Structural and immunological properties of neuron specific protein (NSP) from rat, cat and human brain: comparison to bovine 14-3-2

Prognostic value of neuron specific enolase and IL-10 in ischemic stroke and its correlation with degree of neurological deficit

BACKGROUND

The blood-brain barrier is compromised in stroke patients. The release of neuro-biochemical protein markers, such as Neuron Specific Enolase (NSE) into the circulation may allow the pathophysiology and prognosis of patients with cerebrovascular diseases to be evaluated further.

METHOD

Present study aimed to investigate the predictive value of NSE and Interleukin-10 (IL-10) with respect to early neurobehavioral outcome which evaluated by National Institute of Health Stroke Scale (NIHSS). We investigated 100 patients of ischemic stroke and blood samples were taken within first 72 h of stroke onset. NSE and IL-10 were analyzed by commercially available ELISA kits. The neurological status was evaluated by a standardized NIHSS at the time of admission.

RESULTS

NSE was significantly increased (17.95±4.54 vs 7.48±1.51 {ng/ml} p≤0.05) and IL-10 significantly decreased (11.79±2.77 vs 15.72±2.69 {pg/ml} p≤0.05) in patients when compared with controls. NSE also significantly (r=0.8, p≤0.001) correlated with degree of neurological deficit but IL-10 level in serum did not show any significant correlation with NIHSS score at the time of admission.

CONCLUSIONS

Serum concentrations of NSE and IL-10 have a high predictive value for early neurobehavioral outcome after acute stroke.

Neuron-specific enolase reflects metabolic activity in mesencephalic neurons of the rat

Numerous studies on the local rate of energy metabolism of various brain regions during development and following experimental manipulation have been conducted using 2-deoxyglucose uptake and cytochrome oxidase (CO) histochemistry, both considered to be reliable indicators of long-term and short-term alterations in neuronal activity, respectively. Another method which has been related to neuronal activity is neuron-specific enolase (NSE) immunohistochemistry. An isoenzyme of enolase, a key element in the glycolytic pathway, NSE is present in neurons and neural-related cells e.g. neuroendocrine cells, pituicytes, and many tumor cells, but not in glia. The distribution on adjacent tissue sections of immunoreactive NSE and histochemically determined CO were mapped in the rat mesencephalon and adrenal medulla. Both methods showed highly restricted localization of staining which coincided with few exceptions in the most reactive areas, namely the superior colliculus, medial and lateral geniculate nuclei, red nucleus, lateral mammillary nucleus, interpeduncular nucleus and substantia nigra pars lateralis and pars reticulata. Immunoreactivity of varying intensity for NSE was also observed in perikarya and in processes of numerous scattered neurons throughout the mesencephalon, including the substantia nigra pars compacta, and reticular formation. The general correspondence in staining patterns between CO and NSE in the midbrain, supports the utility of NSE as a useful index of metabolic activity in neurons.

Development of a radioimmunoassay for neurone specific enolase (NSE) and its application in the study of patients receiving intra hepatic arterial streptozotocin and floxuridine

A radioimmunoassay has been developed for neurone specific enolase (NSE) and used to measure serum NSE levels in patients with neuroendocrine and non-neuroendocrine tumours following intra hepatic arterial chemotherapy. Ten patients were studied, 7 receiving streptozotocin and floxuridine for neuroendocrine tumours and three receiving cisplatinum for non-neuroendocrine neoplasms. All ten patients had liver metastases. In patients with tumours of neuroendocrine origin, a significant increase in serum NSE was recorded within 24 h of therapy. Slight increases in serum NSE levels were also recorded in three patients with non neuroendocrine tumours. These increases may reflect lysis of neuroendocrine cells within the tumour. Raised levels in non-neuroendocrine tumour patients may reveal damage done to healthy neuronal and neuroendocrine cells during treatment. NSE may be a useful marker of the extent of cell death following chemotherapy.

Neuron-specific enolase and malignant lymphomas (23 cases)

The immunoreactivity of polyclonal antiserum to neuron-specific enolase (NSE) has been investigated. Twenty-three cases of malignant lymphoma (ML) were studied and compared with previously published reports. In our study 11 out of 23 cases showed strong or weak NSE positivity; any type of ML could be positive or negative even among B or T cell ML. This study indicated that polyclonal NSE is not a specific marker; it might be an inconstant marker of ML with no apparent correlation between reactivity and morphology or phenotype.

