Inherited Disorders of Human Memory: Mental Retardation Syndromes From Mechanisms of Memory by J. David Sweatt, Ph.D. ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP Neurofibromatosis MR NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 PO 4 ras GDPGTP GTP Hydrolysis GAPs GTPase Activating Proteins e.g. NF1, SynGAP GEFs Guanine Nucleotide Exchange Factor Proteins e.g. SOS, cAMP GEF, Ca 2+ /DAG GEF, ras GRF InactiveActive + + Activation of ras Weeber and Sweatt. Neuron 33: K-ras N-ras Farnesyl Transferase Inhibitor Costa et al (2002) Nature 415: Ras-dependent Spatial Learning in Nf1 +/- Animals Ras-dependent LTP deficits in Nf1 +/- animals Costa et al (2002) Nature 415: ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP Neurofibromatosis MR NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP Neurofibromatosis MR NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 Coffin-Lowry Syndrome ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP Neurofibromatosis MR NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 Coffin-Lowry Syndrome Rubinstein-Taybi Syndrome Current Model of Fragile X Mental Retardation Coding Region Regulatory Region CGG Expansion in Regulatory Region Point Mutation in Coding Region Disruption Of FMR1 Gene Loss of FMR1 Protein (FMRP) FMR1/FXR Interaction domain Ribosome Interaction Domain RGG Box KH Domain KH Domain RGG Box = Arginine & Glycine-rich domain KH domain = Ribonucleoprotein K homology domain FMRP = 63K RNA binding protein that binds to poly (G) and poly (U) structures FMR1 Gene Gene Structure FMRP Structure ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP Neurofibromatosis MR NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 Coffin-Lowry Syndrome Rubinstein-Taybi Syndrome Fragile X Syndrome Enhanced LTP in FMR2 knockout mice Gu et al. (2002) J. Neurosci. 22: Angelman Syndrome- Clinical Features Severe MR Absent speech Happy disposition Seizures Ube3a codes for an E6-AP Ubiquitin Ligase Ube3a Ubiquitin Ligase Maternal Imprinting of Ube3a Expression of E6-AP in the Hippocampus and Cerebellum Ube3a Deletion, MutationUniparental Disomy Mismethylation The Ubiquitination Pathway Step 1 Step 2 Complex Formation Step 3 Step 4 Step 5 E1 Charging E2 Charging E2E3 Transfer Target Poly- Ubiquitination E1 Ub ATP E2 Ligase Ub E3 Ligase Target Protein E2 Ub E3 Target Protein Ub Weeber and Sweatt (2000) Recent Res. Devel. Neurochem. 3: Selective Deficit in Context-dependent Fear conditioning in Ube3a Maternal Deficient Mice Jiang et al (1998) Neuron 21: Impairment of hippocampal LTP in Ube3a Maternal Deficient mice Jiang et al (1998) Neuron 21: AS mouse model LTP Saturating HFS-induced LTP NMDAR Independent LTP Pathogenesis of Angelman Syndrome E6-AP P53 HHR23A E6-AP MCM7 ? Adenylyl Cyclase ATP CaMCa ++ PLC Ras B-Raf Rap1 Raf-1 Ras MEK ERK PKC CaMKII PKA DAG cAMP Ca ++ Channel NMDA Receptor A Total Kinase Concentrations are Normal A Increased P-Thr 286 CaMKII in AS Mice P-PKC P-PKA P-ERK p42 P-CaMKII * Total CaMKII P-Thr 286 CaMKII WT m-/p+ Immunoreactivity (% of Control) Reduced Post-Hoc CaMKII Phosphorylation Thr 286 Regulatory Subunit Ca 2+ CAM CaMKII Catalytic Subunit CaMKII Catalytic Subunit Autonomously Active P Thr 286 Ca 2+ CAM Regulatory Subunit Hippocampal CaMKII Activity Thr 286Thr 305 Regulatory Subunit Ca 2+ CAM CaMKII Catalytic Subunit CaMKII Catalytic Subunit P P Thr 286 Thr 305 Ca 2+ CAM Regulatory Subunit Inactive Wildtypem-/p * Immunoreactivity (% of Control) CaMKII Total CaMKII Thr 305/306 CaMKII Hippocampal HomogenatesPurified CaMKII WTm-/p+WTm-/p+ Control Peptide Block Ctrl +Ca 2+ /CaM Ctrl +Ca 2+ /CaM Ctrl +Ca 2+ /CaM CaMKII Wildtypem-/p * Immunoreactivity (% of Control) CaMKII Total CaMKII Thr 305/306 CaMKII Hippocampal HomogenatesPurified CaMKII WTm-/p+WTm-/p+ Control Peptide Block Ctrl +Ca 2+ /CaM Ctrl +Ca 2+ /CaM Ctrl +Ca 2+ /CaM CaMKII 100 Hz/1s No CaMKII CaMKII T305D Mice are Impaired in LTP Inhibited Wild type Time (min) WT T305D CaMKII Elgersma et al. T305D Mutants Have Impaired Fear-Conditioned Learning Elgersma et al. Cam KII Catalytic Subunit P P Thr 286 Thr 305 Ca 2+ CAM Regulatory Subunit Inactive NR1 NR2B CaMKII P PP1 PP2A ? E6-AP P AS Mouse Model-Conclusions Aberrant hyper-autophosphorylation of CaMKII in Angelman mouse hippocampus. Altered phosphatase activity (PP1 and/or PP2A). Alterations in CaMKII autophosphorylation can explain the physiologic and behavioral deficits in our model. A role for CaMKII activity in human learning. rho PAK, ROCK LIMK-1 (Williams Syndrome) Actin Depolymerization Factor (ADF) / cofilin Actin CytoskeletonLoss of LIMK-1 causes increased actin turnover Altered Dendritic Spine Augmented LTP, Learning Impairments rac PKC Direct phosphorylation (inhibitory) ADF / Cofilin promotes Actin depolymerization Williams Syndrome Rho PAK3 (p21 Activated Kinase) JNK p38 Cytoskeletonraf-1LTD disruption? Dbl ( Diffuse B-cell Lymphoma) Rho GEF6 Rho GAP Rho GDI GEFs + _ Nonsyndromic X-Linked Mental Retardation Mental Retardation Syndromes Disruptions of memory-related signal transduction systems. Impact of basic research on clinically relevant studies, and vice-versa. Identifying new avenues of treatment. ERK1/2 MEK1/2 Raf1 R1R1 Grb SOS Ras PKC R2R2 B-Raf PKA R3R3 Rap AC Gene Expression Mnk1/2 eIF4E Protein Synthesis MAPs Spine Structure CRE CREB P CBP RSK2 GEF NF1 GAP Neurofibromatosis MR NO. Ca 2+ G Protein NF1 Ca 2+ Nucleus R 4 Coffin-Lowry Syndrome Rubinstein-Taybi Syndrome Fragile X Syndrome