PKA rapidly enhances proteasome assembly and activity in in vivo canine hearts.
Proteasome regulates diverse cellular functions by eliminating ubiquitinated proteins. Protein kinase A (PKA) is a key regulator of proteasome activity. However, it remains unknown how PKA regulates proteasome activity and whether it controls proteasome activity in in vivo hearts. Both the in vitro peptidase assay and the in-gel peptidase assays showed that the treatment with PKA for 30 min dose-dependently activated purified 26S proteasome. Simultaneously, PKA treatment enhanced phosphorylation and assembly of purified 26S proteasome evaluated by non-reducing native polyacrylamide gel electrophoresis, either of which was blunted by the pretreatment with a PKA inhibitor, H-89. In in vivo canine hearts, proteasome assembly and activity were enhanced 30 min after the exogenous or endogenous stimulation of PKA by the intracoronary administration of isoproterenol or forskolin for 30 min or by ischemic preconditioning (IP) with 4 times of repeated 5 min of ischemia. The intracoronary administration of H-89 blunted the enhancement of proteasome assembly and activity by IP. Myocardial proteasome activity at the end of ischemia was decreased compared with the control, however, it did not differ from the control in dogs with IP. IP decreased the accumulation of ubiquitinated proteins in the canine ischemia/reperfusion myocardium, which was blunted by the intracoronary administration of a proteasome inhibitor, epoxomicin. However, proteasome activation by IP was not involved in its infarct size-limiting effects. These findings indicate that PKA rapidly enhances proteasome assembly and activity in in vivo hearts. Further investigation will be needed to clarify pathophysiological roles of PKA-mediated proteasome activation in ischemia/reperfusion hearts.
Asai
Mitsutoshi
M
Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
Tsukamoto
Osamu
O
Minamino
Tetsuo
T
Asanuma
Hiroshi
H
Fujita
Masashi
M
Asano
Yoshihiro
Y
Takahama
Hiroyuki
H
Sasaki
Hideyuki
H
Higo
Shuichiro
S
Asakura
Masanori
M
Takashima
Seiji
S
Hori
Masatsugu
M
Kitakaze
Masafumi
M
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004285:Dogs; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008954:Models, Biological; D009203:Myocardial Infarction / Q000139:chemically induced / Q000201:enzymology / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000139:chemically induced / Q000201:enzymology / Q000473:pathology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000302:isolation & purification / Q000378:metabolism*; D061988:Proteasome Inhibitors; D021122:Protein Subunits / Q000378:metabolism; D013997:Time Factors; D054875:Ubiquitination / Q000187:drug effects
D061988:Proteasome Inhibitors; D021122:Protein Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; D046988:Proteasome Endopeptidase Complex; D007545:Isoproterenol