It has been demonstrated previously by us that cyclin D1 and ClC-3 play important roles in regulation of the cell cycle in nasopharyngeal carcinoma cells. The action of cyclin D1 on the functional activities and expression of chloride channels were investigated in nasopharyngeal carcinoma CNE-2Z cells in this study. The results indicated that enhanced cyclin D1 expression increased the activation of volume-activated chloride currents and promoted the expression of ClC-3 chloride channel proteins. The fluorescence resonance energy transfer (FRET) experiments demonstrated that the distance between cyclin D1 and ClC-3 was less than 10nm, and there existed interaction between the two proteins. ClC-3 was partially colocalized with cyclin D1 and CDK4/6. Dialyzing CDK4 antibodies into cells via recording pipettes activated a chloride current, but dialysis of CDK6 antibodies inhibited basal and volume-activated Cl(-) currents. The CDK4/6 inhibitor fascaplysin chloride hydrate (highly selective for CDK4/cyclin D1 with IC(50) = 0.35 μM and less selective for CDK6/D1 with IC(50) = 3.4 μM) activated a chloride current in low concentration, but did not show significantly facilitative effects on the current in high concentration. In conclusion, our data suggest that the ClC-3 chloride channel is an important target of cyclin D1. Cyclin D1 may regulate the functional activities of the chloride channel via CDK4 and CDK6, and/or the expression of the chloride channel. Cyclin D1-CDK4 complexes may phosphorylate chloride channels resulting in inhibition or inactivation of the channels, and cyclin D1-CDK6 complexes may facilitate the activation of chloride channels.
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