Extracellular adenosine triphosphate affects neural cell adhesion molecule (NCAM)-mediated cell adhesion and neurite outgrowth

The neural cell adhesion molecule (NCAM) plays an important role in synaptic plasticity in embryonic and adult brain. Recently, it has been demonstrated that NCAM is capable of binding and hydrolyzing extracellular ATP. The purpose of the present study was to evaluate the role of extracellular ATP in NCAM-mediated cellular adhesion and neurite outgrowth. We here show that extracellularly added adenosine triphosphate (ATP) and its structural analogues, adenosine-5'-O-(3-thiothiophosphate), beta, gamma-methylenadenosine-5'-triphosphate, beta, gamma-imidoadenosine-5-triphosphate, and UTP, in varying degrees inhibited aggregation of hippocampal neurons. Rat glial BT4Cn cells are unable to aggregate when grown on agar but acquire this capacity when transfected with NCAM. However, addition of extracellular ATP to NCAM-transfected BT4Cn cells inhibited aggregation. Furthermore, neurite outgrowth from hippocampal neurons in cultures allowing NCAM-homophilic interactions was inhibited by addition of extracellular nucleotides. These findings indicate that NCAM-mediated adhesion may be modulated by extracellular ATP. Moreover, extracellularly added ATP stimulated neurite outgrowth from hippocampal neurons under conditions non-permissive for NCAM-homophilic interactions, and neurite outgrowth stimulated by extracellular ATP could be inhibited by a synthetic peptide corresponding to the so-called cell adhesion molecule homology domain (CHD) of the fibroblast growth factor receptor (FGFR) and by FGFR antibodies binding to this domain. Antibodies against the fibronectin type-III homology modules of NCAM, in which a putative site for ATP binding and hydrolysis is located, also abolished the neurite outgrowth-promoting effect of ATP. The non-hydrolyzable analogues of ATP all strongly inhibited neurite outgrowth. Our results indicate that extracellular ATP may be involved in synaptic plasticity through a modulation of NCAM-mediated adhesion and neurite outgrowth.

Structure and interactions of NCAM modules 1 and 2, basic elements in neural cell adhesion

The structure in solution of the second Ig-module fragment of residues 117-208 of NCAM has been determined. Like the first Ig-module of residues 20-116, it belongs to the I set of the immunogloblin superfamily. Module 1 and module 2 interact weakly, and the binding sites of this interaction have been identified. The two-module fragment NCAM(20-208) is a stable dimer. Removal of the charged residues in these sites in NCAM(20-208) abolishes the dimerization. Modeling the dimer of NCAM(20-208) to fit the interactions of these charges produces one coherent binding site for the formation of two antiparallel strands of the first two NCAM modules. This mode of binding could be a major element in trans-cellular interactions in neural cell adhesion.

Prospective six year follow up of patients withdrawn from a randomised study comparing parenteral gold salt and methotrexate

OBJECTIVE

To confirm the impression of a better outcome of patients withdrawn from parenteral gold salt therapy compared with those withdrawn from methotrexate.

METHODS

Patients with early, active, and erosive RA were randomised for a double blind trial to receive either weekly 15 mg intramuscular methotrexate or 50 mg goldsodiumthiomalate. If the drug had to be withdrawn because of side effects treatment was continued with the other drug in still active disease. Patients with insufficient response were treated with a combination of both drugs. All patients were followed up by an extended clinical and radiographic evaluation.

RESULTS

64 patients each were allocated to methotrexate and gold treatment. After 72 months a complete record was available for 88% of patients. Within the first 36 months 38 patients withdrew from gold treatment (95% because of side effects) and 23 patients withdrew from methotrexate (57% because of side effects). A significant 40% to 70% improvement of all parameters (erythrocyte sedimentation rate, C reactive protein, swollen and tender joints, radiological progression) compared with baseline was observed in patients completing their randomised treatment with gold or methotrexate. The same improvement over three years was seen in patients who withdrew from gold treatment, while patients withdrawing from methotrexate experienced a deterioration of their disease.

CONCLUSION

Withdrawals represent the majority of patients in long term drug trials. Patients with early RA stopping gold because of side effects show almost the same sustained improvement as patients continuing gold or methotrexate. Patients withdrawn from methotrexate experience a reactivation of their disease.

