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

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 effects 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 sufficient 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.