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N Lamandé

Publications and source records attributed to N Lamandé.

13 recordsLinked to original sources
PubMed2000

Thyroid hormones differentially modulate enolase isozymes during rat skeletal and cardiac muscle development.

During muscle development, an isozymic transition of the glycolytic enzyme enolase occurs from the embryonic and ubiquitous alphaalpha-isoform to the muscle-specific betabeta-isoform. Here, we demonstrate a stimulatory role of thyroid hormones on these two enolase genes during rat development in hindlimb muscles and an inhibitory effect on the muscle-specific enolase gene in cardiac muscle. In hindlimb muscles the ubiquitous alpha-transcript level is diminished by hypothyroidism, starting at birth. On the contrary, the more abundant muscle-specific beta-transcript is insensitive to hypothyroidism before establishment of the functional diversification of fibers and is greatly decreased thereafter. Our data support the hypothesis of a role of thyroid hormones in coordinating the expressions of contractile proteins and metabolic enzymes during muscle development. The subcellular localization of isoenolases, established here, is not modified by hypothyroidism. Our results underline the specificity of action of thyroid hormones, which modulate differentially two isozymes in the same muscle and regulate, in opposite directions, the expression of the same gene in two different muscles.

Animals↗
PubMed1999

The beta enolase subunit displays three different patterns of microheterogeneity in human striated muscle.

In higher vertebrates, the glycolytic enzyme enolase (2-phospho-D-glycerate hydrolyase; EC 4.2.1.11) is active as a dimeric protein formed from three subunits--alpha: ubiquitous, beta: muscle specific, and gamma: neuron specific--encoded by different genes. In the present study, we have shown that an antiserum previously produced against the mouse beta beta enolase is also a specific reagent for the muscle specific human enolase. Using this antiserum to study human muscles, we demonstrated novel patterns of the beta subunit microheterogeneity which are distinctive from those observed previously in rodents and which appear to be independent of age, gender and muscular activity. Two variants of the beta subunit differing by their size have been detected: one heavy form of 46 kDa (beta H) and one light form of 45 kDa (beta L). Muscle biopsies expressed either beta H or beta L or beta H + beta L, and all muscles of an individual expressed the same variants. The products of in vitro translation of RNA prepared from human muscle displayed beta subunit variants identical to those of the protein present in the biopsy. Therefore the differences observed between individuals reveal a difference already present at the level of the RNA transcripts. These observations suggest the existence of an yet undescribed polymorphism of the human beta enolase gene which could affect the coding sequence. Comparative immunocytochemical and histochemical analyses of biopsies demonstrated that the beta subunit was expressed in all fast fibres (type II), but not in slow fibres (type I). No difference was observed in the intensity of beta enolase immunolabelling between the various types (IIA, IIAB, IIB) of fast fibres. No significant difference in fibre type composition and histological appearance was visible between muscles presenting either one of the three patterns of microheterogeneity.

Adult↗
PubMed1997

Biochemical characterization of the mouse muscle-specific enolase: developmental changes in electrophoretic variants and selective binding to other proteins.

The glycolytic enzyme enolase (EC 4.2.1.11) is active as dimers formed from three subunits encoded by different genes. The embryonic alphaalpha isoform remains distributed in many adult cell types, whereas a transition towards betabeta and gammagamma isoforms occurs in striated muscle cells and neurons respectively. It is not understood why enolase exhibits tissue-specific isoforms with very close functional properties. We approached this problem by the purification of native betabeta-enolase from mouse hindlimb muscles and by raising specific antibodies of high titre against this protein. These reagents have been useful in revealing a heterogeneity of the beta-enolase subunit that changes with in vivo and in vitro maturation. A basic carboxypeptidase appears to be involved in generating an acidic beta-enolase variant, and may regulate plasminogen binding by this subunit. We show for the first time that pure betabeta-enolase binds with high affinity the adjacent enzymes in the glycolytic pathway (pyruvate kinase and phosphoglycerate mutase), favouring the hypothesis that these three enzymes form a functional glycolytic segment. betabeta-Enolase binds with high affinity sarcomeric troponin but not actin and tropomyosin. Some of these binding properties are shared by the alphaalpha-isoenolase, which is also expressed in striated muscle, but not by the neuron-specific gammagamma-enolase. These results support the idea that specific interactions with macromolecules will address muscle enolase isoforms at the subcellular site where ATP, produced through glycolysis, is most needed for contraction. Such a specific targeting could be modulated by post-translational modifications.

Animals↗
PubMed1995

Transcriptional up-regulation of the mouse gene for the muscle-specific subunit of enolase during terminal differentiation of myogenic cells.

