Advancing Kir4.2 Channel Ligand Identification through Collision-Induced Affinity Selection Mass Spectrometry

The inwardly rectifying potassium Kir4.2 channel plays a crucial role in regulating membrane potentials and maintaining potassium homeostasis. Kir4.2 has been implicated in various physiological processes, including insulin secretion, gastric acid regulation, and the pathogenesis of central nervous system diseases. Despite its significance, the number of identified ligands for Kir4.2 remains limited. In this study, we established a method to directly observe ligands avoiding a requirement to observe the high-mass ligand-membrane protein-detergent complexes. This method used collision-induced affinity selection mass spectrometry (CIAS-MS) to identify ligands dissociated from the Kir4.2 channel-detergent complex. The CIAS-MS approach integrated all stages of affinity selection within the mass spectrometer, offering advantages in terms of time efficiency and cost-effectiveness. Additionally, we explored the effect of collisional voltage ramps on the dissociation behavior of the ligand and the ligand at different concentrations, demonstrating dose dependency.