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The Journal of Neuroscience, May 1, 2002, 22(9):3359-3365
Phosphatidylinositol 3-Kinase Is Required for the Expression But
Not for the Induction or the Maintenance of Long-Term Potentiation in
the Hippocampal CA1 Region
Pietro Paolo
Sanna1,
Maurizio
Cammalleri1, 2,
Fulvia
Berton1, 2,
Cindy
Simpson1,
Robert
Lutjens1,
Floyd E.
Bloom1, and
Walter
Francesconi1, 2
1 Department of Neuropharmacology, The Scripps Research
Institute, La Jolla, California 92037, and 2 Universita'
degli Studi Di Pisa, Dipartimento di Fisiologia e Biochimica "G.
Moruzzi", Pisa, Italy 56127
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ABSTRACT |
Several signal transduction pathways have been implicated in the
induction of long-term potentiation (LTP), yet the signal transduction
mechanisms behind the maintenance-expression phase of LTP are
still poorly understood. We investigated the role of phosphatidylinositol 3-kinase (PI3-kinase) in LTP at Schaffer collateral/commissural fiber-CA1 synapses in rat hippocampal slices using biochemical approaches and extracellular electrophysiological recordings. We observed that PI3-kinase activity was induced in the CA1
region during LTP of field EPSPs (fEPSPs) and that two structurally unrelated PI3-kinase inhibitors, LY294002 and wortmannin, abated established LTP, suggesting that PI3-kinase is involved in the
maintenance-expression phase of LTP. However, LTP recovered after
washout of the reversible PI3-kinase inhibitor LY294002, confirming
that LTP maintenance and expression are distinct events and indicating
that PI3-kinase activity is required for LTP expression rather than for
its maintenance. Interestingly, preincubation with LY294002 did not
prevent LTP induction. In fact, if LY294002 was withdrawn 5 min after
high-frequency stimulation, an LTP of fEPSP was seen. Last, a
voltage-dependent calcium channel-dependent form of LTP in the CA1
could also be reversibly abated by LY294002, raising the possibility
that PI3-kinase could be required for the expression of multiple forms
of synaptic potentiation.
Key words:
long-term potentiation; synaptic plasticity; hippocampus; PI3-kinase; signal transduction; NMDA; voltage-dependent calcium
channels; AMPA
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INTRODUCTION |
Activity-dependent synaptic changes
are believed to be crucial in learning and memory. Long-term
potentiation (LTP) of EPSPs is a long-lasting increase of synaptic
strength that can be induced with tetanic stimulation of afferent
fibers (Malenka and Nicoll, 1999 ). At Schaffer collateral/commissural
fiber-CA1 synapses, LTP is characterized by a persistent enhancement
of the responses of AMPA-sensitive glutamatergic receptors
(Malenka and Nicoll, 1999; Malinow et al., 2000). Such an enhancement
is currently believed to be primarily attributable to increased
postsynaptic density of AMPA receptors (Malenka and Nicoll, 1999;
Luscher et al., 2000; Malinow et al., 2000). Induction of LTP is
triggered by an initial elevation of cytosolic calcium to which both
NMDA receptors and L-type voltage-dependent calcium channels (VDCC) can
contribute (Teyler et al., 1994; Malenka and Nicoll, 1999). Multiple
signal transduction pathways are then recruited to translate the
Ca2+ signal into increased synaptic
strength, including  -calcium/calmodulin-dependent protein kinase II
(CaMKII), which is believed to play a pivotal role (Malenka and Nicoll,
1999). However, although prevailing views implicate CaMKII also in the
maintenance-expression of LTP, specific inhibitors of CaMKII do not
abate LTP when applied after its induction (Malinow et al., 1989; Ito
et al., 1991; Bortolotto and Collingridge, 1998; Chen et al., 2001) nor
do inhibitors of other kinases implicated in LTP, such as
mitogen-activated protein kinase (MAPK) and Src (English and
Sweatt, 1997; Salter, 1998). These observations suggest that distinct
signal transduction events could be involved in the induction and in
the maintenance-expression phases of LTP. A distinction has also been
proposed between the maintenance and the expression of LTP (Malinow et
al., 1988). In fact, it has been observed that the wide-spectrum kinase
inhibitor H-7 can abate established LTP in a reversible manner,
suggesting that the molecular mechanisms underlying the maintenance of
LTP are not affected by this inhibitor, despite the inhibition of LTP
expression (Malinow et al., 1988). A late phase of LTP has also been
identified that is protein kinase A (PKA) dependent and requires
de novo gene expression (Frey et al., 1993; Huang, 1998).
In the present study, we investigated the role of phosphatidylinositol
3-kinase (PI3-kinase) (Whitman et al., 1988; Wymann and Pirola, 1998;
Leevers et al., 1999) in the early phase of LTP at Schaffer
collateral/commissural fiber-CA1 synapses using biochemical and
electrophysiological approaches. PI3-kinase phosphorylates the D-3
position of the inositol ring of phosphoinositides (PtdIns) (Whitman et
al., 1988), which are also the precursors for the second messengers
phosphoinositols and diacylglycerol (Clapham, 1995). Current views
suggest that D-3-phosphorylated PtdIns act as membrane-embedded second
messengers in the regulation of a broad array of biological functions
(Whitman et al., 1988; Wymann and Pirola, 1998; Leevers et al., 1999).
Among PI3-kinase downstream effectors are phosphoinositide-dependent
kinases 1 (PDK1) and the members of the AGC subfamily of protein
kinases Akt (also known as protein kinase B),
p70S6k, and atypical protein kinase C
isozymes, such as PKC (Whitman et al., 1988; Wymann and Pirola,
1998; Leevers et al., 1999). PDK1 is involved in the activation of
other PI3-kinase targets, including Akt and
p70S6k, which are believed to mediate most
of the PI3-kinase effects (Franke et al., 1997; Chou et al., 1998; Chan
et al., 1999; Romanelli et al., 1999).
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MATERIALS AND METHODS |
Hippocampal slice preparations and electrophysiological
techniques. Hippocampal slices were prepared as described
previously (Sanna et al., 2000). Briefly, we killed Wistar rats
(28-35 d of age) by decapitation under halothane (3% in air)
anesthesia. The brains were then rapidly removed and transferred into
ice-cold artificial CSF (ACSF) [in mM:
130 NaCl, 3.5 KCl, 24 NaHCO3, 1.25 NaH2PO4, 2.2 CaCl2, 10 glucose, and 2 MgSO4, pH 7.4 (oxygenated by
bubbling a mixture of 95%
O2-5%CO2)] and sliced
with a Leica (Wetzlar, Germany) VT1000E automatic vibratome
slicer to obtain transverse hippocampal slices (400 µm). Hippocampal
slices were collected in oxygenated ACSF and preincubated for at least
1 hr at room temperature. For recording, slices were transferred to a
submerged recording chamber, perfused with oxygenated ACSF, and
maintained at 31 ± 1°C. They were further incubated for at least 40 min before the recording session. The flow was maintained at
1.2 ml/min in a chamber volume of 1.5 ml. Drug applications were
performed by changing the chamber infusion to ACSF containing the
agent. Microelectrodes, pulled from 1.5-mm-outer diameter glass tubing
with the use of a Flaming/Brown micropipette puller (Sutter
Instruments, Novato, CA), were filled with ACSF (resistance of 3-5
M ). Bipolar stimulating electrodes were placed in the stratum
radiatum to activate the Schaffer collateral/commissural fibers (see
below, LTP paradigms). Recordings of field EPSPs (fEPSPs) were made in
the middle of the stratum radiatum with an Axoclamp 2B (Axon
Instruments, Foster City, CA). Test intensities were set to obtain
fEPSP slopes of ~50% of those at which population spikes were
detectable based on input-output curves obtained in each slice. An
average of five stimulus-evoked responses was collected every 3 min. As
an indicator of synaptic efficacy, we measured the initial slope of the
rising phase of the fEPSP because it is not affected by population
spikes or altered by EPSP-spike (E-S) potentiation (Abraham et
al., 1987). The initial slope of fEPSP was measured near its onset for
an interval of 1.2 msec. The acquisition and analysis were performed
with the LABVIEW software package (National Instruments, Austin, TX).
