Coordinate reciprocal trends in glycolytic and mitochondrial transcript accumulations during the in vitro differentiation of human myoblasts

Abstract

Changes in the mRNA levels during mammalian myogenesis were compared for seven polypeptides of mitochondrial respiration (the mitochondrial DNA-encoded cytochrome oxidase subunit III, ATP synthase subunit 6, NADH dehydrogenase subunits 1 and 2, and 16S ribosomal RNA; the nuclear encoded ATP synthase beta subunit and the adenine nucleotide translocase) and three polypeptides of glycolysis (glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase, and triose-phosphate isomerase). Progressive changes during the conversion from myoblasts to myotubes were monitored under both atmospheric oxygen (normoxic) and hypoxic environments. Northern analyses revealed coordinate, biphasic, and reciprocal expression of the respiratory and glycolytic mRNAs during myogenesis. In normoxic cells the mitochondrial respiratory enzymes were highest in myoblasts, declined 3- to 5-fold during commitment and exist from the cell cycle, and increased progressively as the myotubes matured. By contrast, the glycolytic enzyme mRNAs rose 3- to 6-fold on commitment and then progressively declined. When partially differentiated myotubes were switched to hypoxic conditions, the glycolytic enzyme mRNAs increased and the respiratory mRNAs declined. Hence, the developmental regulation of muscle bioenergetic metabolism appears to be regulated at the pretranslational level and is modulated by oxygen tension.

Down‐regulation of mitochondrial mRNAs in the mdx mouse model for Duchenne muscular dystrophy

“…It is likely that such key genes for ATP production cannot undergo manyfold deregulation, especially in tissues such as brain and muscle, which rely more on mitochondrial ATP production. Variations in the expression of mitochondrial genes were thus reported to be 2-to 4-fold during myogenic differentiation [30], and 1.5-to g-fold in more extreme situations such as mitochondrial myopathies [15] and cancer cells [28]. In addition, the general trend in mdx and DMD muscles of a shift towards oxidative slow-type muscle fibers [3,18,20,25], richer in mitochondrial DNA and RNA [31], partially reduces the decrease in the overall mitochondrial RNA content here.…”

Evolution of the coordinate regulation of glycolytic enzyme genes by hypoxia

“…Southern blots illustrating strong conservation of glycolytic enzyme gene sequences across species. Cells or tissues from the indicated organisms were lysed and genomic DNA was extracted by standard techniques (Webster, 1987;Webster et al, 1990;Lonberg and Gilbert, 1985). DNA was digested with restriction enzyme EcoRI, separated on agarose gels and blotted onto nitrocellulose.…”

Hypoxia Response Elements in the Aldolase A, Enolase 1, and Lactate Dehydrogenase A Gene Promoters Contain Essential Binding Sites for Hypoxia-inducible Factor 1

“…Regardless of etiology, hypoxia is sensed by individual cells which undergo metabolic adaptations to compensate for an inadequate O 2 supply. A major intracellular adaptation to severe hypoxia is the transition from oxidative phosphorylation to glycolysis as the principal means of generating ATP (1,2). When tissue culture cells were subjected to hypoxia, expression of genes encoding respiratory chain components decreased and expression of genes encoding glycolytic enzymes increased (2).…”

“…A major intracellular adaptation to severe hypoxia is the transition from oxidative phosphorylation to glycolysis as the principal means of generating ATP (1,2). When tissue culture cells were subjected to hypoxia, expression of genes encoding respiratory chain components decreased and expression of genes encoding glycolytic enzymes increased (2). As in the case of the EPO (3,4) and VEGF (5-7) genes, increased expression of genes encoding glycolytic enzymes in hypoxic cells is due at least in part to increased gene transcription (8).…”