Abstract 4136861: Title: Protein interaction profiling of the Kv11.1 potassium channel reveals new therapeutic targets for Long QT Syndrome

Background: The voltage-gated potassium ion channel K V 11.1 plays a crucial role in cardiac repolarization. Genetic variants in K V 11.1 lead to Long QT Syndrome (LQTS), a condition associated with fatal arrhythmias. Approximately 90% of missense variants linked to LQTS cause intracellular protein transport (trafficking) dysfunction. Some K V 11.1 channel blockers act as chemical chaperones (e.g., E-4031) and increase K V 11.1 channel trafficking. However, these drugs cannot be used in LQTS patients. The underlying mechanisms, such as the protein networks involved in folding and quality control for K V 11.1 channel trafficking remain largely unexplored. Methods: We used affinity-purification (e.g., coimmunoprecipitation) coupled with mass spectrometry to quantify protein interaction changes in human embryonic kidney cells expressing wild-type K V 11.1 or two trafficking-deficient channel variants in the presence or absence of chemical chaperone E-4031. After co-immunoprecipitations and protein digestions, peptides were identified using multiplexed mass spectrometry. Results: We identified 572 protein interactions enriched in K V 11.1-expressing cells. We used bioinformatic analysis to make a cellular model showcasing likely K V 11.1 protein interactions localization from early biogenesis and transcription to plasma membrane expression (Figure 1). We revealed proteins responsible for protein folding, translation, proteasomal degradation, and others with most protein interactions significantly elevated in the genetic variants compared to wild-type (Figure 2). Upon 24-hour treatment with E-4031, some of these interactions were reduced towards wild-type and indicated potential molecular targets for therapeutic intervention (Figure 3). Conclusions: We report the discovery of novel K V 11.1 protein-protein interactions that could be therapeutically targeted to improve K V 11.1 trafficking and treat Long QT Syndrome.