Protein kinase A catalytic subunit alters cardiac mitochondrial redox state and membrane potential via the formation of reactive oxygen species.
BACKGROUND
The identification of protein kinase A (PKA) anchoring proteins on mitochondria implies a direct effect of PKA on mitochondrial function. However, little is known about the relationship between PKA and mitochondrial metabolism.


RESULTS
The effects of PKA on the mitochondrial redox state (flavin adenine dinucleotide (FAD)), mitochondrial membrane potential (DeltaPsi(m)) and reactive oxygen species (ROS) production were investigated in saponin-permeabilized rat cardiomyocytes. The PKA catalytic subunit (PKAcat; 50 unit/ml) increased FAD intensities by 56.6+/-7.9% (p<0.01), 2'7'-dichlorofluorescin diacetate (DCF) intensities by 10.5+/-3.3 fold (p<0.01) and depolarized DeltaPsi(m) to 48.1+/-9.5% of the control (p<0.01). Trolox (a ROS scavenger; 100 micromol/L) inhibited PKAcat-induced DeltaPsi(m), FAD and DCF alteration. PKAcat-induced DeltaPsi(m) depolarization was inhibited by an inhibitor of the inner membrane anion channel (IMAC), 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS: 1 micromol/L) but not by an inhibitor of mitochondrial permeability transition pore (mPTP), cyclosporine A (100 nmol/L).


CONCLUSIONS
PKAcat alters FAD and DeltaPsi(m) via mitochodrial ROS generation, and PKAcat-induced DeltaPsi(m) depolarization was not caused by mPTP but rather by DIDS-sensitive mechanisms, which could be caused by opening of the IMAC. The effects of PKA on mitochondrial function could be related to myocardial function under the condition of extensive beta-adrenergic stimulation.
Nagasaka
Shiro
S
Division of Cardiology, Internal Medicine III, Hamamatsu University School of Medicine, Hamamatsu, Japan.
Katoh
Hideki
H
Niu
Chun Feng
CF
Matsui
Saori
S
Urushida
Tsuyoshi
T
Satoh
Hiroshi
H
Watanabe
Yasuhide
Y
Hayashi
Hideharu
H
D000818:Animals; D002384:Catalysis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D007473:Ion Channels; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008929:Mitochondria, Heart / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*
D007473:Ion Channels; D021122:Protein Subunits; D017382:Reactive Oxygen Species; D017868:Cyclic AMP-Dependent Protein Kinases