%0 Journal Article
%A Rojo, Ana 
%A Salinas, Marta 
%A Salazar Roa, María
%A Takahashi, Shigeru 
%A Suske, Guntram 
%A Calvo, Victor 
%A Sagarra, María Rosa de 
%A Cuadrado, Antonio 
%T Regulation of heme oxygenase-1 gene expression through the phosphatidylinositol 3-kinase/PKC-zeta pathway and Sp1
%D 2006
%@ 0891-5849
%U https://hdl.handle.net/20.500.14352/97400
%X The molecular mechanisms involved in modulation of the antioxidant cell defence by survival signals remain largely unexplored. Here, we report a mechanistic connection between the survival signal elicited by nerve growth factor (NGF) and the antioxidant cell defence represented by heme oxygenase-1 (HO-1) at the level of a newly identified Sp1 site in the human ho1 proximal promoter. By using luciferase reporter constructs we identified a PI3K-responsive region containing a GC-box that resembled the response element for Sp1. Indeed, transfection of Sp1-deficient SL2 cells, electrophoretic mobility shift assays, the use of the GC-box binding drug mithramycin, and mutation of the GC-box provided evidence for a Sp1-like site in the PI3K-sensitive region. Then, we observed with the use of a Sp1–Gal4 chimera that PI3K regulates the transactivating capacity of Sp1. Cotransfection of active PI3K and PKC-ζ expression vectors resulted in substantial increase of Sp1 phosphorylation and in synergistic activation of both Sp1-Gal4 and endogenous Sp1. Moreover, these effects were mimicked by cotransfection of active MEK and ERK expression vectors and were blocked by the MEK inhibitor PD98059. Inhibition of HO-1 with Sn protoporphyrin IX and blockage of Sp-1-mediatied upregulation of HO-1 with mithramycin attenuated antioxidant and cytoprotective functions of NGF against hydrogen peroxide. This study elucidates how NGF contributes to protection of target cells against oxidative stress.
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