Intracellular recordings were made using glass micropipettes filled
with 2 M K-acetate, pH 7.3 (80-120 M). Cells
with stable resting membrane potentials (r.m.p.) during the recording
section were selected (r.m.p.,  67.4 ± 0.75 mV; input
resistance, 36 ± 5.1 M; n = 5). Stimuli of
0.08 msec duration and 0.9 ± 0.05 mA intensity were applied once
every 20 sec to the Schaffer collateral/commissural fibers to evoke EPSPs NMDA. Before each synaptic activation, the input resistance was
measured injecting into the cell a pulse of current (200 msec, 0.2
nA). The bridge balance and r.m.p. were carefully adjusted as needed.
All of the data presented were obtained in slices from multiple
animals
LTP paradigms. fEPSPs were recorded for at least 20 min
before high-frequency stimulation (HFS) to ensure stability of
excitability. fEPSP slopes were normalized as the percentage of mean
fEPSP over such period of time. fEPSPs at the time point preceding HFS
were used as the basal fEPSP level. A two-pathway paradigm was used in
which two stimulating electrodes were placed in the stratum radiatum on
opposite sides of the recording electrode to stimulate two separate
groups of Schaffer collateral/commissural fibers. The pathway
stimulated by the electrode on the medial side of the stratum radiatum
was designated as S1, and the pathway stimulated by the electrode on
the lateral (fimbrial) side was called S2. The independence of the two
pathways was demonstrated by the absence of paired-pulse facilitation
of fEPSP when two sets of orthodromic stimuli (0.08 msec duration) were
delivered to the two pathways at 40 msec interval (in either order,
S1-S2 or S2-S1); however, paired-pulse facilitation of fEPSP was
observed when the stimuli were applied to the same electrode.
Independence of the two pathways was also demonstrated by the lack of
potentiation in the untetanized pathway (S1) after induction of LTP to
the tetanized one (S2). Test stimuli were delivered at one per 15 sec. For LTP induction, two trains of 500 msec duration each at
100 Hz with an interval of 10 sec at the test intensity were delivered
to one of the pathways. Results obtained with the two-pathway paradigm
were confirmed in a single pathway paradigm and by inverting the order
of stimulation of the two pathways. Some experiments (see Fig. 2) were
performed in the single-pathway paradigm in the same manner. An L-type
VDCC-dependent LTP was obtained in the CA1 with 10 trains of 200 Hz,
each 200 msec long, delivered at 5 sec intervals in the presence of
D-AP-5 (50 µM) and
bicuculline (10 µM), as described by Grover and
Yan (1999). LY294002, wortmannin, nifedipine, and
D-AP-5 were obtained from Calbiochem (San Diego,
CA). We operationally define as interfering with LTP induction
treatments that can prevent LTP only when applied during tetanic
stimulation but that do not abate established LTP. Conversely, we
define as interfering with LTP expression treatments capable of
reversibly abating established LTP after tetanic stimulation, whereas
only a treatment with a reversible mechanism of action that would
permanently abate LTP could be seen as an inhibitor of LTP maintenance.
Kinase assay and Western blotting. The PI3-kinase assay was
performed as described previously (Macara et al., 1984; Alessi et al.,
1996), with minor modifications. We obtained tissue extract by
sonication of CA1 hippocampal regions in 50 µl of lysis buffer containing 10 mM Tris-HCl, pH 7.6, 50 mM NaCl, 30 mM
Na4P2O7, 1% NP-40, and protease (10 µg/ml leupeptin, 2.5 µl/ml aprotinin, and 1 mM PMSF) and phosphatase inhibitors (20 mM NaF and 1 mM activated
Na3VO4). Homogenized
samples were clarified by centrifugation for 10 min at 15,000 rpm at
4°C. PI3-kinase activity was analyzed in immunoprecipitates obtained
with 5 µl of an anti-phosphotyrosine antibody (Sigma, St. Louis, MO)
performed at 4°C with gentle shaking, using an agarose-conjugated
goat anti-mouse antiserum (Sigma). The PI3-kinase reaction mixture
contained 20 mM HEPES, 10 mM MgCl2, 100 µM
Na3VO4, 40 µM cold ATP, 3.5 µl of
[ -32P]ATP (1 mCi, 3000 Ci/mmol; NEN,
Boston, MA), and 0.3 µg of PI (Avanti, Alabaster, AL) from a stock
prepared in 50 mM HEPES, 1 mM EDTA, pH 7.0, and 0.5% w/v cholic acid, after
drying under a stream of N2. After incubation at
room temperature for 20 min, reactions were stopped with 114 µl of
2.4 M HCl in 50% MeOH. Phospholipids were then
extracted in 50 µl of chloroform separated by thin-layer chromatography (TLC) on plates (Whatman, Clifton, NJ) prerun for 3 hr
with 1.2% potassium oxalate
(C2O4K2)
w/v in 50% MeOH in H2O. TLC running buffer
consisted of H20/MeOH/glacial acetic
acid/acetone/chloroform (7:13:12:15:40). After running for 1 hr, TLC
plates were dried and exposed on Kodak Biomax MS film (Eastman Kodak,
Rochester, NY). We performed Western blots as described previously
(Sanna et al., 2000) and exposed them on Kodak Biomax MS film.
Autoradiograms were scanned and the signal quantified with the NIH
Image 1.61 software package. Statistical analyses were performed by
ANOVA with Statview software (Abacus Concepts, Calabasas, CA).
Antibodies to phosphorylated Akt (Thr308) and phosphorylated
p70S6K (Thr389) were obtained from Cell
Signaling Technology (Beverly, MA). These residues are phosphorylated
in a PI3-kinase-dependent manner and are predictors of the activation
of the two kinases (Alessi et al., 1996; Balendran et al., 1999).
Antibodies to total Akt (Santa Cruz Biotechnology, Santa Cruz, CA) and
total p70S6K (Cell Signaling Technology)
served as controls.
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RESULTS |
PI3-kinase and its downstream effectors are persistently activated
during LTP
We induced LTP of fEPSP at Schaffer collateral/commissural
fiber-CA1 synapses in hippocampal slices with an HFS paradigm
consisting of two trains of electrical stimuli of 100 Hz with a
duration of 500 msec each at an interval of 10 sec. The CA1 region was rapidly dissected and immediately frozen for biochemical analyses at
different time points before and after delivery of LTP-inducing HFS.
All slices used for biochemistry were monitored electrophysiologically. By use of a PI3-kinase assay, we observed that the activity of PI3-kinase in CA1 regions was significantly (p < 0.05) elevated in tetanized slices during both the post-tetanic
potentiation (PTP) and LTP, 30 min after HFS (Fig.
1A). Consistently,
phosphorylation of the PI3-kinase downstream effectors Akt and
p70S6K was also significantly
(p < 0.05) induced during PTP and LTP (Fig.
