2. Directed Mutagenesis. Results: Here we present the crystal structure of the
AICD of human APP695 in complex with the C-terminal phosphotyrosine
binding domain of Fe65 (Fe65-PTB2) at 2.1 A˚ resolution. In contrast to
classical PTB domain/peptide interactions focusing on the NPX(p)Y con-
sensus motif of the peptide, the AICD/Fe65-PTB2 complex involves two
surrounding alpha-helices resulting in a three times enlarged and unique in-
terface. The N-terminal helix of the AICD is capped by threonine 668,
which upon phosphorylation regulates complex dissociation and its in-
creased phosphorylation is an important pathologic trait of Alzheimer dis-
ease. The crystallographic analysis is complemented by NMR, ITC, and
site directed mutagenesis data. Conclusions: The three-dimensional struc-
ture of the AICD/Fe65-PTB2 complex gives a detailed view on a central
protein complex involved in APP physiology and Alzheimer disease pathol-
ogy. An impressive number of cell biological, molecular biological, and
biochemical data can now be integrated in a solid mechanistic model for
complex regulation by the Alzheimer disease relevant phosphorylation of
threonine 668 within the AICD. The knowledge of the AICD/Fe65-PTB2
complex structure and of its regulation sets the basis for a new structure
based approach in the treatment of Alzheimer disease.
P4-227 NEURONAL DESTRUCTION BYAb OLIGOMERS IS
LINKED TO NMDA-RECEPTOR SIGNALING
Klaus G. Reymann1
, Raik Ro¨nicke1
, Marina Mikhaylova1
,
Sabine Ro¨nicke2
, Georg Reiser2
, Michael Kreutz1
, 1
Leibniz Institute for
Neurobiology, Magdeburg, Germany; 2
Institute for Neurobiochemistry,
Otto-von-Guericke-University Magdeburg, Magdeburg, Germany. Contact
e-mail: reymann@ifn-magdeburg.de
Background: Increasing evidences are suggesting that Ab oligomers
cause an impairment of neuronal function and morphology, prior to neuro-
nal cell death. In particular, there are convincing observations that submi-
cromolar concentrations of Ab oligomers can impair synaptic plasticity,
like long-term potentiation (LTP) and reduce the spine number of neuronal
cells. The loss of synaptic contact and decrease of neuronal activity likely
lead to a lasting and progressive neuronal degeneration. Trying to identify
the targets, which mediate the disruption of neuronal function, several
studies indicate the NMDA receptor to be involved. Methods: Utilizing
neuronal single cell culture and hippocampal slices from rat and mouse,
we investigated Ab oligomer mediated neuronal impairment in different
systems. Results: We could not observe cell death, but a general disrup-
tion of neuronal function and integrity, indicated by an impaired LTP,
a decreased number of spines and a loss of neuronal connectivity.
Interestingly, all of these Ab effects were accompanied by an NMDA re-
ceptor-dependent activation of Jacob, a protein, recently described to be
a crucial part of the CREB shut-off pathway, causing neuronal devastation
(Dieterich DC, Karpova A, Mikhaylova M, et al., PLoS Biol. 2008
Feb;6(2):e34). Conclusions: We conclude that Ab oligomers can affect
neurons in a multifaceted detrimental way, which are all linked to
NMDA receptor and Jacob activation and therefore could share common
mechanism.
P4-228 O-GLCNAC REGULATION OF HIPPOCAMPAL
SYNAPTIC PLASTICITY IN WILD TYPE AND
3XTG-AD MICE
Keith Vosseller1
, Yuliya Skorobogatko1
, Jared A. Bryfogle1
,
Frank M. LaFerla2
, David J. Vocadlo3
, Melanie Tallent1
, 1
Drexel University
College of Medicine, Philadelphia, PA, USA; 2
University of California
Irvine, Irvine, CA, USA; 3
Simon Fraser University, Burnaby, BC, Canada.
