title: Redox-sensitive sulfenic acid modification regulates surface expression of the cardiovascular voltage-gated potassium channel Kv1.5.
abstract: BACKGROUND
  Kv1.5 (KCNA5) is expressed in the heart, where it underlies the I(Kur) current that controls atrial repolarization, and in the pulmonary vasculature, where it regulates vessel contractility in response to changes in oxygen tension. Atrial fibrillation and hypoxic pulmonary hypertension are characterized by downregulation of Kv1.5 protein expression, as well as with oxidative stress. Formation of sulfenic acid on cysteine residues of proteins is an important, dynamic mechanism for protein regulation under oxidative stress. Kv1.5 is widely reported to be redox-sensitive, and the channel possesses 6 potentially redox-sensitive intracellular cysteines. We therefore hypothesized that sulfenic acid modification of the channel itself may regulate Kv1.5 in response to oxidative stress.
  
  
  OBJECTIVE
  To investigate how oxidative stress, via redox-sensitive modification of the channel with sulfenic acid, regulates trafficking and expression of Kv1.5.
  
  
  RESULTS
  Labeling studies with the sulfenic acid-specific probe DAz and horseradish peroxidase-streptavidin Western blotting demonstrated a global increase in sulfenic acid-modified proteins in human patients with atrial fibrillation, as well as sulfenic acid modification to Kv1.5 in the heart. Further studies showed that Kv1.5 is modified with sulfenic acid on a single COOH-terminal cysteine (C581), and the level of sulfenic acid increases in response to oxidant exposure. Using live-cell immunofluorescence and whole-cell voltage-clamping, we found that modification of this cysteine is necessary and sufficient to reduce channel surface expression, promote its internalization, and block channel recycling back to the cell surface. Moreover, Western blotting demonstrated that sulfenic acid modification is a trigger for channel degradation under prolonged oxidative stress.
  
  
  CONCLUSIONS
  Sulfenic acid modification to proteins, which is elevated in diseased human heart, regulates Kv1.5 channel surface expression and stability under oxidative stress and diverts channel from a recycling pathway to degradation. This provides a molecular mechanism linking oxidative stress and downregulation of channel expression observed in cardiovascular diseases.
authors: Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI 48109-5632, USA.
authors: Laurie K
authors: LK
authors: Svoboda
authors: Khalilah G
authors: KG
authors: Reddie
authors: Lian
authors: L
authors: Zhang
authors: Eileen D
authors: ED
authors: Vesely
authors: Elizabeth S
authors: ES
authors: Williams
authors: Sarah M
authors: SM
authors: Schumacher
authors: Ryan P
authors: RP
authors: O'Connell
authors: Robin
authors: R
authors: Shaw
authors: Sharlene M
authors: SM
authors: Day
authors: Justus M
authors: JM
authors: Anumonwo
authors: Kate S
authors: KS
authors: Carroll
authors: Jeffrey R
authors: JR
authors: Martens
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001281:Atrial Fibrillation / Q000378:metabolism* / Q000473:pathology; D016022:Case-Control Studies; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D051666:Kv1.5 Potassium Channel / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D023421:Models, Animal; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D051381:Rats; D017382:Reactive Oxygen Species; D015398:Signal Transduction / Q000502:physiology; D013434:Sulfenic Acids / Q000378:metabolism*
chemical_list: D051666:Kv1.5 Potassium Channel; D017382:Reactive Oxygen Species; D013434:Sulfenic Acids