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Inherited Disorders of Human Memory: Mental Retardation Syndromes From Mechanisms of Memory by J. David Sweatt, Ph.D.
Inherited Disorders of Human Memory:
Mental Retardation Syndromes
From Mechanisms of Memory by J. David Sweatt, Ph.D.
ERK1/2
MEK1/2
Raf1
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
ERK1/2
MEK1/2
Raf1
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
Neurofibromatosis MR
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
PO4
ras rasGDP GTP
GTP
GTP Hydrolysis
GAPsGTPase Activating Proteins
e.g. NF1, SynGAP
GEFsGuanine Nucleotide
Exchange Factor Proteins
e.g. SOS, cAMP GEF,
Ca2+/DAG GEF, ras GRF
Inactive Active
++
Activation of ras
Weeber and Sweatt. Neuron 33:845-848.
K-ras
N-ras
Farnesyl Transferase Inhibitor
Costa et al (2002) Nature 415:526-530.
Ras-dependent Spatial Learning in Nf1+/- Animals
Ras-dependent LTP deficits in Nf1+/- animals
Costa et al (2002) Nature 415:526-530.
ERK1/2
MEK1/2
Raf1
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
Neurofibromatosis MR
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
ERK1/2
MEK1/2
Raf1
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
Neurofibromatosis MR
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
Coffin-Lowry Syndrome
ERK1/2
MEK1/2
Raf1
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
Neurofibromatosis MR
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
Coffin-Lowry Syndrome
Rubinstein-TaybiSyndrome
Current Model of Fragile X Mental RetardationCoding Region
Regulatory Region
CGG Expansion in Regulatory Region
Point Mutation in Coding Region
DisruptionOf FMR1 Gene
Loss ofFMR1 Protein (FMRP)
FMR1/FXRInteraction domain
RibosomeInteraction
Domain
RGG BoxKHDomain
KHDomain
RGG Box = Arginine & Glycine-rich domainKH domain = Ribonucleoprotein K homology domain
FMRP = 63K RNA binding protein that binds to poly (G) and poly (U) structures
FMR1 GeneGeneStructure
FMRPStructure
ERK1/2
MEK1/2
Raf1
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
Neurofibromatosis MR
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
Coffin-Lowry Syndrome
Rubinstein-TaybiSyndrome
Fragile X Syndrome
Enhanced LTP in FMR2 knockout mice
A
C D-20 -10 0 10 20 30 40 50 60
50
100
150
200
250
MutantWildtype
Time (min)
Slo
pe
fE
PS
P(S
tan
da
rdiz
ed
to
Ba
se
lin
e)
Time (min)
B
-20 -10 0 10 20 30 40 50 6050
100
150
200
250
WildtypeMutant
Slo
pe
fE
PS
P(S
tan
da
rdiz
ed
to
Ba
se
lin
e)
-20 -10 0 10 20 30 40 50 60 70 800
100
200
300
MutantWildtype
Time (min)
Slo
pe
fE
PS
P(S
tan
da
rdiz
ed
to
Ba
se
lin
e)
-30 -20 -10 0 10 20 30 40 50 6050
100
150
200
WildtypeMutant
Time (min)
Slo
pe
fE
PS
P(S
tan
da
rdiz
ed
to
Ba
se
lin
e)
Gu et al. (2002) J. Neurosci. 22:2753-2763.
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, Mutation Uniparental Disomy Mismethylation
The Ubiquitination Pathway
Step 1
Step 2
Complex Formation
Step 3
Step 4
Step 5
E1 Charging
E2 Charging
E2—E3 Transfer
TargetPoly-
Ubiquitination
E1
E1E1
UbUb
ATP
E2LigaseUb
E3Ligase
TargetProtein
E2Ub
E3 TargetProtein
Ub
Ub Ub
UbUb
Ub
Weeber and Sweatt (2000) Recent Res. Devel. Neurochem. 3:289-299.
Selective Deficit in Context-dependent Fear conditioning in Ube3a Maternal Deficient Mice
Jiang et al (1998) Neuron 21:799-811.
Impairment of hippocampal LTP in Ube3a Maternal Deficient mice
Jiang et al (1998) Neuron 21:799-811.
AS mouse model LTP
-20 -10 0 10 20 30 40 50 60 70 80 90 100 110 12050
100
150
200
250
m-/p+m+/p+
2 trains of 100 Hz for 1 sec/ 20sec apart
Time (min)
% S
lop
e fE
PS
P(S
tan
dar
diz
ed t
o B
asel
ine)
Saturating HFS-induced LTP
-20 -10 0 10 20 30 40 50 60 70 80 90 100 110 12050
100
150
200
250
300
350
m+/p+m-/p+
6X 2 Trains of 100 Hz Stimulation
% S
lop
e fE
PS
P(S
tan
dar
diz
ed t
o B
asel
ine)
-20 -10 0 10 20 30 40 50 60 7050
100
150
200
250
m-/p+m+/p+
APV1 train 200Hz for 1 sec
Time (min)
% S
lop
e fE
PS
P(S
tan
dar
diz
ed t
o B
asel
ine)
NMDAR Independent LTP
Pathogenesis of Angelman Syndrome
E6-AP
P53 HHR23A E6-AP MCM7?
