PGAM-M expression is regulated pretranslationally in hindlimb muscles and under altered loading conditions

• Published in: Journal of applied physiology (1985) 1999-01, Vol.86 (1), p.236-242
• Main Authors: Kell, Rachel, Pierce, Heather, Swoap, Steven J
• Format: Article
• Language: English
• Subjects: Anatomy & physiology; Animals; Biological and medical sciences; Blotting, Western; DNA - biosynthesis; DNA - physiology; Enzymes; Female; Fundamental and applied biological sciences. Psychology; Gene Transfer Techniques; Genes, Reporter; Hindlimb - physiology; Hindlimb Suspension - physiology; Isoenzymes - biosynthesis; Muscle Proteins - biosynthesis; Muscle, Skeletal - enzymology; Muscle, Skeletal - physiology; Muscular system; Phosphoglycerate Mutase - biosynthesis; Rats; Rats, Sprague-Dawley; RNA, Messenger - biosynthesis; Skeletal system; Space life sciences; Striated muscle. Tendons; Transcription, Genetic - physiology; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1999.86.1.236

Department of Biology, Williams College, Williamstown, Massachusetts 01267 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. muscle; transcription; somatic gene transfer; luciferase; fiber type