title: Glycogen synthase kinase-3 plays a central role in mediating glucocorticoid-induced apoptosis.
abstract: It is still unclear how glucocorticoids (GCs) induce apoptosis of thymocytes and T lymphoma cells. Emergence of GC-resistant lymphoma cells is a major obstacle in GC therapy, emphasizing the need for novel strategies that maintain the sensitivity of lymphoma cells to the proapoptotic effects of GC. We have undertaken a kinome study to elucidate the signal transduction pathways involved in mediating GC-induced apoptosis. Our study shows that glycogen synthase kinase (GSK3) plays a central role in promoting GC-induced apoptosis. In the absence of a ligand, GSK3alpha, but not GSK3beta, is sequestered to the glucocorticoid receptor (GR). Exposure to GCs leads to dissociation of GSK3alpha from GR and subsequent interaction of GSK3alpha and GSK3beta with the proapoptotic Bim protein, an essential mediator of GC-induced apoptosis. Chemical inhibition of GSK3 by SB216763, BIO-Acetoxime, or LiCl and GSK3 inhibition using a dominant-negative mutant of GSK3 impede this cell death process, indicating that GSK3 is involved in transmitting the apoptotic signal. GC resistance in lymphoma cells can be relieved by inhibiting the phosphatidylinositol-3 kinase-Akt survival pathway, which inactivates GSK3. Notch1, a transcription factor frequently activated in T acute lymphoblastic leukemia cells, confers GC resistance through activation of Akt. Altogether, this study illuminates the link connecting upstream GR signals to the downstream mediators of GC-induced apoptosis. Our data suggest that targeting protein kinases involved in GSK3 inactivation should improve the outcome of GC therapy.
authors.affiliation: The Lautenberg Center of Immunology, Institute of Medical Research, Faculty of Medicine, Hebrew University, Jerusalem, Israel.
authors.forename: Rachel
authors.initials: R
authors.lastname: Spokoini
authors.forename: Shlomit
authors.initials: S
authors.lastname: Kfir-Erenfeld
authors.forename: Eitan
authors.initials: E
authors.lastname: Yefenof
authors.forename: Ronit Vogt
authors.initials: RV
authors.lastname: Sionov
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D005938:Glucocorticoids; D008024:Ligands; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011965:Receptors, Glucocorticoid; D051880:Receptors, Notch; D003907:Dexamethasone; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha