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PubMed1996

The enolase superfamily: a general strategy for enzyme-catalyzed abstraction of the alpha-protons of carboxylic acids.

We have discovered a superfamily of enzymes related by their ability to catalyze the abstraction of the alpha-proton of a carboxylic acid to form an enolic intermediate. Although each reaction catalyzed by these enzymes is initiated by this common step, their overall reactions (including racemization, beta-elimination of water, beta-elimination of ammonia, and cycloisomerization) as well as the stereochemical consequences (syn vs anti) of the beta-elimination reactions are diverse. Analysis of sequence and structural similarities among these proteins suggests that all of their chemical reactions are mediated by a common active site architecture modified through evolution to allow the enolic intermediates to partition to different products in their respective active sites via different overall mechanisms. All of these enzymes retain the ability to catalyze the thermodynamically difficult step of proton abstraction. These homologous proteins, designated the "enolase superfamily", include enolase as well as more metabolically specialized enzymes: mandelate racemase, galactonate dehydratase, glucarate dehydratase, muconate-lactonizing enzymes, N-acylamino acid racemase, beta-methylaspartate ammonia-lyase, and o-succinylbenzoate synthase. Comparative analysis of structure-function relationships within the superfamily suggests that carboxyphosphonoenolpyruvate synthase, another member of the superfamily, does not catalyze the reaction proposed in the literature but catalyzes an enolase-like reaction instead. The established and deduced structure-function relationships in the superfamily allow the prediction that other apparent members of the family for which no catalytic functions have yet been assigned will also perform chemistry involving abstraction of the alpha-protons of carboxylic acids.

Amino Acid Sequence↗
PubMed2001

The structure of 3-methylaspartase from Clostridium tetanomorphum functions via the common enolase chemical step.

Methylaspartate ammonia-lyase (3-methylaspartase, MAL; EC ) catalyzes the reversible anti elimination of ammonia from L-threo-(2S,3S)-3-methylaspartic acid to give mesaconic acid. This reaction lies on the main catabolic pathway for glutamate in Clostridium tetanomorphum. MAL requires monovalent and divalent cation cofactors for full catalytic activity. The enzyme has attracted interest because of its potential use as a biocatalyst. The structure of C. tetanomorphum MAL has been solved to 1.9-A resolution by the single-wavelength anomalous diffraction method. A divalent metal ion complex of the protein has also been determined. MAL is a homodimer with each monomer consisting of two domains. One is an alpha/beta-barrel, and the other smaller domain is mainly beta-strands. The smaller domain partially occludes the C terminus of the barrel and forms a large cleft. The structure identifies MAL as belonging to the enolase superfamily of enzymes. The metal ion site is located in a large cleft between the domains. Potential active site residues have been identified based on a combination of their proximity to a metal ion site, molecular modeling, and sequence homology. In common with all members of the enolase superfamily, the carboxylic acid of the substrate is co-ordinated by the metal ions, and a proton adjacent to a carboxylic acid group of the substrate is abstracted by a base. In MAL, it appears that Lys(331) removes the alpha-proton of methylaspartic acid. This motif is the defining mechanistic characteristic of the enolase superfamily of which all have a common fold. The degree of structural conservation is remarkable given only four residues are absolutely conserved.

Amino Acid Sequence↗
PubMed1997

Polysialylated neural cell adhesion is involved in target-induced morphological differentiation of arcuate dopaminergic neurons.

We have previously shown that the morphological and biochemical maturation of developing rat hypothalamic dopaminergic neurons is accelerated when they are cocultivated with pituitary intermediate lobe cells, one of their targets. Only two subsets of hypothalamic dopaminergic neurons (arcuate, A12, and periventricular, A14, nuclei) may project to the pars intermedia. In order to determine whether the two populations are equally responsive to coculture conditions, we microdissected the hypothalamus of 17-day-old rat fetuses in two fragments containing cell bodies from the A12 and from the A14 regions, prepared neuronal cultures from both portions and incubated them separately with intermediate lobe cells. The presence of intermediate lobe cells increased tyrosine hydroxylase levels in both dopaminergic neuron subsets, but morphological differentiation was accelerated in dopaminergic neurons originating in the arcuate nucleus only. We then investigated whether physical contact between developing arcuate neurons and their target cells was a prerequisite of the morphological effect by interposing a semipermeable membrane between cultivated neurons and intermediate lobe cells in transwell culture dishes. The morphological effect was no longer observed under transwell coculture conditions, pointing to the involvement of membrane-bound molecules. Accordingly, the stimulating effect of coculture on arcuate dopaminergic neurons was completely abolished by the removal of polysialic acid on neural cell adhesion molecules by endoneuraminidase N treatment. Thus, maturation of A12 and A14 dopaminergic neurons exhibits differential susceptibility to intermediate lobe target cells, and polysialylated-NCAM is required for the contact-dependent effect.

Animals↗
PubMed2005

Training specificity, graft development and graft-mediated functional recovery in a rodent model of Huntington's disease.

Neuronal function and morphology are affected by the environment and the behavioral experience. Here we report on the effects of differential training protocols on the development and the functional recovery mediated by intrastriatal striatal grafts. Rats were trained exclusively on the left or the right paw to perform on the skilled staircase task before being lesioned unilaterally in the dorsal striatum with quinolinic acid. E15 whole ganglionic eminence suspension grafts were implanted into the lesioned striatum. Subsequent testing probed unilateral performance of the affected contralateral paw, as well as bilateral performance. The grafted animals were initially as impaired as the lesioned, but partially recovered their performance with additional training. Grafted animals with appropriate previous experience initially performed better on the staircase test, but the advantage was transient. Furthermore, the grafted animals performed better with their affected paw under forced choice than under conditions when both paws were simultaneously probed. Improvements of the grafted animals were also observed on tests of forelimb akinesia and asymmetry. Morphological data suggest that the training conditions influenced the development specifically of striatal-like, but not of non-striatal like, neurones within the grafts. The grafts were smaller containing less striatal-like neurones in animals that were trained on the contralateral side prior to lesioning and grafting. The results support the hypothesis that unilateral training sensitizes the striatum that subserves the motor learning, leading to exacerbated excitotoxic lesions and to an environment less conducive for graft development.

Animals↗
PubMed2003

Tumour markers are poor predictors for relapse or progression in neuroblastoma.

The value of the tumour markers vanillylmandelic acid (VMA) and homovanillic acid (HVA) in urine (u) and serum (s), neurone-specific enolase (NSE), and lactate dehydrogenase (LDH) in the early prediction of relapse/progression in neuroblastoma is not known. We analysed the data of neuroblastoma patients who had successfully completed first-line treatment and had laboratory results available from their initial diagnosis and from relapse/progression (n=196). Patients' overall survival from relapse or progression was 21.5+/-4.2% (mean+/-standard deviation). At diagnosis, we found abnormal results in 75% for VMA and/or HVA (s), 92% for VMA and/or HVA (u), 90% for NSE, and 81% for LDH. We found a lower incidence of abnormal results at relapse or progression with 40% for VMA and/or HVA (s), 54% for HVA and/or VMA (u), 61% for NSE, and 48% for LDH. Sensitivity of all markers was higher for metastatic compared with local recurrence. NSE was the best, being able to detect 42% of the localised relapses, 77% of the combined local/metastatic relapses, and 69% of the metastatic recurrences. Relapse or progression in neuroblastoma cannot be detected reliably by monitoring tumour markers alone. Therefore, follow-up of neuroblastoma patients must include clinical assessment and imaging studies.

Adolescent↗
PubMed1995

Identification and gene expression of anaerobically induced enolase in Echinochloa phyllopogon and Echinochloa crus-pavonis.