1B-D). Inhibition of PI3-kinase with the specific
inhibitor of PI3-kinase LY294002 (100 µM)
(Vlahos et al., 1994) prevented increased phosphorylation of Akt and
p70S6K after HFS (Fig.
1E,F).
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Figure 1.
PI3-kinase and its downstream effectors Akt and
p70S6K are activated in LTP. A,
PI3-kinase activity was increased after LTP-inducing HFS.
PI3-kinase activity was tested in CA1 protein extracts using
phosphatidylinositol as a substrate in the presence of
[-32P]ATP. Accumulation of radioactive
phosphatidylinositol-3P (PIP) was increased shortly
after HFS (PTP) and 30 min after HFS
(LTP) when compared with untetanized control slices
(C). B-D, Phosphorylation of
PI3-kinase downstream effectors Akt and p70S6K was
also significantly increased (p < 0.05 for
both), as revealed by Western blotting with specific phosphorylation
state-specific antibodies. C, D, Mean
phosphorylation of Akt and p70S6K, respectively;
error bars indicate SEM. *p < 0.05 indicates
different from control. E, Incubation of hippocampal
slices with the PI3-kinase-specific inhibitor LY294002 (100 µM) prevented increased phosphorylation of Akt and
p70S6K 30 min after HFS; representative blots.
F, Cumulative results from these experiments.
*p < 0.05 indicates different from basal;
 p < 0.05 indicates different from potentiated
slices.
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PI3-kinase is required for LTP expression but not for the
maintenance or the induction of LTP
LTP of fEPSP was induced at Schaffer collateral/commissural
fiber-CA1 synapses in hippocampal slices with the HFS paradigm described above. A 20 min bath application of the PI3-kinase inhibitor LY294002 (100 µM) 30 min after delivery of HFS abated
established LTP of fEPSP in the tetanized pathway without affecting
fEPSPs in the untetanized one of a two-pathway paradigm (Fig.
2A). In these slices
(n = 7), mean ± SE normalized fEPSP slopes of the tetanized pathway were 171.3 ± 2.6% of baseline before
application of LY294002. During application of the drug, fEPSP slope of
the tetanized pathway decreased to baseline levels (94.5 ± 1.0%). However, fEPSPs recovered to a potentiated level (154.9 ± 1.0%) ~40 min after LY294002 washout (Fig. 2A).
This result suggests that PI3-kinase activity is required for the
expression rather than the maintenance of LTP. The concentration of
LY294002 used here is in the high range of doses used in tissue culture
(Vogelbaum et al., 1998; Akasaki et al., 1999; Cox et al., 1999; Sajan
et al., 1999) in which drug-effective doses are usually lower than in
slice preparations. When tested on a battery of purified ATP-requiring enzymes, including PKC, PKA, MAPK, Src, epidermal growth factor receptor, and PI4-kinase, LY294002 had no effect on the activity of any of them at a concentration of 50 µM,
whereas its IC50 on purified PI3-kinase was 1.4 µM (Vlahos et al., 1994). At 100 µM, LY294002 did not cause cellular toxicity as
measured by MTT oxidation (Vlahos et al., 1994).
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Figure 2.
Inhibitors of PI3-kinase abate established LTP of
fEPSP in the CA1 region. Synaptic potentials were simultaneously
monitored in two independent pathways [white circles,
stimulus 1 (S1); black squares, stimulus 2 (S2)]. The
structurally unrelated inhibitors of PI3-kinase LY294002 (100 µM) and wortmannin (5 µM) were applied 30 min after delivery of HFS to one of the two pathways (S2).
Insets are representative traces of extracellular fEPSPs
recorded at the times marked by lowercase letters. Each
representative trace is an average of five responses.
Graphs represent the mean normalized fEPSP slopes plotted against time.
Arrows indicate when tetanic stimulation to one pathway
(black squares) was given at time 0. A, A
transient 20 min application of LY294002 (100 µM) 30 min
after LTP induction abated LTP in the potentiated pathway
(n = 7) (black squares), but no
change was seen in the untetanized pathway (white
circles). B, Similar results were obtained with
wortmannin, a structurally unrelated PI3-kinase inhibitor (5 µM) (n = 5). As expected, inhibition
by wortmannin was irreversible.
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To validate the specificity of the effect of LY294002 on established
LTP, we tested the structurally unrelated PI3-kinase inhibitor
wortmannin (Powis et al., 1994; Norman et al., 1996). Like LY294002,
wortmannin (5 µM) could abate established LTP in the
tetanized pathway when applied 30 min after tetanization (Fig. 2B). In these slices, as seen with LY294002, a 20 min
application of wortmannin reversed established LTP (n = 5) to baseline levels (fEPSP slope, 98.8 ± 3.0%). Treatment with
wortmannin did not affect fEPSP slopes in the untetanized pathway (Fig.
2B). However, whereas LY294002 is a reversible
inhibitor of PI3-kinase (Vlahos et al., 1994), wortmannin is an
irreversible one (Powis et al., 1994; Norman et al., 1996).
Predictably, therefore, LTP expression did not recover after wortmannin
withdrawal (Fig. 2B).
In hippocampal slices continuously incubated in LY294002 (100 µM), no LTP of fEPSP was observed after delivery of HFS
(Fig. 3A). However, if
LY294002 was withdrawn 5 min after HFS, an LTP of fEPSP was seen (Fig.
3B). In fact, in these slices (n = 6), mean ± SE normalized fEPSP slope was 157.1 ± 5.1% at 60 min after HFS (Fig. 3B). This result indicates that
PI3-kinase activity is not required for LTP induction. As expected,
pretreatment with wortmannin prevented LTP induction in the CA1, and no
LTP was seen during washout (data not shown). PTP was not significantly affected by bath application of LY294002 (100 µM), nor was paired-pulse facilitation, which,
like PTP, is a presynaptic form of short-term plasticity (Kamiya and
Zucker, 1994; Fisher et al., 1997). Intracellular recording from CA1
pyramidal neurons (n = 5) also demonstrated that a 20 min application of LY294002 (100 µM) did not
modify the amplitudes of NMDA glutamate receptor-mediated EPSPs
pharmacologically isolated with the AMPA receptor antagonist CNQX (10 µM), the GABAA receptor
antagonist bicuculline (30 µM), and the
GABAB receptor antagonist CGP55845A (1 µM) (Fig. 3C). Resting membrane
potentials and input resistance were also unaffected by bath
application of LY294002 (100 µM)
(n = 5) (data not shown).
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Figure 3.
PI3-kinase is not required for LTP induction.
A, Hippocampal slices continuously incubated in LY294002
(100 µM) did not display LTP of fEPSP after delivery of
HFS (n = 6). B, If LY294002 was
withdrawn 5 min after HFS, an LTP of fEPSP was seen
(n = 6). C, Pharmacologically
isolated NMDA receptor-mediated EPSP amplitudes were not modified by a
20 min application of LY294002 (100 µM) (102.2 ± 2.5%) as revealed by intracellular recordings from CA1 pyramidal
neurons (n = 5).
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PI3-kinase is required for the expression of
VDCC-dependent LTP
Activation of NMDA receptors is the primary trigger for LTP with
the HFS protocol used above. In fact, although induction of LTP in this
manner is prevented by the NMDA receptor antagonist D-AP-5
(50 µM), it is not prevented by the L-type VDCC blocker nifedipine (30 µM) (Fig.
