CK1δ inhibition disrupts the PAC-2 cell circadian clock.

Dose-response of PF-670462, a pan-CK1δ/ε inhibitor and PF-4800567, a selective inhibitor of CK1ε, in the zebrafish PAC-2 cell line. Bioluminescence assay of cells transfected with per1b:Luc (A and C) or Ebox:Luc (B and D), and treated with PF-670462 (A and B) or with PF-4800567 (C and D) at the indicated time (arrow). Cells were maintained under LD cycles, and then the inhibitor was added to the cell culture 1.5 h before lights on (black arrows) at different concentrations (PF-670462: 0.5 μM- light blue line, 1 μM- blue line, 2 μM-green line, 5 μM- red line. PF-4800567: 5 μM- green line, 7.5 μM- light blue line and 10 μM- blue line). Controls were treated with DMSO (black line) or with culture medium (gray line). After three LD cycles cell were transferred to DD. Bioluminescence is plotted on the y-axis and time (hours) on the x-axis. White/black bars show the light and dark periods, respectively. Clock-controlled rhythmic promoter was disrupted by PF-67046 but not by PF-4800567, thus CK1δ activity appears to be important for peripheral circadian clock function.