Caveolin‐3 regulates subcellular targeting of Kir2.1 channels

Abstract

Inwardly rectifying potassium channels, Kir2 in particular, are crucial in shaping the action potential and stabilizing the resting potential. However, little is known about the subcellular localization of the Kir2.1 channel, an important component of the background current, IK1, in cardiac myocytes. The present study was designed to determine whether Kir2.1 channels are localized to the caveolar plasma membrane and regulated by caveolin‐3. We found that about 40% (43.81±3.75%, n=3) of the cellular Kir2.1 was retained in the caveolin‐enriched fractions in the adult rat cardiomyocytes. In contrast, clathrin heavy‐chain was detected across a broad range of the gradient fractions. Cholesterol was shown to be enriched in the cavelin‐rich fractions. Co‐immunoprecipitation from cardiac myocytes indicated that Kir2.1 was associated with caveolin‐3. Expression of caveolin‐3 in HEK293T cells transfected with Kir2.1 significantly increased Kir2.1 level in the caveolin‐enriched fraction by 60% (63.26±8.33%, n=3). Further, immunofluorescent staining showed that a significant portion of Kir2.1 colocalized with caveolin‐3 in both transfected HEK293T cells and cardiomyoctes. In conclusion, we demonstrate that a significant portion of Kir2.1 channels targets to the caveolin‐enrich plasma membrane of rat cardiac myocytes, and the caveolae‐targeting of recombinant Kir2.1 channels is regulated by caveolin‐3.