Properties and application to immunoassay of monoclonal antibodies to neuron-specific γγ enolase

Two monoclonal antibodies to human and bovine neuron-specific γγ enolase have been produced in the isolated hybrid cell lines, which were obtained by fusion between γγ-immunized mouse spleen cells and mouse myeloma cells (P3-NS-1/1-Ag4-1), followed by a screening procedure with an enzyme immunoassay. The monoclonal antibody to human γγ enolase (E1-G3) and that to bovine γγ enolase (B1-D6) consisted of γ2a/κ and γl/κ immunoglobulin chains, respectively. Both antibodies could bind with the respective antigen with a molar ratio of about 1:1, and were found to be specific for the γ subunit of enolase, showing reactivities with human γγ and αγ, rat γγ and αγ, and bovine γγ enolases. However, the antibodies did not cross-react with the α or β subunit of human and rat enolase isozymes. Both antibodies could partially inhibit the activity of γγ and αγ enolases. E1-G3 antibody inhibited γγ and αγ enolase activity by 70 and 30%, respectively, and B1-D6 antibody, by 90 and 40%, respectively. Both antibodies had no effect on the activity of αα and ββ enolases of human and rat origins. The applicability of E1-G3 and B1-D6 antibodies to the sandwich-type enzyme immunoassay for neuron-specific enolase (enolase γ subunit) was examined, and it was found that the assay system using E1-G3 and B1-D6 as the labeled antibodies were sufficiently sensitive for the assay of serum neuron-specific enolase concentrations.     

THE NATURE OF THE TWO PROTEINS OF BRAIN SPECIFIC ANTIGEN 14-3-2

The three isoenzymes of rat brain enolase (2-phospho d -glycerate hydrolase EC 4.2.1.11.) χχ, χγ and γγ were separated by ion-exchange chromatography and were tested for reaction with an antiserum against brain specific antigen 14-3-2. This monospecific antiserum affects the enolase activity of only the χγ and γγ isoenzymes. Immunoelectrophoretic experiments show that the two proteins which react as 14-3-2 both contain γ enolase subunits, and one of these also contains χ enolase subunits. It is concluded that the 14-3-2 antigen and the γ enolase subunit are identical, and that the two proteins which react immunologically as 14-3-2 are the χγ and γγ enolase isoenzymes.     

Transition between isozymic forms of enolase during in vitro differentiation of neuroblastoma cells—II

An analysis of enolase expression during differentiation of neuroblastoma clones in homogeneous culture is presented. The enolases expressed in these neuroblast-like cells are identical to those of mouse brain with respect to the examined properties.Our biochemical investigation has premitted us to demonstrate formally that neuroblastoma cells undergo a transition from the embryonic αα form to the neuronal γγ form and contain both enolases as well as the αγ hybrid form during maturation. These results suggest that the same phenomenon must exist in vivo for neuroblasts. In neuroblastoma cells, an increase in both αγ and γγ neuron specific enolases is related to cell maturation and expression of the αγ form precedes that of the γγ form during differentiation. Modulation of neuronal enolase activities is similar in the various conditions of differentiation studied and appears not to be necessarily related with morphological differentiation, although concomitant with an arrest of cell division. The evolution of specific neuronal enolases in neuroblastoma cells parallels that observed in vivo, in brain from embryonic day 15 to post-natal day 7. Moreover, at least one treatment (dimethylsulfoxide) causes an important decrease in the high specific αα activity of these cells as occurs in vivo. This enolase can therefore also be considered as a biochemical marker for neuroblastoma maturation.As observed with other markers and other cell types, neuroblastoma cells in culture express an immature biochemical differentiation of the enolase isozymes.     

