AMP-activated protein kinase (AMPK) plays a key role in energy homeostasis and is activated in response to contraction-induced ATP depletion in skeletal muscle via a rise in intracellular AMP/ADP concentrations. AMP can be deaminated by AMP-deaminase to IMP, which is hydrolysed to inosine by cytosolic 5'-nucleotidase-II (NT5C2). AMP can also be hydrolysed to adenosine by cytosolic 5'-nucleotidase-IA (NT5C1A). Previous gene silencing and overexpression studies indicated control of AMPK activation by NT5C enzymes. In the present study using gene knockout mouse models, we investigated effects of NT5C1A and NT5C2 deletion on intracellular adenine nucleotide levels and AMPK activation in electrically stimulated skeletal muscles. Surprisingly, NT5C enzyme knockout did not lead to enhanced AMP or ADP concentrations in response to contraction, with no potentiation of increases in AMPK activity in extensor digitorum longus (EDL) and soleus mouse muscles. Moreover, dual blockade of AMP metabolism in EDL using an AMPD inhibitor combined with NT5C1A deletion did not enhance rises in AMP and ADP or increased AMPK activation by electrical stimulation. The results on muscles from the NT5C knockout mice contradict previous findings where AMP levels and AMPK activity were shown to be modulated by NT5C enzymes.
- Copyright © 2017, American Journal of Physiology-Endocrinology and Metabolism