Haloperidol induces the nuclear translocation of phosphatidylinositol 3'-kinase to disrupt Akt phosphorylation in PC12 cells.
OBJECTIVE
The antipsychotic drug haloperidol (HAL) has been linked to apoptosis and to inhibition of prosurvival Akt signalling in pheochromocytoma (PC12) and neuronal cell cultures. However, the mechanism involved is unclear.


METHODS
We used HAL to induce cytotoxicity in preneuronal PC12 cells. The expression and the subcellular localization of selected components of the PI3K-Akt survival cascade were monitored with standard biochemical approaches, such as subcellular fractionation, western blot analysis, gene transfer and fluorescence microscopy.


RESULTS
PC12 cell stimulation with the epidermal growth factor (used as a control) results in normal processing of phosphatidylinositol 3'-kinase (PI3K)-Akt signalling (e.g., localization of PI3K to the plasma membrane and phosphorylation of Akt (Ser473). Surprisingly, HAL induces PI3K-generated phosphoinositol [phosphatidylinositol-3,4,5-triphosphate (PIP3), which conflicts with its ability to inhibit Akt. In fact, the production of PIP3s is nuclear, as assessed by the localized concentration of a fluorophore-tagged PIP3-targeting pleckstrin homology protein and a fluorophore-tagged substrate-trapping mutant of the phosphoinositide phosphatase, phosphatase and tensin homologue deleted on chromosome 10 (PTEN). However, phosphoinositide-dependent protein kinase 1 (PDK1, the activating kinase of Akt) does not colocalize to the nucleus with the PI3K complex. This effectively inactivates both cytoplasmic and nuclear pools of Akt.


CONCLUSIONS
The differential compartmentalization of effectors of the PI3K-PDK1-Akt pathway is a unique means by which HAL disrupts Akt functioning in PC12 cells.
Dai
Yunxiu
Y
Cell Signalling Laboratory, Neuropsychiatry Research Unit, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada.
Wei
Zelan
Z
Sephton
Chantelle F
CF
Zhang
Di
D
Anderson
Deborah H
DH
Mousseau
Darrell D
DD
D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D006220:Haloperidol / Q000494:pharmacology*; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics*; D051381:Rats; D014162:Transfection; D014178:Translocation, Genetic / Q000187:drug effects*