Expression of the neuron-specific protein, 14-3-2, and steroid sulfatase in neuroblastoma cell hybrids

Sulfated proteoglycans synthesized by Neuro 2a neuroblastoma cells: comparison between cells with and without ganglioside-induced neurites

Mouse neuroblastoma Neuro 2a cells are known to extend neurite-like processes in response to gangliosides added to the culture medium. We compared the structural features of proteoglycans (PG) synthesized by conventional Neuro 2a cells with those of neurite-bearing cells. Two different proteoglycans labeled with [35S]sulfate, namely, chondroitin sulfate proteoglycan (CS-PG) and heparan sulfate proteoglycan (HS-PG), were found both in the cell layer and in the culture medium of the conventional cells. CS-PG isolated from the cell layer had a Kav value of 0.38 on Sepharose CL-6B, and had CS side chains with Mr of 27,000. HS-PG in the cell layer was slightly larger (Kav of 0.33) in terms of hydrodynamic size than CS-PG, and the apparent Mr of the heparan sulfate side chains was 10,000. The structural parameters of CS-PG and HS-PG isolated from the medium were almost identical to those of the PGs in the cell layer. In addition to these PGs, single-chain HS, with an average Mr of 2,500, was observed only in the cell layer and this component was the major sulfated component in the cell layers of both control and ganglioside treated cells. The neurite-bearing cells also synthesized both CS-PG and HS-PG which were very similar in hydrodynamic size to those synthesized by the conventional cells, but the size of HS side chains was greater. Radioactivity, as 35S, of each sulfated component from the ganglioside-treated culture seemed to be slightly less than that of the corresponding component from the control culture. These findings indicate that the marked morphological change in Neuro 2a cells, induced by gangliosides is not accompanied by major changes in the synthesis of PGs.

Promotion of neuritogenesis in mouse neuroblastoma cells by exogenous gangliosides. Relationship between the effect and the cell association of ganglioside GM1

Ganglioside GM1 promoted neuritogenesis of neuroblastoma cells, neuro-2a clone, in monolayer culture. GM1 bound to neuro-2a cells in three distinct forms, one removable by treatment with serum-containing solutions, one serum-resistant and labile to trypsin treatment, and one resistant to serum and trypsin treatments. The proportions among the three forms of cell-associated GM1 varied in relation to duration of exposure to ganglioside, ganglioside concentration in the medium, and number of cells in culture. The form removable by serum was predominant at the initial stages of association and at the highest ganglioside concentrations (over 10(-6)M); the trypsin-labile and -stable forms tended to increase with increasing cell number and decreasing ganglioside concentration. The neuritogenic effect of GM1 was higher when neuro-2a cells were incubated for 24 h in the presence of GM1 and fetal calf serum. Under this condition the percentage of neurite-bearing cells increased from 11% of control to 62% at the optimal ganglioside concentration of 10-4M. The effect was still present, although to a lower extent (from 11% to 28% of neurite-bearing cells), when cells were first exposed for only 2 h to GM1, then washed and incubated for 24 h in the presence of fetal calf serum. The trypsin-labile and -stable forms of cell-associated GM1 had a fundamental role in the effect, whereas the form removable by serum was not involved. The preparation of GM1 used was extremely pure (99%) and, in particular, had a peptide contamination, if any, less than 1:20,000-1:50,000.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the expression of the alpha alpha form of enolase during neuroblastoma differentiation

The relative amounts of the different enolase isozymes present in neuroblastoma cells change during differentiation. When differentiation is induced by low serum in the presence of DMSO (dimethyl sulfoxide), there is a 50% decrease in the concentration of enolase activity associated with the form alpha alpha, and an increase in the activity associated with the gamma-containing isozymes (alpha gamma plus gamma gamma); in the absence of DMSO, there is no decrease in alpha alpha or in total enolase activity. In order to study the mechanism of the changes in alpha alpha, cells differentiated with low serum with and without DMSO were compared. Measurements of the concentration of the alpha antigen by microcomplement fixation and by immunotitration demonstrate that the decreased enolase activity in DMSO cells is due to a decreased concentration of the alpha antigen. Measurements of the relative rate of synthesis of the antigen show that the decreased concentration of the alpha antigen is due to a decreased rate of synthesis. Enolase in differentiated cells is sufficiently stable (t1/2 greater than 100 h) that a comparison of the relative rates of degradation has not been possible. The decreased synthesis of the alpha subunit of enolase that occurs under these conditions appears to be a useful model system for studying the de-expression of the alpha gene that occurs in vivo during neuronal differentiation.