Follow-up findings in regional cerebral blood flow (r-CBF)-SPECT in a case of idiopathic childhood hemidystonia. Functional neuroimaging and pathophysiological implications

A 9 1/2-year-old girl suffered from intermitting tremor and jitteriness of her left hand and oral muscles every 4 to 6 weeks with long lasting episodes. Clinically myoclonias and dystonic positioning of the left arm, hand and facial muscles were seen. No evidence of trauma, infection or inborn errors of metabolism was found. Successful therapy with carbamazepine was initiated while L-DOPA failed. An ictal 99m-Tc-HMPAO-SPECT showed severe asymmetry with focal hyperperfusion of the contralateral right thalamus and basal ganglia as well as of the bifrontal cortex, whereas no anatomical lesions were found by MRI. In contrast, an interictally performed 99m-Tc-HMPAO SPECT showed hypoperfusion of the right thalamus and normalisation of the frontal perfusion under medical treatment. These 99m-Tc-HMPAO-SPECT findings may provide new insights into the localisation and pathophysiological pathways of idiopathic childhood dystonia.

Effects of taurine depletion on cell migration and NCAM expression in cultures of dissociated mouse cerebellum and N2A cells

Cultures of dissociated cerebellum from 5- to 6-day-old mice as well as of the N2A neuronal cell line were exposed to guanidino ethane sulfonate (GES, 2-5 mM) to reduce the cellular taurine content. Control cultures were kept in culture medium or medium containing 2-5 mM GES plus 2-5 mM taurine to restore the intracellular taurine content. Taurine depletion led to changes in the expression of certain splice variants of NCAM mRNA such as the AAG and the VASE containing forms, while no differences were seen in the expression of the three forms of NCAM protein. In the N2A cells taurine depletion led to a decreased migration rate of the cells. The results suggest that the reduced migration rate of neurons caused by taurine depletion may be correlated to changes in expression of certain adhesion molecules such as NCAM. Moreover, taurine appears to be involved in regulation of transcription processes.

Fra-1 induces morphological transformation and increases in vitro invasiveness and motility of epithelioid adenocarcinoma cells

Two cell lines originating from a common ancestral tumor, CSML0 and CSML100, were used as a model to study AP-1 transcription factors at different steps of tumor progression. CSML0 cells have an epithelial morphology; they express epithelial but not mesenchymal markers and are invasive neither in vitro nor in vivo. CSML100 possesses all characteristics of a highly progressive carcinoma. These cells do not form tight contacts, are highly invasive in vitro, and are metastatic in vivo. AP-1 activity was considerably higher in CSML100 cells than in CSML0 cells. There was a common predominant Jun component, namely, JunD, detected in both cell lines. We found that the enhanced level of AP-1 in CSML100 cells was due to high expression of Fra-1 and Fra-2 proteins, which were undetectable in CSML0 nuclear extracts. Analysis of the transcription of different AP-1 members in various cell lines derived from tumors of epithelial origin revealed a correlation of fra-1 expression with mesenchymal characteristics of carcinoma cells. Moreover, we show here for the first time that the expression of exogenous Fra-1 in epithelioid cells results in morphological changes that resemble fibroblastoid conversion. Cells acquire an elongated shape and become more motile and invasive in vitro. Morphological alterations were accompanied by transcriptional activation of certain genes whose expression is often induced at late stages of tumor progression. These data suggest a critical role of the Fra-1 protein in the development of epithelial tumors.

