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

Abstract

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.

Novel murine clonal cell lines either express slow or mixed (fast and slow) muscle markers following differentiation in vitro

“…Under these optimized conditions, we were able to show that there was a switch in the expression of enolase from the embryonic ␣-isoform toward the muscle specific ␤-enolase, never previously observed in vitro. It is likely that both heterodimers (␣␤) and homodimers (␤␤) of muscle-specific enolase isoforms are expressed, as previously observed during in vivo muscle development (Keller et al, 1995). These myotubes also express embryonic and neonatal MHC isoforms, similarly to in vivo regenerating myofibers (Kalhovde et al, 2005).…”

“…The active enolase enzyme, which catalyses the interconversion of 2-phospho-glycerate to phosphoenolpyruvate, in the glycolysis pathway is a dimer. The subunits of the dimer are encoded by three different genes, ␣, ␤ and ␥, and both the ␣␤ hetero-and ␤␤ homodimers are specific to striated muscles (Keller et al, 1995;Fougerousse et al, 2001). Expression levels of ␤-enolase are at least twofold higher in fast-twitch muscle, which relies on glycolysis compared to slow muscles such as the Soleus, which mostly relies on oxidative energy metabolism (Keller et al, 1995).…”

“…The subunits of the dimer are encoded by three different genes, ␣, ␤ and ␥, and both the ␣␤ hetero-and ␤␤ homodimers are specific to striated muscles (Keller et al, 1995;Fougerousse et al, 2001). Expression levels of ␤-enolase are at least twofold higher in fast-twitch muscle, which relies on glycolysis compared to slow muscles such as the Soleus, which mostly relies on oxidative energy metabolism (Keller et al, 1995). Thus, ␤-enolase is a good marker of fast-glycolytic fibers (Fougerousse et al, 2001;Hourde et al, 2005Hourde et al, , 2006.…”

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

“…Analytical SDS\PAGE was conducted using the Hoeffer miniature slab gel electrophoresis unit followed by Western blot analyses, as previously described [11].…”

“…In the mouse embryo, β-enolase transcripts are detected in cardiac tube and newly formed myotomes. The gene is further up-regulated at various stages of muscle development, and appears to be under innervational and hormonal control [9][10][11]. At the adult stage, β-enolase transcript and subunit accumulate preferentially in fasttwitch fibres of hindlimb muscles, where the ββ isoenzyme accounts for more than 90 % of total enolase activity [9,[11][12][13].…”