Electron-immunocytochemical localization of neuron-specific enolase in cytoplasm and on membranes of primary and metastatic cerebral tumours and on glial filaments of glioma cells

A series of primary and metastatic human brain tumours was evaluated immunocytochemically for the electron microscopic localization of neuron-specific enolase (NSE). All contained cells which, regardless of the cell type, demonstrated an irregular distribution of NSE in their cytoplasm and on membranes. This was in contrast to the staining pattern in normal central nervous system (CNS) cells which, as previously reported (Vinores et al. 1984b), show only diffuse cytoplasmic staining usually not associated with membranes. In the tumours, the interior of nuclei and the cristae and matrices of mitochondria were consistently negative, as in normal CNS cells. Except in one low-grade fibrillary astrocytoma, the cytoplasmic filaments in neoplastic astrocytes were often, but not invariably, stained for NSE. The fine structural localization of NSE in neoplastic cells suggests that the conversion of 2-D-glycerophosphate to phosphoenolpyruvate by enolase may occur on the membrane and, in the case of astrocytic tumours, on the cytoplasmic filaments as well as in the cytoplasm. When cells which contain only the non-neuronal form of enolase (NNE) transform to neoplastic cells, they may acquire the ability to produce NSE. This presumably enables them to accommodate the increased metabolic demands of neoplasia by allowing them to elude the regulatory controls that are specific for NNE.

Enolase isoenzymes in human gliomas

Gamma-enolase (one of the three possible subunits of the dimeric enzyme enolase (EC 4.2.1.11)) has been reported as a marker for human neurons. Studies investigating the presence of gamma-enolase in human gliomas have given conflicting results, but a definite finding is important for further studies of the biology of these tumors and the possible use of gamma-enolase as a marker for tumors originating in nervous tissue or for neuronal damage. Using electrophoresis of tumor tissue extracts as well as immunohistochemistry the authors have demonstrated the presence of gamma-enolase in human gliomas. Analysis of the gamma-enolase content in the plasma of patients with brain neoplasms further revealed that, although this enzyme may be present in the tumor itself, its concentration in blood is not a reliable marker for a tumor of the human central nervous system.

Characteristics of human medulloblastoma cell line TE-671 under different growth conditions in vitro: a morphological and immunohistochemical study

The human medulloblastoma cell line, TE-671, was studied in vitro both in monolayer culture and in a three-dimensional culture system using gelfoam as the supporting matrix. Flow cytometry studies of cells grown in monolayer culture revealed a unimodal, tetraploid DNA content. Most cells in both in vitro systems contained neuron-specific enolase (NSE), actin, and tubulin, while only occasional cells or cell clusters contained the 68,000 molecular weight subunit of neurofilaments (NF mol. wt 68,000) or microtubule-associated protein 2 (MAP-2). In monolayer culture, long cellular processes containing NSE, NF mol. wt 68,000 and MAP-2, which were present at 2 days, were nearly absent by 7 days. All antigens were present at 4 days in the organ culture system; by 72 days, cells still stained positively for NF mol. wt 68 000 and MAP-2, but staining for NSE, actin, and beta-tubulin was diminished as compared to 4 days. Retinoic acid (RA) in the 13-cis isomer form at 10(-6) M was applied to monolayer cultures at day 1 for 6 days and to gelfoam cultures at day 1 for 28 days. RA did not significantly alter cell proliferation up to 7 days in vitro and did not appreciably affect cellular expression of NSE, NF mol. wt 68 000, MAP-2, beta-tubulin, or actin in either system. By electron microscopy, most cells grown under different culture conditions with or without RA treatment appeared to be undifferentiated and polygonal, with occasional cytoplasmic annulate lamellae. The immunohistochemical and ultrastructural features reported indicate that the TE-671 medulloblastoma line is composed primarily of primitive neuroepithelial cells with a limited potential for neuronal differentiation. This differentiation was not promoted by RA or by an in vitro system known to favour differentiation in a number of human and animal nervous system tumours. The findings suggest that the cells of the TE-671 line lack either receptors for retinoic acid or the capacity to respond to bound retinoic acid.