4). Even when such a tetanization
protocol was delivered in the presence of nifedipine (30 µM), inhibition of PI3-kinase with LY294002 (100 µM) abated established LTP of fEPSP without affecting the
untetanized pathway (n = 6) (Fig. 4). As in the
experiments described above, the effect of LY294002 was reversible, and
potentiation recovered during washout (Fig. 4). However, with a
stronger tetanization protocol (see Materials and Methods) (Teyler et
al., 1994; Grover and Yan, 1999), an L-type VDCC-dependent form of LTP
can also be induced at Schaffer collateral/commissural fibers-CA1
synapses in the presence of the NMDA blocker
D-AP-5 (50 µM) (Teyler et
al., 1994; Grover and Yan, 1999). The dependence of this LTP on VDCC is
demonstrated by its sensitivity to nifedipine (30 µM) (data not shown) (Teyler et al., 1994;
Grover and Yan, 1999). Thus, we investigated whether inhibition of
PI3-kinase could also abate such VDCC-dependent LTP. We observed that,
when applied 30 min after induction of VDCC-dependent LTP, LY294002 (100 µM) abated established potentiation of
fEPSP in the tetanized pathway without affecting fEPSP slopes in the
untetanized one (Fig. 4). In these slices (n = 6),
mean ± SE normalized fEPSP slopes of the tetanized pathway were
160.7 ± 0.5% of baseline before application of LY294002 (100 µM). A 20 min bath application of LY294002 30 min after delivery of HFS abated established LTP of fEPSP to baseline
levels (109.5 ± 1.2%). The fEPSPs recovered to a potentiated
level (138.5 ± 0.7%) 40-50 min after LY294002 washout (Fig. 4).
These results suggest that PI3-kinase is required for the expression of
both a strictly NMDA-dependent and a VDCC-dependent form of LTP at
Schaffer collateral/commissural fiber-CA1 synapses.
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Figure 4.
PI3-kinase is required for the expression of both
NMDA- and VDCC-dependent forms of CA1 LTP.
A, L-type VDCC-dependent form of LTP of fEPSP was
induced at Schaffer collateral/commissural fiber-CA1 synapses in the
presence of D-AP-5 (50 µM). A 20 min
application of LY294002 (100 µM) 30 min after the
induction of VDCC-dependent LTP abated LTP in the tetanized pathway
(n = 6) (black squares), but no
change was seen in the fEPSP in the untetanized pathway (white
circles). B, Inhibition of PI3-kinase with
LY294002 (100 µM) also abated NMDA-dependent LTP induced
in the presence of nifedipine (30 µM).
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DISCUSSION |
We observed that PI3-kinase activity was induced during LTP
of fEPSP at Schaffer collateral/commissural fiber-CA1
synapses. Two structurally unrelated PI3-kinase inhibitors, LY294002
and wortmannin, abated established LTP when applied after delivery of
HFS, suggesting that PI3-kinase is involved in the
maintenance-expression phase of LTP. After withdrawal of LY294002,
a reversible inhibitor of PI3-kinase, fEPSPs returned to a potentiated
level. Additionally, PI3-kinase activity was dispensable for LTP
induction, because delivery of HFS during perfusion with LY294002 did
not prevent LTP expression after washout of this inhibitor, suggesting
that different signal transduction mechanisms are involved in the
induction and in the expression-maintenance phases of LTP. Last, a
VDCC-dependent form of LTP was also reversibly abated by LY294002.
Several signal transduction pathways have been implicated in the
induction of LTP in the CA1 region, including CaMKII, Src, PKC, and
MAPK (Salter, 1998; Malenka and Nicoll, 1999; Winder and Sweatt,
2001). The cAMP-PKA- cAMP response element-binding protein pathway
has been shown to be required for the late phase of LTP in the CA1
region (Frey et al., 1993; Bourtchuladze et al., 1994), although a role
in early events can also be demonstrated in certain paradigms (Blitzer
et al., 1995). However, the signal transduction events behind the
maintenance-expression phase of LTP are still poorly understood
(Malenka and Nicoll, 1999). In fact, although established LTP can be
abated by a broad-spectrum Ser/Thr kinase inhibitor at high doses
(Malinow et al., 1988), specific inhibitors of CaMKII, Src, PKC, or the
ERK-MAPK pathway, although they can prevent LTP induction when applied
during HFS, do not affect established LTP (Malinow et al., 1989; Ito et
al., 1991; English and Sweatt, 1997; Bortolotto and Collingridge, 1998; Salter, 1998; Chen et al., 2001). Established LTP was found to be
selectively abated by two inhibitors of PI3-kinase, LY294002 and
wortmannin. The reversibility of the action of LY294002 on established
LTP confirms that LTP maintenance and expression are distinct events,
as proposed by Malinow et al. (1988), and indicates that PI3-kinase is
required for the expression rather than the maintenance of LTP (Fig.
5). PI3-kinase activity was also
dispensable for LTP induction. In fact, if HFS was delivered during
incubation of hippocampal slices with LY294002, an LTP of fEPSP was
seen during withdrawal of the drug. A necessary role for PI3-kinase in
the maintenance-expression phase of LTP is corroborated by the fact
that wortmannin, a PI3-kinase inhibitor structurally unrelated to
LY294002, could also selectively abate established LTP. However, unlike
LY294002, wortmannin blocks PI3-kinase irreversibly by covalent
modification of the kinase, and, thus, PI3-kinase activity cannot
recover without new protein synthesis (Powis et al., 1994; Norman et
al., 1996). Therefore, wortmannin did not allow us to differentiate
between LTP maintenance and expression because LTP did not recover
after withdrawal of the inhibitor. Additionally, when we pretreated
hippocampal slices with wortmannin, LTP in the CA1 was prevented, and
the irreversible action of the drug did not allow it to recover during
washout. Consistently, LTP was not seen in the dentate gyrus in animals
pretreated with wortmannin (Kelly and Lynch, 2000). Although the term
"expression" was used in that report (Kelly and Lynch, 2000),
pretreatment with an irreversible inhibitor like wortmannin does not
allow one to distinguish between inhibition of LTP induction and of the
maintenance-expression phase of LTP. Recently, preincubation with
inhibitors of PI3-kinase was also shown to prevent LTP of fEPSP in the
basolateral amygdala (Lin et al., 2001).
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Figure 5.
A model for the role of PI3-kinase in LTP. AMPA
receptors composed of subunits 2 and 3 (GluR2/3) are believed to be
responsible for basal AMPA responses. They are present at variable
levels at postsynaptic sites in which they constitutively cycle between
intracellular compartments and presynaptic membranes (Passafaro et al.,
2001; Shi et al., 2001). Addition of GluR1 AMPA receptors in complex
with GluR2 (GluR1/2) to postsynaptic membranes is believed to be the
basis for LTP (Shi et al., 2001). We showed here that PI3-kinase is
required for LTP but not for basal AMPA transmission. This observation
is consistent with a role for PI3-kinase in the insertion of AMPA
receptors during LTP but not in regulating basal AMPA receptor density.
Consistent with this view, it has been shown recently that
NMDA-dependent exocytosis of GluR1-containing AMPA receptor in primary
hippocampal neurons is PI3-kinase dependent, unlike the exocytosis of
GluR2 subunits not associated with GluR1 (Passafaro et al., 2001).
Interestingly, delivery of HFS during perfusion with the reversible
PI3-kinase inhibitor LY294002 did not prevent expression of LTP after
washout of this inhibitor, and addition of LY294002 to established LTP
caused a reversible inhibition of LTP. The former observation suggests
that PI3-kinase is not responsible for the induction of LTP. The latter
observation confirms that LTP maintenance and expression are distinct
events (Malinow et al., 1988) and indicates that PI3-kinase activity is
required for LTP expression rather than for its maintenance.
