An essential function of phosphatidylinositol phosphates in activation of plant shaker-type K+ channels.

A prominent regulatory property of plant shaker-type K+ channels is the 'rundown' that causes channel closure upon membrane excision from the cell, implicating intracellular factor(s) in maintaining channel activity. One such factor has been identified as hydrolysable ATP-Mg although the mechanism for ATP function remains unknown. Here we report identification of phosphatidylinositol (PI) phosphates (PIPs) as essential regulators for the voltage-dependent and -independent activation of plant shaker-type channels such as SKOR, an outward rectifying K+ channel. Inhibition of PI kinase activity abolished the function of ATP-Mg in restoration of rundown channel activity, demonstrating that PIPs production by PI kinases and ATP-Mg underlies ATP-induced activation of the rundown channel. We also identified aluminum block as a common feature of the plant shaker-type channels and provided evidence that aluminum block of these channels may result from Al interaction with PIPs.