Hypoxia induced hERG trafficking defect leads to apoptosis: involvement of NADPH oxidase generated ROS and Hsp90 (710.2)

Abstract

The alpha subunit of the voltage gated human ether‐go‐go‐related (hERG) potassium channel regulates cell excitability in a broad range of cell lines. hERG channels are also expressed in a variety of cancer cells and control cell proliferation and apoptosis. Sustained hypoxia (SH) alters gating properties of hERG currents in neuroblastoma (SH‐SY5Y) cells. In the present study, we examined the molecular mechanisms underlying SH altered hERG currents in SH‐SY5Y cells. Patch‐clamp studies revealed that 4days of SH decreased hERG tail currents by 40‐50%. SH down regulated the surface expression of the fully glycosylated form (fg) of hERG protein with accumulation of the endoplasmic reticulum (cg) form. These effects were stimulus dependent and reversible. Accumulation of cg form by SH was due to impaired trafficking of hERG protein. Prolonged association with molecular chaperone Hsp90 resulting in complex oligomeric insoluble aggregates contribute to SH induced ER retention and defective trafficking. SH increased NADPHoxidase‐2 (Nox2)‐mediated ROS generation. Silencing Nox2 prevented SH‐induced degradation of fg and accumulation of cg forms. HERG downregulation by hypoxia resulted in reduced cell proliferation, altered cell cycle distribution and increase in apoptotic cells and all these effects were prevented by genetic silencing of Nox2.Grant Funding Source: HL‐90554