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We then investigated whether the expression of LTP induced with a
different triggering mechanism at Schaffer collateral/commissural fiber-CA1 synapses would also display the same PI3-kinase dependence. As mentioned above, we observed that activation of PI3-kinase with our
standard HFS paradigm was dependent on NMDA receptors rather than VDCC.
Consistently, we observed that a strictly NMDA-dependent LTP induced in
the presence of nifedipine was reversibly abated by the PI3-kinase
inhibitor LY294002. We then investigated whether LY294002 could also
reversibly abate a form of VDCC-dependent LTP at Schaffer
collateral/commissural fiber-CA1 synapses. In fact, activation of VDCC
can induce an LTP that, perhaps because of the extrasynaptic
localization of VDCC, appears to recruit a different set of signal
transduction pathways than those required for NMDA-dependent LTP (Cavus
and Teyler, 1996). However, we observed that VDCC-dependent LTP induced
by strong tetanization in the presence of D-AP-5 was
reversibly abated by LY294002, like NMDA-dependent LTP. This result
raises the possibility that PI3-kinase could be a final common pathway
for the expression of multiple forms of synaptic potentiation.
It is believed currently that central to synaptic plasticity are
dynamic modifications of dendritic spines leading to changes in the
density of AMPA receptors on postsynaptic membranes (Malenka and
Nicoll, 1999; Luscher et al., 2000; Malinow et al., 2000) (but see
Grosshans et al., 2002). Cytoskeletal elements such as actin have been
implicated in regulating spine morphology (Halpain, 2000; Matus, 2000)
and AMPA redistribution (Allison et al., 1998; Shen et al., 2000).
Mounting evidence supports that PI3-kinase and its effectors are part
of the actin polymerizing system in several cell types, including
neurons (Wymann and Arcaro, 1994; Higaki et al., 1996; Burnett et al.,
1998). PI3-kinase has also been shown to be involved in multiple
aspects of membrane trafficking in different cell types. Among them is
the surface translocation of glucose transporters (Corvera and Czech,
1998), Na+/H+
exchanger (Kurashima et al., 1998; Janecki et al., 2000; Yudowski et
al., 2000), and transferrin receptor (Shepherd et al., 1995), all of
which cycle between the plasmalemma and intracellular membrane compartments. Thus, PI3-kinase could play a role in the cytoskeletal and signaling events responsible for regulating AMPA receptor density
at postsynaptic sites. AMPA receptors of different subunit composition
appear to be responsible for basal AMPA responses and for the increased
AMPA-mediated transmission seen in LTP (Shi et al., 1999; Luscher et
al., 2000; Malinow et al., 2000; Shi et al., 2001). AMPA receptors in
the hippocampus are mostly hetero-oligomers composed of GluR1/GluR2 or
GluR2/GluR3 subunits (Wenthold et al., 1996). GluR2/3 AMPA receptors
are present at variable levels at postsynaptic sites, and they
constitutively cycle between intracellular compartments and presynaptic
membranes through the interaction of GluR2 with
N-ethylmaleimide-sensitive factor and group II PDZ (postsynaptic density-95/Discs large/zona occludens-1) domain proteins (Sheng and Pak, 2000; Passafaro et al., 2001; Shi et al.,
2001). AMPA receptors containing subunits 1 and 2 (GluR1/2) are
delivered to postsynaptic sites after LTP induction through the
interaction of GluR1 and group I PDZ domain proteins (Shi et al.,
2001). Some synapses are believed to lack AMPA receptors, the so-called
"silent synapses," and to be converted to functional synapses
during LTP (Malenka and Nicoll, 1999; Luscher et al., 2000). We
observed that PI3-kinase inhibitors can abate LTP but do not affect
basal AMPA transmission. This suggests a requirement of PI3-kinase for
the insertion and/or continued surface expression of additional AMPA
receptors during LTP but not for regulating basal AMPA receptor density
(Fig. 5). Consistent with this view, it has been shown recently that
exocytosis of GluR1-containing AMPA receptor can be induced in primary
hippocampal neurons by NMDA or insulin in a PI3-kinase-dependent manner
(Passafaro et al., 2001). However, exocytosis of GluR2 subunits not
associated with GluR1 in primary hippocampal neurons is unaffected by
the PI3-kinase inhibitor wortmannin (Passafaro et al., 2001).
The present data demonstrate that PI3-kinase is required for the
expression but not for the induction or maintenance of LTP at Schaffer
collateral/commissural fiber-CA1 synapses. Although several signal
transduction pathways are known to be involved in the induction of LTP,
PI3-kinase is the first one to be found to be required for its
expression. Both NMDA-dependent and VDCC-dependent forms of LTP at
Schaffer collateral/commissural fiber-CA1 synapses were found to
require PI3-kinase activity for their expression, suggesting that
PI3-kinase could be a final common pathway in the expression of
multiple forms of synaptic potentiation.
| |
FOOTNOTES |
Received Oct. 29, 2001; revised Feb. 1, 2002; accepted Feb. 4, 2002.
This study was supported in part by National Institutes of Health
Grants MH62140 and MH64376 (P.P.S. and W.F.) and P50AA06420 (F.E.B. and
P.P.S.). We are grateful to Drs. George Siggins, Paul Schweitzer, and
Steven Henriksen (from The Scripps Research Institute) for critical
review of this manuscript and Dr. George Koob (also from The Scripps
Research Institute) for his support and encouragement.
Correspondence should be addressed to Pietro Paolo Sanna or Walter
Francesconi, Department of Neuropharmacology, The Scripps Research
Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037. E-mails:
psanna{at}scripps.edu and wfranc{at}scripps.edu.
| |
REFERENCES |
-
Abraham WC,
Gustafsson B,
Wigstrom H
(1987)
Long-term potentiation involves enhanced synaptic excitation relative to synaptic inhibition in guinea-pig hippocampus.
J Physiol (Lond)
394:367-380[Abstract/Free Full Text].
-
Akasaki T,
Koga H,
Sumimoto H
(1999)
Phosphoinositide 3-kinase-dependent and -independent activation of the small GTPase Rac2 in human neutrophils.
J Biol Chem
274:18055-18059[Abstract/Free Full Text].
-
Alessi DR,
Andjelkovic M,
Caudwell B,
Cron P,
Morrice N,
Cohen P,
Hemmings BA
(1996)
Mechanism of activation of protein kinase B by insulin and IGF-1.
EMBO J
15:6541-6551[Web of Science][Medline].
-
Allison DW,
Gelfand VI,
Spector I,
Craig AM
(1998)
Role of actin in anchoring postsynaptic receptors in cultured hippocampal neurons: differential attachment of NMDA versus AMPA receptors.
J Neurosci
18:2423-2436[Abstract/Free Full Text].
-
Balendran A,
Currie R,
Armstrong CG,
Avruch J,
Alessi DR
(1999)
Evidence that 3-phosphoinositide-dependent protein kinase-1 mediates phosphorylation of p70 S6 kinase in vivo at Thr-412 as well as Thr-252.
J Biol Chem
274:37400-37406[Abstract/Free Full Text].
-
Blitzer RD,
Wong T,
Nouranifar R,
Iyengar R,
Landau EM
(1995)
Postsynaptic cAMP pathway gates early LTP in hippocampal CA1 region.
Neuron
15:1403-1414[Web of Science][Medline].
-
Bortolotto ZA,
Collingridge GL
(1998)
Involvement of calcium/calmodulin-dependent protein kinases in the setting of a molecular switch involved in hippocampal LTP.