Biodeterioration of natural stone with special reference to nitrifying bacteria

An evaluation of field data from historical buildings in Germany showed that chemoorganotrophic bacteria are the most numerous microorganisms in building stones, followed by fungi and nitrifying bacteria. Chemoorganotrophic bacteria and fungi were present in almost every sample. Ammonia and nitrite oxidizers were found in 55 and 62% of the samples, respectively. Within months, natural stone was colonized by chemoorganotrophic microorganisms. The highest cell numbers were usually found near the surface. The colonization of natural stone by nitrifying bacteria took several years. The highest cell numbers were in some cases found underneath the surface. Nitrifying bacteria showed a preference for calcareous material with a medium pore radius between 1 and 10 microns. Cell numbers of nitrifying bacteria did not correlate to the nitrate content of the stone material. We demonstrated that the stone inhabiting microflora can cause significant loss of nitrate by denitrification. Our data strongly suggested that microbial colonization of historical buildings was enhanced by anthropogenic air pollution. Samples taken from stone material with a pore radius < or = 1 micron had significantly higher cell numbers when they were covered with black crusts. A comparison of samples taken between 1990-1995 from buildings throughout Germany showed that in Eastern Germany a significantly stronger colonization with facultatively methylotrophic bacteria and nitrifying bacteria existed. The same was true for natural stone from an urban exposure site when compared to material from a rural exposure site. Data from outdoor exposure and laboratory simulation experiments indicated that the colonization of calcareous stone by nitrifying bacteria was enhanced by chemical weathering.

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.

[Absorption of nitric oxide by a strain of Bacillus stearothermophilus and its use in a bioreactor for purifying air]

A new Bacillus stearothermophilus strain, INMI 50, was isolated and identified. Cells of this strain immobilized on a ceramic carrier demonstrated a high NO uptake in a bioreactor. The bioreactor volume was 4 l; air flow, 100 l/h; initial NO concentration, 5 ppm; and temperature, 60 degrees C. Glycerol or 1,2-propanediol was used as carbon and energy source. The uptake of NO was 60-90% of the initial concentration over six months of continuous operation of the bioreactor. The developed procedure can be used for removal of nitrogen oxide from products of combustion of diesel fuel or from air in production areas.

Studies on the teratogen pharmacophore of valproic acid analogues: evidence of interactions at a hydrophobic centre

Propyl-4-yn-valproic acid (2-propyl-4-pentynoic acid), an analogue of valproic acid with a triple bond in one alkyl side chain, potently induces exencephaly in mice. Given that propyl-4-yn-valproic acid is a branched chain carboxylic acid, we synthesized a series of analogues with n-alkyl side chains of increasing length and correlated their potential to induce neural tube defects and to inhibit proliferation and induce differentiation in cells of neural origin, the latter being crucial to the orderly structuring of the embryo. All analogues significantly increased the incidence of neural tube defects in the embryos of dams exposed to a single dose of 1.25 mmol/kg on day 8 of gestation. This effect occurred in a dose-dependent manner and the rate of exencephaly increased with the progressive increase in n-alkyl side chain length. Moreover, increasing chain length resulted in a dose-dependent inhibition of C6 glioma proliferation rate over a concentration range of 0-3 mM and this was independent of the cell type employed and mode of estimating proliferative rate. The antiproliferative action of these analogues was associated with profound shape change in neuro-2A neuroblastoma involving extensive neuritogenesis and an associated increase in neural cell adhesion molecule (NCAM) prevalence at points of cell-cell contact, the latter exhibiting a dose-dependent increase when the n-alkyl chain was extended to five carbon units. These results suggest an interaction with a specific site in which the n-alkyl side is proposed to serve as an 'anchor' within a hydrophobic pocket to facilitate the ionic and/or H-bonding of the carboxylic acid and high electron density of the carbon-carbon triple bond.

Valproic acid, but not its non-teratogenic analogue 2-isopropylpentanoic acid, affects proliferation, viability and neuronal differentiation of the human teratocarcinoma cell line NTera-2

The antiepileptic drug valproic acid (VPA) is an established human teratogen that affects neural development in human fetuses exposed to the drug during early pregnancy. The development of simple cell culture models that reflect normal neuronal development will be useful for the screening of neural developmental toxicity of new drugs and for the identification of the specific molecular targets for the teratogenic action. The present study tests a human NT2 cell line for its suitability to serve as such a model. Treatment with VPA, but not with its non-teratogenic-analogue, 2-isopropylpentanoic acid (IPPA), inhibited cell growth, had a cytotoxic effect and blocked retinoic acid-induced neuronal differentiation of NT2 cells. Differentiation was evaluated by immunostaining for neurofilament proteins, microtubule associated proteins-2 (MAP-2), tau and neural cell adhesion molecule, NCAM. However once differentiation had taken place, VPA did not revert this process, although it did affect neuronal aggregation and neurite fasciculation. These results suggest that the human NT2 cell line might be useful for identifying drugs affecting neuronal development in humans.