Enolase (2-phospho-D-glycerate hydrolase, EC 4.2.1.11) has been identified as an anaerobic stress protein in Echinochloa oryzoides based on the homology of its internal amino acid sequence with those of enolases from other organisms, by immunological reactivity, and induction of catalytic activity during anaerobic stress. Enolase activity was induced 5-fold in anoxically treated seedlings of three flood-tolerant species (E. oryzoides, Echinochloa phyllopogon, and rice [Oryza sativa L.]) but not in the flood-intolerant species (Echinochloa crus-pavonis). A 540-bp fragment of the enolase gene was amplified by polymerase chain reaction from cDNAs of E. phyllopogon and maize (Zea mays L.) and used to estimate the number of enolase genes and to study the expression of enolase transcripts in E. phyllopogon, E. crus-pavonis, and maize. Southern blot analysis indicated that only one enolase gene is present in either E. phyllopogon or E. crus-pavonis. Three patterns of enolase gene expression were observed in the three species studied. In E. phyllopogon, enolase induction at both the mRNA and enzyme activity levels was sustained at all times with a further induction after 48 h of anoxia. In contrast, enolase was induced in hypoxically treated maize root tips only at the mRNA level. In E. crus-pavonis, enolase mRNA and enzyme activity were induced during hypoxia, but activity was only transiently elevated. These results suggest that enolase expression in maize and E. crus-pavonis during anoxia are similarly regulated at the transcriptional level but differ in posttranslational regulation, whereas enolase is fully induced in E. phyllopogon during anaerobiosis.

Amino Acid Sequence↗
PubMed1995

X-ray structure and catalytic mechanism of lobster enolase.

Enolase prepared from lobster tail muscle yielded trigonal crystals with one 47 kDa subunit per asymmetric unit. X-ray data were collected on the apoenzyme at 2.4 A resolution and on a complex with Mn2+ and the inhibitor phosphoglycolate at 2.2 A resolution. The corresponding cDNA was amplified from a library of lobster muscle cDNA, and a sequence corresponding to residues 27-398 was determined. It is highly homologous to other enolases, including yeast enolase for which an X-ray structure is available. Yeast enolase was used as a starting point for crystallographic refinement, which led to models of lobster enolase having R-factors below 22% and good stereochemistry. These models are very similar to yeast enolase; they have the same fold with a beta 3 alpha 4 N-terminal domain followed by an atypical alpha/beta barrel. Lobster apoenolase and the ternary complex differ only in the position of three mobile loops. In the complex, a single Mn2+ ion is seen ligated to three carboxylates and three water molecules. Phosphoglycolate binds near, but not directly to, the metal. His 157, which belongs to one of the mobile loops, is in contact with the C2 atom of the ligand. A water molecule hydrogen-bonds to the carboxylate of the ligand and to those of Glu 166 and Glu 209. We suggest that His 157 is the base that abstracts the C2H proton, whereas the water molecule is part of a proton relay system keeping the substrate in the carboxylic acid form where the pKa of the C2H group is low enough for proton transfer to His 157. The resulting catalytic mechanism is different from those proposed on the basis of the yeast enzyme X-ray structures, but it fits with earlier biochemical and spectroscopic data.

Amino Acid Sequence↗
PubMed1991

Differential susceptibilities of spinal cord neurons to retinoic acid-induced survival and differentiation.

In a previous study, we demonstrated trophic effects of vitamin A and its active metabolite, retinoic acid (RA), on perinatal rat spinal cord neurons and astrocytes in vitro. We now report that RA increases the survival of cholinergic neurons without affecting that of GABAergic neurons. These results were supported by measured levels of acetylcholinesterase (AChE), choline acetyltransferase (ChAT), and glutamic acid decarboxylase (GAD) activities, key enzymes of acetylcholine and gamma-aminobutyric acid metabolism, respectively, which showed RA-induced increases in AChE and ChAT levels but no elevations of GAD activity. In contrast to these phenotype-specific effects, most neurons showed RA-induced increases in neuritic outgrowth, density, and silver impregnation. Taken together, these results demonstrate neurotransmitter-specific and generalized effects of RA on developing CNS neurons.

Acetylcholinesterase↗
PubMed2005

Isolation and characterization of neural precursor cells from the Sox1-GFP reporter mouse.