AdenylylCyclase
ATP
CaMCa++
PLC
RasB-RafRap1
Raf-1Ras
MEK
ERK
PKC CaMKII PKA
DAG cAMP
Ca++
ChannelNMDA
Receptor
0
25
50
75
100
125PKC PKA ERK CaMKII
Imm
unor
eact
ivity
(% o
f Con
trol)
ATotal Kinase Concentrations
are Normal
AIncreased P-Thr286 CaMKII in AS Mice
P-PKC
P-PKA
P-ERK p
42
P-CaM
KII0
20406080
100120140160180 *
Total CaMKII P-Thr 286CaMKII
WT WTm-/p+ m-/p+Im
mun
orea
ctiv
ity(%
of
Con
trol
)
Reduced Post-Hoc CaMKII Phosphorylation
Wt m-/p+ Wt m-/p+0
20
40
60
80
100
120
*
N/D N/D
No Ca2+/CaM With Ca2+/CaM
WT WTm-/p+ m-/p+
Den
sity
(%
of
Co
ntr
ol)
Thr 286
Regulatory Subunit
Ca2+
CAMCaMKIICatalytic Subunit
CaMKIICatalytic Subunit
AutonomouslyActive
P
Thr 286
Ca2+CAM
Regulatory Subunit
WT m-/p+0.0
0.2
0.4
0.6
*
WT m-/p+0.000
0.025
0.050
0.075
0.100
0.125
CaM
KII
Act
ivit
y(p
mol
/min
/ug)
No Ca2+/CaM With Ca2+/CaM
Hippocampal CaMKII Activity
Thr 286 Thr 305
Regulatory Subunit
Ca2+
CAMCaMKIICatalytic Subunit
CaMKIICatalytic Subunit
P
P
Thr 286
Thr 305
Ca2+CAM
Regulatory Subunit
Inactive
Wildtype m-/p+0
25
50
75
100
125
150
*
Imm
un
ore
ac
tiv
ity
(% o
f C
on
tro
l)
CaMKII
TotalCaMKII Thr305/306 CaMKII
Hippocampal HomogenatesPurified CaMKII
WT m-/p+ WT m-/p+
Control Peptide Block
Ctrl +Ca2+/CaM Ctrl +Ca2+/CaM Ctrl +Ca2+/CaM
CaMKIICaMKII
CaMKII
Wildtype m-/p+0
25
50
75
100
125
150
*
Imm
un
ore
ac
tiv
ity
(% o
f C
on
tro
l)
CaMKII
TotalCaMKII Thr305/306 CaMKII
Hippocampal HomogenatesPurified CaMKII
WT m-/p+ WT m-/p+
Control Peptide Block
Ctrl +Ca2+/CaM Ctrl +Ca2+/CaM Ctrl +Ca2+/CaM
CaMKIICaMKII
CaMKII
100 Hz/1s
No CaMKII
CaMKII T305D Mice are Impaired in LTP
Inhibited
Wild type
60
80
100
120
140
160
180
200
220
-10 0 10 20 30 40 50 60
Time (min)
WT
T305D
CaMKII
Elgersma et al.
Contextual fear conditioning
0
10
20
30
40
50
pre-CS context 24 hr
% ti
me
free
zing
WTT305D
Contextual fear conditioning
0
10
20
30
40
50
60
70
pre-CS context 24 hr
% ti
me
free
zing
WTTT305/6VA
Contextual fear conditioning
0
10
20
30
40
50
60
70
pre-CS context 24 hr
% ti
me
free
zing
WTCaMKII²
T305D Mutants Have Impaired Fear-Conditioned Learning
Elgersma et al.
Cam KIICatalytic Subunit
P
P
Thr 286
Thr 305
Ca2+CAM
Regulatory Subunit
Inactive
NR
1
NR
2B
CaMKII P
CaMKII
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 Cytoskeleton—Loss of LIMK-1causes increased actin turnover
Altered Dendritic Spine
Augmented LTP, Learning Impairments
rac PKC
Direct phosphorylation(inhibitory)
ADF / Cofilin promotesActin depolymerization
Williams Syndrome
Rho
PAK3 (p21 Activated Kinase)
JNK p38
Cytoskeletonraf-1LTD disruption?
Dbl (Diffuse B-cell Lymphoma)Rho GEF6
Rho GAPRho 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
R1Grb
SOSRas
PKC
R2
B-Raf
PKA
R3
Rap
AC
Gene Expression
Mnk1/2
eIF4E
Protein Synthesis
MAPs
Spine Structure
CRE
CREB
P
CBP
RSK2
GEF
NF1GAP
Neurofibromatosis MR
NO.
Ca2+
G Protein
NF1
Ca2+
Nucleus
R4
Coffin-Lowry Syndrome
Rubinstein-TaybiSyndrome
Fragile X Syndrome