The glycolytic enzyme enolase (EC 4.2.1.11) exists as dimers formed from three structurally related subunits alpha, beta, and gamma, encoded by separate genes. The gene encoding the beta-subunit is expressed only in striated muscles. We have previously shown that the beta-enolase gene belongs to a small subset of muscle-specific genes showing transcriptional activity in cultured myoblasts, prior to withdrawal from the cell cycle. An increase in the level of beta-enolase mRNA occurs during terminal differentiation of myoblasts. To investigate the mechanisms underlying this increase, we have simultaneously estimated, under steady state conditions, the rate of synthesis and the stability of beta-enolase mRNA in proliferating C2.7 myoblasts as well as in differentiating myotubes. The method used is based on the isolation of newly synthesized RNA from the total RNA pool, following pulse-labeling of intact cells in the presence of 4-thiouridine. The results described here demonstrate a coordinate increase in newly synthesized and total beta-enolase mRNA, while the mRNA half-life, about 4 hr, remains unchanged in the course of terminal differentiation. The expression of the gene for insulin-like growth factor-II (IGF-II), a major positive regulator of myogenesis, was analyzed using the same approach. It is concluded that the up-regulation of beta-enolase as well as IGF-II gene expression in differentiating muscle cells reflects an increased rate of entry of newly synthesized mRNAs into the general pool of transcripts without changes in their respective half-lives.

Animals↗
PubMed1995

Differential expression of alpha- and beta-enolase genes during rat heart development and hypertrophy.

We have analyzed the transition between isoforms of the glycolytic enzyme enolase (2-phospho-D-glycerate hydrolyase; EC 4.2.1.11) in rat heart during normal and pathological growth. A striking fall in embryonic alpha-enolase gene expression occurs during cardiac development, mostly controlled at pretranslational steps. In fetal and neonatal hearts, muscle-specific beta-enolase gene expression is a minor contributor to total enolase. Control mechanisms of beta-enolase gene expression must include posttranscriptional steps. Aortic stenosis induces a rapid and drastic decrease in beta-enolase transcript level in cardiomyocytes, followed by the fall in beta-subunit level. In contrast, alpha-enolase transcript level is not significantly altered, although the corresponding subunit level increases in nonmuscle cells. We conclude that, like fetal heart, hypertrophic heart is characterized by a high ratio of alpha- to beta-enolase subunit concentrations. This study indicates that the decrease in beta-enolase gene expression may be linked to beneficial energetic changes in contractile properties occurring during cardiac hypertrophy.

Aging↗
PubMed1994

Coexpression of alpha and gamma enolase genes in neurons of adult rat brain.

Enolase (EC 4.2.1.11) is a glycolytic enzyme active as a dimer. In adult brain extracts, three forms, alpha alpha, alpha gamma and gamma gamma, have been described, with the alpha gamma hybrid accounting for 30% of total enolase activity (Fletcher et al., Dev Biol 65:462-475, 1978; Lucas et al., Dev Neurosci 10:91-98, 1988). Previous biochemical studies strongly suggest that this hybrid is not generated artefactually during the extraction procedures (Keller et al., J Neurochem 36:1389-1397, 1981; Shimizu et al., BBA 748:278-284, 1983). Immunocytological observations have demonstrated the cell specific localization of the alpha subunit in astrocytes and of the gamma subunit in neurons at the adult stage, but failed to identify a cell type containing both the alpha and gamma subunits necessary for the formation of the alpha gamma hybrid isoform (Ghandour et al., Exp Brain Res 41:271-279, 1981; Vinores et al., J Histochem Cytochem 32:1295-1302, 1984; Iwanaga et al., Arch Histol Cytol [Suppl] 52:13-24, 1989). We sought to approach this question by performing in situ hybridization studies in order to visualize the alpha and gamma mRNAs. In agreement with the immunocytological reports, we observe a specific accumulation of the gamma enolase transcripts in neurons and a high accumulation of alpha enolase transcripts in some glial cells such as the ependymocytes lining the ventricles. Our observations, following hybridization with 35S labeled oligonucleotide specific probes on adjacent thin sections, demonstrate for the first time that transcription of both alpha and gamma enolase genes occurs in many neurons of different brain regions. These results render highly probable the formation of the alpha gamma hybrid in mature neurons. Furthermore, we observe a differential expression of the genes encoding the alpha and gamma enolase subunits in various neuronal populations of the brain. The implications of these observations are discussed.

Animals↗
PubMed1992

Activation of the gene encoding the glycolytic enzyme beta-enolase during early myogenesis precedes an increased expression during fetal muscle development.

We define the spatial and temporal patterns of expression of the gene encoding the glycolytic enzyme, beta-enolase, during mouse ontogenesis. Transcripts were detected by in situ hybridization using 35S labelled cRNA probes. The beta-enolase gene is expressed only in striated muscles. It is first detected in the embryo, in the cardiac tube and in newly formed myotomes. In the muscle masses of the limb, beta gene expression occurs at a low level in primary fibers, and subsequently greatly increases at a time which corresponds to the onset of innervation and secondary fiber formation. Later in development, it becomes undetectable in slow-twitch fibers. Our results demonstrate the multistep regulation of the beta-enolase gene. The regulation of this muscle-specific gene in somites is discussed in terms of the myogenic sequences of the MyoD family shown to be present when it is activated.

Animals↗
PubMed1992

Modulation of embryonic and muscle-specific enolase gene products in the developing mouse hindlimb.