High rate of aerobic nitrification and denitrification by Nitrosomonas eutropha grown in a fermentor with complete biomass retention in the presence of gaseous NO2 or NO

A pure culture of the obligately lithoautotrophic ammonia-oxidizer Nitrosomonas eutropha was grown in a laboratory-scale bioreactor with complete biomass retention. The air supply was supplemented with nitrogen dioxide (NO2; 25 or 50 ppm) or nitric oxide (NO; 25 or 50 ppm). Compared to cultures grown without these nitrogenous oxides, the addition of NO2 or NO to the culture resulted in a significant increase of the nitrification rate, specific activity of ammonia oxidation, growth rate, and maximum cell densities. In contrast, the growth yield slightly decreased in the presence of NO or NO2. Maximum cell densities of about 2 x 10(10) cells ml-1 and a maximum nitrification rate of about 221 mmol NH4+ l-1 day-1 were obtained after 3 weeks in the presence of 50 ppm NO2. Furthermore, in the stationary phase about 50% of the nitrite produced was aerobically denitrified to dinitrogen (N2) and traces of nitrous oxide (N2O). When cells were supplemented with NO, a high rate of aerobic denitrification occurred only during the first days of the exponential growth phase.

Anaerobic ammonia oxidation by cell-free extracts of Nitrosomonas eutropha

Cell-free extracts of Nitrosomonas eutropha oxidized ammonia to nitrite with NO2 (N2O4) as electron acceptor. The ammonia oxidation activity was shown to be sensitive against oxygen. In the absence of oxygen ammonia and NO2 were consumed in a ratio of approximately 1:2 and hydroxylamine occurred as an intermediate. NO was released in amounts equimolar to the consumption of NO2. After passing the cell suspension through a French pressure cell and fractionating it by density gradient centrifugation using a linear sucrose gradient, two soluble and two membrane fractions were detectable. Highest ammonia oxidation activity was measured in the membrane fractions and highest hydroxylamine oxidation activity in the soluble fractions. The KS values of the ammonia oxidizing system in cell-free extracts was about 20 microns NH3 and remained unchanged between pH 7.25 to 8.25.

A simple procedure for morphometric analysis of processes and growth cones of neurons in culture using parameters derived from the contour and convex hull of the object

Morphometric estimation of neuronal processes is currently laborious and time-consuming, since the individual processes (axons and dendrites) have to be traced manually. In order to facilitate the measurement of cellular processes, we have tested a series of parameters derived from the contour and the convex hull of an object and estimated to which extent they reflect process length and number. The parameters included the area, perimeter and form factor of the object and convex hull, their ratios as well as object length, breadth, width, length/width and spreading index. Some new parameters derived from the contour and convex hull of the object, were also computed: process index (the number of areas contained within the convex hull outside the object contour), process domain (the total area contained within the convex hull outside the object contour), their ratio and the square root of the process domain (SR process domain). In total, 18 parameters were estimated. Populations of motoneurons, growth cones of cerebellar granule cells and N2a neuroblastoma cells were utilized due to their diversity in morphological features. The processes of each object were drawn by hand to establish the actual length and number. Total process length per object correlated strongly with object perimeter, process domain and SR process domain. The number of processes per object correlated well with perimeter ratio, process index and form factor, whereas object length, convex hull perimeter and spreading index correlated acceptably with the average process length. Using these parameters for the evaluation of neurite outgrowth in developing of hippocampal neurons in vitro, variables such as object perimeter, process domain and SR process domain were found to be very well suited for estimation of the total length of neurites. We conclude that based on the contour and convex hull of an object it is possible to calculate a series of parameters which may substitute direct measurements of process length.

