Autocatalytic tyrosine nitration of prostaglandin endoperoxide synthase-2 in LPS-stimulated RAW 264.7 macrophages.
In the literature, biological tyrosine nitrations have been reported to depend not only on peroxynitrite but also on nitrite/hydrogen peroxide linked to catalysis by myeloperoxidase. In endotoxin-stimulated RAW 264.7 macrophages, we have detected a major nitrotyrosine positive protein band around 72 kDa and identified it as prostaglandin endoperoxide synthase-2 (PGHS-2). Isolated PGHS-2 in absence of its substrate arachidonate was not only tyrosine-nitrated with peroxynitrite, but also with nitrite/hydrogen peroxide in complete absence of myeloperoxidase. Our data favor an autocatalytic activation of nitrite by PGHS-2 with a subsequent nitration of the essential tyrosine residue in the cyclooxygenase domain. Under inflammatory conditions, nitrite formed via NO-synthase-2 may therefore act as an endogenous regulator for PGHS-2 in stimulated macrophages. Nitration of PGHS-2 by the autocatalytic activation of nitrite further depends on the intracellular concentration of arachidonate since arachidonate reacted competitively with nitrite and could prevent PGHS-2 from nitration when excessively present.
Schildknecht
Stefan
S
Department of Biology, University of Konstanz, Germany.
Heinz
Kathrin
K
Daiber
Andreas
A
Hamacher
Jürg
J
Kavaklí
Cengiz
C
Ullrich
Volker
V
Bachschmid
Markus
M
D000818:Animals; D002384:Catalysis; D002460:Cell Line; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D009566:Nitrates / Q000276:immunology / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000276:immunology / Q000378:metabolism*; D014443:Tyrosine / Q000276:immunology / Q000378:metabolism*
D008070:Lipopolysaccharides; D009566:Nitrates; D014443:Tyrosine; D011451:Prostaglandin-Endoperoxide Synthases