title: Reactive oxygen species signaling facilitates FOXO-3a/FBXO-dependent vascular BK channel β1 subunit degradation in diabetic mice.
abstract: 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.
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota, USA. lu.tong@mayo.edu
authors.forename: Tong
authors.initials: T
authors.lastname: Lu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Chai
authors.forename: Ling
authors.initials: L
authors.lastname: Yu
authors.forename: Livius V
authors.initials: LV
authors.lastname: d'Uscio
authors.forename: Zvonimir S
authors.initials: ZS
authors.lastname: Katusic
authors.forename: Tongrong
authors.initials: T
authors.lastname: He
authors.forename: Hon-Chi
authors.initials: HC
authors.lastname: Lee
mesh_terms: D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044783:F-Box Proteins / Q000378:metabolism*; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005947:Glucose / Q000008:administration & dosage; D007211:Indoles / Q000494:pharmacology; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000378:metabolism*; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D018715:Microscopy, Video; D009124:Muscle Proteins / Q000096:biosynthesis; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D019255:NADPH Oxidases / Q000096:biosynthesis; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D064546:Protein Kinase C beta; D059748:Proteolysis; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D044843:SKP Cullin F-Box Protein Ligases / Q000096:biosynthesis; D013844:Thiazoles / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D044783:F-Box Proteins; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; C425931:GW 501516; D007211:Indoles; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D008301:Maleimides; D009124:Muscle Proteins; D017382:Reactive Oxygen Species; D013844:Thiazoles; C099154:ruboxistaurin; D019255:NADPH Oxidases; C440907:FBXO32 protein, human; C486691:Fbxo32 protein, mouse; D044843:SKP Cullin F-Box Protein Ligases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D005947:Glucose