Cytoplasmic polyadenylation element binding protein-dependent protein synthesis is regulated by calcium/calmodulin-dependent protein kinase II.
Phosphorylation of cytoplasmic polyadenylation element binding protein (CPEB) regulates protein synthesis in hippocampal dendrites. CPEB binds the 3' untranslated region (UTR) of cytoplasmic mRNAs and, when phosphorylated, initiates mRNA polyadenylation and translation. We report that, of the protein kinases activated in the hippocampus during synaptic plasticity, calcium/calmodulin-dependent protein kinase II (CaMKII) robustly phosphorylated the regulatory site (threonine 171) in CPEB in vitro. In postsynaptic density fractions or hippocampal neurons, CPEB phosphorylation increased when CaMKII was activated. These increases in CPEB phosphorylation were attenuated by a specific peptide inhibitor of CaMKII and by the general CaM-kinase inhibitor KN-93. Inhibitors of protein phosphatase 1 increased basal CPEB phosphorylation in neurons; this was also attenuated by a CaM-kinase inhibitor. To determine whether CaM-kinase activity regulates CPEB-dependent mRNA translation, hippocampal neurons were transfected with luciferase fused to a 3' UTR containing CPE-binding elements. Depolarization of neurons stimulated synthesis of luciferase; this was abrogated by inhibitors of protein synthesis, mRNA polyadenylation, and CaMKII. These results demonstrate that CPEB phosphorylation and translation are regulated by CaMKII activity and provide a possible mechanism for how dendritic protein synthesis in the hippocampus may be stimulated during synaptic plasticity.
Atkins
Coleen M
CM
Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239, USA.
Nozaki
Naohito
N
Shigeri
Yasushi
Y
Soderling
Thomas R
TR
D020413:3' Untranslated Regions / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D017774:Long-Term Potentiation / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009473:Neuronal Plasticity / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000502:physiology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013569:Synapses / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D039221:mRNA Cleavage and Polyadenylation Factors / Q000378:metabolism*
D020413:3' Untranslated Regions; C490387:Cpeb1 protein, mouse; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D039221:mRNA Cleavage and Polyadenylation Factors; D011494:Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases