Non‐transcriptional Role of HIF‐2α in Hypoxia‐Evoked hERG K ⁺ Channel Trafficking

Human ether‐a‐go‐go‐related (hERG) K + channel regulates cell excitability in a variety of cells. hERG protein is synthesized in the endoplasmic reticulum (ER) as an immature core glycosylated protein (cg) which is exported to the Golgi apparatus for glycosylation and eventually transported to the plasma membrane as fully glycosylated mature protein (fg). Sustained hypoxia (SH) down regulates the fg form with accumulation of the cg form, resulting in defective trafficking. Systemic and cellular responses to SH require activation of hypoxia‐inducible factors 1 and 2 (HIF‐1 and HIF‐2), which are composed of HIF‐1α or HIF‐2α heterodimerized with HIF‐1β. In the present study, we examined the role of HIFs in SH‐induced hERG trafficking defect. Experiments were performed on SH‐SY5Y neuroblastoma cells exposed to either 4 days of SH (1.5% O 2 ) or normoxia (20% O 2 ). Silencing HIF‐2α but not HIF‐1α by short‐hairpin RNA (shRNA) blocked ER accumulation. Co‐immunoprecipitation assay revealed physical interaction of HIF‐2α with hERG cg form. Silencing HIF‐1β, which is required for HIF‐2 transcriptional activity, did not rescue the SH‐induced hERG trafficking defect, suggesting that HIF‐2α has a non‐transcriptional role in regulating hERG trafficking during hypoxia. Supported by NIH‐HL‐090554