Purification of two enolases from human brain using a chromatofocusing column

When a purified preparation of rat αγ enolase (2-phospho-D-glycerate hydrolyase, EC 4.2.1.11) was applied to a chromatofocusing column, the enolase was almost completely dissociated and recombined to form αα and γγ enolases, which were eluted at different fractions from the column. Using these phenomena, two homo-dimer forms (αα and γγ) of human brain enolase were purified from a crude preparation of the hybrid αγ enolase by the chromatofocusing, and subsequent chromatography on a QAE-Sephadex column (αα) or a DEAE-Sephadex column (γγ). Each purified preparation showed a single band on SDS-gel electrophoresis with a relative mobility corresponding to a molecular weight of about 50 000. Amino acid analysis, peptide mapping analysis with a limited proteolysis and immunochemical studies of the purified αα and γγ enolases revealed that the two subunits, α and γ, are distinct proteins. The antisera to human αα or γγ enolase cross-reacted with the respective form of rat enolase.     

Clonal characterization of mouse mammary luminal epithelial and myoepithelial cells separated by fluorescence-activated cell sorting

Summary Lineage analysis in vitro of heterogeneous tissues such as mammary epithelium requires the separation of constituent cell types and their growth as clones. The separation of virgin mouse mammary luminal epithelial and myoepithelial cells by fluorescence-activated cell-sorting, their growth at clonal density, and the phenotyping of the clones obtained with cell-type specific markers are described in this paper. Epithelial cells were isolated by collagenase digestion followed by trypsinization, and the luminal and myoepithelial cells were flow-sorted with the rat monoclonal antibodies 33A10 and JB6, respectively. Sorted cells were cloned under, using low oxygen conditions (<5% vol/vol), in medium containing cholera toxin and insulin, with an irradiated feeder layer of 3T3-L1 cells. Clones were characterized morphologically, and antigenically by multiple immunofluorescence with a panel of antibodies to cytoskeletal antigens specific to either luminal epithelial or myoepithelial cells in situ. Whereas sorted myoepithelial cells gave a single clone type, sorted luminal cells gave three morphological clone types, two of which grew rapidly. All myoepithelially derived clones showed a limited proliferative capacity in vitro, in contrast to their rat and human counterparts, as shown in previous studies. The present results with sorted mouse cells have also allowed the stability of the differentiated phenotype in mouse, rat, and human mammary luminal epithelial and myoepithelial cells in primary clonal culture to be compared. They show that the mouse mammary cells are the least stable in terms of expression of differentiation-specific cytoskeletal markers in vitro.     

Absence of extensive recombination between inter- and intraspecies mitochondrial DNA in mammalian cells

Recombination of mammalian mitochondrial DNA (mtDNA) was examined using mouse X rat somatic cell hybrid clones and rat cybrid clones. The mouse X rat hybrids were isolated by fusion of chloramphenicol-sensitive (CAPs) mouse and CAP-resistant (CAPr) rat cells. The rat cybrids were isolated by fusion of rat cells with type B mtDNA and enucleated cells with type A mtDNA. Genetic and physical analyses showed that the mtDNAs of the hybrids and cybrids were simple mixtures of the two parental mtDNAs except in the following two cases: One was subclone H2-9 of mouse X rat hybrids, which was CAPr even though mtDNA from the CAPs mouse parent was predominantly retained. The other was rat cybrid subclones, Y12-24 and -61, which showed specific loss of one Hinf I fragment of type B mtDNA, B10. These observations suggest that, in contrast to the case with plant mtDNA, recombination of mammalian mtDNA occurs rarely, if at all.     

Sequence and expression of human protein kinase C-epsilon.

Two human homologues of protein kinase C-epsilon (E1 and E2) were isolated from two distinct cDNA libraries. Sequence comparisons to PKC-epsilon cDNAs from several species indicated that each of these human epsilon clones contained cloning artifacts. Thus, a composite PKC-epsilon (E3) clone was derived from clones E1 and E2. Human PKC-epsilon (E3) has an overall sequence identity of 90-92% at the nucleotide level compared to the previously characterized mouse, rat and rabbit clones. At the amino acid level, the deduced human epsilon sequence shows a 98-99% identity with the mouse, rat and rabbit sequences. Expression of the human PKC-epsilon clone in Sf9 cells confirmed that the recombinant protein displayed protein kinase C activity and phorbol ester binding activity. The recombinant protein was also recognized by two distinct epsilon-specific polyclonal antibodies.     