Neuropharmacology
37:535-544[Web of Science][Medline].
-
Bourtchuladze R,
Frenguelli B,
Blendy J,
Cioffi D,
Schutz G,
Silva AJ
(1994)
Deficient long-term memory in mice with a targeted mutation of the cAMP-responsive element-binding protein.
Cell
79:59-68[Web of Science][Medline].
-
Burnett PE,
Blackshaw S,
Lai MM,
Qureshi IA,
Burnett AF,
Sabatini DM,
Snyder SH
(1998)
Neurabin is a synaptic protein linking p70 S6 kinase and the neuronal cytoskeleton.
Proc Natl Acad Sci USA
95:8351-8356[Abstract/Free Full Text].
-
Cavus I,
Teyler T
(1996)
Two forms of long-term potentiation in area CA1 activate different signal transduction cascades.
J Neurophysiol
76:3038-3047[Abstract/Free Full Text].
-
Chan TO,
Rittenhouse SE,
Tsichlis PN
(1999)
AKT/PKB and other D3 phosphoinositide-regulated kinases: kinase activation by phosphoinositide-dependent phosphorylation.
Annu Rev Biochem
68:965-1014[Web of Science][Medline].
-
Chen HX,
Otmakhov N,
Strack S,
Colbran RJ,
Lisman JE
(2001)
Is persistent activity of calcium/calmodulin-dependent kinase required for the maintenance of LTP?
J Neurophysiol
85:1368-1376[Abstract/Free Full Text].
-
Chou MM,
Hou W,
Johnson J,
Graham LK,
Lee MH,
Chen CS,
Newton AC,
Schaffhausen BS,
Toker A
(1998)
Regulation of protein kinase C zeta by PI 3-kinase and PDK-1.
Curr Biol
8:1069-1077[Web of Science][Medline].
-
Clapham DE
(1995)
Calcium signaling.
Cell
80:259-268[Web of Science][Medline].
-
Corvera S,
Czech MP
(1998)
Direct targets of phosphoinositide 3-kinase products in membrane traffic and signal transduction.
Trends Cell Biol
8:442-446[Web of Science][Medline].
-
Cox D,
Tseng CC,
Bjekic G,
Greenberg S
(1999)
A requirement for phosphatidylinositol 3-kinase in pseudopod extension.
J Biol Chem
274:1240-1247[Abstract/Free Full Text].
-
English JD,
Sweatt JD
(1997)
A requirement for the mitogen-activated protein kinase cascade in hippocampal long term potentiation.
J Biol Chem
272:19103-19106[Abstract/Free Full Text].
-
Fisher SA,
Fischer TM,
Carew TJ
(1997)
Multiple overlapping processes underlying short-term synaptic enhancement.
Trends Neurosci
20:170-177[Web of Science][Medline].
-
Franke TF,
Kaplan DR,
Cantley LC
(1997)
PI3K: downstream AKTion blocks apoptosis.
Cell
88:435-437[Web of Science][Medline].
-
Frey U,
Huang YY,
Kandel ER
(1993)
Effects of cAMP simulate a late stage of LTP in hippocampal CA1 neurons.
Science
260:1661-1664[Abstract/Free Full Text].
-
Grosshans DR,
Clayton DA,
Coultrap SJ,
Browning MD
(2002)
LTP leads to rapid surface expression of NMDA but not AMPA receptors in adult rat CA1.
Nat Neurosci
5:27-33[Web of Science][Medline].
-
Grover LM,
Yan C
(1999)
Blockade of GABAA receptors facilitates induction of NMDA receptor-independent long-term potentiation.
J Neurophysiol
81:2814-2822[Abstract/Free Full Text].
-
Halpain S
(2000)
Actin and the agile spine: how and why do dendritic spines dance?
Trends Neurosci
23:141-146[Web of Science][Medline].
-
Higaki M,
Sakaue H,
Ogawa W,
Kasuga M,
Shimokado K
(1996)
Phosphatidylinositol 3-kinase-independent signal transduction pathway for platelet-derived growth factor-induced chemotaxis.
J Biol Chem
271:29342-29346[Abstract/Free Full Text].
-
Huang EP
(1998)
Synaptic plasticity: going through phases with LTP.
Curr Biol
8:R350-R352[Web of Science][Medline].
-
Ito I,
Hidaka H,
Sugiyama H
(1991)
Effects of KN-62, a specific inhibitor of calcium/calmodulin-dependent protein kinase II, on long-term potentiation in the rat hippocampus.
Neurosci Lett
121:119-121[Web of Science][Medline].
-
Janecki AJ,
Janecki M,
Akhter S,
Donowitz M
(2000)
Basic fibroblast growth factor stimulates surface expression and activity of Na+/H+ exchanger NHE3 via mechanism involving phosphatidylinositol 3-kinase.
J Biol Chem
275:8133-8142[Abstract/Free Full Text].
-
Kamiya H,
Zucker RS
(1994)
Residual Ca2+ and short-term synaptic plasticity.
Nature
371:603-606[Medline].
-
Kelly A,
Lynch MA
(2000)
Long-term potentiation in dentate gyrus of the rat is inhibited by the phosphoinositide 3-kinase inhibitor, wortmannin.
Neuropharmacology
39:643-651[Web of Science][Medline].
-
Kurashima K,
Szabo EZ,
Lukacs G,
Orlowski J,
Grinstein S
(1998)
Endosomal recycling of the Na+/H+ exchanger NHE3 isoform is regulated by the phosphatidylinositol 3-kinase pathway.
J Biol Chem
273:20828-20836[Abstract/Free Full Text].
-
Leevers SJ,
Vanhaesebroeck B,
Waterfield MD
(1999)
Signalling through phosphoinositide 3-kinases: the lipids take centre stage.
Curr Opin Cell Biol
11:219-225[Web of Science][Medline].
-
Lin C,
Yeh S,
Lu K,
Leu T,
Chang W,
Gean P
(2001)
A role for the pi-3 kinase signaling pathway in fear conditioning and synaptic plasticity in the amygdala.
Neuron
31:841-851[Web of Science][Medline].
-
Luscher C,
Nicoll RA,
Malenka RC,
Muller D
(2000)
Synaptic plasticity and dynamic modulation of the postsynaptic membrane.
Nat Neurosci
3:545-550[Web of Science][Medline].
-
Macara IG,
Marinetti GV,
Balduzzi PC
(1984)
Transforming protein of avian sarcoma virus UR2 is associated with phosphatidylinositol kinase activity: possible role in tumorigenesis.
Proc Natl Acad Sci USA
81:2728-2732[Abstract/Free Full Text].
-
Malenka RC,
Nicoll RA
(1999)
Long-term potentiation
 a decade of progress?
Science
285:1870-1874[Abstract/Free Full Text]. -
Malinow R,
Madison DV,
Tsien RW
(1988)
Persistent protein kinase activity underlying long-term potentiation.
Nature
335:820-824[Medline].
-
Malinow R,
Schulman H,
Tsien RW
(1989)
Inhibition of postsynaptic PKC or CaMKII blocks induction but not expression of LTP.
Science
245:862-866[Abstract/Free Full Text].
-
Malinow R,
Mainen ZF,
Hayashi Y
(2000)
LTP mechanisms: from silence to four-lane traffic.
Curr Opin Neurobiol
10:352-357[Web of Science][Medline].
-
Matus A
(2000)
Actin-based plasticity in dendritic spines.
Science
290:754-758[Abstract/Free Full Text].
