Inhibition of phosphatase activity prolongs NMDA-induced modification of the postsynaptic density.
NMDA-induced modification of postsynaptic densities (PSDs) was studied by immunoelectron microscopy. Treatment of cultured hippocampal neurons with NMDA for 2 min promotes a 2.3 fold thickening of the PSD and a 4 fold increase in PSD-associated CaMKII immunolabel. These changes are reversed 5 min after the removal of NMDA and Ca2+ from the medium. In addition, following NMDA treatment, PSDs exhibit a 7.5 fold increase in labeling with an antibody specific to the (Thr286) phospho-form of CaMKII, indicating that CaMKII translocated to the PSD is phosphorylated. When the phosphatase inhibitors, calyculin A or okadaic acid, are included in the medium, the NMDA-induced thickening of the PSD as well as the increase in PSD-associated CaMKII immunolabeling are largely maintained (75% and 88% of the peak values respectively) at 5 min after removal of NMDA and Ca2+ from the medium. These results imply that NMDA receptors can mediate activity-induced changes in the PSD and that phosphatases of type 1 and/or 2A are involved in the reversal of these changes.
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000201:enzymology / Q000648:ultrastructure; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism*; D013570:Synaptic Membranes / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D000906:Antibodies; D004791:Enzyme Inhibitors; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010744:Phosphoric Monoester Hydrolases