Enolase isoenzymes as markers of differentiation in teratocarcinoma cells and normal tissues of mouse

The changing profile of enolase (EC 4.2.1.11) isoenzymes in differentiating mouse cells has been traced by the use of specific antisera to the three subunits α, β, and γ. The amounts of the isoenzymes were measured in a variety of tissues during normal mouse development and during the differentiation of mouse teratocarcinoma cells in culture and as tumors. One isoenzyme is predominant in the early cells of the developing mouse embryo, namely, the homodimer made up of α subunits. The same isoenzyme is also the sole form detected in undifferentiated teratocarcinoma (embryonal carcinoma) cells. The isoenzyme form remains unchanged in developing primitive and definitive endoderm of the embryo. Similarly, endoderm cells formed by differentiation of embryonal carcinoma cells contained only αα enolase. In contrast, during the development of striated muscle and of brain, increasing proportions of β and γ subunits, respectively, were detected. Thus enolase was found to be a marker of the differentiation of these tissues. This conclusion was substantiated by finding significant amounts of the β subunit in teratocarcinoma cell cultures which had formed beating striated muscle in vitro.     

Long-term proliferation of mouse thymic epithelial cells in culture

Summary Epithelial cells from the normal mouse thymus were successfully cultivated on tissue culture plastic when plated with lethally irradiated support cells of the LA7 rat mammary tumor line. As the irradiated LA7 cells slowly decreased in number the thymus cells proliferated concomitantly to form a confluent monolayer. The cells now in culture have been subcultured 8 times, have doubled in number at least 30 times, and are still proliferating vigorously. The culture technique also supported clonal growth from a single cell, and nine clones have been isolated. The colony-forming efficiency of thymic cells plated at low concentrations was about 8%. These cultures were never overgrown by fibroblasts. The thymus cells were characterized as epithelial by the presence of cytoplasmic keratin and numerous desmosomes and tonofilaments. They were shown to be mouse cells by immunocytochemistry with species specific antibodies, by isoenzyme analysis, and by karyology. The cells stained when reacted with antibodies to tubulin, vimentin, and actin, but not with antibodies to Thy-1.2, Lyt-1, Lyt-2, Ia, or H-2 proteins. More than 85% of the cells had a normal mouse diploid chromosome number of 40. This culture technique opens the way for future studies of T-cell education with homogeneous thymic epithelial cell populations both in vitro and after reimplantation into genetically defined strains of mice. This work was supported by the Veterans Administration, Washington, D.C.     

Developmental profile of three enolase isozymes in rat brain determination from one-cell embryo to adult brain

Levels of three enolase isozymes (αα, αγ and γγ) were determined in rat tissues from one-cell embryo to adult brain with a sensitive enzyme immunoassay system. Each embryo of the early stage (gestational age, 0–3 days) contained about 5 × 10^?17 mol of αα enolase. The nervous system-specific αγ and γγ enolases would be detected in the embryos of 6–8 days, which contain no histologically recognizable neurones. The 8-day embryos contained 4.3 × 10^?17 and 3.4 × 10^?16 mol of αγ and γγ enolases. Amounts of all the three enolases were increased with growth of the embryo. The nervous system-specific enolases (αγ and γγ) in the brain kept increasing until 1–2 months of postnatal age, whereas the αα enolase level in the brain was relatively constant after the 15-day embryo through the adult rat.     