-
Norman BH,
Shih C,
Toth JE,
Ray JE,
Dodge JA,
Johnson DW,
Rutherford PG,
Schultz RM,
Worzalla JF,
Vlahos CJ
(1996)
Studies on the mechanism of phosphatidylinositol 3-kinase inhibition by wortmannin and related analogs.
J Med Chem
39:1106-1111[Web of Science][Medline].
-
Passafaro M,
Piëch V,
Sheng M
(2001)
Subunit-specific temporal and spatial patterns of AMPA receptor exocytosis in hippocampal neurons.
Nat Neurosci
4:917-926[Web of Science][Medline].
-
Powis G,
Bonjouklian R,
Berggren MM,
Gallegos A,
Abraham R,
Ashendel C,
Zalkow L,
Matter WF,
Dodge J,
Grindey G,
Vlahos CJ
(1994)
Wortmannin, a potent and selective inhibitor of phosphatidylinositol-3-kinase.
Cancer Res
54:2419-2423[Abstract/Free Full Text].
-
Romanelli A,
Martin KA,
Toker A,
Blenis J
(1999)
p70 S6 kinase is regulated by protein kinase Czeta and participates in a phosphoinositide 3-kinase-regulated signalling complex.
Mol Cell Biol
19:2921-2928[Abstract/Free Full Text].
-
Sajan MP,
Standaert ML,
Bandyopadhyay G,
Quon MJ,
Burke Jr TR,
Farese RV
(1999)
Protein kinase C-zeta and phosphoinositide-dependent protein kinase-1 are required for insulin-induced activation of ERK in rat adipocytes.
J Biol Chem
274:30495-30500[Abstract/Free Full Text].
-
Salter MW
(1998)
Src, N-methyl-D-aspartate (NMDA) receptors, and synaptic plasticity.
Biochem Pharmacol
56:789-798[Web of Science][Medline].
-
Sanna PP,
Berton F,
Cammalleri M,
Tallent MK,
Siggins GF,
Bloom FE,
Francesconi W
(2000)
A role for Src kinase in spontaneous epileptiform activity in the CA3 region of the hippocampus.
Proc Natl Acad Sci USA
97:8653-8657[Abstract/Free Full Text].
-
Shen L,
Liang F,
Walensky LD,
Huganir RL
(2000)
Regulation of AMPA receptor GluR1 subunit surface expression by a 4.1 N-linked actin cytoskeletal association.
J Neurosci
20:7932-7940[Abstract/Free Full Text].
-
Sheng M,
Pak DT
(2000)
Ligand-gated ion channel interactions with cytoskeletal and signaling proteins.
Annu Rev Physiol
62:755-778[Web of Science][Medline].
-
Shepherd PR,
Nave BT,
Siddle K
(1995)
Involvement of PI 3-kinase in stimulation of glucose transport and recruitment of transferrin receptors in 3T3-L1 adipocytes.
Biochem Soc Trans
23:201S[Medline].
-
Shi S,
Hayashi Y,
Esteban JA,
Malinow R
(2001)
Subunit-specific rules governing AMPA receptor trafficking to synapses in hippocampal pyramidal neurons.
Cell
105:331-343[Web of Science][Medline].
-
Shi SH,
Hayashi Y,
Petralia RS,
Zaman SH,
Wenthold RJ,
Svoboda K,
Malinow R
(1999)
Rapid spine delivery and redistribution of AMPA receptors after synaptic NMDA receptor activation.
Science
284:1811-1816[Abstract/Free Full Text].
-
Teyler TJ,
Cavus I,
Coussens C,
DiScenna P,
Grover L,
Lee YP,
Little Z
(1994)
Multideterminant role of calcium in hippocampal synaptic plasticity.
Hippocampus
4:623-634[Web of Science][Medline].
-
Vlahos CJ,
Matter WF,
Hui KY,
Brown RF
(1994)
A specific inhibitor of phosphatidylinositol 3-kinase, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002).
J Biol Chem
269:5241-5248[Abstract/Free Full Text].
-
Vogelbaum MA,
Tong JX,
Rich KM
(1998)
Developmental regulation of apoptosis in dorsal root ganglion neurons.
J Neurosci
18:8928-8935[Abstract/Free Full Text].
-
Wenthold RJ,
Petralia RS,
Blahos II J,
Niedzielski AS
(1996)
Evidence for multiple AMPA receptor complexes in hippocampal CA1/CA2 neurons.
J Neurosci
16:1982-1989[Abstract/Free Full Text].
-
Whitman M,
Downes CP,
Keeler M,
Keller T,
Cantley L
(1988)
Type I phosphatidylinositol kinase makes a novel inositol phospholipid, phosphatidylinositol-3-phosphate.
Nature
332:644-646[Medline].
-
Winder DG,
Sweatt JD
(2001)
Roles of serine/threonine phosphatases in hippocampal synaptic plasticity.
Nat Rev Neurosci
2:461-474[Web of Science][Medline].
-
Wymann M,
Arcaro A
(1994)
Platelet-derived growth factor-induced phosphatidylinositol 3-kinase activation mediates actin rearrangements in fibroblasts.
Biochem J
298:517-520.
-
Wymann MP,
Pirola L
(1998)
Structure and function of phosphoinositide 3-kinases.
Biochim Biophys Acta
1436:127-150[Medline].
-
Yudowski GA,
Efendiev R,
Pedemonte CH,
Katz AI,
Berggren PO,
Bertorello AM
(2000)
Phosphoinositide-3 kinase binds to a proline-rich motif in the Na+, K+-ATPase alpha subunit and regulates its trafficking.
Proc Natl Acad Sci USA
97:6556-6561[Abstract/Free Full Text].
Copyright © 2002 Society for Neuroscience 0270-6474/02/2293359-07$05.00/0
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|
|
P. Mannella and R. D. Brinton
Estrogen receptor protein interaction with phosphatidylinositol 3-kinase leads to activation of phosphorylated akt and extracellular signal-regulated kinase 1/2 in the same population of cortical neurons: a unified mechanism of estrogen action.
J. Neurosci.,
September 13, 2006;
26(37):
9439 - 9447.
[Abstract]
[Full Text]
[PDF]
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S.-C. Mao, Y.-H. Hsiao, and P.-W. Gean
Extinction Training in Conjunction with a Partial Agonist of the Glycine Site on the NMDA Receptor Erases Memory Trace.
J. Neurosci.,
August 30, 2006;
26(35):
8892 - 8899.
[Abstract]
[Full Text]
[PDF]
|
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A. W. Baxter and D. J. A. Wyllie
Phosphatidylinositol 3 kinase activation and AMPA receptor subunit trafficking underlie the potentiation of miniature EPSC amplitudes triggered by the activation of L-type calcium channels.
J. Neurosci.,
May 17, 2006;
26(20):
5456 - 5469.
[Abstract]
[Full Text]
[PDF]
|
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Y. L. Ma, M. C. Tsai, W. L. Hsu, and E. H.Y. Lee
SGK protein kinase facilitates the expression of long-term potentiation in hippocampal neurons.
Learn. Mem.,
March 1, 2006;
13(2):
114 - 118.
[Abstract]
[Full Text]
[PDF]
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M. W. Barnett, R. F. Watson, T. Vitalis, K. Porter, N. H. Komiyama, P. N. Stoney, T. H. Gillingwater, S. G. N. Grant, and P. C. Kind
Synaptic Ras GTPase Activating Protein Regulates Pattern Formation in the Trigeminal System of Mice
J. Neurosci.,
February 1, 2006;
26(5):
1355 - 1365.