Two independent mechanisms of induction of 2':3'-cyclic-nucleotide 3'-phosphohydrolase in glioma cells by cyclic AMP and high cell density

Specific activity of the myelin enzyme, 2':3'-cyclic-nucleotide 3'-phosphohydrolase (EC 3.1.4.37), increases 2- to 10-fold when sparsely inoculated cultures of C6 rat glioma cells are allowed to grow to high cell density. Cyclic-nucleotide phosphohydrolase specific activity is also induced in C6 cells and in oligodendrocytes by dibutyryl cyclic AMP or by agents that elevate intracellular cyclic AMP. In this report, we have compared the density-dependent induction of cyclic-nucleotide phosphohydrolase activity with the cyclic AMP-dependent induction. Dibutyryl cyclic AMP induced cyclic-nucleotide phosphohydrolase specific activity in both sparse and dense cultures which had very different density-dependent cyclic-nucleotide phosphohydrolase activities. Induction of both cyclic-nucleotide phosphohydrolase specific activity and intracellular cyclic AMP content by norepinephrine also occurred to a similar degree in sparse and dense cultures. Similar results were obtained for several clones of C6 cells, and for a clone of oligodendrocyte x C6 cell hybrids. Induction of cyclic-nucleotide phosphohydrolase by norepinephrine or dibutyryl cyclic AMP was not due to a change in cell density or rate of cell proliferation, nor did cell density have any appreciable effect on cyclic AMP content of the cells. These results show that regulation of cyclic-nucleotide phosphohydrolase activity in C6 cells involves two distinct mechanisms.

Culture and characterization of epithelial cells from bovine choroid plexus

Epithelial cells were isolated from choroid plexus, which plays a major role in cerebrospinal fluid production and regulation. Incubation of bovine choroid plexuses with pronase released cells which attached to plastic dishes with a plating efficiency of 5%. The cells were predominantly polygonal as judged by phase-contrast microscopy. These polygonal cells undergo limited cell division and survive for 1-2 weeks in culture before being overgrown by fibroblasts. The fibroblastic cells could be selectively removed from the cultures but the addition of 100 microgram/ml cis-hydroxyproline to the medium for several days. The specific activities of three membrane-bound enzymes, gamma-glutamyl transpeptidase, alkaline phosphatase, and leucine aminopeptidase were compared in selective cultures of polygonal cells and fibroblasts. Polygonal cells were found to have 4-5 times the gamma-glutamyl transpeptidase of fibroblasts, whereas fibroblasts have 2-3 times the alkaline phosphatase of polygonal cells. Leucine aminopeptidase levels in the two cultures were roughly equivalent. The polygonal cells rapidly lost gamma-glutamyl transpeptidase activity over a 4-day period in culture but acquired increased levels of leucine aminopeptidase. Alkaline phosphatase remained roughly constant. Under similar conditions fibroblasts showed a 3- to 4-fold increase in the specific activities of all three enzymes; these changes coincided with a substantial increase in cell density. Based on morphology, resistance to cis-hydroxyproline, absence of antihemophilic factor antigen, and enzymatic characteristics, we believe the polygonal cells to be of epithelial origin.

Regulation of neuron-specific enolase in NG108-15 hybrid cells and C6BU-1 glioma cells

Distribution of three isoenzymes of brain enolase (2-phospho-D-glycerate hydro-lyase, EC 4.2.1.11) (alpha alpha, alpha gamma and gamma gamma forms) in clonal cell lines of neuroblastoma (NS20Y and N18TG-2), glioma (C6BU-1), and hybrid cells NG108-15, NCB20, Nbr10A, Nbr20A, N4G-B-a and N4G-C-a) was examined with a sensitive enzyme immunoassay system, that uses a rabbit antibody to rat brain enolase alpha alpha or gamma gamma. All cell lines tested were found to possess the enolase which contains gamma subunit (a neuron-specific protein), although the alpha alpha enolase (non-neuronal enolase) was the dominant from in these cells. A clonal rat glioma (C6BU-1) cell contained about 40, 1 and 0.07 microgram/mg protein of alpha alpha, alpha gamma and gamma gamma enolases, respectively, at the confluent stage. Inclusion of 1 mM dibutyryl cyclic AMP or 10 micrometers prostaglandin E1 plus 1 mM theophylline in the culture medium of a hybrid cell (NG108-15, mouse neuroblastoma x rat glioma) resulted in a more than 2-fold increase in the concentrations of alpha gamma and gamma gamma in the cell within a few days, with little change in the alpha alpha enolase concentration. A similar increase in the concentration of gamma subunit by the nucleotide (but not by prostaglandin E1 plus theophylline) was also observed in the glioma cell (C6BU-1) line. The results suggest that the gamma subunit or the neuron-specific protein can be regulated in NG108-15 and C6BU-1 cells in a cyclic AMP-dependent fashion.

Distribution of the neuronal specific protein, 14-3-2, in central nervous system lesions of tuberous sclerosis

The distribution of a neuronal specific enolase (14-3-2) in the central nervous system (CNS) lesions of tuberous sclerosis (TS) was examined using antiserum to 14-3-2 and the peroxidase antiperoxidase (PAP) method of Sternberger. In cortical tubers all the giant cells had intense cytoplasmic staining. Only occasional cells in the subependymal nodules were stained. All cells in the subependymal giant cell tumors were intensely stained. This indicates that the cortical giant cells and the giant cell subependymal tumors are of neuronal rather than astrocytic origin.