鼠源性抗雄性特异性抗原噬菌体Fab抗体的制备及分析

利用噬菌体抗体库筛选技术获得抗雄性特异性抗原的噬菌体Fab抗体,首次采用雄鼠脾细胞对鼠源性抗雄性特异性抗原噬菌体Fab抗体库进行3轮亲和富集和2轮雌鼠脾细胞吸附,对筛选后特异性噬菌体Fab抗体进行ELISA分析,重组率鉴定及基因测序分析。结果显示,5次筛选后的15个菌落中有9个能产生抗雄性特异性抗原特异性噬菌体抗体,噬菌体Fab抗体的基因重组率为60%,E5克隆的重链、轻链可变区序列分别属于VH1和VκⅣ基因家族,这为挑选出高亲和力的抗雄性特异性抗原噬菌体Fab抗体奠定了实验基础,将推进雄性特异性抗原及其抗体的研究进程,并为性别控制研究开创新途径。     

Monoclonal antibodies to rat brain astroglial cells—Their characterization and application for isolation of astroglial subpopulations

Three monoclonal antibodies (MAbs) specifically recognizing rat astrocyte cell surface proteins have been characterized and their antigen binding specificities determined. One of these MAbs has been employed to isolate a distinct subpopulation of astroglial cells using immunoaffinity chromatography.

MAbs to rat astroglial cell surface proteins, generated by fusion of mouse Sp2/O-Ag 14 myeloma cells and spleen cells from Balb/C mice immunized with purified astroglial cells, were screened for their cell binding specificities using ELISA and indirect immunofluorescence assay. The antigen binding specificity of three of these clones, which displayed specific binding to astrocytes, was determined by radioiodination of whole astrocytes and precipitation of the iodinated surface proteins by the MAbs. Immunoaffinity chromatography, using IgG from one of the clones coupled to CNBr activated Sepharose 6MB, demonstrated the potential usefulness of such MAbs in isolating a specific subpopulation of astroglial cells.     

Characterization of a slowly proliferative cell along the oligodendrocyte differentiation pathway

A single bipotential glial progenitor cell of newborn rat optic nerve (the O-2A progenitor) characterized by its reactivity with antibodies to surface gangliosides (A2B5) and the presence of vimentin, can grow in microcultures in conditions which favor this progenitor's differentiation into oligodendrocytes. We selected at 8 days larger clones derived from such bipolar progenitors which had steadily proliferated on a layer of Type-1 astrocytes during the first week. Clonal growth and ratio of progenitor cells to oligodendrocytes was measured over the next two weeks by phase microscopy and double immunofluorescence labeling for the specific markers A2B5, GC (galactocerebroside, a surface marker for differentiated oligodendrocytes), O4 (a glycolipid marker of oligodendrocytes and some progenitors), GFAP (an astrocyte specific intermediate filament protein) and vimentin. Two types of clones were identified: type A clones (the majority), which were still slowly expanding at three weeks, and type B clones (the minority), which had stopped proliferating during the second week. In type A clones, some cells became GC positive multipolar oligodendrocytes, while other multipolar cells remained GC negative for days and expressed A2B5 and O4, but not GFAP or vimentin. Type B clones contained only GC positive, vimentin negative oligodendrocytes, which were generated during the second week and then decreased in number because of their restricted lifespan. Type B clones only developed in the presence of insulin or neurons. The number of GC negative cells in type A clones increased when insulin or neurons were deleted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunocytochemical Examination of Neural Rat and Mouse Primary Cultures Using Monoclonal Antibodies Raised Against Pyruvate Carboxylase