[Abstract]
[Full Text]
[PDF]
|
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J. Jaworski, S. Spangler, D. P. Seeburg, C. C. Hoogenraad, and M. Sheng
Control of Dendritic Arborization by the Phosphoinositide-3'-Kinase-Akt-Mammalian Target of Rapamycin Pathway
J. Neurosci.,
December 7, 2005;
25(49):
11300 - 11312.
[Abstract]
[Full Text]
[PDF]
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J. Magrane, K. M. Rosen, R. C. Smith, K. Walsh, G. K. Gouras, and H. W. Querfurth
Intraneuronal {beta}-Amyloid Expression Downregulates the Akt Survival Pathway and Blunts the Stress Response
J. Neurosci.,
November 23, 2005;
25(47):
10960 - 10969.
[Abstract]
[Full Text]
[PDF]
|
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G. Lenz and J. Avruch
Glutamatergic Regulation of the p70S6 Kinase in Primary Mouse Neurons
J. Biol. Chem.,
November 18, 2005;
280(46):
38121 - 38124.
[Abstract]
[Full Text]
[PDF]
|
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Y. Qin, Y. Zhu, J. P. Baumgart, R. L. Stornetta, K. Seidenman, V. Mack, L. van Aelst, and J. J. Zhu
State-dependent Ras signaling and AMPA receptor trafficking
Genes & Dev.,
September 1, 2005;
19(17):
2000 - 2015.
[Abstract]
[Full Text]
[PDF]
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M. M. Ramsey, M. M. Adams, O. J. Ariwodola, W. E. Sonntag, and J. L. Weiner
Functional Characterization of Des-IGF-1 Action at Excitatory Synapses in the CA1 Region of Rat Hippocampus
J Neurophysiol,
July 1, 2005;
94(1):
247 - 254.
[Abstract]
[Full Text]
[PDF]
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O. Tschopp, Z.-Z. Yang, D. Brodbeck, B. A. Dummler, M. Hemmings-Mieszczak, T. Watanabe, T. Michaelis, J. Frahm, and B. A. Hemmings
Essential role of protein kinase B{gamma} (PKB{gamma}/Akt3) in postnatal brain development but not in glucose homeostasis
Development,
July 1, 2005;
132(13):
2943 - 2954.
[Abstract]
[Full Text]
[PDF]
|
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N. Strutz-Seebohm, G. Seebohm, A. F. Mack, H.-J. Wagner, L. Just, T. Skutella, U. E. Lang, G. Henke, M. Striegel, M. Hollmann, et al.
Regulation of GluR1 abundance in murine hippocampal neurones by serum- and glucocorticoid-inducible kinase 3
J. Physiol.,
June 1, 2005;
565(2):
381 - 390.
[Abstract]
[Full Text]
[PDF]
|
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|
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|
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C.-L. Su, C.-H. Chen, H.-Y. Lu, and P.-W. Gean
The Involvement of PTEN in Sleep Deprivation-Induced Memory Impairment in Rats
Mol. Pharmacol.,
November 1, 2004;
66(5):
1340 - 1348.
[Abstract]
[Full Text]
[PDF]
|
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T. Numakawa, T. Ishimoto, S. Suzuki, Y. Numakawa, N. Adachi, T. Matsumoto, D. Yokomaku, H. Koshimizu, K. E. Fujimori, R. Hashimoto, et al.
Neuronal Roles of the Integrin-associated Protein (IAP/CD47) in Developing Cortical Neurons
J. Biol. Chem.,
October 8, 2004;
279(41):
43245 - 43253.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
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Z.-Y. Zhuang, H. Xu, D. E. Clapham, and R.-R. Ji
Phosphatidylinositol 3-Kinase Activates ERK in Primary Sensory Neurons and Mediates Inflammatory Heat Hyperalgesia through TRPV1 Sensitization
J. Neurosci.,
September 22, 2004;
24(38):
8300 - 8309.
[Abstract]
[Full Text]
[PDF]
|
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|
|
|
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D. A. Richards, V. de Paola, P. Caroni, B. H. Gahwiler, and R. A. McKinney
AMPA-receptor activation regulates the diffusion of a membrane marker in parallel with dendritic spine motility in the mouse hippocampus
J. Physiol.,
July 15, 2004;
558(2):
503 - 512.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L. Hou and E. Klann
Activation of the Phosphoinositide 3-Kinase-Akt-Mammalian Target of Rapamycin Signaling Pathway Is Required for Metabotropic Glutamate Receptor-Dependent Long-Term Depression
J. Neurosci.,
July 14, 2004;
24(28):
6352 - 6361.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. Klann, M. D. Antion, J. L. Banko, and L. Hou
Synaptic Plasticity and Translation Initiation
Learn. Mem.,
July 1, 2004;
11(4):
365 - 372.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
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D. J. Levinthal and D. B. DeFranco
Transient Phosphatidylinositol 3-Kinase Inhibition Protects Immature Primary Cortical Neurons from Oxidative Toxicity via Suppression of Extracellular Signal-regulated Kinase Activation
J. Biol. Chem.,
March 19, 2004;
279(12):
11206 - 11213.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Cammalleri, R. Lutjens, F. Berton, A. R. King, C. Simpson, W. Francesconi, and P. P. Sanna
Time-restricted role for dendritic activation of the mTOR-p70S6K pathway in the induction of late-phase long-term potentiation in the CA1
PNAS,
November 25, 2003;
100(24):
14368 - 14373.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. A. Cousin, C. S. Malladi, T. C. Tan, C. R. Raymond, K. J. Smillie, and P. J. Robinson
Synapsin I-associated Phosphatidylinositol 3-Kinase Mediates Synaptic Vesicle Delivery to the Readily Releasable Pool
J. Biol. Chem.,
August 1, 2003;
278(31):
29065 - 29071.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. C. Yang, Y. L. Ma, S. K. Chen, C. W. Wang, and E. H. Y. Lee
Focal Adhesion Kinase Is Required, But Not Sufficient, for the Induction of Long-Term Potentiation in Dentate Gyrus Neurons In Vivo
J. Neurosci.,
May 15, 2003;
23(10):
4072 - 4080.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
P. Opazo, A. M. Watabe, S. G. N. Grant, and T. J. O'Dell
Phosphatidylinositol 3-Kinase Regulates the Induction of Long-Term Potentiation through Extracellular Signal-Related Kinase-Independent Mechanisms
J. Neurosci.,
May 1, 2003;
23(9):
3679 - 3688.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
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|
N. H. Komiyama, A. M. Watabe, H. J. Carlisle, K. Porter, P. Charlesworth, J. Monti, D. J. C. Strathdee, C. M. O'Carroll, S. J. Martin, R. G. M. Morris, et al.
SynGAP Regulates ERK/MAPK Signaling, Synaptic Plasticity, and Learning in the Complex with Postsynaptic Density 95 and NMDA Receptor
J. Neurosci.,
November 15, 2002;
22(22):
9721 - 9732.
[Abstract]
[Full Text]
[PDF]
|
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|
|
|
|
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M. Sheng and M. J. Kim
Postsynaptic Signaling and Plasticity Mechanisms
Science,
October 25, 2002;
298(5594):
776 - 780.
[Abstract]
[Full Text]
[PDF]
|
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|
|
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P. K. Dash, S. A. Mach, S. Blum, and A. N. Moore
Intrahippocampal Wortmannin Infusion Enhances Long-Term Spatial and Contextual Memories
Learn. Mem.,
July 1, 2002;
9(4):
167 - 177.
[Abstract]
[Full Text]
[PDF]
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TOP
ABSTRACT
INTRODUCTION