Detection and localization of 14-3-2 protein in primary cultures of embryonic rat brain

The development of embryonic rat brain in cell cultures was studied by an immunocytochemical method based on the detection of 14-3-2 protein (neuron-specific enolase or NSE), a neuron-specific protein. This protein was already present in undifferentiated neurons (less than 5 days in culture), being dispersed throughout the cytoplasm, though seemingly concentrated in the vicinity of polyribosomal structures. It was not found in nuclei, in mitochondria or in the Golgi apparatus. During neuron differentiation, the location of 14-3-2 protein was related to neurite development insofar as it was detected along the axon and even in what could be taken to be the presynaptic region of numerous interneuron contacts. In contact areas, a thickening of the junction membrane was observed but the presence of 14-3-2 protein was always unilateral demonstrating the absence of a true synapse and reflecting the halt in neurite development observed after 15 days in culture. The presence of 14-3-2 protein in the cell cultures was confirmed by a microcomplement fixation assay. The protein detected in cell cultures had the same immunological properties as that found in the 17-day-old embryo, but was slightly different from that found in adult rat brain. This observation can be confronted with the lack of neuron maturation in the immunocytochemical studies.

Complexity of polysomal polyadenylated RNA in undifferentiated and differentiated neuroblastoma cells

Using cDNA probes, we have analysed the sequence complexity and the frequency distribution of the polysomal poly(A)-containing RNA from neuroblastoma cells at two different developmental states: either as round, immature neuroblasts, or as differentiated cells exhibiting the morphological properties of mature neurons. The total complexities measured for mRNA from undifferentiated and differentiated cells are identical and correspond to approximately 7000 average-sized sequences of 1750 nucleotides distributed in the same three abundance classes. We have determined the homology between the mRNA populations corresponding to the two developmental states by heterologous cross-hybridization: all the sequence from differentiated cells are present in the polysomes of undifferentiated cells. Conversely, the mRNA from differentiated cells fails to hybridize with about 15% of hybridizable cDNA corresponding to undifferentiated cells. This difference probably results from the disappearance of some mRNA species and may be related to the terminal differentiation of neuroblastoma cells.

Rabies viruses increase in virulence when propagated in neuroblastoma cell culture

Several strains of attenuated rabies virus lacking the capacity to kill adult mice acquired a high lethal potential for mice after one to five serial passages in murine or human neuroblastoma cells. The virulence acquired after passage in neuroblastoma cells is a stable genetic trait retained during subsequent passage of viruses in nonneuroblastoma cell systems.

Poly(A)-containing RNA in neuroblastoma: immature and differentiated cells in culture

We have analysed the poly(A)-containing RNA from neuroblastoma cells at two different developmental states: either as round, immature neuroblasts grown in suspension, or as differentiated cells exhibiting the morphological properties of mature neurons, when attached to a culture dish. Suspension-grown and monolayer cells were pulse-labelled with tritiated uridine. The profile of cytoplasmic poly(A)-containing RNA from suspension cells is highly heterogeneous with peaks ranging from 16-30 S. The profile obtained from differentiated cells appears somewhat distinct from the previous one. This is evidenced by a relative decrease in the 26-S peak and a virtual disappearance of the 16-S component. In order to compare the 'steady-state' patterns of poly(A)-containing RNA in these two developmental stages, polysomal RNA was prepared from unlabelled cells. Following sucrose gradient sedimentation, each fraction was hybridized to [3H]poly(U). Examination of the two RNA hybridization profiles reveals striking similarities suggesting that 'steady-state' messenger populations include, on the average, the same subspecies. The 16-S fraction, which was not observed after the pulse-labelling of the monolayer culture, is detected here by hybridization to [3H]poly(U) when using polysomal poly(A)-containing RNA from monolayer cells as substrate. These results suggest that terminal differentiation of neuroblastoma cells is not accompanied by major alterations of the transcription program and is paralleled by a marked stabilization of the 16-S species.

Differences between murine C1300 neuroblastoma clones detected by rosette formation with nerve growth factor-coated sheep red blood cells

The expression of receptors for nerve growth factor (NGF) on the cell surface was assayed by rosette formation with ligand-coated sheep red blood cells (SRBC). Cell clones derived from the murine C1300 neuroblastoma and from hybrids between a neuroblastoma clone and L cell clones showed a wide variation in the capacity to form rosettes with NGF-coated SRBC. All the neuroblastoma, L cell and hybrid clones formed rosettes with phytohemagglutinin-coated SRBC and none formed rosettes with cytochrome c- or ferritin-coated SRBC or with SRBC not coated with ligand.