Presenter: Elizabeth L. MacKenzie
Advisor(s): Yoshiaki Tsuji
Author(s): Elizabeth L. MacKenzie and Yoshiaki Tsuji
Graduate Program: Environmental and Molecular Toxicology
Title: Calcineurin/NFAT Target the Antioxidant Responsive Element and Mediate Induction of Phase II Genes by Calcium
Abstract: Calcium is a ubiquitous and important second messenger that plays a critical role in the immune response, cardiac development, and osteoclastogenesis; however, calcium is also very toxic to cells and intracellular calcium concentration elevation leads to apoptosis. A mechanism for cytoprotective response to calcium overload has not been identified. Calcineurin (CN) is a calcium dependent phosphatase that is involved in the propagation of apoptosis and inflammation; however, in our current study we discovered that CN induces phase II cytoprotective genes through its classical substrate Nuclear Factor of Activated T-Cells (NFAT). Calcium ionophore (CI) treatment induced both mRNA and protein of Ferritin H and Glutathione-S-transferase (GST) and activated promoter-luciferase reporters containing the respective antioxidant responsive element of each phase II gene. CI induced NFAT nuclear translocation and enhanced its binding to the antioxidant responsive element (ARE) of the human Ferritin H gene, as assessed by electrophoretic mobility shift assay. Transfection of a constitutively active CN mimicked this effect, activating ARE-Luc and enhancing NFAT binding to the ARE. Furthermore, the activation was abrogated by Cyclosporin A (CsA) pretreatment. Taken together these results indicate that CN is a critical upstream sensor of calcium stress that induces the binding of NFAT to the ARE of phase II detoxification genes thereby causing transcriptional activation in a cytoprotective response.