Abstract
Differential display polymerase chain reaction was used to identify genes regulated by the mood-stabilizing drug valproate (VPA). Four differentially displayed valproate-regulated gene fragments were isolated in rat cerebral cortex after i.p. injection of sodium VPA (300 mg/kg) for 3 weeks, and their expression was confirmed by Northern and slot blot analysis in rat cerebral cortex and C6 glioma cells. Sequencing analysis revealed three previously unidentified cDNA fragments in addition to a sequence with 100% homology with a molecular chaperone, 78-kDa glucose-regulated protein (GRP78). VPA treatment did not increase mRNA expression of 70-kDa heat shock protein, which is a related stress-induced molecular chaperone protein. All four candidate genes, includingGRP78, showed similar VPA concentration-dependent increases in mRNA abundance. Another commonly prescribed mood-stabilizing anticonvulsant, carbamazepine, also increasedGRP78 mRNA expression in C6 glioma cells, whereas lithium had no effect at doses up to 2 mM. Immunoblotting revealed that GRP78 protein levels were also increased in C6 glioma cells treated with VPA under the same conditions. Nuclear runoff analysis showed that VPA increased GRP78 gene transcription. Because GRP78 possesses molecular chaperone activity, binds Ca2+ in the endoplasmic reticulum, and protects cells from the deleterious effects of damaged proteins, the present findings suggest that VPA (and possibly carbamazepine) treatment may target one or more of these processes.
Footnotes
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Send reprint requests to: Dr. L. Trevor Young, Department of Psychiatry, McMaster University, 1200 Main St. W. HSC Room 3G57, Hamilton, Ontario, Canada, L8N 3Z5. E-mail: youngt{at}fhs.mcmaster.ca
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This work was supported by a Stanley Foundation Research Grant (L.T.Y). J.F.W. is a Canadian Psychiatric Research Foundation fellow. L.T.Y. is a career scientist of the Ontario Ministry of Health.
- Abbreviations:
- CNS
- central nervous system
- VRG
- valproate-regulated gene
- GRP78
- 78-kDa glucose-regulated protein
- HSP70
- 70-kDa heat shock protein
- VPA
- valproate
- BD
- bipolar disorder
- PCR
- polymerase chain reaction
- SSPE
- sodium chloride/sodium dihydrogen phosphate/EDTA
- bp
- base pairs
- CBM
- carbamazepine
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- Received June 15, 1998.
- Accepted November 25, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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