Sustained depolarization decreases calcium/calmodulin-dependent protein kinase II activity and gene expression in dopamine neurons.
Altered gene expression mediated by calcium/calmodulin-dependent protein kinase II (CaMKII) and other intracellular signaling molecules plays an important role in activity-dependent neuroplasticity. We discovered that sustained depolarization induced by KCl, a commonly used paradigm for studying activity-dependent gene expression, surprisingly caused a decrease in CaMKII activity in rat mesencephalic dopamine neurons. This decrease in CaMKII activity, after 2 days of depolarization, occurred in the presence of a continued elevation in intracellular calcium concentration. An increase in calyculin-sensitive phosphatase activity was at least partly responsible for the decrease in CaMKII activity. Phosphatase assays revealed that activity but not the abundance of protein phosphatase-2A was increased by sustained depolarization. Decreased CaMKII activity was accompanied by a selective decrease in dopamine transporter (DAT) mRNA, while tyrosine hydroxylase and actin mRNA abundance was unaltered. On the other hand, brain-derived neurotrophic factor (BDNF) mRNA abundance was increased by sustained depolarization, further demonstrating the specificity of changes. Depolarization also caused a significant decrease in DAT protein abundance and DAT-mediated uptake. Taken together, these data illustrate a novel signaling paradigm in which the activity of protein phosphatase-2A is associated with CaMKII activity and gene expression.
Padmanabhan
S
S
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912, USA.
Prasad
B M
BM
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000235:genetics; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D008564:Membrane Potentials / Q000235:genetics*; D008636:Mesencephalon / Q000166:cytology / Q000201:enzymology*; D009473:Neuronal Plasticity / Q000235:genetics; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D054648:Protein Phosphatase 2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017557:Ventral Tegmental Area / Q000166:cytology / Q000201:enzymology
D050483:Dopamine Plasma Membrane Transport Proteins; D012333:RNA, Messenger; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D054648:Protein Phosphatase 2; D010744:Phosphoric Monoester Hydrolases; D002118:Calcium; D004298:Dopamine