CNGA2 contributes to ATP-induced noncapacitative Ca2+ influx in vascular endothelial cells.

ATP can activate several Ca(2+) influx channels in vascular endothelial cells. For example, it stimulates TRPC channels via capacitative and noncapacitative Ca(2+) entry (CCE and non-CCE, respectively) mechanisms; it also directly acts on P2X purinoceptors, resulting in Ca(2+) influx. In the present study, we tested the hypothesis that cyclic nucleotide-gated (CNG) channels also contribute to ATP-induced non-CCE. Two selective inhibitors of CNG channels, L-cis-diltiazem and LY-83583, and CNGA2-specific siRNA were used to study the involvement of CNGA2 in ATP-induced non-CCE in endothelial cells. Ca(2+) influx was studied using Ca(2+)-sensitive fluorescence dyes Fluo-3 and Fluo-4. L-cis-diltiazem and LY-83583 markedly reduced ATP-induced non-CCE in 3 types of endothelial cells including the H5V endothelial cell line, the primary cultured bovine aortic endothelial cells and the endothelial cells within isolated mouse aortic strips. The CNGA2-specific siRNA also reduced the ATP-induced non-CCE in H5V endothelial cells. The Ca(2+) influx was inhibited by Rp-8-CPT-cAMPS, MDL-12330A, SQ-22536 and MRS-2179, but not by ODQ or NF-157. Taken together, the present study demonstrated that CNGA2 channels contribute to ATP-induced non-CCE in vascular endothelial cells. It is likely that ATP acts through P2Y(1)receptors and adenylyl cyclases to stimulate CNGA2.