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From Mechanisms of Memory, second edition By J. David Sweatt, Ph.D. Chapter 9: Biochemical Mechanisms for Information Storage at the Cellular Level
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Chapter 9: Dendritic Spine
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Figure 1 Release Process *PKC AMPAR NMDAR Phosphorylation & Insertion Ca ++ Retrograde Messenger? *CaMKII *PKM zeta *PKC Synaptic Tag K + Channels Protein Synthesis ? ? * = Persistently Activated Cytoskeleton Changes ? ? 1 1 1 1 2 2 2 3 3 Summary: Three Primary Issues Related to Mechanisms for E-LTP
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Figure 2 A B C D Structures of Calcium-Binding Proteins
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Figure 3 TTT CatalyticAutoinhibitorySelf-association Inhibitory Calmodulin Binding 286 Autonomous Activity 305/306 Inhibitory A BC Structure of CAMKII
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Figure 4 NMDA Receptor CaMKII Transient CaMKII Activation Thr 286 Autophosphorylation (persistently active) NMDAR Association (persistently active) CaMKII Ca ++ / CaM Three Different Effects of Ca/CaM on CaMKII
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Figure 5 Catalysis of cAMP by Adenylyl Cyclases
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Figure 6 LTP in Adenylyl Cyclase-Deficient Mice
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Figure 7 Regulatory DomainCatalytic Domain Delta Epsilon Eta Theta Mu Novel Lambda/Iota Zeta Atypical alpha Beta Gamma Classical CalciumATPSubstratePhospholipidPS Hinge Region Auto- phosphorylation sites Domain Structures of Isoforms of PKC
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Figure 8 A. PKC Beta Knockout B. PKC Gamma Knockout C. PKC Alpha Knockout Hippocampal LTP in PKC Isoform-Specific Knockout Mice
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Figure 9 PKM mRNA Formation from Internal Promoter within PKC Gene
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Figure 10 PKM and LTP Maintenance
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TABLE I: PROPOSED MECHANISMS FOR GENERATING PERSISTING SIGNALS IN E-LTP MOLECULEMECHANISMROLE CaMKIISelf-perpetuating autophosphorylationEffector phosphorylation, coupled with low phosphatase activityStructural changes Various PKCs Direct, irreversible covalent modification by reactive oxygen speciesEffector phosphorylation PKM De novo synthesis of a constitutivelyEffector phosphorylation active kinase
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TABLE II: PROPOSED MECHANISMS FOR AUGMENTING AMPA RECEPTOR FUNCTION IN E-LTP MechanismLikely molecular basis Increased single-channel conductanceDirect phosphorylation of AMPA receptor alpha subunits by CaMKII or PKC Increased steady-state levels of AMPAR CaMKII (+ PKC?) phosphorylation of AMPAR- associated trafficking and scaffolding proteins Insertion of AMPAR into silent synapses CaMKII phosphorylation of GluR1-associated trafficking proteins
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Figure 11 AMPA Receptor Regulation During LTP
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Figure 12 AMPAR NMDAR AMPAR SAP97 4.1 actin actinin CaMKII * CaMKII Ca ++ trigger for E-LTP NMDAR AMPAR src CaMKII * PKC * PSD-95 * = Autophosphorylated CaMKII, Autonomous PKC Stabilization ? Membrane insertion Membrane insertion Glutamate Receptor Insertion and Stabilization in E-LTP
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Figure 13 NMDA Receptor Ca ++ NO - O2-O2- NOS ? PKC oxidation ONOO - O2-O2- *PKC GAP43 ↑ release ? ↑ CaM Retrograde Signaling in E-LTP
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Figure 14 Activity-Dependent Regulation of Local Protein Synthesis and Spine Morphological Changes in LTP
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Perpetuated Structural/ Functional Change Altered Synthesis of Specific Proteins = The Trigger Effector Protein Complex = The Readout * MEMORY STORAGE Constitutive Protein Synthesis Induced Protein Synthesis * New Spine Structure, Potentiated Synapse,etc. Memory-Causing Event Dendritic Spine “Housekeeping Proteins” Constitutive Effector Protein Signal to Specific Proteins mRNA NMDA Receptor Altered Protein Synthesis as Trigger for Memory Positive Feedback to Synthesis or Recruitment = The Maintenance Mechanism
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Blue Box 1 CAMKII as a Temporal Integrator
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Blue Box 2 Presynaptic Postsynaptic NMDA Receptor PKC Presynaptic? Release Process Ca ++ NOS NO· O 2 - (Superoxide) ONOO - peroxynitrite ? Other Sources cys { } cys Persistently Active PKC Zn ++ release PKC O2-O2- Ca++/CaM Oxidative Activation of PKC in LTP
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Blue Box 3 Sites of Cleavage of Phospholipids by Phospholipases
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Blue Box 4 New gene products or proteins Signal to nucleus New gene products or proteins Synaptic Potentiation Locally generated tag captures new gene product Synaptic tag NMDAR Synaptic Tagging and the E-LTP/ L-LTP Transition
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