We have made use of a reporter mouse line in which enhanced green fluorescence protein (GFP) is inserted into the Sox1 locus. We show that the GFP reporter is coexpressed with the Sox1 protein as well as with other known markers for neural stem and progenitor cells, and can be used to identify and isolate these cells by fluorescence-activated cell sorting (FACS) from the developing or adult brain and from neurosphere cultures. All neurosphere-forming cells with the capacity for multipotency and self-renewal reside in the Sox1-GFP-expressing population. Thus, the Sox1-GFP reporter system is highly useful for identification, isolation and characterization of neural stem and progenitor cells, as well as for the validation of alternative means for isolating neural stem and progenitor cells. Further, transplantation experiments show that Sox1-GFP cells isolated from the foetal brain give rise to neurons and glia in vivo, and that many of the neurons display phenotypic characteristics appropriate for the developing brain region from which the Sox1-GFP precursors were derived. On the other hand, Sox1-GFP cells isolated from the adult subventricular zone or expanded neurosphere cultures gave rise almost exclusively to glial cells following transplantation. Thus, not all Sox1-GFP cells possess the same capacity for neuronal differentiation in vivo.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1992

A reassessment of histologic classification and an immunohistochemical study of 88 retinoblastomas. A special reference to the advent of bipolar-like cells.

BACKGROUND: Despite perpetual efforts of investigators, the histogenesis of retinoblastoma is still in dispute and histologic classification satisfactorily predictive of prognosis does not seem to be in use. METHODS: The authors studied 88 cases of retinoblastoma clinicopathologically and immunohistochemically, paying special attention to the presence of a "bipolar-like cell" element that would be used as one of the criteria for the diagnosis of differentiated retinoblastoma. RESULTS: Twelve cases of retinoblastoma with the bipolar-like cell element in the absence of rosettes and 41 cases of the tumor with rosettes were classified as differentiated retinoblastomas. The other 35 cases without rosettes or bipolar-like cells were classified as undifferentiated tumors. Tumor cells forming rosettes usually had positive results for synaptophysin and neuron-specific enolase (NSE) and negative results for glial fibrillary acidic protein (GFAP) and S-100 protein; however, undifferentiated cells had negative results for these four antibodies. The bipolar-like cells had positive results for synaptophysin and NSE but negative results for GFAP and S-100 protein. Twelve tumors with bipolar-like cells that lacked rosettes showed no optic nerve invasion, and the patients had a significantly better prognosis (100% 5-year survival rate) than 35 patients with undifferentiated tumors (71% 5-year survival rate) (P < 0.01). CONCLUSIONS: The findings support a neuronal origin of the tumor and indicate that, not only the rosettes symbolizing the photoreceptor differentiation, but also other neuronal elements, such as bipolar-like cells, can be used as criteria for histologic classification of retinoblastoma.

Adolescent↗
PubMed1999

Adult-derived neural precursors transplanted into multiple regions in the adult brain.

Neural stem cells persist in the adult brain subventricular zone (SVZ). These cells generate a large number of new neurons that migrate to the olfactory bulb, where they complete their differentiation. Here, we transplanted cells carrying beta-galactosidase under the control of neuron-specific enolase promoter (NSE::LacZ) from the SVZ of adult mice into the striatum cortex and olfactory bulb, with or without an excitotoxin lesion. Between 2 and 8 weeks after transplantation, grafted cells were present in the recipient regions, but extensive migration and differentiation into mature neurons of grafted cells were only observed in the olfactory bulb. Clusters of graft-derived neuroblasts forming chain-like structures were observed within or close to the grated sites in the cortex and striatum; electron microscopy confirmed that graft-derived cells in the olfactory bulb and a small number in the striatum were neurons. Surprisingly, most of the cells expressing NSE::LacZ outside the olfactory bulb were astrocytes. We conclude that primary precursors from the SVZ migrate and differentiate effectively only within the environment of the olfactory bulb. Only limited survival and differentiation were observed in other brain regions studied.

Animals↗
PubMed2002

Systemic administration of kainic acid in adult rat stimulates expression of the chemokine receptor CCR5 in the forebrain.

