Contraction-mediated phosphorylation of AMPK is lower in skeletal muscle of adenylate kinase-deficient mice

1 Medical Pharmacology and Physiology, College of Medicine, University of Missouri-Columbia, Columbia, Missouri; 2 Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, Netherlands; and 3 Biomedical Sciences, College of Veterinary Medicine and 4 Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, Missouri Submitted 22 July 2005 ; accepted in final form 21 September 2005 The activity of AMP-activated protein kinase (AMPK) increases during muscle contractions as a result of elevated AMP concentration. We tested whether activation of AMPK would be altered during contractions in adenylate kinase (AK) 1-deficient (AK1 –/– ) mice, because they have a reduced capacity to form AMP. The right gastrocnemius-soleus-plantaris muscle group was stimulated via the sciatic nerve at 2 Hz for 30 min in both wild-type (WT) and AK1 –/– animals. Initial force production was not different between the two groups (129.2 ± 3.3 g vs. 140.9 ± 8.5 g for WT and AK1 –/– , respectively); however, force production by AK1 –/– mice was significantly greater over the 30-min stimulation period, and final tension was 85 ± 4.5% of initial in WT and 102 ± 3.2% of initial in AK1 –/– mice. Western blot analysis showed that AMPK phosphorylation with contractions was clearly increased in WT muscles (4.0 ± 1.1 above resting values), but did not change noticeably with AK deficiency (1.6 ± 0.4 above WT resting values). However, increases in phosphorylation of acetyl CoA carboxylase were robust in both WT and AK1 –/– muscles and not different between the two groups. These results suggest that reduced formation of AMP during contractions in skeletal muscle of AK1 –/– mice results in reduced phosphorylation of AMPK. However, altered AMPK signaling was not apparent in the phosphorylation status of acetyl CoA carboxylase, a typical marker of AMPK activity. acetyl CoA carboxylase; muscle contraction Address for reprint requests and other correspondence: R. L. Terjung, Biomedical Sciences, E102 Vet. Med. Bldg., Univ. of Missouri-Columbia, Columbia, MO 65211 (e-mail: terjungr{at}missouri.edu )