocking neurite outgrowth. Likewise, NCAM-triggered neurite outgrowth is also completely blocked by a specific FGF receptor inhibitor, indicating that cosignaling via raft-associated kinases and FGF receptor is essential for neuritogenesis.

NCAM regulates cell motility

Cell migration is required during development of the nervous system. The regulatory mechanisms for this process, however, are poorly elucidated. We show here that expression of or exposure to the neural cell adhesion molecule (NCAM) strongly affected the motile behaviour of glioma cells independently of homophilic NCAM interactions.

Expression of the transmembrane 140 kDa isoform of NCAM (NCAM-140) caused a significant reduction in cellular motility, probably through interference with factors regulating cellular attachment, as NCAM-140-expressing cells exhibited a decreased attachment to a fibronectin substratum compared with NCAM-negative cells. Ectopic expression of the cytoplasmic part of NCAM-140 also inhibited cell motility, presumably via the non-receptor tyrosine kinase p59fyn with which NCAM-140 interacts.

Furthermore, we showed that the extracellular part of NCAM acted as a paracrine inhibitor of NCAM-negative cell locomotion through a heterophilic interaction with a cell-surface receptor. As we showed that the two N-terminal immunoglobulin modules of NCAM, which are known to bind to heparin, were responsible for this inhibition, we presume that this receptor is a heparan sulfate proteoglycan. A model for the inhibitory effect of NCAM is proposed, which involves competition between NCAM and extracellular components for the binding to membrane-associated heparan sulfate proteoglycan.

Extracellular matrix molecules, long-term potentiation, memory consolidation and the brain angiotensin system

Considerable evidence now suggests an interrelationship among long-term potentiation (LTP), extracellular matrix (ECM) reconfiguration, synaptogenesis, and memory consolidation within the mammalian central nervous system. Extracellular matrix molecules provide the scaffolding necessary to permit synaptic remodeling and contribute to the regulation of ionic and nutritional homeostasis of surrounding cells. These molecules also facilitate cellular proliferation, movement, differentiation, and apoptosis. The present review initially focuses on characterizing the ECM and the roles of cell adhesion molecules (CAMs), matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), in the maintenance and degradation of the ECM. The induction and maintenance of LTP is described. Debate continues over whether LTP results in some form of synaptic strengthening and in turn promotes memory consolidation. Next, the contribution of CAMs and TIMPs to the facilitation of LTP and memory consolidation is discussed. Finally, possible roles for angiotensins, MMPs, and tissue plasminogen activators in the facilitation of LTP and memory consolidation are described. These enzymatic pathways appear to be very important to an understanding of dysfunctional memory diseases such as Alzheimer's disease, multiple sclerosis, brain tumors, and infections.

N-CAM modulates tumour-cell adhesion to matrix by inducing FGF-receptor signalling

Loss of expression of neural cell-adhesion molecule (N-CAM) is implicated in the progression of tumour metastasis. Here we show that N-CAM modulates neurite outgrowth and matrix adhesion of beta-cells from pancreatic tumours by assembling a fibroblast-growth-factor receptor-4 (FGFR-4) signalling complex, which consists of N-cadherin, FGFR-4, phospholipase C gamma (PLC-gamma), the adaptor protein FRS2, pp60(c-src), cortactin and growth-associated protein-43 (GAP-43). Dominant-negative FGFR-4, inhibitors of FGFR signalling and anti-beta(1)-integrin antibodies repress matrix adhesion induced by N-CAM. FGF ligands can replace N-CAM in promoting matrix adhesion but not neurite outgrowth. The results indicate that N-CAM stimulates beta1-integrin-mediated cell-matrix adhesion by activating FGFR signalling. This is a potential mechanism for preventing the dissemination of metastatic tumour cells.

