Reactive oxygen species signaling facilitates FOXO-3a/FBXO-dependent vascular BK channel β1 subunit degradation in diabetic mice

Diabetes. 2012 Jul;61(7):1860-8. doi: 10.2337/db11-1658. Epub 2012 May 14.


Activity of the vascular large conductance Ca(2+)-activated K(+) (BK) channel is tightly regulated by its accessory β(1) subunit (BK-β(1)). Downregulation of BK-β(1) expression in diabetic vessels is associated with upregulation of the forkhead box O subfamily transcription factor-3a (FOXO-3a)-dependent F-box-only protein (FBXO) expression. However, the upstream signaling regulating this process is unclear. Overproduction of reactive oxygen species (ROS) is a common finding in diabetic vasculopathy. We hypothesized that ROS signaling cascade facilitates the FOXO-3a/FBXO-mediated BK-β(1) degradation and leads to diabetic BK channel dysfunction. Using cellular biology, patch clamp, and videomicroscopy techniques, we found that reduced BK-β(1) expression in streptozotocin (STZ)-induced diabetic mouse arteries and in human coronary smooth muscle cells (SMCs) cultured with high glucose was attributable to an increase in protein kinase C (PKC)-β and NADPH oxidase expressions and accompanied by attenuation of Akt phosphorylation and augmentation of atrogin-1 expression. Treatment with ruboxistaurin (a PKCβ inhibitor) or with GW501516 (a peroxisome proliferator-activated receptor δ activator) reduced atrogin-1 expression and restored BK channel-mediated coronary vasodilation in diabetic mice. Our results suggested that oxidative stress inhibited Akt signaling and facilitated the FOXO-3a/FBXO-dependent BK-β(1) degradation in diabetic vessels. Suppression of the FOXO-3a/FBXO pathway prevented vascular BK-β(1) degradation and protected coronary function in diabetes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arteries / drug effects
  • Arteries / metabolism
  • Cells, Cultured
  • Diabetes Mellitus, Experimental / drug therapy
  • Diabetes Mellitus, Experimental / metabolism*
  • Enzyme Inhibitors / pharmacology
  • F-Box Proteins / metabolism*
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors / metabolism*
  • Glucose / administration & dosage
  • Indoles / pharmacology
  • Large-Conductance Calcium-Activated Potassium Channel beta Subunits / metabolism*
  • Maleimides / pharmacology
  • Mice
  • Microscopy, Video
  • Muscle Proteins / biosynthesis
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism
  • NADPH Oxidases / biosynthesis
  • Patch-Clamp Techniques
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / biosynthesis
  • Protein Kinase C beta
  • Proteolysis
  • Proto-Oncogene Proteins c-akt / metabolism
  • Reactive Oxygen Species / metabolism*
  • SKP Cullin F-Box Protein Ligases / biosynthesis
  • Thiazoles / pharmacology
  • Vasodilation / drug effects
  • Vasodilation / physiology


  • Enzyme Inhibitors
  • F-Box Proteins
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors
  • FoxO3 protein, mouse
  • GW 501516
  • Indoles
  • Large-Conductance Calcium-Activated Potassium Channel beta Subunits
  • Maleimides
  • Muscle Proteins
  • Reactive Oxygen Species
  • Thiazoles
  • ruboxistaurin
  • NADPH Oxidases
  • FBXO32 protein, human
  • Fbxo32 protein, mouse
  • SKP Cullin F-Box Protein Ligases
  • Proto-Oncogene Proteins c-akt
  • Protein Kinase C
  • Protein Kinase C beta
  • Glucose