Phosphorylation of AMPA receptor subunits is differentiallyregulated by phospholipase A2 inhibitors
Caroline Menarda,∗, Christian Patenaudea, Guy Massicottea,b
a Departement de chimie-biologie, Universit´e du Quebeca Trois-Rivieres, C.P. 500, Trois-Rivi`eres, Que., Canada G9A 5H7b Departement de pharmacologie, Facult´e de medecine, Universit´e de Montreal, Montreal, Que., Canada
Received 8 April 2005; received in revised form 3 June 2005; accepted 8 July 2005
NMDA) subtypes of glutamate receptors. Incubation of rat brain sections with 3�M BEL enhanced phosphorylation on the serine (31 residue of the AMPA receptor GluR1 subunit in synaptosomal P2 fractions, whereas AACOCF3 at the same concentratio
n increased phosphorylation on residues Ser880/891 of GluR2/3 subunits. These effects were restricted to the AMPA receptoro changes in phosphorylation were elicited on the NMDA receptor NR1 subunit. The effects of BEL and AACOCF3 were noturing blockade of protein phosphatases since AMPA receptor phosphorylation was still apparent in the presence of okadaic acid
hat the PLA2 inhibitor-induced increase in AMPA receptor phosphorylation does not rely on a decrease in dephosphorylationowever, pretreatment of rat brain sections with a cell-permeable protein kinase C (PKC) inhibitor prevented BEL- and AACOCF3hosphorylation on the Ser831 and Ser880/891 sites of GluR1 and GluR2/3 subunits, respectively. These results suggest thatPLA2 and iPLA2 systems may differentially influence AMPA receptor properties and function in the rat brain through mechanisms iKC activity.2005 Elsevier Ireland Ltd. All rights reserved.
hospholipases A2 (PLA2s) are a large and diverse super-amily of enzymes which primarily catalyze the hydrolysisf membrane phospholipids at the sn-2 position to generate
ysophospholipids and free fatty acids[13]. These enzymesre well known for their involvement in the regulation of
nflammation, immune function and smooth muscle con-raction through the production of arachidonic acid and
its subsequent metabolism to eicosanoids (prostaglanleukotrienes, etc.) via cyclooxygenase and lipoxygeenzymes[13]. More than 19 isoforms of PLA2s havebeen identified so far and classified in three main gronamely, the cytosolic calcium-dependent group (cPLA2), thecalcium-independent group (iPLA2), and the secreted grouIn the brain, cPLA2 and iPLA2 systems have attracted cosiderable attention because of their possible involvemelearning and memory[7], the formation of long-term potetiation [15], and the development of several neurologdiseases[23].
Recent experimental results have provided evidenceconstitutive iPLA2 activity interacts with synaptic funtion by modulating phosphorylation of the alpha-aminohydroxy-5-methylisoxazole-4-propionate (AMPA) subty
52 C. Menard et al. / Neuroscience Letters 389 (2005) 51–56
of glutamate receptors in pyramidal neurons of the hippocam-pus [16,22]. Although the molecular link between iPLA2and AMPA receptor phosphorylation remains to be eluci-dated, it has been found that endogenous iPLA2 activitycontrols AMPA-mediated synaptic transmission by limitingphosphorylation on serine (Ser) sites of the GluR1 subunit.This observation is of particular interest because AMPAreceptor modulation represents one of the basic mechanismsregulating glutamatergic responses and toxicity in many neu-ronal networks[10]. Whether such modulation occurs underthe influence of calcium-dependent forms of the enzyme(cPLA2) remains, however, largely unknown. In this respect,the aim of the present study was to further investigate theinfluence of PLA2 systems on the properties of glutamatereceptors. In particular, we compared the effects of cPLA2and iPLA2 inhibitors on the phosphorylation of both AMPAandN-methyl-d-aspartate (NMDA) receptor subunits.
Male Sprague-Dawley rats were purchased from CharlesRiver Canada (St-Constant, Quebec) at the age of 1 month(100–125 g) and were used 1 week after their arrival. Theywere kept in individual cages under a 12:12-h light-darkcycle in a facility that met laboratory standards (NIH Pub-lication No. 86-23, revised 1985) and Canadian Council onAnimal Care guidelines. They were anesthetised, and theirbrains were quickly removed and frozen in isopentane at−20◦C. Horizontal 30-�m thick brain sections were cut ina ted-s hel sec-t e fori
subunit (0.5�g/mL, Santa Cruz Biotechnology) were addedto the supernatant and incubated overnight with agitation at4◦C. Immunoreactive complexes were recovered by centrifu-gation and washed with lysis buffer. Proteins were finallyeluted in 4× sample buffer and heated at 100◦C for 5 min.
