N-glycosylation–dependent regulation of hK(2P)17.1 currents

Two pore-domain potassium (K(2P)) channels mediate potassium background currents that stabilize the resting membrane potential and facilitate action potential repolarization. In the human heart, hK(2P)17.1 channels are predominantly expressed in the atria and Purkinje cells. Reduced atrial hK(2P)17.1 protein levels were described in patients with atrial fibrillation or heart failure. Genetic alterations in hK(2P)17.1 were associated with cardiac conduction disorders. Little is known about posttranslational modifications of hK(2P)17.1. Here, we characterized glycosylation of hK(2P)17.1 and investigated how glycosylation alters its surface expression and activity. Wild-type hK(2P)17.1 channels and channels lacking specific glycosylation sites were expressed in Xenopus laevis oocytes, HEK-293T cells, and HeLa cells. N-glycosylation was disrupted using N-glycosidase F and tunicamycin. hK(2P)17.1 expression and activity were assessed using immunoblot analysis and a two-electrode voltage clamp technique. Channel subunits of hK(2P)17.1 harbor two functional N-glycosylation sites at positions N65 and N94. In hemi-glycosylated hK(2P)17.1 channels, functionality and membrane trafficking remain preserved. Disruption of both N-glycosylation sites results in loss of hK(2P)17.1 currents, presumably caused by impaired surface expression. This study confirms diglycosylation of hK(2P)17.1 channel subunits and its pivotal role in cell-surface targeting. Our findings underline the functional relevance of N-glycosylation in biogenesis and membrane trafficking of ion channels.