Simultaneous expression of glial fibrillary acidic (GFA) protein and neuron-specific enolase (NSE) by the same reactive or neoplastic astrocytes

In normal cells of the central nervous system (CNS), glial fibrillary acidic (GFA) protein is demonstrable by immunohistochemistry in fibrillated astrocytes, and neuron-specific enolase (NSE) in neurons and their processes. However, it has been shown that NSE may also be expressed in reactive astrocytes and in various neoplastic cells of non-neuronal origin, including those of astrocytomas and glioblastomas. In the present study, a double-labelling technique using immunoperoxidase (PAP) and immunofluorescence (FITC) was employed to determine whether GFA protein and NSE could be expressed simultaneously by the same cell. This was found to be the case in some, but not in all reactive astrocytes in the human brain. In glial tumours, many of the neoplastic cells in the glioblastomas and astrocytomas examined demonstrated either GFA protein or NSE, but usually not both. However, occasional neoplastic cells in those gliomas were found to show both proteins. Because of the relatively low sensitivity of the FITC technique, the percentage of cells expressing both proteins could not be determined, but it is clearly possible for a single reactive or neoplastic astrocyte to demonstrate both GFA protein and NSE.

Neurone specific enolase: a useful diagnostic serum marker for small cell carcinoma of the lung

Among lung cancers small cell carcinoma is the most sensitive to chemotherapy and radiation. This has emphasised the importance of an accurate diagnosis of this cell type, and the present study examined the use of serum neurone specific enolase (NSE) as a diagnostic marker for small cell carcinoma. NSE was measured in pretreatment sera from 103 patients with small cell carcinoma and in sera from relevant controls, including patients with other lung cancers, non-malignant lung diseases, and healthy adults. Serum NSE concentration was raised (greater than 25 ng/ml) in 72% of patients with small cell carcinoma. Ninety one per cent of patients with extensive disease and 50% of patients with limited disease were serum NSE positive. Patients with extensive disease in general had higher serum NSE concentrations than patients with limited disease. No definite difference in serum NSE positivity could be shown between oat cell and intermediate cell subtypes. Out of 51 patients with other lung cancers, four (8%) had a raised serum concentration, whereas all patients with non-malignant diseases and healthy individuals had normal serum NSE concentrations. Serum NSE determination seems to be a valuable tool for the diagnosis of small cell carcinoma.

Neuron-specific enolase as a marker for intestinal neurons. An immunocytochemical study of the human intestinal tract

Surgical specimens from various parts of the human intestinal tract as well as suction biopsy specimens, including mucosa and submucosa of the rectum, were fixed in formalin and embedded in paraffin by routine procedures. The distribution of immunoreactive areas indicating the presence of neuron-specific enolase (NSE) was then determined by using a sheep anti-human-NSE antiserum prepared in our laboratory. The immunocytochemical method revealed, in distinct contrast to other tissue components, the cell bodies of ganglion cells in the submucosa (Meissner's plexus) and in the muscle layers (Auerbach's plexus). The nerve bundles of the submucosa, of the muscle layers, and of the subserosal connective tissue were also stained, whereas the thin nerve processes of the mucosa were identified only rarely. The smooth muscle cells were stained weakly, but this reaction did not interfere with the identification of the neurons and their processes. Immunocytochemical demonstration of NSE is obviously a valuable additional method for visualization of the intrinsic intestinal innervation. It might well be that this technique will be of advantage in the diagnosis of pathologic processes, such as those occurring in Hirschsprung's disease and allied conditions.

Identification of neuron-specific enolase and nonneuronal enolase in human and rat brain on two-dimensional polyacrylamide gels

The location of the enzymes neuron-specific enolase and nonneuronal enolase on two-dimensional gels generated from tissue samples obtained from fresh human and rat cortex has been identified. This identification is based upon the following criteria: comigration on polyacrylamide gels with the appropriate purified protein and staining on nitrocellulose protein blots of human and rat cortex using antibodies specific for each protein. The results show that our preparation of neuron-specific enolase from rat and human brain is highly pure, as only one spot is obtained on two-dimensional gels. Further, the antiserum to neuron-specific enolase is highly specific, as it reacts only with neuron-specific enolase on nitrocellulose blots derived from two-dimensional gels of cortical tissue. The location of these proteins is of interest because it positively identifies two major brain proteins on two-dimensional polyacrylamide gels of fresh cortical tissue. This information will be useful in a variety of future studies aimed at both identifying specific proteins on two-dimensional gels and observing the effects of experimental manipulations on brain and other neuronal proteins.

Hybridization and isolation of human-rat beta gamma enolase

A human-rat hybrid form of enolase (beta gamma) was prepared by dissociation and reassociation of a mixture of human beta beta and rat gamma gamma enolases, followed by isolation of the hybrid form from the parental homodimeric enolases with DEAE-Sephadex column chromatography. The human-rat beta gamma enolase had a specific activity similar to those of human beta beta and rat gamma gamma enolases. The optimal pH, stability against heating, and Km for 2-phosphoglycerate of the hybrid enolase were also similar to those of the homodimeric enolases.

