Map of the Kir2.1 interactome using BioID

Kir2.1, an inward rectifier potassium channel, plays an important role in controlling membrane potential specially in cardiomyocytes. Here we explore its interactome via proximity biotin labeling and affinity purification approach (BioID). First, BioID membrane controls were generated with randomly selected transmembrane domains from yeast proteins, demonstrating the identification of membrane-associated proteins more than GFP or NLS controls. Using this control and a mutation from Andersen-Tawil syndrome which causes Kir2.1 Golgi accumulation, we have identified the most comprehensive Kir2.1 interactome and also found clues to its spatial information in subcellular levels. The interactome is showing that Kir2.1 in plasma membrane is surrounded by desmosome, integrin, cadherin and dystrophin-glycoprotein complex complexes, and supported by MAGUK family scaffold proteins. On the other hand, Kir2.1 mutant BioID revealed the COPII-mediated delivery of Kir2.1 from ER to Golgi and lysosome-mediated degradation of Golgi-accumulated and/or retrograde Kir2.1. Validating the interactome with co-immunoprecipitation, confocal microscope, and patch clamp analysis, we concluded that Kir2.1 is located in the defined membrane environment and is actively regulated by endosomal sorting for lysosome degradation.