title: Chronic lithium treatment antagonizes glutamate-induced decrease of phosphorylated CREB in neurons via reducing protein phosphatase 1 and increasing MEK activities.
abstract: The cyclic AMP response element binding protein (CREB) has major roles in mediating adaptive responses at glutamatergic synapses and in the neuroprotective effects of neurotrophins. CREB has been implicated as a potential mediator of antidepressant actions. In vitro, chronic lithium treatment has been shown to promote neuronal cell survival. In the present study, we have used cultures of cerebellar granule neurons to analyze the effects of acute and chronic lithium treatment on the response to toxic concentrations of glutamate. Such concentrations of glutamate decrease the phosphorylation of CREB at serine(133) in an N-methyl-D-aspartate (NMDA) receptor-dependent manner. Chronic, but not acute, lithium treatment suppresses glutamate-induced decreases in phosphorylated CREB, and transfection studies indicate that chronic lithium, in the presence of a glutamate stimulus, markedly increases CRE-driven gene expression. Experiments with selected pharmacological reagents indicate that the glutamate-induced decreases in phosphorylated CREB are regulated primarily by protein phosphatase 1. Chronic lithium treatment not only decreases protein phosphatase 1 activity under these circumstances, but also augments glutamate-induced increases in MEK activity. PD 98059, a MEK inhibitor, prevents chronic lithium treatment from increasing phosphorylated CREB levels in glutamate-treated neurons. We conclude from these results that chronic lithium treatment is permissive for maintaining higher phosphorylated CREB levels in the presence of glutamate in part by decreasing protein phosphatase 1 activity and in part by increasing MEK activity. Higher levels of phosphorylated CREB and CRE-responsive genes such as bcl-2 may be responsible for lithium's reported effects on neuronal survival.
authors.affiliation: Molecular Neurobiology Section, National Institute of Mental Health, National Institutes of Health, Building 10 Center Drive, Room 4C206, MSC 1363 Bethesda, MD 20892-1363, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Kopnisky
authors.forename: E
authors.initials: E
authors.lastname: Chalecka-Franaszek
authors.forename: M
authors.initials: M
authors.lastname: Gonzalez-Zulueta
authors.forename: D-M
authors.initials: DM
authors.lastname: Chuang
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D002867:Chromones / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D008094:Lithium / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002867:Chromones; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D009025:Morpholines; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D008094:Lithium; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1