Activity of neuron-specific enolase in normal and lesioned rat brain

Rat brain contains 3 forms of enolase, a neuron-specific form (NSE), a hybrid form, and a non-neuronal form (NNE) which were separated by DEAE-cellulose column chromatography. The enolase activity corresponding to each form of the enzyme eluted from the columns was determined spectrophotometrically. Using this assay procedure, an activity ratio (%NNE/%NSE) was calculated for cerebellum, brainstem, sciatic nerve, adrenals and liver. The results indicated excellent agreement between this enzymatically determined ratio and published values of a similar ratio (NNE/NSE) determined by radioimmunoassay for enzyme protein. Following in vivo destruction of neurons by intracerebral injection of the selective neurotoxin, kainic acid, there was a significant decrease in the activity of NSE and hybrid enolase (neuronal forms) and no change in the activity of NNE (glial form). These data indicate that separation and measurement of enolase species is useful to determine levels of these species in normal tissue and to estimate neuronal damage biochemically in brain lesions.

Perineural spread by squamous carcinomas of the head and neck: a morphological study using antiaxonal and antimyelin monoclonal antibodies

Perineural spread has been demonstrated histologically in 65/180 (36%) major surgical resections for squamous carcinomas of the head and neck; the incidence in a smaller necropsy series was 18/20 (90%). Perineural infiltration was observed most commonly in the vicinity of carcinomas arising in the buccal cavity (31/63, 50%) and, at all sites, it was most commonly encountered near tumours less than or equal to 2.5 cm in diameter. Perineural spread near cervical node metastases was, by contrast, uncommon in the surgical series. Tumour within perineural spaces tends to be concentrated at the margin of the nerve and shows only limited extension inwards, but cells may track upwards and downwards within the spaces. Distant spread for greater than 2 cm is unusual, and interval sampling of involved nerves in necropsy material indicates that most perineural tumour cells are confined to the distal 1 cm of the affected nerve. Infiltrated nerves regularly show varying degrees of myelin and axonal degeneration, probably anoxic in origin, and segmental infarction of nerve trunks was observed in three patients. Fine changes in axons and myelin have been regularly demonstrated with two monoclonal antibodies, and the use of these new reagents is described.

Localization of monoamine oxidases A and B in primate brains relative to neuron-specific and non-neuronal enolases

Using serotonin and phenylethylamine deamination as measures of MAO A and MAO B activity respectively, positive correlations were observed between the activities of MAO A and MAO B in different areas of rhesus monkey and human brains. When the activities of MAO A and MAO B were compared with those of neuron-specific enolase and nonneuronal enolase (isozymes which are markers for neurons and glia), a slight but non-significant correlation was observed, suggesting that a simple distribution of MAO A in neurons and MAO B in glia is unlikely. This conclusion is supported by studies using synaptosomes, but contrasts with that from investigations of MAO from peripheral tissues, where experiments indicate that MAO A is predominantly localized in neurones.

The development of immunoreactivity for neuron-specific enolase of preoptic and septal neurons in dissociated cultures

The immunocytochemical visualization of neuron-specific enolase, which is a marker protein for differentiated neurons, was applied to follow the differentiation of preoptic and septal neurons in dissociated cultures. From 4 to 24 days in vitro, the relative numbers of stained neurons were counted and the staining intensity of individual neurons determined by absorbency measurements using a television-based densitometer. Whereas few stained cells could be observed at 4 DIV, 80% of the neurons were neuron-specific enolase-positive at 13 days in vitro. This value remained constant up to 24 days in vitro. The density of the immunoreaction product increased dramatically from 13 to 17 days in vitro and was still higher at 24 days in vitro. The glial and ependymal cells of the carpet, as well as neuroblasts, remained unstained. Comparison with morphological observations and immunocytochemical demonstration of neuronal peptides made earlier shows that expression of neuron-specific enolase closely parallels neuronal differentiation. These observations indicate that cultures derived from preoptic and septal neurons represent a viable model system for the study of neuronal maturation in vitro.

