Proteasome degradation of GRK2 during ischemia and ventricular tachyarrhythmias in a canine model of myocardial infarction.
Arrhythmia-prone subepicardial border zone (EBZ) tissue demonstrates decreased G protein receptor kinase 2 (GRK2) activity and increased sensitivity to isoproterenol 6-24 h after coronary artery ligation (CAL) in the dog. With the use of a semiquantitative immunofluorescence technique, the relative fluorescence intensity (RF) of GRK2 in EBZ decreased to 24% of that in a remote site (RS) (P < 0.01, n = 30 cells from 3 dogs), whereas GRK5 RF did not change. Confocal studies of cardiac tissue from transgenic mice overexpressing GRK2 validated the use of a semilogarithmic relationship between RF and GRK2 activity. As shown with the use of quantitative real-time RT-PCR, both GRK2 and GRK5 mRNA were not decreased at 24 h in EBZ (n = 6 dogs) relative to RS control, indicating that the decrease of GRK2 in the EBZ is likely due to posttranscriptional degradation following CAL. Pretreatment of six dogs with the selective proteasome inhibitor bortezomib provided 100% (EBZ) and 50% (infarct) protection against loss of GRK2 at 24 h. There was an absence of rapid (>300 beats/min) and very rapid (>360 beats/min) ventricular triplets that are highly predictive of sudden cardiac death during ECG monitoring in the bortezomib-pretreated animals in contrast to nonpretreated infarcted animals. We have demonstrated that the dramatic decrease in GRK2 in cardiac ischemic tissue can be largely blocked by prior proteasome blockade and that this is associated with significant cardioprotection against malignant ventricular tachyarrhythmias.
Dept. of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Xichun
X
Yu
Shijun
S
Huang
Eugene
E
Patterson
Marion W
MW
Garrett
Kenneth M
KM
Kaufman
Jordan P
JP
Metcalf
Meili
M
Zhu
Samuel T
ST
Dunn
David C
DC
Kem
D000818:Animals; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D016757:Death, Sudden, Cardiac; D004285:Dogs; D004562:Electrocardiography; D054774:G-Protein-Coupled Receptor Kinase 5; D015151:Immunoblotting; D008026:Ligation; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009203:Myocardial Infarction / Q000201:enzymology*; D017202:Myocardial Ischemia / Q000201:enzymology*; D009206:Myocardium / Q000166:cytology / Q000201:enzymology; D010496:Pericardium / Q000166:cytology / Q000201:enzymology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017180:Tachycardia, Ventricular / Q000201:enzymology*
D001897:Boronic Acids; D011719:Pyrazines; D000069286:Bortezomib; D017346:Protein Serine-Threonine Kinases; D054774:G-Protein-Coupled Receptor Kinase 5; D046988:Proteasome Endopeptidase Complex