Vascular K ATP channels: dephosphorylation and deactivation.

Vascular ATP-sensitive potassium (K(ATP)) channels (Kir6.1/SUR2B) are regulated by both cell metabolism and chemical transmitters. They are the target for a number of vasodilators and vasoconstrictors whose mechanisms of action involve activation of protein kinase A (PKA) and protein kinase C (PKC), respectively. The article by Orie et al. in this issue of the BJP sheds new light on the (opposing) role of protein phosphatases in the regulation of this ion channel activity. Their data suggest that calcineurin, a Ca(2+)-dependent protein phosphatase, modulates Kir6.1/SUR2B by inhibiting PKA-dependent phosphorylation of the channel. This novel mechanism may provide a modulation opposing the action of vasodilators on the K(ATP) channel.