{"doi":"10.1101/2025.04.25.650734","title":"Hypoxia Exacerbates Kir2.1 Channel Dysfunction in an Andersen-Tawil Syndrome Variant Through a SUMO-Dependent Mechanism","abstract":"Background: Andersen-Tawil Syndrome type 1 (ATS1) is a multisystem channelopathy that predisposes patients to ventricular dysrhythmias and increases the risk of sudden cardiac death. ATS1 arises from loss-of-function mutations in Kir2.1, the inward rectifying potassium channel responsible for most of IK1 in ventricular cardiomyocytes. IK1 is suppressed by SUMOylation, a post-translational modification upregulated in hypoxia, a known proarrhythmic stimulus. We investigated whether current from the ATS1-linked variant Kir2.1-R67Q is inhibited by hypoxia and whether this suppression can be reversed by pharmacological inhibition of the SUMO pathway. Methods: We used patch-clamp recording to measure IK1 and Kir2.1 currents under acute hypoxia, with and without the SUMO pathway inhibitor TAK-981. To quantify SUMOylation stoichiometry, we applied single molecule photobleaching. A multidisciplinary approach combining electrophysiology, molecular modeling, and optogenetic phosphoinositide was used to measure the impact of Kir2.1-R67Q and SUMOylation on channel interactions with phosphatidylinositol 4,5-bisphosphate (PIP2), a required gating cofactor. Results: Kir2.1 can be modified by up to two SUMO proteins attached to diagonally opposite subunits, with each SUMOylation event reducing current by ~20%. Heterozygouse channels containing two R67Q subunits were more susceptible to hypoxic suppression than wild type. TAK-981 blocked hypoxic inhibition of IK1 in ventricular cardiomyocytes and abolished Kir2.1 SUMOylation. In cells expressing Kir2.1-R67Q, TAK-981 significantly increased currents and mitigated hypoxic suppression. Computational modeling and optogenetic dephosphorylation revealed that both the R67Q mutation and converge to disrupt Kir2.1- PIP2 interactions, producing synergistic inhibition of channel function. Conclusions: Hypoxia-induced SUMOylation and the R67Q mutation synergistically suppress Kir2.1 activity by impairing channel-PIP2 interactions. TAK-981 restores IK1 by preventing SUMOylation under hypoxic conditions and enhancing current through Kir2.1-R67Q channels. These findings support a two-hit model of arrhythmogenesis in ATS1 and identify SUMO pathway inhibition as a potential therapeutic strategy to reduce arrhythmic risk in affected patients.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2025,"id":565050,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9565,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":958571,"name":"Yu Xu","orcid":"0000-0002-2428-0428","position":1,"is_corresponding":false},{"id":172832,"name":"Xinyi Ma","orcid":null,"position":2,"is_corresponding":false},{"id":1062888,"name":"Anne K. Yauch","orcid":"0009-0000-1955-3658","position":3,"is_corresponding":false},{"id":605758,"name":"Elizabeth H. Scholl","orcid":"0000-0003-2727-1954","position":4,"is_corresponding":false},{"id":958572,"name":"Yuchen Yang","orcid":"0000-0001-7127-1930","position":5,"is_corresponding":false},{"id":898843,"name":"Kirin D. Gada","orcid":"0000-0002-8621-432X","position":6,"is_corresponding":false},{"id":604907,"name":"Takeharu Kawano","orcid":null,"position":7,"is_corresponding":false},{"id":1468210,"name":"Meng Cui","orcid":"0000-0003-3821-0559","position":8,"is_corresponding":false},{"id":325170,"name":"Leigh D. Plant","orcid":"0000-0002-1622-1655","position":9,"is_corresponding":false},{"id":958573,"name":"Aishwarya Chandrashekar","orcid":"0009-0003-0633-1572","position":0,"is_corresponding":true}],"reference_count":0,"raw_metadata":null,"created_at":"2026-07-19T02:56:24.872312Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}