Abstract Body (Do not enter title and authors here): Background: The voltage-gated potassium ion channel K_V11.1 plays a crucial role in cardiac repolarization. Genetic variants in K_V11.1 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_V11.1 channel blockers act as chemical chaperones (e.g., E-4031) and increase K_V11.1 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_V11.1 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_V11.1 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_V11.1-expressing cells. We used bioinformatic analysis to make a cellular model showcasing likely K_V11.1 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_V11.1 protein-protein interactions that could be therapeutically targeted to improve K_V11.1 trafficking and treat Long QT Syndrome.