Cyclic nucleotide-gated channels mediate membrane depolarization followingactivation of store-operated calcium entry in endothelial cells

Calcium agonists induce membrane depolarization in endothelial cells throug h an unknown mechanism. Present studies tested the hypothesis that pulmonar y artery endothelial cells express a cyclic nucleotide-gated (CNG) cation c hannel activated by store-operated calcium entry to produce membrane depola rization. In the whole-cell configuration, voltage-clamped cells revealed a large non-inactivating, outwardly rectifying cationic current in the absen ce of extra- or intracellular Ca2+ that was reduced upon replenishment of C a2+. The inward current was non-selective for K+, Na+, Cs+, and Rb+ and was not inhibited by high tetraethylammonium concentrations. cAMP and cGMP sti mulated the current and changed the cation permeability to favor Na+. Moreo ver, 8-bromo-cAMP stimulated the current in voltage-clamped cells in the pe rforated patch mode. The cationic current was inhibited by the CNG channel blocker LY83,583, and reverse transcriptase-polymerase chain reaction cloni ng identified expression of a CNG channel resembling that seen in olfactory neurons. Activation of store-operated calcium entry using thapsigargin inc reased a current through the CNG channel. Stimulation of the current parall eled pulmonary artery endothelial cell membrane depolarization, and both th e current and membrane depolarization were abolished using LY83,583, Taken together, these data demonstrate activation of store-operated calcium entry stimulates a CNG channel producing membrane depolarization. Such membrane depolarization may contribute to slow feedback inhibition of store-operated calcium entry.