Polarized localization of phosphatidylserine in the endothelium regulates Kir2.1

Lipid regulation of ion channels is largely explored using in silico modeling with minimal experimentation in intact tissue; thus, the functional consequences of these predicted lipid -channel interactions within native cellular environments remain elusive. The goal of this study is to investigate how lipid regulation of endothelial Kir2.1 - an inwardly rectifying potassium channel that regulates membrane hyperpolarization - contributes to vasodilation in resistance arteries. First, we show that phosphatidylserine (PS) localizes to a specific subpopulation of myoendothelial junctions (MEJs), crucial signaling microdomains that regulate vasodilation in resistance arteries, and in silico data have implied that PS may compete with phosphatidylinositol 4,5-bisphosphate (PIP2) binding on Kir2.1. We found that Kir2.1-MEJs also contained PS, possibly indicating an interaction where PS regulates Kir2.1. Electrophysiology experiments on HEK cells demonstrate that PS blocks PIP2 activation of Kir2.1 and that addition of exogenous PS blocks PIP2-mediated Kir2.1 vasodilation in resistance arteries. Using a mouse model lacking canonical MEJs in resistance arteries (Elnfl/fl/Cdh5-Cre), PS localization in endothelium was disrupted and PIP2 activation of Kir2.1 was significantly increased. Taken together, our data suggest that PS enrichment to MEJs inhibits PIP2-mediated activation of Kir2.1 to tightly regulate changes in arterial diameter, and they demonstrate that the intracellular lipid localization within the endothelium is an important determinant of vascular function.

Automated summary

The study investigates lipid regulation of the endothelial Kir2.1 channel and its contribution to vasodilation in resistance arteries. It is found that phosphatidylserine (PS) competes with phosphatidylinositol 4,5-bisphosphate (PIP2) binding on Kir2.1, and PS blocks PIP2 activation of Kir2.1 in HEK cells and resistance arteries. The localization of intracellular lipids within the endothelium is an important determinant of vascular function.