Mitochondrial matrix phosphoproteome: effect of extra mitochondrial calcium.
Post-translational modification of mitochondrial proteins by phosphorylation or dephosphorylation plays an essential role in numerous cell signaling pathways involved in regulating energy metabolism and in mitochondrion-induced apoptosis. Here we present a phosphoproteomic screen of the mitochondrial matrix proteins and begin to establish the protein phosphorylations acutely associated with calcium ions (Ca(2+)) signaling in porcine heart mitochondria. Forty-five phosphorylated proteins were detected by gel electrophoresis-mass spectrometry of Pro-Q Diamond staining, while many more Pro-Q Diamond-stained proteins evaded mass spectrometry detection. Time-dependent (32)P incorporation in intact mitochondria confirmed the extensive matrix protein phosphoryation and revealed the dynamic nature of this process. Classes of proteins that were detected included all of the mitochondrial respiratory chain complexes, as well as enzymes involved in intermediary metabolism, such as pyruvate dehydrogenase (PDH), citrate synthase, and acyl-CoA dehydrogenases. These data demonstrate that the phosphoproteome of the mitochondrial matrix is extensive and dynamic. Ca(2+) has previously been shown to activate various dehydrogenases, promote the generation of reactive oxygen species (ROS), and initiate apoptosis via cytochrome c release. To evaluate the Ca(2+) signaling network, the effects of a Ca(2+) challenge sufficient to release cytochrome c were evaluated on the mitochondrial phosphoproteome. Novel Ca(2+)-induced dephosphorylation was observed in manganese superoxide dismutase (MnSOD) as well as the previously characterized PDH. A Ca(2+) dose-dependent dephosphorylation of MnSOD was associated with an approximately 2-fold maximum increase in activity; neither the dephosphorylation nor activity changes were induced by ROS production in the absence of Ca(2+). These data demonstrate the use of a phosphoproteome screen in determining mitochondrial signaling pathways and reveal new pathways for Ca(2+) modification of mitochondrial function at the level of MnSOD.
Hopper
Rachel K
RK
Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-1061, USA.
Carroll
Stefanie
S
Aponte
Angel M
AM
Johnson
D Thor
DT
French
Stephanie
S
Shen
Rong-Fong
RF
Witzmann
Frank A
FA
Harris
Robert A
RA
Balaban
Robert S
RS
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015180:Electrophoresis, Gel, Two-Dimensional; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis; D010766:Phosphorylation; D010770:Phosphotransferases / Q000032:analysis; D015398:Signal Transduction / Q000502:physiology; D013194:Staining and Labeling / Q000379:methods; D013482:Superoxide Dismutase / Q000378:metabolism; D013552:Swine
D024101:Mitochondrial Proteins; D013482:Superoxide Dismutase; D010770:Phosphotransferases; D010744:Phosphoric Monoester Hydrolases; D002118:Calcium