FACS experiments on HEK293T cells transfected with a plasmid carrying the construct GFP-hHCN4-HA-tag. The green GFP signal reports in this case the synthesis of hHCN4 and the red HA-tag the positive insertion of the channel in the plasma membrane. Left: Representative histogram of normalized red fluorescence intensity signal in green positive population. Right: Plot of the geometric means of six technical replicates. APC geometric means were 3,135 ± 367 in control runs, and 2,542 ± 430 after AICAR treatment (paired t test, P = 0.044).