Acid sensitive background potassium channels K2P3.1 and K2P9.1 undergo rapid dynamin-dependent endocytosis

Acid-sensitive, two-pore domain potassium channels, K_2P3.1 and K_2P9.1, are implicated in cardiac and nervous tissue responses to hormones, neurotransmitters and drugs. K_2P3.1 and K_2P9.1 leak potassium from the cell at rest and directly impact membrane potential. Hence altering channel number on the cell surface drives changes in cellular electrical properties. The rate of K_2P3.1 and K_2P9.1 delivery to and recovery from the plasma membrane determines both channel number at the cell surface and potassium leak from cells. This study examines the endocytosis of K_2P3.1 and K_2P9.1. Plasma membrane biotinylation was used to follow the fate of internalized GFP-tagged rat K_2P3.1 and K_2P9.1 transiently expressed in HeLa cells. Confocal fluorescence images were analyzed using Imaris software, which revealed that both channels are endocytosed by a dynamin-dependent mechanism and over the course of 60 min, move progressively toward the nucleus. Endogenous endocytosis of human K_2P3.1 and K_2P9.1 was examined in the lung carcinoma cell line, A549. Endogenous channels are endocytosed over a similar time-scale to the channels expressed transiently in HeLa cells. These findings both validate the use of recombinant systems and identify an endogenous model system in which K_2P3.1 and K_2P9.1 trafficking can be further studied.