Abstract
Neuronal activity augments maturation of mushroom-shaped spines to form excitatory synapses, thereby strengthening synaptic transmission. We have delineated a Ca(2+)-signaling pathway downstream of the NMDA receptor that stimulates calmodulin-dependent kinase kinase (CaMKK) and CaMKI to promote formation of spines and synapses in hippocampal neurons. CaMKK and CaMKI form a multiprotein signaling complex with the guanine nucleotide exchange factor (GEF) betaPIX and GIT1 that is localized in spines. CaMKI-mediated phosphorylation of Ser516 in betaPIX enhances its GEF activity, resulting in activation of Rac1, an established enhancer of spinogenesis. Suppression of CaMKK or CaMKI by pharmacological inhibitors, dominant-negative (dn) constructs and siRNAs, as well as expression of the betaPIX Ser516Ala mutant, decreases spine formation and mEPSC frequency. Constitutively-active Pak1, a downstream effector of Rac1, rescues spine inhibition by dnCaMKI or betaPIX S516A. This activity-dependent signaling pathway can promote synapse formation during neuronal development and in structural plasticity.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Animals, Newborn
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Calcium-Calmodulin-Dependent Protein Kinase Kinase / metabolism*
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Calcium-Calmodulin-Dependent Protein Kinase Type 1 / metabolism*
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Cell Cycle Proteins / metabolism*
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Cells, Cultured
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Dendritic Spines / physiology*
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Enzyme Inhibitors / pharmacology
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Guanine Nucleotide Exchange Factors / metabolism*
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Hippocampus / cytology
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Humans
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Membrane Potentials / drug effects
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Membrane Potentials / radiation effects
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Mutation / physiology
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Neurons / cytology
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Neurons / physiology*
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Organ Culture Techniques
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Patch-Clamp Techniques / methods
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RNA, Small Interfering / pharmacology
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Rats
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Rats, Sprague-Dawley
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Rho Guanine Nucleotide Exchange Factors
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Serine / genetics
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Serine / metabolism
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Signal Transduction / physiology*
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Synapses / physiology*
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Transfection / methods
Substances
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Cell Cycle Proteins
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Enzyme Inhibitors
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Guanine Nucleotide Exchange Factors
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RNA, Small Interfering
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Rho Guanine Nucleotide Exchange Factors
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Serine
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Calcium-Calmodulin-Dependent Protein Kinase Kinase
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Calcium-Calmodulin-Dependent Protein Kinase Type 1