[Clinico-radiologic problems in the study of the male breast in gynecomastia]

INTRODUCTION

Gynecomasty is usually classified as normal of abnormal, except for 25% of cases which are classified as idiopathic because their causes and pathogenesis remain unknown. Gynecomasty is diagnosed mainly on clinical grounds, while integrated imaging, sometimes combined with cytology, is used to distinguish benign from malignant forms. Bilateral gynecomasty is easy to diagnose, especially when patients report assuming particular drugs or present other risk factors, but unilateral or asymmetrical gynecomasty is a diagnostic problem. Primary male breast cancer usually presents as a unilateral hard mass, often infiltrating the dermis and with early lymph node metastases; it is associated with gynecomasty in 20% of cases.

MATERIAL AND METHODS

We examined 76 men (age range, 15-75 years) referred for breast enlargement; the patients with radiologic findings of breast adiposis were not included in our series. All patients were submitted to standard projection mammography with a high resolution dedicated film and to real time US with high frequency probes (7.5-12 MHz).

RESULTS

Breast enlargement was unilateral in 48% of cases and bilateral in 52%. The radiologic patterns, compared with histologic or clinical-therapeutic follow-up, permitted the correct diagnosis in 72 of 76 patients (94%). The extant four patients had chronic inflammation (3 cases) and a malignant tumor with questionable imaging features. Overall imaging findings were: 55 cases (72%) of actual gynecomasty--unilateral in 17 and bilateral in 38 cases--9 unilateral malignant tumors (12%), eleven cases of inflammation (14%) and 1 case (2%) of unilateral metastasis from plasmocytoma. Sixteen (29%) actual gynecomasty patients (21% of the whole series) had a nodular form (unilateral in 6 and bilateral in 10 cases), 23 (42% and 30% of the whole series) had a dendritic form (unilateral in 7 and bilateral in 16 cases) and 16 (29%, 21% of the whole series) had a glandular form.

CONCLUSIONS

Diagnosing gynecomasty is relatively easy in the patients with bilateral forms with a positive history of associated exogenous or endogenous factors, while focal unilateral or asymmetrical forms are difficult to distinguish into benign and malignant. The radiologic pattern may be questionable especially in chronic inflammation and in some malignant forms and must therefore be integrated with cytologic or surgical findings.

[Role of diagnostic imaging of the breast in patients treated with postsurgical radiotherapy or presurgical radiotherapy or chemotherapy]

INTRODUCTION

In the last 25 years, random trials on the advantages of combined surgery and irradiation/chemotherapy of breast cancer demonstrated similar survival rates to those of massive surgery. However, both irradiation and chemotherapy have advanced and now yield good local control of the disease, so that even large breast cancers can be made operable. Breast cancer follow-up is carried out with imaging and clinical examinations to detect early locoregional recurrences, contralateral lesions and distant recurrences: to this purpose, we carried out a comparative study of all imaging modalities.

MATERIAL AND METHODS

We retrospectively reviewed the data of 42 breast cancer (T2-T3 N0-N+) patients of the Senology Center of the Catholic University (Rome, Italy) treated with irradiation and/or chemotherapy for tumor debulking to permit conservative surgery. We investigated the sensitivity and the indications of mammography, B-mode and color Doppler US and MRI in measuring the exact tumor size and detecting locoregional metastatic nodes.

RESULTS

After 3 years' treatment, our recurrence rate (19%) is a little higher than those in the major international trials (4.2-9% and 5 tears). The recurrence was on the surgical scar in 75% of cases (6/8), while multifocal tumors were found in 25% of cases. US was the most accurate method in measuring tumor size in 90% of cases (18/20), while mammography frequently overstaged the lesion and yielded exact measurements in 65% of cases (13/20). MRI was as accurate as US, but this technique is too expensive and little available in Italy. US accurately diagnosed lymph node recurrences (70% sensitivity), but MR rate was even higher (80%), while mammography and color Doppler US had only 5-10%. As for treatment outcome, an irregular and blurred nodule or multifocal lesions at mammography indicate poor/no response, while a much smaller radial scar than at previous similar follow-ups indicates treatment success.

CONCLUSIONS

When correctly integrated, mammographic, US and MR patterns permit exact tumor size measurement and show possible locoregional lymph node involvement in the patients submitted to conservative surgery and irradiation/chemotherapy. In contrast, color Doppler findings remain poorly specific in this disease, with about 55% sensitivity. Therefore, radiologic studies, with clinical and laboratory data, have a major prognostic value in assessing the biological response to combined treatment.

Demonstration of an extracellular ATP-binding site in NCAM: functional implications of nucleotide binding

A minor fraction of the total ecto-type (E-type) ATPase activity of rat synaptosomes has been detected in immunoprecipitates of the neural cell adhesion molecule, NCAM, indicating that this either is an intrinsic enzymatic activity of NCAM or of an ATPase tightly associated to NCAM [Dzhandzhugazyan & Bock (1993) FEBS Lett. 336, 279-283]. We here demonstrate ATPase activity in preparations of the lipid-anchored as well as the transmembrane NCAM isoforms immunoisolated from transfected L-cells. A fraction of the E-type ATPase activity is spontaneously released from synaptosomes. Released material was fractionated by various chromatographic procedures and an extracellular fragment of NCAM was shown to co-elute with the major part of the enzymatic activity. Furthermore, it was shown that agarose-coupled NCAM-antibodies retained 85% of the ATPase activity released from synaptosomes after treatment with phosphatidylinositol-specific phospholipase C. These findings restricted the association or expression of the enzymatic activity to the extracellular part of NCAM. An affinity reagent, 5'-p-fluorosulfonylbenzoyl adenosine, FSBA, was shown to inhibit ATPase activity of immunoisolated NCAM, and incorporation of FSBA was detected in all three major NCAM isoforms (A, B, and C). An excess of ATP prevented both inactivation of the enzyme and affinity labeling of NCAM. Thus, NCAM contains an ATP-binding site, and this site is localized extracellularly and probably has the catalytic function. Binding of the substrate or FSBA protected a proteolytic cleavage site in NCAM localized close to the membrane presumably by induction of a local conformational change in NCAM, indicating a mechanism by which ATP may regulate NCAM adhesion and adhesion-triggered processes. A possible role of this mechanism in synaptic plasticity and memory consolidation is proposed.

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.

Leiomyoma of the esophagus. (A case report)

Leiomyoma is the most common benign tumor of the esophagus. Its occurrence is fairly infrequent and in 50% of cases is asymptomatic. The case of esophageal leiomyoma (EL) which attracted our attention is of interest. The patient, a 44 years old women clinically assessed for cardiac rhythm disturbance with no compliant of dysphagia, had two locations of EL, demonstrated by x-ray, computed tomography and esophagoscopy. The treatment was performed in two phases, surgical and endoscopic, in relation to the non identification of the upper EL through the left thoracetomy. The various technical possibilities must all be evaluated in relation to every single case.

NCAM-fibronectin-type-III-domain substrata with and without a six-amino-acid-long proline-rich insert increase the dendritic and axonal arborization of spinal motoneurons

The neural cell adhesion molecule (NCAM) is a modulator of neurite outgrowth in vitro and in vivo. To see if single or tandem extracellular NCAM domains can influence neurite outgrowth, motoneurons from embryonic rat spinal cord were cultured on several NCAM fusion protein substrata. Motoneurons growing on either of two fusion proteins comprising the combined two fibronectin type III homology domains of NCAM with or without a six-amino-acid-long, proline-rich insert (F3I,II+ and F3I,II, respectively) usually developed three or more neurites per cell. Motoneurons grown on NCAM-immunoglobulin domain I (IgI), by contrast, developed many unipolar and bipolar cells, a situation also seen when motoneurons were cultured on control substrata. The neuritic trees of motoneurons grown on F3I,II and F3I,II+ appeared broader and rounder than motoneurons cultured on either control or IgI substrata, and the spreading indices of motoneurons grown on F3I,II and F3I,II+ were significantly lower than when the other substrata were used. Neither of the NCAM-F3 fusion proteins stimulated the outgrowth of single neurites. By contrast, IgI substratum was able to stimulate neurite outgrowth over control substrata. Both NCAM-F3 substrata induced branches in axons and dendrites, whereas IgI substratum did not affect neurite branching significantly. These data indicated that neurite outgrowth and neurite branching on the chosen substrata were not closely linked to each other. Furthermore, the branching characteristics of motoneuron neurites potentially depend on their differentiation states and, possibly, on the conformation of the two NCAM-F3 domains.

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.