Oligodendrocyte precursor migration and differentiation: combined effects of PSA residues, growth factors, and substrates

Using the oligosphere strategy (V. Avellana-Adalid et al., 1996, J. Neurosci. Res. 45, 558-570), we compared the migratory behavior of oligodendrocyte preprogenitors (OPP) that expressed the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) and of GD3-positive oligodendrocyte progenitors (OP). To study the role of PSA in OPP migration, we used endoneuraminidase-N, which specifically cleaves PSA from NCAM. Kinetic data showed that (i) migration velocity decreased with time and was favored on polyornithine compared to Matrigel; (ii) cells emerging from spheres enriched in PSA-NCAM+ OPP migrated farther than those from spheres enriched in GD3+ OP, their migration being enhanced by the addition of growth factors; (iii) removal of PSA from NCAM moderately reduced OPP migration and induced their differentiation in GD3+ OP and GFAP+ astrocytes; (iv) blocking integrins reduced their migration, suggesting an alternative mechanism of migration. Altogether these data illustrate that motility and differentiation of OPP involve the combinatorial action of PSA-NCAM, molecules of the ECM and their receptors, and growth factors.

Identification of a neuritogenic ligand of the neural cell adhesion molecule using a combinatorial library of synthetic peptides

The neural cell adhesion molecule (NCAM) plays a key role in neural development, regeneration, and learning. In this study, we identified a synthetic peptide-ligand of the NCAM Ig1 module by combinatorial chemistry and showed it could modulate NCAM-mediated cell adhesion and signal transduction with high potency. In cultures of dissociated neurons, this peptide, termed C3, stimulated neurite outgrowth by activating a signaling pathway identical to that activated by homophilic NCAM binding. A similar effect was shown for the NCAM Ig2 module, the endogenous ligand of NCAM Ig1. By nuclear magnetic resonance spectroscopy, the C3 binding site in the NCAM Ig1 module was mapped and shown to be different from the binding site of the NCAM Ig2 module. The C3 peptide may prove useful as a lead in development of therapies for neurodegenerative disorders, and the C3 binding site of NCAM Ig1 may represent a target for discovery of nonpeptide drugs.

I-type lectins in the nervous system

The number of animal lectins, basically defined upon their interaction with specific carbohydrate structures, is growing considerably during the last few years. Among these proteins the recently identified subfamily of I-type lectins consists of mainly transmembranous glycoproteins belonging to the immunoglobulin superfamily. Most of the I-type lectins participate in cell adhesion events, as are the different sialoadhesins recognizing sialylated glycan structures, which represent the best characterized subgroup. I-type lectins are abundant in the nervous system and have been implicated in a number of morphogenetic processes as fundamental as axon growth, myelin formation and growth factor signaling. In the present review, we summarize the structural and functional properties of I-type lectins expressed in neural tissues with a main focus on the sialoadhesin myelin-associated glycoprotein, the neural cell adhesion molecule and the fibroblast growth factor receptors.

The neural cell adhesion molecule (NCAM) in development and plasticity of the nervous system

The neural cell adhesion molecule (NCAM) is a member of the immunoglobulin superfamily and is strongly expressed in the nervous system. NCAM is found in three major forms, of which two--NCAM-140 and NCAM-180--are transmembrane proteins, while the third--NCAM-120--is attached to the membrane via a glycosylphosphatidyl inositol anchor. In addition, soluble NCAM forms exist in brain, cerebrospinal fluid, and plasma. NCAM mediates cell adhesion through homophilic as well as through heterophilic interactions. Following NCAM binding, transmembrane signalling is believed to be activated, resulting in increased intracellular calcium. By mediating cell adhesion to other cells and to the extracellular matrix and by activating intracellular signaling pathways, NCAM influences cell migration, neurite extension, and fasciculation, and possibly formation of synapses in the brain. From studies on NCAM knock-out mice, NCAM have been shown to be crucial for the formation of the olfactory bulb and the mossy fiber system in the hippocampus. In addition, NCAM is important for neuronal plasticity in the adult brain associated with learning and regeneration.

Expression of the neural cell adhesion molecule in astrocytic tumors: an inverse correlation with malignancy

BACKGROUND

Cell adhesion molecules are among the key factors in the development of the malignant potential of brain tumors. The aim of this study was to investigate the expression of the neural cell adhesion molecule (NCAM) in human astrocytic tumors and assess any relationship between NCAM expression and the degree of malignancy.

METHODS

The expression of NCAM was examined in 52 astrocytic tumors by Western blot analysis. From them the authors selected 23 adult supratentorial ordinary astrocytic tumors and performed quantitative Western blot analysis for each isoform (NCAM 172-180, NCAM 145, NCAM 125-130) to investigate any correlation between the expression of each NCAM isoform and the histologic and biologic malignancy (histology, proliferating cell indices [PCIs] determined by MIB-1 immunohistochemistry, and manifestation on magnetic resonance images [MRIs]). Immunohistochemistry with antihuman NCAM monoclonal antibody was also performed on the tumors from which cryostat sections were available.

RESULTS

Most of the astrocytomas and anaplastic astrocytomas revealed 3 bands at 180, 145, and 125-130kD, whereas in glioblastomas the bands tended to diminish. The expression of each NCAM isoform in astrocytic tumors decreased in proportion to the progression of the histologic malignancy, and the results were also corroborated by immunohistochemical evaluation. An inverse correlation was also observed between the amount of NCAM expression and MIB-1 PCIs. NCAM expression was hardly detectable in those tumors with highly invasive manifestation on MRIs.

CONCLUSIONS

To the authors' knowledge, this study provides the first direct evidence that NCAM is down-regulated in the development of the malignancy of astrocytic tumors; and it is suggested that reduced NCAM expression might be involved in the development of biologic malignancy.

Further studies of elevated cerebrospinal fluid neuronal cell adhesion molecule in schizophrenia

BACKGROUND

The purposes of the present study were to attempt to replicate a previous finding of increased cerebrospinal fluid (CSF) neuronal cell adhesion molecule (N-CAM) in schizophrenia, and to assess whether the increases could be related to medication, clinical state effects, or brain structural measures.

METHODS

CSF N-CAM was measured by the Western blot technique in 45 DSM-III-R diagnosed male schizophrenic patients both on and off haloperidol treatment and in 20 healthy male control subjects.

RESULTS

CSF N-CAM was significantly increased in schizophrenic patients, with no overlap in the ranges, when compared to controls. There were no significant effects of medication or exacerbation on CSF N-CAM. No associations with measures of brain structure were found.

CONCLUSIONS

Because N-CAM levels were not shown to be different on and off treatment or in exacerbated versus nonexacerbated patients, the higher levels seen in schizophrenic patients may be inherent to the disorder and possibly related to neurodevelopment.

Effect of NCAM-transfection on growth and invasion of a human cancer cell line

A cDNA encoding the human transmembrane 140 kDa isoform of the neural cell adhesion molecule (NCAM) was transfected into the highly invasive MDA-MB-231 human breast cancer cell line. Transfectants with a homogeneous expression of NCAM showed a restricted capacity for penetration of an artificial basement membrane. However, when injected into nude mice, both control and NCAM-expressing cell lines produced equally invasive tumors. Tumors generated from NCAM-transfected cells were heterogeneous, containing NCAM-positive as well as NCAM-negative areas, indicating the existence of host factors capable of modulating NCAM expression in vivo. In nude mice, NCAM-transfected cells developed tumors with longer latency periods and slower growth rates than tumors induced by NCAM-negative control cells, implying that NCAM may be involved not only in adhesive and motile behavior of tumor cells but also in their growth regulation. There was no indication of differences in cell proliferative characteristics between the different NCAM-transfected and the control transfected cells as determined by flow cytometric DNA analysis, suggesting an increased cell loss as the reason for decreased in vivo growth rate of the NCAM-transfected cells. The fact that NCAM expression influences growth regulation attributes a pivotal role to this cell adhesion molecule during ontogenesis and tumor development.

The first immunoglobulin-like neural cell adhesion molecule (NCAM) domain is involved in double-reciprocal interaction with the second immunoglobulin-like NCAM domain and in heparin binding

To study the function of the first immunoglobulin (Ig)-like domain of the neural cell adhesion molecule (NCAM), it was produced as a recombinant fusion protein in a bacterial expression system and as a recombinant protein in a eukaryotic expression system of the yeast Pichia pastoris. For comparison, other NCAM domains were also produced as fusion proteins. By means of surface plasmon resonance analysis, it was shown that the first Ig-like NCAM domain binds the second Ig-like NCAM domain with a dissociation constant 5.5 +/- 1.6 x 10(-5) M. Furthermore, it was found that the first Ig-like domain binds heparin. It was also demonstrated that the second Ig-like NCAM domain binds heparin and that both domains bind collagen type I via heparin but not collagen type I directly.

