AMPK activation reduces membrane expression of HCN4 channels in HEK293 cells. Whole-cell recordings from HEK293T cells transfected with hHCN4 in control (black) and after 4-h treatment with the AMPK activator AICAR (1 mM) (red). (A) Representative current traces (left) and activation curves (right). Best fitting with the Boltzmann equation yielded V1/2 = −76.1 ± 1.3 (n = 18) and −75.0 ± 1.6 mV (n = 16) (unpaired t test, P = 0.6105, n.s.); s = 11.8 ± 0.8 and 11.6 ± 0.6 mV, in control and AICAR-treated cells, respectively. (B) Steady-state I/V relations; bar graphs on the left show the distributions of current densities at −130 mV. Mean ± SEM values were −95.3 ± 12.6 (n = 36) and −38.9 ± 5.29 pA/pF (n = 34) in control and AICAR-treated cells, respectively (GLM Gamma, P < 0.0001, ****). Details of statistical analysis are shown in Table S2.