Neuron-specific enolase in relation to differentiation in human neuroblastoma

The presence of the two forms of enolase, neuron-specific enolase (NSE) and non-neuronal enolase (NNE), have been examined in biopsy material of human neuroblastoma, ganglioneuroblastoma, ganglioneuroma and cultured neuroblastoma cells, after separation with ion exchange chromatography. The enolase activities were inhibited in the presence of NaCl but remained active in KCl, which were used in the chromatographic step. The relative NSE levels in the neuroblastoma tissues were found to be lower than in the histopathologically more differentiated forms of the tumour, i.e. ganglioneuroblastoma and ganglioneuroma. The human neuroblastoma in vitro cell lines SK-N-SH, SH-SY5Y, SK-N-MC and IMR-32 contained considerably lower relative levels of NSE compared to the levels in the neuroblastoma biopsies. After treatment of the cultured cells with nerve growth factor or dibutyryl-cAMP some cells showed morphological differentiation and concomitantly an increase in the NSE levels. The results indicate that NSE might be useful as a marker for differentiation in human neuroblastoma.

Brain levels of neuron-specific and nonneuronal enolase in Huntington's disease

Levels of the cell-specific brain isoenzymes of enolase were determined in basal ganglia and cerebral cortical tissue of Huntington's disease and age- and sex-matched control brain. Neuron-specific enolase (NSE) levels are decreased an average of 45% in basal ganglia from patients with Huntington's disease whereas the glial-specific form of enolase, nonneuronal enolase (NNE), is not significantly altered. In contrast, levels of NSE in cerebral cortical tissue from Huntington's disease patients remains unchanged in comparison with controls whereas NNE levels are significantly increased. NNE and NSE levels appear to be specific biochemical indicators of glial and neuronal cell number and viability. Levels of these cell-specific isoenzymes may therefore prove useful in quantitating neuropathological changes in various neurological disorders.

A more sensitive radioimmunoassay for neuron-specific enolase suitable for cerebrospinal fluid determinations

Neuron-specific enolase (NSE) and non-neuronal enolase (NNE) have been shown to be highly specific neuronal and glial products respectively and are therefore useful as biochemical markers of the two major cell types in the vertebrate central nervous system. An iodinated radioimmunoassay (RIA) procedure for human NSE (NSE-H) with approximately 50-fold greater sensitivity than the previously available tritiated assay is described. This assay is capable of detecting 100 pg of NSE-H per assay. NSE levels in human cerebrospinal fluid (CSF) which were previously undetectable with the tritiated RIA are now easily measured and have been shown to be approximately 2 ng/ml of CSF. Furthermore, results obtained with the newly described assay procedure on more concentrated brain tissue extracts are comparable to the tritiated RIA. The iodinated NSE RIA is also shown to be capable of accurately detecting added amounts of NSE in human CSF, indicating the potential clinical usefulness of this assay in determining elevated levels of NSE in CSF.

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.

An ultrastructural immunocytochemical study of nerve-specific protein in rat cerebellum

The ultrastructural localization of the neuron-specific enolase (14-3-2 protein) has been investigated in the cerebellum of the adult rat using the indirect antibody immunohistochemical method. The protein was found exclusively in neurons: perikaryal cytoplasm, axons and dendrites were labelled while nuclei were not. Reaction product was found to be attached to intracytoplasmic membranes, the surface membranes of mitochondria and microtubules in addition to its dispersion as a flocculent material throughout the cytoplasm. All classes of cerebellar neurons were found to be labelled though large variations in the level of labelling between different types of neuron were noted. Purkinje cells appeared to have a much lower cytoplasmic concentration of this protein than other neurons.

Phylogenetic distribution of neuron-specific enolase

Neurons and neuroendocrine cells contain a unique isoenzyme of the glycolytic enzyme enolase which is not found in other cells. This acidic enolase isoenzyme has been designated neuron specific enolase or NSE and is easily identified by its elution on DEAE sephadex. The present study shows that brain tissue from species such as yeast, fish and frog do not contain appreciable amounts of acidic "NSE-like" enolase suggesting that lower species do not have this neuronal isoenzyme.

The etiology of acrylamide neuropathy: possible involvement of neuron specific enolase

The effect of monomeric acrylamide, a potent neurotoxic agent, on total and neuron specific enolase activity was studied in vitro and in vivo. Acrylamide (10 mM) completely inhibited total enolase activity of rat brain soluble fractions. The I50 concentration was 3.7 mM. In rats chronically treated with acrylamide (550 mg/kg total) and exhibiting marked symptoms of neurotoxicity, neuron specific enolase activity was not detectable in sciatic nerves and was only 60% of control activity in brain. Total enolase activity in both central and peripheral nervous tissues was unchanged from control. The results suggest that inhibition of neuron specific enolase may be an important factor in the development of acrylamide neuropathy by interfering with glycolysis in neuronal tissue.