NCAM expression in the pulmonary neural and diffuse neuroendocrine cell system

Neural cell adhesion molecule (NCAM)--a membrane protein involved in cell-cell adhesion within the central and peripheral nervous systems--was demonstrated to be a sensitive and specific marker for neuroepithelial bodies (NEB) and neural tissue elements in the cat lung. Using the streptavidin-biotin immunoperoxidase method, NCAM reactive sites were investigated with monoclonal and polyclonal antibodies on serial section of Bouin fixed, paraffin embedded lung tissue. Moreover, NCAM expression was compared with that of neuron-specific enolase (NSE) on adjacent sections. The most obvious NCAM staining was obtained with the monoclonal antibody. From newborn to adult life, cell surface labeling was identified on NEB cells. In mature cat lung, they were no longer positive. Solitary neuroendocrine cells (NEC) were always negative. In contrast to the transient postnatal immunoreactivity of NEB cells, nerve fibers and ganglion cells were stained throughout all life stages and studied. The distribution of NCAM in NEB, nerve fibers and ganglion cells was similar to that NSE, except in the adult lung. This study reveals that during lung growth shared NCAM antigens exist between the pulmonary nervous and endocrine system, whereas in mature lung NCAM proteins are confined to neural tissue elements. The difference in NCAM expression between NEB and NEC might suggest an involvement of NCAM in the formation of contacts between NEB cells and nerves.

Structural analysis of the murine cell adhesion molecule L1 by electron microscopy and computer-assisted modelling

In the present study we have analysed the morphology of two fragments with apparent molecular weights of 180 and 140 kDA (L1-180 and L1-140) derived from the extracellular region of the murine neural cell adhesion molecule L1. The fragment L1-180 consists of almost the entire extracellular part of the molecule, and is built up of six immunoglobulin-like and five fibronectin type III-like domains. Fragment L1-140 lacks one-half of the third, the fourth and the fifth fibronectin type III-like domains. By electron microscopic analysis of rotary-shadowed molecules, L1-140 and L1-180 revealed fibrillar structures 31-43 nm long and 7-12 nm wide with one pronounced globular terminal domain. As determined by complex formation with an L1 antibody, this terminal part of the molecule is formed by the fibronectin type III-like domains. The individual structures showed variation and complexity, and four distinct aspects were identified. These different forms probably represent two-dimensional projections of the same three-dimensional helical structure. Computer-assisted modelling of the L1 molecule, i.e. the protein backbone, showed no strong intramolecular interaction between the different fibronectin type III- or Ig-like domains, suggesting that the formation of the globular part of the molecule is probably achieved by protein-carbohydrate and/or carbohydrate-carbohydrates rather than protein-protein interactions. In addition, our model proposes that interactions occur within the interfaces between the different domains. The highly conserved amino acid residues in these regions point to the necessity of maintaining the orientation between the different domains.

Analysis of hindbrain neural crest migration in the long-tailed monkey (Macaca fascicularis)

Neural crest cells make a substantial contribution to normal craniofacial development. Despite advances made in identifying migrating neural crest cells in avian embryos and, more recently, rodent embryos, knowledge of crest cell migration in primates has been limited to what was obtained by conventional morphological techniques. In order to determine the degree to which the nonhuman primate fits the mammalian pattern, we studied the features of putative neural crest cell migration in the hindbrain of the long-tailed monkey (Macaca fascicularis) embryo. Cranial crest cells were identified on the basis of reported distributional and morphological criteria as well as by immunocytochemical detection of the neural cell adhesion molecule (N-CAM) that labels a subpopulation of these cells. The persistent labeling of a sufficient number of crest cells with antibodies to N-CAM following their exit from the rostral, pre-otic and post-otic regions of the hindbrain facilitated tracking them along subectodermal pathways to their respective destinations in the first, second and third pharyngeal arches. Peroxidase immunocytochemistry was also employed to localize laminin and collagen-IV in neuroepithelial basement membranes. At stage 10 (8-11 somites), crest emigration occurred in areas of unfused neural folds through focal disruptions in the neuroepithelial basement membrane in both the rostral and pre-otic regions, although there was little evidence of crest migration in the post-otic hindbrain. By stage 11 (16-17 somites), the neural folds were fused (pre- and post-otic hindbrain) or in the process of fusing (rostral hindbrain), yet crest cell emigration was apparent in all three areas through discontinuities in the basement membrane. Emigration was essentially complete at stage 12 (21 somites) as indicated by nearly continuous cranial neural tube basement membranes. At this stage the pre-ganglia (trigeminal, facioacoustic and glossopharyngeal) were consistently stained with N-CAM. The current study has provided new information on mammalian neural crest in a well-established experimental model for normal and abnormal human development, including its use as a model for the retinoic acid syndrome. In this regard, the current results provide the basis for probing the mechanisms of retinoid embryopathy which may involve perturbation of hindbrain neural crest development.