Abstract: Pyruvate carboxylase (EC 6.4.1.1; PC) catalyzes the formation of oxaloacetate by energy-dependent fixation of CO₂ to pyruvate. The aim of the present work was to generate antibodies against PC and use them to localize PC in the cells of astroglia-rich and neuron-rich primary cultures derived from the brains of rats and mice. Mouse monoclonal antibodies raised against the enzyme were shown to be monospecific as indicated by immunoblotting. The staining of the cells for PC appeared in grains. These represent mitochondria, as PC is known as a mitochondrial enzyme. Immunocytochemical examination of astroglia-rich primary cultures of rat or mouse brain cells revealed a colocalization of PC with the astroglial marker glial fibrillary acidic protein (GFAP) in many cells. However, there were GFAP-positive cells showing no specific staining for PC, and vice versa. Also, in neuron-rich primary cultures PC was found only in the ∼10% GFAP-expressing astroglial cells contaminating the neuron-rich primary culture, whereas it was absent from the neurons identified by antibodies against neuron-specific enolase. These results suggest that PC is predominantly an astroglial enzyme and that astroglial cells play an important role in the intermediary and the energy metabolism of the brain.     

Combined immunostaining of neurofilaments, neuron specific enolase, GFAP and S-100. A possible means for assessing the morphological and functional status of the enteric nervous system

Neurofilaments, part of the cytoskeletal network, and neuron specific enolase, a major enzyme in glycolysis, are both present in central and peripheral neurons. Glial fibrillary acidic protein and S-100, on the other hand, are soluble proteins which are found exclusively in the supportive cells of the nervous system, i.e. the glial cells. Examination was made, using immunocytochemistry, of all main areas of the gastrointestinal tract of three mammalian species, rat, pig and man. By applying serial tissue sectioning, it was possible to study the relative occurrences of the two neuronal markers in the same cell bodies and to examine the relationships of the neurons with the glial cells as revealed by the antibodies to glial fibrillary acidic protein and S-100. Both neurofilaments and neuron specific enolase were localised to an extensive system of enteric nerves, with the level of neuron specific enolase-immunoreactivity showing greater variability than that observed using antibodies to neurofilaments. Comparison of the occurrence of neuron specific enolase and neurofilament immunoreactivity in serially sectioned neuronal cell bodies revealed that a minor population stained only with antibodies to neurofilaments. The equivocal or absent neuron specific enolase-immunoreactivity in some perikarya may reflect variations in functional status within the nervous system. Glial fibrillary acidic protein- and S-100-immunoreactivities were confined to glial cells which, in this normal tissue, were always in close association with the neurons.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of type IV collagen and laminin in cultures of skeletal muscle cells and their assembly on the surface of myotubes

The synthesis of two components of the basal lamina, laminin and type IV collagen, and their extracellular deposition on the surface of myotubes was studied in cultures of embryonic mouse and quail skeletal muscle cells and in the rat myoblast cell line L6. Production of type IV collagen and laminin by myoblasts and muscle fibroblasts was demonstrated by incorporation of radioactive amino acids into proteins and by immunoprecipitation with specific antibodies and electrophoretic analysis of labeled proteins. Immunofluorescence staining experiments revealed strong intracellular reactions with antibodies to laminin and type IV collagen in mononucleated myogenic and fibrogenic cells. Cells of fibroblast-like morphology showed a more intense staining than bipolar, spindle-shaped cells which perhaps represented postmitotic myoblasts. Myotubes did not show detectable intracellular staining. The formation of a basal lamina on myotubes was indicated by the deposition of laminin and type IV collagen on the surface of myotubes as viewed by immunofluorescence examination of unfixed cells. Staining for extracellular laminin was stronger in mass cultures than in myogenic clones, suggesting that secretion and deposition of components of the basal lamina on the myotube surface are complex processes which may involve cooperation between myogenic and fibrogenic cells.     

Establishment of mouse-immortalized hybrid clones expressing characteristics of differentiated neurons derived from the cerebellar and brain stem regions.

