AMP-activated protein kinase activator A-769662 is an inhibitor of the Na+-K+-ATPase

Dept. of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
AJP Cell Physiology (Impact Factor: 3.78). 10/2009; 297(6):C1554-66. DOI: 10.1152/ajpcell.00010.2009
Source: PubMed


Muscle contraction and metabolic stress are potent activators of AMP-activated protein kinase (AMPK). AMPK restores energy balance by activating processes that produce energy while inhibiting those that consume energy. The role of AMPK in the regulation of active ion transport is unclear. Our aim was to determine the effect of the AMPK activator A-769662 on Na(+)-K(+)-ATPase function in skeletal muscle cells. Short-term incubation of differentiated rat L6 myotubes with 100 microM A-769662 increased AMPK and acetyl-CoA carboxylase (ACC) phosphorylation in parallel with decreased Na(+)-K(+)-ATPase alpha(1)-subunit abundance at the plasma membrane and ouabain-sensitive (86)Rb(+) uptake. Notably, the effect of A-769662 on Na(+)-K(+)-ATPase was similar in muscle cells that do not express AMPK alpha(1)- and alpha(2)-catalytic subunits. A-769662 directly inhibits the alpha(1)-isoform of the Na(+)-K(+)-ATPase, purified from rat and human kidney cells in vitro with IC(50) 57 microM and 220 microM, respectively. Inhibition of the Na(+)-K(+)-ATPase by 100 microM ouabain decreases sodium pump activity and cell surface abundance, similar to the effect of A-769662, without affecting AMPK and ACC phosphorylation. In conclusion, the AMPK activator A-769662 inhibits Na(+)-K(+)-ATPase activity and decreases the sodium pump cell surface abundance in L6 skeletal muscle cells. The effect of A-769662 on sodium pump is due to direct inhibition of the Na(+)-K(+)-ATPase activity, rather than AMPK activation. This AMPK-independent effect on Na(+)-K(+)-ATPase calls into question the use of A-769662 as a specific AMPK activator for metabolic studies.

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Available from: Alexander V Chibalin, Jan 19, 2016
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    • "Pharmacologic studies have also shown that A-769662 has good specificity with respect to other protein kinases [21] [23]. There is limited evidence to suggest the possibility of off-target effects, including inhibition of proteasomal [40] and sodium potassium ATPase [41] activities. In this regard, our observation that A- 769662 had no effect in AMPK-inactivated KD hearts is a critical finding and points to the AMPK-dependence of this agent. "
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