As chemokines and their receptors are primarily expressed by glial cells in brain parenchyma, a model of glial cell proliferation may be useful to study the regulation of their expression in the brain. The well-established kainic acid seizure model was used in this study, focusing on the expression of the CCR5 chemokine receptor. Adult Sprague-Dawley rats were injected intraperitoneally with kainic acid (12 mg/kg), and in situ hybridization of CCR5 mRNA was performed at 12 h, 1, 3, or 7 days, posttreatment. Autoradiographic films and wet photographic emulsions demonstrated the very low expression of CCR5 mRNA in normal brain parenchyma, as well as in the microvasculature and ventricular/choroid plexus systems. After kainic acid treatment, brain CCR5 mRNA expression increased progressively from 12 h to 7 days, especially in the olfactory system, amygdaloid complex, thalamus, hippocampal formation, septum, and neocortex. This increase paralleled that of activated microglial cells as shown, using the microglial marker, OX-42. Moreover, CCR5 mRNA ISH combined with neuron-specific enolase immunocytochemistry showed that, in addition to its glial expression, CCR5 mRNA is expressed in neurons in the normal brain and, to a lesser extent, after kainate treatment due to neuronal losses. Finally, CCR5 protein is detected by immunocytochemistry in neurodegenerative areas in numerous glial cells, as well as in neurons, as clearly shown in the hippocampal formation. In summary, the chemokine receptor CCR5 is expressed by neuronal and non-neuronal cell types in the normal brain and is upregulated in both cell types after an insult.

Animals↗
PubMed1989

Brain tissue reaction to permselective polymer capsules.

The brain tissue reaction to permselective polymer capsules implanted in rats was evaluated for 1 to 54 weeks. The polymer capsules were well tolerated in all animals and no recognizable neurological or behavioral deficits were associated with the implants. Necrosis at the brain/polymer interface, as assessed with Nissl stain, was not observed. Foreign body giant cells were consistently absent. Immunocytochemically identified reactive neuroglial cells showed a remarkably low-grade tissue response to the synthetic material beyond the first 2 weeks of observation. Immunolabeled cortical neurons revealed conserved columnar arrays around the implants. Transmission electron microscopy showed a minimal degree of collagen deposition compared to implants in peripheral sites, and normal synapses within a few micrometers from the brain/polymer interface, supporting the prospect of biocompatible, immunoisolated xenografts in the central nervous system.

Acrylic Resins↗
PubMed2003

Aspartylglucosaminidase (AGA) is efficiently produced and endocytosed by glial cells: implication for the therapy of a lysosomal storage disorder.

BACKGROUND: Aspartylglucosaminuria (AGU) represents diseases affecting the central nervous system and is caused by a deficiency of a lysosomal enzyme, aspartylglucosaminidase (AGA). AGA, like lysosomal enzymes in general, are good targets for gene therapy since they move from cell to cell using the mannose-6-phosphate receptor. Consequently, only a minority of target cells need to be corrected. Here, we wanted to determine which cell type, neurons or glia would better produce AGA to be transported to adjacent cells for use in possible treatment strategies. METHODS: Adenoviruses containing tissue-specific glial fibrillary acidic protein (GFAP) promoter and neuron-specific enolase (NSE) promoter were generated to target expression of AGA in Aga-deficient mouse primary glial and neuronal cell cultures. In addition an endogenous AGA promoter was used. The experimental design was planned to measure the enzymatic activities in the cells and media of neurons and glia infected with each specific virus. The endocytosis of AGA was analyzed by incubating neuronal and glial cells with media produced by each virus-cell combination. RESULTS: AGA promoter was shown to be a very powerful glia promoter producing 32 times higher specific AGA activity in glia than in neurons. GFAP and NSE promoters also produced a clear overexpression of AGA in glia and neurons, respectively. Interestingly, both the NSE and GFAP promoters were not cell-specific in our system. The amount of exocytosed AGA was significantly higher in glial cells than neurons and glial cells were also found to have a greater capacity to endocytose AGA. CONCLUSIONS: These data indicate the importance of glial cells in the expression and transport of AGA. Subsequently, new approaches can be developed for therapeutic intervention.

Adenoviridae↗
PubMed1992

Neuron-specific enolase-like immunoreactivity in the vertebrate retina: selective labelling of Müller cells in Anura.

