Altering integrin engagement regulates membrane localization of Kir2.1 channels

Abstract

How ion channels localize and distribute on the cell membrane remains incompletely understood. We show that interventions that vary cell adhesion proteins and cell size also affect membrane current density of inward-rectifier potassium channels (Kir2.1) and profoundly alter action potential shape of excitable cells. Using micropatterning to manipulate the localization and size of focal adhesions (FAs) in single HEK293 cells engineered to stably express Kir2.1 channels or in neonatal rat cardiomyocytes, we establish a robust linear correlation between FA coverage and the amplitude of Kir2.1 current at both the local and whole-cell levels. Confocal microscopy showed that Kir2.1 channels accumulate in membrane proximal to FAs. Selective pharmacological inhibition of key mediators of protein trafficking and spatially dependent alterations in the dynamics of Kir2.1 fluorescent recovery after photobleaching revealed that the Kir2.1 channels are transported to the cell membrane uniformly, but are preferentially internalized by endocytosis distal from FAs. Based on these results, we propose an adhesion-regulated membrane localization of ion channels as a fundamental mechanism to control cellular electrophysiology via mechanochemical signals, independent of the direct ion channel mechanogating.