PGAM-M expression is regulated pretranslationally in hindlimb muscles and under altered loading conditions.
Enzymatic activity from the muscle-specific isoform of phosphoglycerate mutase (PGAM-M) is higher within glycolytic skeletal muscles than in oxidative muscles. The hypothesis that PGAM-M is regulated pretranslationally among muscles of the hindlimb was tested using enzymatic assays, Western blots, and Northern blots. We further investigated the regulatory level(s) at which PGAM-M gene expression is controlled during hindlimb unweighting. PGAM-M mRNA and immunoreactive protein levels were fourfold lower in the rat soleus muscle than in the tibialis anterior (TA), plantaris, and extensor digitorum longus muscles. Four weeks of unweighting induced a 2.5-fold increase in PGAM enzymatic activity within the soleus muscle, a 1.8-fold increase in PGAM-M immunoreactivity, and a 3. 5-fold increase in PGAM-M mRNA. To examine potential transcriptional regulatory mechanisms, the proximal 400 bp of the rat PGAM-M promoter were linked to a firefly luciferase and injected into normal and unweighted TA and soleus muscles. Firefly luciferase activity was elevated two- to threefold in the TA and the unweighted soleus over the normal soleus muscle. These data suggest that PGAM-M expression is pretranslationally regulated among muscle types and within unweighted slow-twitch muscle. Furthermore, the proximal 400 bp of the PGAM-M promoter contains cis-acting sequences to allow muscle-type-specific expression of a reporter gene and responsiveness to soleus muscle unweighting.
Kell
R
R
Department of Biology, Williams College, Williamstown, Massachusetts 01267, USA.
Pierce
H
H
Swoap
S J
SJ
D000818:Animals; D015153:Blotting, Western; D004247:DNA / Q000096:biosynthesis / Q000502:physiology; D005260:Female; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D006614:Hindlimb / Q000502:physiology; D019417:Hindlimb Suspension / Q000502:physiology*; D007527:Isoenzymes / Q000096:biosynthesis*; D009124:Muscle Proteins / Q000096:biosynthesis; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000502:physiology*; D010736:Phosphoglycerate Mutase / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic / Q000502:physiology
D007527:Isoenzymes; D009124:Muscle Proteins; D012333:RNA, Messenger; D004247:DNA; D010736:Phosphoglycerate Mutase