Neuron-specific enolase (NSE) immunocytochemistry was carried out in retinae of goldfish, axolotl, clawed frog, cane toad, lizard, chick, guinea-pig, rabbit, rat, cat and human. With the exception of Anura, strong immunoreactivity was seen in the large ganglion, amacrine cells and horizontal cells of the retina in all of the other species. Photoreceptors were found to be labelled in the rat and human retina and only one cone type in rabbit. Photoreceptor pedicles and ellipsoids were stained in the goldfish and the somata and inner segments of some photoreceptors in axolotl. In the axolotl retina, besides neurons, Müller cells (MCs) were also immunolabelled. In the retina of the cane toad and the clawed frog MCs were the only stained elements. Similarly in other parts of the central nervous system of the cane toad, glial elements of the optic tectum and spinal cord were immunoreactive. In contrast, in the peripheral nervous system, neurons of the 1st sympathetic ganglion and the 2nd dorsal root ganglion were labelled. In double-labelling experiments, glial fibrillary acidic protein and NSE showed colocalisation both in the glial elements of the optic tectum and spinal cord and in MCs of the retina of the cane toad.

Ambystoma↗
PubMed1989

The developing neuroepithelium in human embryonic and fetal brain studied with vimentin-immunocytochemistry.

The neuroepithelial cells, which constitute the primordium of the CNS, are potentially capable of generating neuronal and glial cell lineages concomitantly. The appearance and morphological development of vimentin-positive neuroepithelial cells in human embryonic and fetal brain (4-16 weeks) were studied with immunocytochemistry. In embryos aged 4-6 weeks, vimentin-reactivity was seen in all neuroepithelial cells, including those which exhibited mitotic figures. The distribution of reactivity changed according to a general developmental pattern, which commenced and proceeded temporally different in various regions of the CNS. All regions exhibited vimentin-positive neuroepithelial cells, the distribution and morphology of which gradually changed, resulting in lamination of the neural wall into two and subsequently three layers. The neocortex and midline raphe were the only regions to differ significantly from the general pattern. When reactivity to glial fibrillary acidic protein developed at 7-8 weeks, the distribution was very much like that of vimentin at the same stage. Reactivity to glial, neuronal and other cellular markers (S-100, neurofilament, neuron specific enolase, desmin, and cytokeratin) revealed different distributions. Although cells retaining vimentin beyond the ventricular zone stage are radial glial cells and presumptive fibrous astrocytes, it seems unlikely that vimentin is a marker for a distinct cell lineage during early CNS development. It is suggested that all neuroepithelial cells in vivo differentiate to a stage where they express vimentin, and that vimentin may have a functional role in cellular movements and during the interkinetic nuclear migration.

Antibodies, Monoclonal↗
PubMed1994

Analysis of the heterogeneity within bovine pineal gland by immunohistochemistry and in situ hybridization.

In the present study, we demonstrate a cortical and medullary arrangement of parenchymal cells in the bovine pineal gland by using antibodies for neuron-specific enolase, synaptophysin, and hydroxyindole O-methyltransferase (HIOMT) as markers of pinealocytes, and glial fibrillary acidic protein (GFAP) as a marker of interstitial (glial) cells. Furthermore, by means of probes specific for HIOMT mRNA, we have examined possible differences in melatonin synthesis between the cortex and the medulla. Immunoreactive pinealocytes for each antigen investigated are more densely distributed in the cortex than in the medulla. In the cortex, GFAP-positive interstitial cells have large intenselystained somata endowed with several long, thin cytoplasmic processes, whereas in the medulla, they display smaller, less intensely labeled perikarya from which numerous fine short processes emerge. Golgi staining has confirmed these morphological differences between the interstitial cells in the cortex and those in the medulla. An analysis using confocal laser microscopy together with in situ hybridization for HIOMT mRNA has shown that the expression of mRNA transcripts in the cortex is more intense than that in the medulla. The expression of the HIOMT gene in a cluster of cells in the medial habenular nucleus is lower than that in pinealocytes of the pineal organ proper.

Acetylserotonin O-Methyltransferase↗