The glycolytic enzyme enolase (EC 4.2.1.11) is active as dimers formed from three subunits encoded by different genes. The embryonic αα isoform remains distributed in many adult cell types, whereas a transition towards ββ and γγ 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 ββ-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 β-enolase subunit that changes with in i o and in itro maturation. A basic carboxypeptidase appears to be involved in generating an acidic β-enolase variant, and may regulate plasminogen binding by this subunit. We show for the

The dopamine transporter is an essential component of the dopaminergic synapse. It is located in the presynaptic neurons and regulates extracellular dopamine levels. We generated a transgenic mouse line expressing the Cre recombinase under the control of the regulatory elements of the dopamine transporter gene, for investigations of gene function in dopaminergic neurons. The codon‐improved Cre recombinase (iCre) gene was inserted into the dopamine transporter gene on a bacterial artificial chromosome. The pattern of expression of the bacterial artificial chromosome–dopamine transporter–iCre transgene was similar to that of the endogenous dopamine transporter gene, as shown by immunohistochemistry. Recombinase activity was further studied in mice carrying both the bacterial artificial chromosome–dopamine transporter–iCre transgene and a construct expressing the β‐galactosidase gene after Cre‐mediated recombination. In situ studies showed that β‐galactosidase (5‐bromo‐4‐chloroindol‐3‐yl β‐d‐galactoside staining) and the dopamine transporter (immunofluorescence) had identical distributions in the ventral midbrain. We used this animal model to study the distribution of dopamine transporter gene expression in hypothalamic nuclei in detail. The expression profile of tyrosine hydroxylase (an enzyme required for dopamine synthesis) was broader than that of β‐galactosidase in A12 to A15. Thus, only a fraction of neurons synthesizing dopamine expressed the dopamine transporter gene. The bacterial artificial chromosome–dopamine transporter–iCre transgenic line is a unique tool for targeting Cre/loxP‐mediated DNA recombination to dopamine neurons for studies of gene function or for labeling living cells, following the crossing of these mice with transgenic Cre reporter lines producing fluorescent proteins.

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.