Nuclear redox-signaling is essential for apoptosis inhibition in endothelial cells--important role for nuclear thioredoxin-1.
OBJECTIVE
The redox regulator thioredoxin-1 (Trx) is a potent antioxidative enzyme and exerts important cellular functions. Physiological concentrations of reactive oxygen species (ROS) and of nitric oxide (NO) act as second messengers. Previously, we demonstrated that ROS and NO reduced apoptosis in a Trx-dependent manner. The aim of this study was to determine the underlying mechanisms.


RESULTS
First, we investigated the localization of Trx after H2O2 and NO. Both induced nuclear import of Trx, which required karyopherin-alpha. siRNA against karyopherin-alpha inhibited nuclear import of Trx. Analysis of the Trx amino acid sequence and subsequent immunoprecipitation studies revealed that Trx(K81/82E) is not imported into the nucleus under H2O2 treatment and Trx(K81/82/85E) was retained in the cytosol and induced cell death. Trx(K81/82E) abolished the antiapoptotic capacity of H2O2. Glutathione S-transferase P1 (GST-P1) was identified as one major target regulated by H2O2. siRNA against GST-P1 abolished the antiapoptotic effect of H2O2. Cysteine 69, but not cysteines 32 and 35, which are all required for the complete antiapoptotic function of Trx, is not imported into the nucleus.


CONCLUSIONS
H2O2-induced nuclear import of Trx depends on karyopherin-alpha and NO. Trx-dependent induction of GST-P1 expression is required for apoptosis inhibition in endothelial cells.
Schroeder
Peter
P
Institut fuer Umweltmedizinische Forschung, University of Duesseldorf gGmbH, Duesseldorf, Germany.
Popp
Ruediger
R
Wiegand
Barbara
B
Altschmied
Joachim
J
Haendeler
Judith
J
D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000502:physiology*; D051549:Glutathione S-Transferase pi / Q000378:metabolism*; D006801:Humans; D009569:Nitric Oxide; D017382:Reactive Oxygen Species; D015398:Signal Transduction / Q000502:physiology*; D013879:Thioredoxins / Q000378:metabolism*; D014471:Umbilical Veins; D028901:alpha Karyopherins / Q000378:metabolism