For Western Blotting, the aliquots were subjectedto sodium dodecyl sulfate–8% polyacrylamide gel elec-trophoresis, and proteins were transferred onto nitrocellulosemembranes. The membranes were incubated for 1 h at roomtemperature in phosphate-buffered saline containing 5% drynon-fat milk to block nonspecific sites. They were thenincubated with primary antibodies: phospho-GluR1 Ser831(0.5�g/mL, Upstate Biotechnology), phospho-GluR2/3Ser880/891 and phospho-NR1 Ser896/897 (0.5�g/mL,Santa Cruz Biotechnology). Bands corresponding to theGluR and NR subunits were detected with a peroxidase-conjugated secondary antibody (Sigma–Aldrich, St. Louis,MO) and a chemiluminescent peroxide substrate (MJS Biol-ynx, Brockville, Ontario). The immunoblots were analyzedsemi-quantitatively by densitometry with a microcomputerimaging device (Imaging Research, MCID, St. Cather-ines, Ontario) providing peak areas and apparent molecularweights.
The PLA2 inhibitors AACOCF3 (IC50, 2.5�M) and bro-moenol lactone (BEL, IC50, 0.1–1�M) were purchasedfrom BIOMOL Research Laboratories (Plymouth Meet-i tra-ta IC4 ,I teink edf icalr
om-p osth teriao
ono tingfBi tionw r831o em-bI 0/891oBA witht 2/3S R1p es tionwr ho-
cryostat, thaw-mounted on chrome-alum gelatin-coalides, and stored at−70◦C. Only sections obtained at tevel of the dorsal hippocampus were used. Generally, 12ions were placed on four slides to obtain enough tissummunoprecipitation and Western blotting.
Adjacent rat brain sections were preincubated for 60t 35◦C in 45 mL of 100 mM Tris–acetate buffer (pH 7ontaining 100�M EGTA with or without PLA2 inhibitors;he decision to use EGTA was based on previous rendicating that AMPA receptor subunits are very seive to C-terminal degradation by calcium-dependenteases[3]. Moreover, biochemical studies showed that, et concentrations exceeding millimolar levels, EGTA olightly interfered with cPLA2 activity in the brain[8]. Tis-ue was collected, homogenized and centrifuged to oembrane fractions[9]. Homogenates were centrifuged000×g for 10 min, and the supernatants were centrifut 11,500×g for 20 min. The resulting pellet, P2, wefined as the crude synaptosomal fraction, and proteinere measured by Bio-Rad protein assay (Bio-Radratories, Mississauga, Ontario). For immunoprecipita0–100�g of synaptic membranes were suspended inuffer (100 mM Tris–HCl, 100�M EGTA, pH 7.4) contain
ng 1% sodium dodecyl sulfate, heated at 100◦C for 5 min,nd diluted in cold lysis buffer containing 2% Triton X-10rotein A/G-agarose (Upstate Biotechnology, Lake PlaY) and antibodies recognizing the C-terminal domain
he AMPA receptor GluR1 (0.5�g/mL, Upstate Biotechnogy) or GluR2 subunit (0.5�g/mL, Santa Cruz Biotechnogy, Santa Cruz, CA), and for the NMDA receptor N
ng, PA) and dissolved in DMSO (0.2% final concenion). Their chemical structures appear inFig. 1A. Okadaiccid, the inhibitor of protein phosphatases (PP)—PP1,50:2 nM; PP2A, IC50: 0.51 nM; PP2B, IC50: 5000 nM; PP2C
C50: 10,000 nM-and Ro 31-8220, the cell-permeable proinase C (PKC) inhibitor, IC50: 10 nM, were also purchasrom BIOMOL Research Laboratories. All other chemeagents were obtained from Sigma–Aldrich.
Differences in subunit phosphorylation levels were cared by analysis of variance, followed by Bonferroni’s poc analysis (GraphPad Prism 4) with conventional crif statistical significance:P-values <0.05.
