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.