Contact e-mail: keith.vosseller@drexelmed.edu
Background: O-linked N-acetylglucosamine (O-GlcNAc) is a cytosolic
and nuclear carbohydrate post-translational modification, but its functions
are little understood. We recently reported uniquely extensive O-GlcNAc
modification at neuronal synapses, particularly on proteins that regulate
distribution of synaptic vesicle pools. Methods: We examined potential
roles for O-GlcNAc in mouse hippocampal synaptic transmission and
plasticity through in vivo pharmacological modulation of O-GlcNAc
and analysis of biochemical signaling, electrophysiology, and behavioral
learning/memory tests. Results: Pharmacological elevation or reduction
of O-GlcNAc levels had no effect on Schaffer collateral CA1 basal hippo-
campal synaptic transmission. However, in vivo elevation of O-GlcNAc
levels enhanced long term potentiation (LTP), an electrophysiological cor-
relate to some forms of learning/memory. Reciprocally, pharmacological
reduction of O-GlcNAc levels blocked LTP. Elevated O-GlcNAc altered
several phosphorylation events linked to synaptic plasticity, including in-
creased phosphorylation of Synapsin I/II at several sites linked to en-
hanced availability of synaptic vesicles for release, as well as increased
activation specific phosphorylation of Erk 1/2. Hippocampal dependent
spatial learning in mice led to increased O-GlcNAc levels, consistent
with a potential in vivo role for dynamic O-GlcNAc in learning related
synaptic plasticity. Reduced O-GlcNAc has been observed in human Alz-
heimer’s disease. In the Alzheimer’s mouse model 3XTg-AD, we
observed reduced O-GlcNAc on specific synaptic proteins, including
synapsin I. Pharmacological elevation of O-GlcNAc in 9 month 3XTg-
AD mice normalized defects in cognitive hippocampal dependent spatial
learning, and this was accompanied by modulation of several LTP linked
phosphoryaltion events. Conclusions: Thus, O-GlcNAc is a novel regula-
tory signaling component of neuronal synapses, with specific roles in plas-
ticity that involve interplay with phosphorylation, and may represent
a novel therapeutic target for improvement of synaptic deficits and mem-
ory in Alzheimer’s disease.
P4-229 THE ER STRESS TRANSCRIPTION FACTOR XBP1S
PROTECTS AGAINST AMYLOID-BETA
NEUROTOXICITY
Pedro Fernandez-Funez, Sergio Casas-Tinto, Yan Zhang, Marco Morales-
Garza, Diego Rincon-Limas, Univ. Texas Medical Branch, Galveston, TX,
USA. Contact e-mail: pefernan@utmb.edu
Background: Alzheimer’s disease (AD) is a devastating neurodegenera-
tive brain disorder for which there is no cure. The most prominent patho-
logic hallmark in the AD brain is the abnormal accumulation of the
amyloid beta42 (Aß) peptide, but the exact pathways mediating Aß neuro-
toxicity are virtually unknown. For instance, ER stress is activated in AD;
however, mostly indirect evidence suggests that ER stress plays a role in
Aß pathogenesis. Methods: We have used transgenic flies expressing hu-
man Aß to search for new genes with a role in Aß pathogenesis. Then, we
followed with studies in human neuroblastoma cells to validate our obser-
vations in a simplified human model. Results: We report that Aß activates
the ER stress response factor X-box binding protein 1 (XBP1) in trans-
genic flies and in human neuroblastoma, yielding its active form, the tran-
scription factor XBP1s. Remarkably, XBP1s is neuroprotective in flies
expressing Aß and in human neuroblastoma treated with Aß oligomers.
We also demonstrate that XBP1s prevents the accumulation of free Cal-
cium in the cytosol, thus explaining its protective activity. Conclusions:
Together, these results highlight the functional relevance of XBP1s in
the ER stress pathways triggered by AD, and uncover the potential of
XBP1 as a therapeutic target for AD and other diseases characterized by
ER stress.
P4-230 MODULATION OF SYNAPTIC TRANSMISSION BY
Ab PEPTIDES
Herman Moreno1
, Sergio Angulo1
, Efrain Cepeda1
, Isabel Llano2
,
Llinas Rodolfo3
, Scott Small4
, 1
SUNY Downstate, Brooklyn, NY, USA;
2
Universite´ Paris 5, Paris, France; 3
New York University, New York, NY,
USA; 4
Columbia University, New York, NY, USA. Contact e-mail: Herman.
Moreno@downstate.edu
Background: AD mouse models have established that overproduction of
Ab leads to abnormal synaptic transmission. However the pre or post syn-
aptic site of action and the mechanisms responsible for such dysfunction
have not been established. In order to address these issues we have stud-
ied the consequences of acute intracellular and extracellular Ab40 and
Ab42 exposure on synaptic transmission. Methods: Experiments involved
two types of preparations a) squid giant synapse and b) slices of ventral
hippocampus from WT mice. a) Ultrastructutal and electrophysiological
Poster Presentations P4 P497