The influence of PLA2 enzymes on the phosphorylatif AMPA and NMDA receptors was compared by incuba
rozen-thawed rat brain sections with the iPLA2 inhibitorEL or the cPLA2 inhibitor AACOCF3 (Fig. 1A). As shown
n Fig. 1B, in synaptosomal P2 fractions, phosphorylaas markedly enhanced (by about 75%) on residue Sef AMPA receptor GluR1 subunit present in synaptic mranes when brain sections were incubated with 3�M BEL.
n the same sections, phosphorylation on residues Ser88f GluR2/3 subunits was not affected by the iPLA2 inhibitorEL. Interestingly, treatment of rat brain sections with 3�MACOCF3 produced the opposite effect, as incubation
he cPLA2 inhibitor resulted in a 51% increase of GluRer880/891 phosphorylation but did not modify Gluhosphorylation (Fig. 1B). We also investigated, in thame sections, whether NMDA receptor phosphorylaas regulated by PLA2 inhibitors. In contrast to AMPA
C. Menard et al. / Neuroscience Letters 389 (2005) 51–56 53
Fig. 1. cPLA2 and iPLA2 inhibitors differentially modulate the phosphorylation of AMPA receptor subunits. Brain sections were preincubated at 35◦C for60 min with DMSO alone (control) or 3�M of the PLA2 inhibitors BEL or AACOCF3 (chemical structures of both compounds are presented in (A). (B)Immunoblots of control and inhibitor-treated synaptosomal P2 fractions using antibodies against phospho-GluR1 Ser831 (closed bars) and phospho-GluR2/3Ser880/891 (open bars). Blots were digitized, and the intensity of the bands was quantified (grey values). (C) As in B, but using an antibody against phospho-NR1Ser896/897. (D) Same as in B, except that the phosphatase inhibitor okadaic acid (10�M) was added 15 min before preincubation with PLA2 inhibitors. Dataare expressed as percentages of the basal value in control sections and are means± S.E.M. of values obtained from six rats.*P< 0.001 (Bonferroni’s post hocanalysis), inhibitor-treated vs. control sections.
rylation at Ser896/897 of NMDA receptor NR1 subunit(Fig. 1C).
Several studies have indicated that PP play a critical rolein regulating AMPA receptor phosphorylation[20]. There-fore, we determined whether okadaic acid, a potent, selective,and cell-permeable inhibitor of PP (PP1, PP2A, PP2B andPP2C)[24], interfered with BEL- and AACOCF3-inducedchanges in AMPA receptor phosphorylation. A 75-min prein-cubation of brain sections with 10�M okadaic acid aloneresulted in a 20± 5% increase of phosphorylation levels at theSer831 sites of GluR1 subunit with 15± 5% enhancement onresidues Ser880/891 of GluR2/3 subunits. Up-regulation ofAMPA receptor phosphorylation was much higher in synap-tosomal P2 fractions following concomitant incubation ofokadaic acid and PLA2 inhibitors. Fig. 1D illustrates thecapacity of BEL and AACOCF3 to up-regulate AMPA recep-tor phosphorylation in the presence of okadaic acid. It canbe observed that okadaic acid pretreatment does not reducethe effects of PLA2 inhibitors on GluR subunit phosphory-lation. Specifically, we found that GluR1 phosphorylationwas increased by 70± 10% after BEL treatment whereasGluR2/3 phosphorylation was augmented by 50± 6% with
AACOCF3 (Fig. 1D), thus indicating that the effects of PLA2inhibitors are not occluded by okadaic acid.
To further investigate the mechanisms responsible forthe regulation of AMPA receptors, we next explored theinfluence of protein kinase inhibitors on PLA2 inhibitor-mediated phosphorylation of GluR subunits. We report herethe results obtained with one of them, a cell-permeable PKCinhibitor (Ro 31-8220). As illustrated inFig. 2, pretreat-ment of rat brain sections with this PKC inhibitor signifi-cantly reduced the BEL-induced increase of phosphorylationat the Ser831 sites of GluR1 subunit (BEL alone: 61± 9%increase; BEL + PKC inhibitor: 3± 5% increase). Similarly,preincubation of sections with the PKC inhibitor reducedthe effect of AACOCF3 on the phosphorylation of residuesSer880/891 of GluR2/3 subunits (1± 7% increase) whencompared to sections preincubated with AACOCF3 alone(38± 4% increase).
The observation that phosphorylation of AMPA receptorsubunits is influenced by BEL and AACOCF3 predicts thatreceptor levels might also be altered by those compounds[4]. Therefore, we studied the effects of PLA2 inhibitors onthe amount of GluR1 and GluR2/3 proteins in synaptosomal
54 C. Menard et al. / Neuroscience Letters 389 (2005) 51–56
Fig. 2. Phosphorylation of AMPA receptor subunits by PLA2 inhibitorsis blocked by a cell-permeable PKC inhibitor. Brain sections were pre-treated for 15 min at 35◦C with a cell-permeable PKC inhibitor (0.5�M)followed by a 60-min incubation with 3�M BEL or 3�M AACOCF3. (A)Immunoblots of control, BEL-, Ro 31-8220- and Ro 31-8220 + BEL-treatedsynaptosomal P2 fractions using antibodies against phospho-GluR1 Ser831.(B) As in part (A), except that the effects of the PKC inhibitor on AACOCF3-induced changes in AMPA receptor phosphorylation were tested with anantibody against phospho-GluR2/3 Ser880/890 sites. Data are expressed aspercentages of the basal value in control sections and are means± S.E.M. ofvalues obtained from six rats.*P< 0.001 (Bonferroni’s post hoc analysis),inhibitor-treated vs. control sections.
