The chloride channel ClC‐2 contributes to the inwardly rectifying Cl− conductance in cultured porcine choroid plexus epithelial cells

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Abstract
1 The contribution of ClC-2 protein to the inwardly rectifying Cl− conductance in cultured porcine choroid plexus epithelial cells was investigated using Western analysis and whole-cell current recordings. 2 Inwardly rectifying currents were elicited by hyperpolarizing voltage at a potential more negative than −50 mV in the presence of intracellular protein kinase A (PKA). The relative halide selectivity estimated from the shift in the reversal potential (Erev) was I− > Br− > Cl− > F−. 3 Extracellular vasoactive intestinal peptide (VIP) activated the same currents in a dose-dependent manner with a half-maximal concentration of 167·3 nM. H-89 (a PKA inhibitor) interfered with the current activation by VIP. 4 The Cl− channel was inhibited by external Cd2+, Ba2+or H+, but only weakly inhibited by known Cl− channel blockers including glibenclamide, NPPB, DIDS and anthracene-9-carboxylic acid (9AC). 5 A specific antibody to ClC-2 detected a 79 kDa protein in porcine choroid plexus cells, which was reduced in cells treated with antisense oligodeoxynucleotide for ClC-2. Both PKA and VIP failed to activate the inwardly rectifying Cl− currents in cells transfected with the antisense oligodeoxynucleotide, while they activated the currents in cells transfected with GFP alone or the control oligodeoxynucleotide randomized from antisense oligonucleotide. 6 It is concluded that ClC-2 protein contributes to the inwardly rectifying Cl− conductance in porcine choroid plexus epithelial cells.