Adenylate Kinase 1 Deficiency Induces Molecular and Structural Adaptations to Support Muscle Energy Metabolism

Abstract

Genetic ablation of adenylate kinase 1 (AK1), a member of the AK family of phosphotransfer enzymes, disturbs muscle energetic economy and decreases tolerance to metabolic stress, despite rearrangements in alternative high energy phosphoryl transfer pathways. To define the mechanisms of this adaptive response, soleus and gastrocnemius muscles from AK1−/− mice were characterized by cDNA array profiling, Western blot and ultrastructural analysis. We demonstrate that AK1 deficiency induces fiber-type specific variation in groups of transcripts involved in glycolysis and mitochondrial metabolism and in gene products defining structural and myogenic events. This was associated with increased phosphotransfer capacities of the glycolytic enzymes pyruvate kinase and 3-phosphoglycerate kinase. Moreover, in AK1−/− mice, fast-twitch gastrocnemius, but not slow-twitch soleus, had an increase in adenine nucleotide translocator (ANT) and mitochondrial creatine kinase protein, along with a doubling of the intermyofibrillar mitochondrial volume. These results provide molecular evidence for wide-scale remodeling in AK1-deficient muscles aimed at preservation of efficient energetic communication between ATP producing and utilizing cellular sites. Genetic ablation of adenylate kinase 1 (AK1), a member of the AK family of phosphotransfer enzymes, disturbs muscle energetic economy and decreases tolerance to metabolic stress, despite rearrangements in alternative high energy phosphoryl transfer pathways. To define the mechanisms of this adaptive response, soleus and gastrocnemius muscles from AK1−/− mice were characterized by cDNA array profiling, Western blot and ultrastructural analysis. We demonstrate that AK1 deficiency induces fiber-type specific variation in groups of transcripts involved in glycolysis and mitochondrial metabolism and in gene products defining structural and myogenic events. This was associated with increased phosphotransfer capacities of the glycolytic enzymes pyruvate kinase and 3-phosphoglycerate kinase. Moreover, in AK1−/− mice, fast-twitch gastrocnemius, but not slow-twitch soleus, had an increase in adenine nucleotide translocator (ANT) and mitochondrial creatine kinase protein, along with a doubling of the intermyofibrillar mitochondrial volume. These results provide molecular evidence for wide-scale remodeling in AK1-deficient muscles aimed at preservation of efficient energetic communication between ATP producing and utilizing cellular sites. adenylate kinase 1 glyceraldehyde-3-phosphate dehydrogenase creatine kinase muscle-type CK relative light unit arbitrary units pyruvate kinase 3-phosphoglycerate kinase myosin heavy chain lactate dehydrogenase myosin light chain glycerol-3-phosphate dehydrogenase nucleoside diphosphokinase glutamate dehydrogenase The metabolic status of skeletal muscle is reciprocally linked to fiber-type composition and functional demand. This implies that myocytes must undergo constant reprogramming of their gene expression in response to fluctuations in intrinsic or extrinsic physiological signals such as intracellular Ca2+ concentrations, hormonal stimulation, or altered workload (1Olson E.N. Williams R.S. Bioessays. 2000; 22: 510-519Crossref PubMed Scopus (221) Google Scholar, 2Pette D. Vrbova G. Muscle Nerve. 1999; 22: 666-677Crossref PubMed Scopus (206) Google Scholar, 3Schiaffino S. Reggiani C. Physiol. Rev. 1996; 76: 371-423Crossref PubMed Scopus (1277) Google Scholar). Moreover, disturbance of cellular energetics by metabolic inhibitors or genetic mutation may also induce alterations in the muscle phenotype via changes in the gene program for fiber-type specification (4van Deursen J. Heerschap A. Oerlemans F. Ruitenbeek W. Jap P. ter Laak H. Wieringa B. Cell. 1993; 74: 621-631Abstract Full Text PDF PubMed Scopus (277) Google Scholar, 5Moerland T.S. Wolf N.G. Kushmerick M.J. Am. J. Physiol. 1989; 257: C810-C816Crossref PubMed Google Scholar, 6Bergeron R. Ren J.M. Cadman K.S. Moore I.K. P