Neurons switch from non-neuronal enolase to neuron-specific enolase during differentiation

The enolase (EC 4.2.1.11) isoenzymes, neuron-specific enolase (NSE, gamma gamma) and non-neuronal enolase (NNE, alpha alpha), are markers for neurons and glia, respectively, in adult mammalian brain. In developing fetal and early postnatal brain, levels of non-neuronal enolase (NNE) are high. Neuron-specific enolase (NSE) appears only after neurogenesis begins in a given region and only slowly attains adult levels. Immunocytochemistry in developing rat and rhesus monkey brain reveals that proliferative zones that give rise to neurons are NNE(+). Thus, nerve cells must undergo a switch from NNE to NSE. In addition, study of neurons in cerebellum and neocortex reveals that they are NNE(+) during migration and only become NSE(+) in their final location, presumably after making full synaptic connections. Such migrating cells may contain hybrid enolase (alpha gamma) and some (e.g. cerebellar stellate/basket cells) may not completely switch over to NSE even in the adult. Neuron-specific enolase is not only a specific molecular marker for mature nerve cells, but is closely correlated to the differentiated state.

Localization of neuron-specific enolase in mouse spinal neurons grown in tissue culture

Neuron-specific enolase (NSE) is an isoenzyme of the glycolytic enzyme enolase (EC 4.2.1.11) which also has a muscle and liver isoenzyme. Previous work has shown NSE to be specifically localized to neurons and neuroendocrine cells, but the application of NSE as a marker for cell cultures has not been investigated. Primary culture of central nervous system tissue derived from mice have been used to study optimal fixation procedures. The results show that NSE can serve as a useful alternative to non-specific histochemical strains or strictly morphologic criteria for identifying nerve cells.

Neuronal, non-neuronal and hybrid forms of enolase in brain: structural, immunological and functional comparisons

Three forms of the glycolytic enzyme, enolase [2-phospho-D-glycerate hydrolase (E.C. No. 4.2.1.11)] have been prepared from rat whole brain extract. The most acidic enolase form is neuron specific enolase (NSE) which had previously been designated neuron specific protein (NSP). The least acidic form designated non-neuronal enolase (NNE) has been purified and compared structurally, immunologically and functionally to NSE. NNE is a dimer of 86,500 M.W. consistint of two very similar subunits. The data establish that NNE is larger than NSE which has been shown to be composed of two apparently identical 39,000 molecular weight subunits (78,000). NNE is less acidic than NSE having a pI of 5.9 compared to the value of 4.7 for NSE. Structural and immunological analysis establishes that the NNE subunit is distinct from the NSE subunit, and are therfore products of two separate genes. The structural designation of NSE is (gammagamma) and that of NNE (alpha' alpha'). NSE is strictly localized in neurons indicating that the gene coding for the gamma subunit is only expressed in neuronal cells. The intermediate brain enolase form has been partially purified; structural and immunological evidence indicate that it is a hybrid molecule consisting of one NNE subunit and one NSE subunit (alpha'gamma).

Neuron specific protein (NSP) in neuroblastoma cells: relation to differentiation

The spectrum of enolase enzyme forms has been examined in several lines of neuroblastoma cells and compared to those present in whole brain. The neuron specific enolase (NSP) is greatly decreased in the cultured cells as judged by activity profiles and radioimmunoassay. The synthesis of neuronal enolase appears to be extensively depressed in these cells while the total enolase activity is not affected. The non-neuron form of enolase (NNE) apparently compensates for the lack of the neuronal forms in the cultured cells. The preponderance of NNE in cultured neurons suggests that this enzyme is present in immature neurons, and that neuroblastoma cells are not fully differentiated with respect to the enolase function. Dibutyryl cyclic adenosine monophosphate treatment does increase NSP levels in mouse neuroblastoma cells, but not to the levels expected for fully differentiated neurons. The results indicate that NSP is a molecular correlate of fully differentiated neurons.

Brain endolases as specific markers of neuronal and glial cells

There are three distinct enolase isoenzymes in brain; neuron-specific enolase (NSE), formerly referred to as neuron-specific protein, which is specifically localized in neurons, a nonneuronal enolase (NNE), and a third hybrid form. Light microscopy with immunocytochemical techniques has permitted localization of non-neuronal enolase. The NNE is located in glial cells with no staining of endothelial cells or neurons. Thus, NSE and NNE can be used as specific metabolic markers for neurons and glial cells, respectively.