Nitrosylation of cytochrome c during apoptosis.
Cytochrome c released from mitochondria into the cytoplasm plays a critical role in many forms of apoptosis by stimulating apoptosome formation and subsequent caspase activation. However, the mechanisms regulating cytochrome c apoptotic activity are not understood. Here we demonstrate that cytochrome c is nitrosylated on its heme iron during apoptosis. Nitrosylated cytochrome c is found predominantly in the cytoplasm in control cells. In contrast, when cytochrome c release from mitochondria is inhibited by overexpression of the anti-apoptotic proteins B cell lymphoma/leukemia (Bcl)-2 or Bcl-X(L), nitrosylated cytochrome c is found in the mitochondria. These data suggest that during apoptosis, cytochrome c is nitrosylated in mitochondria and then rapidly released into the cytoplasm in the absence of Bcl-2 or Bcl-X(L) overexpression. In vitro nitrosylation of cytochrome c increases caspase-3 activation in cell lysates. Moreover, the inhibition of intracellular cytochrome c nitrosylation is associated with a decrease in apoptosis, suggesting that cytochrome c nitrosylation is a proapoptotic modification. We conclude that nitrosylation of the heme iron of cytochrome c may be a novel mechanism of apoptosis regulation.
Schonhoff
Christopher M
CM
Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
Gaston
Benjamin
B
Mannick
Joan B
JB
D000165:Acridine Orange / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D003574:Cytochrome c Group / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000494:pharmacology; D006418:Heme / Q000378:metabolism*; D006736:Horses; D006801:Humans; D007501:Iron / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D011233:Precipitin Tests; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction; D013053:Spectrophotometry; D013997:Time Factors; D014466:Ultraviolet Rays; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism
C494811:BCL2L1 protein, human; D003574:Cytochrome c Group; D005456:Fluorescent Dyes; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D019014:fas Receptor; D006418:Heme; D007501:Iron; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000165:Acridine Orange; D009584:Nitrogen