Two clonal immortalized neurons designated CL8c4.7 and CL8a5.2 were established by somatic cell fusion between a hypoxanthine phosphoribosyltransferase-(HPRT-) deficient neuroblastoma N18TG2 and newborn mouse cerebellar/brain stem neurons. In the serum-containing medium without extra differentiating agents, both clones exhibited a morphology of differentiated neurons. They contained high levels of glutamate but no gamma-aminobutyric acid (GABA). The CL8a5.2 clone synthesized choline acetyltransferase and serotonin. In immunocytochemical studies, both clones expressed 200 kD neurofilament protein, neuron-specific enolase, microtubule-associated protein 2 (MAP2), tau protein, neuronal cell adhesion molecule (N-CAM), HNK-1, Thy-1.2, saxitoxin-binding sodium channel protein, and glutamate. Synaptophysin immunoreactivity was identified in the neuritic terminals of CL8c4.7 cells. Most of these antigens were barely detectable on N18TG2 cells. Electrophysiologically, both clones generated action potentials in response to electrical stimuli. The hybrid clones that express characteristics of differentiated neurons derived from the cerebellar and brain stem regions might be invaluable for the study of the molecular basis of neuronal differentiation and degeneration in these regions.     

cDNA cloning of mouse myelin-associated glycoprotein: a novel alternative splicing pattern

The structures of three forms of mouse myelin-associated glycoprotein mRNAs were determined from full-length cDNA clones. Two forms of mRNAs have been reported to be different by alternate inclusion of exon 2 and 12 in rat brain. One of the three forms of clones obtained here appeared to be a novel mRNA which lacked both the exon 2 and 12 portions, although others were identical splicing patterns to those of rat. Northern blot analysis using specific probes to mRNAs with or without the exon 2 portion in normal and quaking mouse confirmed that the splicing of exon 2 and 12 occurred independently.     

Identification and immunological characterization of a novel 40-kDa protein linked to CD98 antigen.

Monoclonal antibodies (mAbs) were obtained from hybridoma clones established by cell fusion between mouse myeloma cells and spleen cells from a mouse immunized against an affinity-purified 40-kDa component of rat 125-kDa glycoprotein (GP125). Two mAbs designated as 3F2 and 6B4 detected a 40-kDa and a 125-kDa band under reducing and nonreducing conditions, respectively, in extracts prepared from rat, mouse and human tumor cells. Association of the 40-kDa protein with CD98 was revealed by sandwich-type enzyme-linked immunosorbent assay. The two mAbs were strongly reactive with various tumor cells and activated lymphocytes, but were only weakly reactive with resting lymphocytes. Confocal microscopy indicated colocalization of CD98 and the 40-kDa protein defined with 3F2 and 6B4 at the cell surface and perinuclear regions. On immunohistochemical analysis of frozen sections of rat tongue, the anti-rat CD98 mAb B3 selectively stained the basal layer and 3F2 stained the upper epithelial part in addition to the basal layer, indicating the existence of CD98-unlinked 40-kDa protein.     

Antibodies to mouse lung capillary endothelium

We are interested in developing monoclonal antibodies (MoAbs) that recognize specific cell types in the lung of BALB/c mice. Normal mouse lung homogenate was used to immunize F344 rats and hybridomas were produced by fusion of rat spleen cells with mouse myeloma SP 2/0. Two hybridomas were selected which produced MoAbs active in immunohistochemistry of lung cells. MoAb 273-34A and 411-201B both show extensive peroxidase staining of capillary endothelial cells within alveolar walls of lungs at the light microscopic level. To demonstrate cell specificity, immunoelectron microscopy with gold-labeled antibody was performed. Lightly fixed lungs were frozen and thin-sectioned before staining with MoAb and 5-nm gold particles coupled to secondary antibody. Quantitative analyses of these cryosections show that both antibodies, used at optimal concentrations, are specific for binding to capillary endothelial cells. More than 95% of the gold particles are associated with capillary endothelial cells on the thin side of the alveolar wall. When capillaries adjoined thick septa containing interstitial cells, about two thirds of the gold particles were associated with endothelial cells and about one quarter with interstitial cells. These MoAbs should be useful in studying the role of endothelial cells in toxic lung injury.