Glia maturation factor overexpression in neuroblastoma cells activates glycogen synthase kinase-3beta and caspase-3.
In the present study we report that a replication-defective adenovirus construct of GMF cDNA (GMF-V) induced overexpression of GMF protein in neuroblastoma (N18) cells caused cytotoxicity and loss of cell viability. A significant increase in activation of GSK-3beta occurred after infection with GMF-V when compared with mock and lacZ controls. Overexpression of GMF also increased caspase-3 activity, an early marker of apoptosis. Depletion of GMF gene by introducing GMF-specific siRNA (GsiRNA) completely blocked both activation of GSK-3beta and caspase-3 activation whereas a control scrambled siRNA (CsiRNA) had no effect. A cell-permeable peptide inhibitor of GSK-3beta, and lithium completely prevented GMF-dependent activation of caspase-3. These results demonstrate that GSK-3 mediates activation of the death domain caspase by GMF overexpression. We also show that the phosphorylation of GSK-3-dependent site of Tau was a consequence of GMF-overexpression in N18 cells. Taken together our results imply that GMF is involved in the signaling leading to the activation of GSK-3beta and caspase-3 in N18 cells and strongly suggest its involvement in neurodegeneration since GSK-3beta is known to hyperphosphorylate tau which is associated with the neurotoxicity of neurofibrillary tangles in Alzheimer's disease.
Veterans Affair Medical Center, Iowa City, IA, USA. asgar-zaheer@uiowa.edu
Asgar
A
Zaheer
Scott
S
Knight
Ashna
A
Zaheer
Marcus
M
Ahrens
Shailendra K
SK
Sahu
Baoli
B
Yang
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism*; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D020904:Glia Maturation Factor / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D014162:Transfection
D020904:Glia Maturation Factor; D034741:RNA, Small Interfering; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D053148:Caspase 3