Macaque intra-arterial trophoblast and extravillous trophoblast of the cell columns and cytotrophoblastic shell express neural cell adhesion molecule (NCAM)

BACKGROUND

During placental development in higher primates trophoblast cells originating in the cell columns migrate along endometrial surfaces to form the cytotrophoblastic shell. A subpopulation of these cells invades uterine arteries, where they migrate on the surface of endothelium, against the flow of blood. These intra-arterial cells become sequestered in the walls of the arteries where they are referred to as intramural trophoblast. Because migration depends upon binding the cell surface to other cells or to extracellular matrix, we investigated the potential role of neural cell adhesion molecule (NCAM, CD56) in arterial invasion by trophoblast cells.

METHODS

Tissues from macaque placentas and endometrium were fixed and embedded in paraffin. Standard immunoperoxidase methods were used to identify NCAM.

RESULTS

NCAM labeled cells were present within spiral arteries of the decidua basalis. Trophoblast cells within or adjacent to the arterial lumen were distinctly NCAM positive, whereas most intramural trophoblast cells revealed reduced or no reactivity for NCAM. Maternal endothelial cells and villous trophoblast cells were negative. Uterine veins were tapped by trophoblast but did not contain migratory cells. The cell columns of early pregnancy contained cells outlined by rims of reactivity for NCAM. Labeled cells were also seen in the cytotrophoblastic shell, arranged as discontinuous groups. These groups variably occupied the entire thickness of the shell, or only the proximal (adjacent to the intervillous space) or distal layers of the shell. Later in gestation, the cytotrophoblastic shell developed a different pattern of staining, such that only cells located nearer to the intervillous space or near the tips of the anchoring villi were positive.

CONCLUSIONS

We conclude that NCAM is one of a group of cell adhesion molecules that participates in trophoblast cell adhesion during migration within maternal arteries. NCAM appears to be active in trophoblast-trophoblast cell interactions. It may also contribute to binding trophoblast cells to the surfaces of arterial endothelium as well as extracellular matrix molecules of the arterial wall. After secondary invasion into the arterial walls NCAM is down-regulated, possibly in response to the appearance of extracellular matrix capsules, where other cell adhesion molecules may appear.

Targeted mutation of Ncam to produce a secreted molecule results in a dominant embryonic lethality

The neural cell adhesion molecule (NCAM) is a membrane-associated member of the immunoglobulin superfamily capable of both homophilic and heterophilic binding. To investigate the significance of this binding, a gene targeting strategy in embryonic stem (ES) cells was used to replace the membrane-associated forms of NCAM with a soluble, secreted form of its extracellular domain. Although the heterozygous mutant ES cells were able to generate low coat color chimeric mice, only the wild-type allele was transmitted, suggesting the possibility of dominant lethality. Analysis of chimeric embryos with high level of ES cell contribution revealed severe growth retardation and morphological defects by E8.5-E9.5. The second allele was also targeted, and embryos derived almost entirely from the homozygous mutant ES cells exhibited the same lethal phenotype as observed with heterozygous chimeras. Together, these results indicate that dominant lethality associated with the secreted NCAM does not require the presence of membrane-associated NCAM. Furthermore, the data indicate that potent bioactive cues or signals can be generated by NCAM.

Regulation of amyloid protein precursor (APP) binding to collagen and mapping of the binding sites on APP and collagen type I

The specific binding of the amyloid precursor protein (APP) to extracellular matrix molecules suggests that APP regulates cell interactions and has a function as a cell adhesion molecule and/or substrate adhesion molecule. On the molecular level APP has binding sites for collagen, laminin, and glycosaminoglycans which is a characteristic feature of cell adhesion molecules. We have examined the interactions between the APP and collagen types I and IV and identified the corresponding binding sites on APP and collagen type I. We show that APP bound most efficiently to collagen type I in a concentration-dependent and specific manner in the native and heat-denatured states, suggesting an involvement of a contiguous binding site on collagen. This binding site was identified on the cyanogen bromide fragment alpha 1(I)CB6 of collagen type I, which also binds heparin. APP did not bind to collagen type I-heparin complexes, which suggests that there are overlapping binding sites for heparin and APP on collagen. We localized the site of APP that mediates collagen binding within residues 448-465 of APP695, which are encoded by the ubiquitously expressed APP exon 12, whereas the high affinity heparin binding site of APP is located in exon 9. Since a peptide encompassing this region binds to collagen type I and inhibits APP-collagen type I binding in nanomolar concentrations, this region may comprise the major part of the collagen type I binding site of APP. Moreover, our data also indicate that the collagen binding site is involved in APP-APP interaction that can be modulated by Zn(II) and heparin. Taken together, the data suggest that the regulation of APP binding to collagen type I by heparin occurs through the competitive binding of heparin and APP to collagen.

Neural cell adhesion molecule (NCAM) as a quantitative marker in synaptic remodeling

The neural cell adhesion molecule (NCAM) participates in adhesion and neuritic outgrowth during nervous system development. In the adult brain, NCAM is considered to be involved in neuronal sprouting and synaptic remodeling. The NCAM concentration of brain tissue has proved to be a useful marker of these processes, especially when viewed in comparison with the concentration of a marker of mature synapses, e.g. D3-protein (SNAP-25) or synaptophysin. The present review focusses on studies of adult brain in which NCAM concentration estimates and NCAM/D3 ratios have been used to evaluate the rate of synaptic remodeling in brain damage and degenerative diseases.

A monoclonal antibody against Meningococcus group B polysaccharides used to immunocapture and quantify polysialylated NCAM in tissues and biological fluids

Polysialylated isoforms of neural cell adhesion molecule (PSA-NCAM) are transiently expressed in many tissues during development and in discrete areas of the adult central nervous system. In pathological situations, they are expressed by poorly differentiated tumor cells of neuroectodermal origin and by regenerating muscle. An ELISA is introduced here to estimate the relative concentrations of PSA-NCAM expressed by tissues or released into biological fluids. In this double-sandwich assay, an anti-PSA antibody (anti-MenB) was adsorbed onto plastic plates and permitted the immunocapture of PSA-bearing molecules. It is demonstrated that these molecules are major NCAM. The second antibody was directed against an amino acid sequence shared by NCAM isoforms in several species. The standard curves were established using Nonidet P40 extracts of human or mouse embryonic brain known to be rich in PSA-NCAM. The sensitivity of the assay allows for quantitation of PSA-NCAM in muscle during regeneration and in small samples of cerebrospinal fluid from patients with medulloblastoma metastasis.

The ability to re-express polysialylated NCAM in soleus muscle after denervation is reduced in aged rats compared to young adult rats

The neural cell-adhesion molecule, NCAM, contains an unusual homopolymer of sialic acid units, polysialic acid. This carbohydrate seems to be involved in neurite outgrowth, bundling and branching, processes which are important during reinnervation. In aged rats, reinnervation of denervated muscle fibres is incomplete. In this study, age-related changes in the degree of polysialylation of NCAM re-expressed after denervation were examined using a monoclonal antibody recognizing polysialic acid and a polyclonal antibody recognizing NCAM. The results show that, after denervation, the degree of polysialylation on NCAM was clearly reduced in rat soleus muscle of aged, compared to young, adult rats. This age-related change in expression of polysialic acid probably influences the reinnervation process in aged muscle.