Cell cycle-dependent expression of volume-activated chloride currents in nasopharyngeal carcinoma cells

Abstract

Patch-clamping and cell image analysis techniques were used to study the expression of the volume-activated Cl− current, I Cl(vol), and regulatory volume decrease (RVD) capacity in the cell cycle in nasopharyngeal carcinoma cells (CNE-2Z). Hypotonic challenge caused CNE-2Z cells to swell and activated a Cl− current with a linear conductance, negligible time-dependent inactivation, and a reversal potential close to the Cl− equilibrium potential. The sequence of anion permeability was I− > Br− > Cl− > gluconate. The Cl− channel blockers tamoxifen, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and ATP inhibited I Cl(vol). Synchronous cultures of cells were obtained by the mitotic shake-off technique and by a double chemical-block (thymidine and hydroxyurea) technique. The expression of I Cl(vol) was cell cycle dependent, being high in G1 phase, downregulated in S phase, but increasing again in M phase. Hypotonic solution activated RVD, which was cell cycle dependent and inhibited by the Cl− channel blockers NPPB, tamoxifen, and ATP. The expression of I Cl(vol) was closely correlated with the RVD capacity in the cell cycle, suggesting a functional relationship. Inhibition of I Cl(vol) by NPPB (100 μM) arrested cells in G0/G1. The data also suggest that expression of I Cl(vol) and RVD capacity are actively modulated during the cell cycle. The volume-activated Cl− current associated with RVD may therefore play an important role during the cell cycle progress.