Published online 3 January 2006 doi:10.1084/jem.20050433
Rockefeller University Press, 0022-1007 $8.00
JEM, Volume 203, Number 1, 189-201
Role of mitochondrial glucocorticoid receptor in glucocorticoid-induced apoptosis
Ronit Vogt Sionov1,
Orly Cohen1,
Shlomit Kfir1,
Yael Zilberman2, and
Eitan Yefenof1
1 The Lautenberg Center for General and Tumor Immunology, The Hebrew University-Hadassah Medical School and 2 Department of Pharmacology, Faculty of Dental Medicine Founded by the Alpha-Omega Fraternity, 91120 Jerusalem, Israel
CORRESPONDENCE Eitan Yefenof: yefenof{at}cc.huji.ac.il
The mechanisms by which glucocorticoid receptor (GR) mediates glucocorticoid (GC)-induced apoptosis are unknown. We studied the role of mitochondrial GR in this process. Dexamethasone induces GR translocation to the mitochondria in GC-sensitive, but not in GC-resistant, T cell lines. In contrast, nuclear GR translocation occurs in all cell types. Thymic epithelial cells, which cause apoptosis of the PD1.6 T cell line in a GR-dependent manner, induce GR translocation to the mitochondria, but not to the nucleus, suggesting a role for mitochondrial GR in eliciting apoptosis. This hypothesis is corroborated by the finding that a GR variant exclusively expressed in the mitochondria elicits apoptosis of several cancer cell lines. A putative mitochondrial localization signal was defined to amino acids 558580 of human GR, which lies within the NH2-terminal part of the ligand-binding domain. Altogether, our data show that mitochondrial and nuclear translocations of GR are differentially regulated, and that mitochondrial GR translocation correlates with susceptibility to GC-induced apoptosis.
Abbreviations used: ALL, acute lymphoblastic leukemia; COX, cytochrome C oxidase; DBD, DNA-binding domain; Dex, dexamethasone; GC, glucocorticoid; GR, glucocorticoid receptor; GRE, glucocorticoid response element; hGR, human GR; LBD, ligand binding domain; mGR, membrane glucocorticoid receptor; MLS, mitochondrial localization signal; NLS, nuclear localization signal; PML, promyelocytic leukemia; TEC, thymic epithelial cell.

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