During striated muscle development, the glycolytic enzyme enolase (EC 4.2.1.11) undergoes an isozymic transition, from the embryonic alpha alpha form towards the muscle-specific forms alpha beta and beta beta. The regulation of this transition was analyzed in mouse hindlimb muscles from embryonic day 15 (E15) to the adult stage. The quantitative modulations of the levels of the transcripts and subunits of alpha and beta enolase genes were determined. The absolute amounts of alpha and beta enolase mRNAs were estimated using in vitro synthesized transcripts as calibration standards, thus allowing an evaluation of their relative contribution at each stage examined. The muscle-specific beta enolase mRNA is already present at E15. Its level then increases and, from E17, this transcript becomes predominant. This accumulation is biphasic: a steep prenatal rise, corresponding to a net increase per fiber, accompanies the formation of secondary myofibers and the development of innervation; a second rise, beginning at postnatal day 5, is temporally correlated with the definitive specialization of the myofibers. Most of the decrease in alpha mRNA level occurs postnatally. No temporal or quantitative correlation between the up-regulation of beta mRNA and the down-regulation of alpha mRNA levels is observed throughout hindlimb muscle development. Quantitative immunoblotting analyses carried out in parallel show that the enolase isozymic transition is mainly controlled at the mRNA level.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

Murine muscle-specific enolase: cDNA cloning, sequence, and developmental expression.

In vertebrates, the glycolytic enzyme enolase (EC 4.2.1.11) is present as homodimers and heterodimers formed from three distinct subunits of identical molecular weight, alpha, beta, and gamma. We report the cloning and sequencing of a cDNA encoding the beta subunit of murine muscle-specific enolase. The corresponding amino acid sequence shows greater than 80% homology with the beta subunit from chicken obtained by protein sequencing and with alpha and gamma subunits from rat and mouse deduced from cloned cDNAs. In contrast, there is no homology between the 3' untranslated regions of mouse alpha, beta, and gamma enolase mRNAs, which also differ greatly in length. The short 3' untranslated region of beta enolase mRNA accounts for its distinct length, 1600 bases. It is known that a progressive transition from alpha alpha to beta beta enolase occurs in developing skeletal muscle. We show that this transition mainly results from a differential regulation of alpha and beta mRNA levels. Analysis of myogenic cell lines shows that beta enolase gene is expressed at the myoblast stage. Moreover, transfection of premyogenic C3H10T1/2 cells with MyoD1 cDNA shows that the initial expression of beta transcripts occurs during the very first steps of the myogenic pathway, suggesting that it could be a marker event of myogenic lineage determination.

Actins↗
PubMed1986

Isolation of murine neuron-specific and non-neuronal enolase cDNA clones.

cDNA clones corresponding to subunits of neuron-specific (gamma gamma and alpha gamma) and non-neuronal (alpha alpha) enolase isozymes were characterized from two mouse brain cDNA libraries. Our hybridization data revealed a partial homology of the coding sequences of mouse alpha, mouse gamma and rat gamma mRNAs. The noncoding sequences, however, appear to be specific for each mouse mRNA. Although coding for two polypeptides of the same molecular weight, the mRNA for the gamma subunit (2600 bases) is larger than that for the alpha subunit (1900 bases). The noncoding sequences for neuron-specific gamma mRNA (about 1300 bases) are therefore longer than those of the non-nervous tissue specific alpha mRNA (about 600 bases).

Animals↗
PubMed1986

Dissociated cells of foetal rat pallium grown in culture medium supplemented with noradrenaline: effects on the expression of neuron-specific enolase and cell adhesion molecule L1.

The possible influence of noradrenaline (NA) upon cell differentiation has been studied by comparing NA-supplemented cultures of foetal pallial cells with control cultures grown in normal medium. Two days after plating, the cultures were processed for immunocytochemical detection of either an adhesion molecule and marker of early stages of neuronal differentiation (L1) or a marker expressed at relatively late stages (gamma-enolase). In both cases, the NA supplement reduced the expression of the antigen. The effects were more clear-cut for the late than for the early marker. In conclusion, the NA supplement to the culture medium, in our model, seemed to have a 'differentiation regulating' rather than a 'neurotrophic' function sensu stricto. It remains to be clarified, however, to which extent this finding can be generalized to in vivo situations.

Animals↗
PubMed1983

Developmental changes in translatable mRNAs for the cerebral enolase isozymes alphaalpha and gammagamma.

Using the rabbit reticulocyte cell-free translation system we have estimated during ontogenesis the proportions of in vitro translatable alpha and gamma brain enolase mRNAs, which are two minor mRNA species. No polypeptide precursor to these enzyme subunits appears to be synthesized during translation in vitro. During brain development, the changes in translatable alpha and gamma mRNA content seem to parallel those of the corresponding antigens. The proportion of each of the enolase mRNAs is highest in adult mouse brain. Mechanisms controlling alpha and gamma antigen expression are discussed. In order to prepare the specific cDNA probes, purification of alpha and gamma mRNAs was undertaken.

Animals↗