Protein kinase inhibitors block the stimulation of the AMP‐activated protein kinase by 5‐amino‐4‐imidazolecarboxamide riboside

Abstract

The AMP-activated protein kinase (AMPK) is the central component of a protein kinase cascade that plays a major role in energy sensing. AMPK is activated pharmacologically by 5-amino-4-imidazolecarboxamide (AICA) riboside monophosphate (ZMP), which mimics the e¡ects of AMP on the AMPK cascade. Here we show that uptake of AICA riboside into cells, mediated by the adenosine transport system, is blocked by a number of protein kinase inhibitors. Under these conditions, ZMP does not accumulate to su⁄cient levels to stimulate AMPK. Our results demonstrate that careful interpretation is required when using AICA riboside in conjunction with protein kinase inhibitors to investigate the physiological role of AMPK. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

AMP-activated Protein Kinase and the Regulation of Autophagic Proteolysis

“…4). It was shown previously that compound C, in addition to its action as an inhibitor of AMPK (18), can also inhibit AMPK activity by competing with AICAR transport across the plasma membrane, thus affecting intracellular conversion of AICAR to ZMP (20). This was confirmed in Table 1 showing that 40 M compound C partly inhibited both AICAR consumption and ZMP production.…”

“…Having thus established that compound C can inhibit AMPK activity in intact hepatocytes, whether by a direct effect on the enzyme or indirectly by competing with AICAR for transport into the cells (20), we tested its effect on autophagy. If AMPK activation inhibits autophagy as suggested (11), one would expect compound C to be able to reverse the inhibition of autophagy by metformin.…”

Activation of AMP-activated Protein Kinase Regulates Hippocampal Neuronal pH by Recruiting Na+/H+ Exchanger NHE5 to the Cell Surface

“…One potential caveat to the use of pharmacological agents such as AICAR and CC to manipulate AMPK activity is that they have been reported to have off-target effects that could potentially affect interpretation of the results (67)(68)(69)(70). AICAR is an adenosine analogue that is carried into cells by the equilibrative nucleoside transporter and then phosphorylated to ZMP, an AMP analogue.…”

AMP-activated protein kinase (AMPK) activating agents cause dephosphorylation of Akt and glycogen synthase kinase-3

“…These results demonstrate that AICAR, as well as phenformin, caused dephosphorylation of Akt and GSK3, but this occurred with a time course that was delayed compared with AMPK activation suggesting that AICAR regulated the phosphorylations of Akt and GSK3 independently of its effects on AMPK. Unfortunately, Compound C cannot be used in conjunction with AICAR because it blocks the uptake of AICAR into cells [39] so we could not test directly if blocking AMPK activity with Compound C reduced the AICARinduced dephosphorylation of Akt and GSK3.…”