P2 fractions. In this respect, we observed that preincubationof rat brain sections with BEL or AACOCF3 did not elicitany significant change in the amount of GluR proteins inthis fraction (Fig. 3A). No significant difference in NR1 pro-tein levels was detected in synaptosomal fractions preparedfrom both control and BEL- or AACOCF3-treated sections(Fig. 3B). Similarly, both inhibitors did not cause any signif-icant changes in the amount of the NR2A subunit of NMDAreceptors (data not shown). As a control, we also determinedthe levels of AMPA receptor subunits in the synaptosomal P2fraction of samples that were initially immunoprecipitatedwith C-terminal GluR1, GluR2 and NR1 antibodies. Again,under these conditions, there was no significant increase inGluR1, GluR2 and NR1 levels in sections pretreated withBEL or AACOCF3 (Fig. 3C).
The results presented in this study suggest that GluR sub-units of AMPA receptors are differentially regulated by PLA2
Fig. 3. Levels of glutamate receptor subunits in synaptic membranes are notinfluenced by cPLA2 and iPLA2 inhibitors. Brain sections were preincu-bated at 35◦C for 60 min with DMSO alone (control), 3�M BEL or 3�MAACOCF3. Synaptosomal P2 fractions were prepared by subcellular frac-tionation. (A) Immunoblots of control and inhibitor-treated fractions usingantibodies against the C-terminal domains of GluR1 (closed bars) and GluR2(open bars) subunits. Blots were digitized, and the intensity of the bands wasquantified (grey values). (B) As in part (A), but using a C-terminal antibodyagainst the NR1 subunit. (C) Immunoblots of immunoprecipitated synapto-somal P2 fractions using C-terminal antibodies against GluR1 (closed bars),GluR2 (open bars) and NR1 (hatched bars) subunits. Data are expressed aspercentages of the basal value in control sections and are means± S.E.M.of values obtained from six rats.
C. Menard et al. / Neuroscience Letters 389 (2005) 51–56 55
enzymes. Our data indicate that phosphorylation of GluR1subunit occurs in rat brain sections preincubated with theiPLA2 inhibitor BEL, whereas treatment with the cPLA2inhibitor AACOCF3 produces selective phosphorylation ofGluR2/3 subunits. Phosphorylation of NMDA receptor sub-units was completely insensitive to both cPLA2 and iPLA2inhibitors, reinforcing the possibility that only the AMPAsubtype of glutamate receptors is regulated by PLA2 enzymes[15]. Although we did not verify, in our preparation, if BELand AACOCF3 are selective blockers of iPLA2 and cPLA2respectively, there are reasons to believe that both inhibitorsare acting on specific PLA2 systems. First, biochemical stud-ies on constitutive cPLA2 and iPLA2 have demonstratedthat both forms of activities can be detected in rat brainhomogenates[17,26]. From a pharmacological perspective,it was also found that AACOCF3 (not BEL) can selectivelyblock cPLA2 activity in the brain[5], whereas iPLA2 activitywas reported to be inhibited by BEL and not by AACOCF3,at least for concentrations up to 5�M [11]. Hence, underour conditions, we believe that the effects on AMPA recep-tor phosphorylation generated by BEL and AACOCF3 mightresult from preferential actions on iPLA2 and cPLA2 activ-ities, respectively. Of course, additional experiments usingantisense oligonucleotides that inhibit the expression of dif-ferent PLA2 isoforms would provide better indications of thespecific roles of PLA systems in the regulation of AMPAr
e forpi ter-a eret ve top herfi see thatb hadn LAi F3-i n beb ug-g rp her n of� smamp eoe art-m ertd tioni con-sc s areia
could alter GluR phosphorylation by changing AMPAreceptor conformation, thus exposing their phosphorylationsites.
As reported previously, we observed in the current inves-tigation that the iPLA2 inhibitor BEL promotes phospho-rylation at Ser sites of GluR1 subunit of AMPA receptors[16]. In a recent study, we have also demonstrated that injec-tion of iPLA2 inhibitors into postsynaptic CA1 pyramidalneurons generated a gradual and robust enhancement in theamplitude of AMPA receptor-mediated excitatory postsy-naptic currents[22]. Given the observations described hereregarding a possible role of PKC in the regulation of GluR1subunit by iPLA2 enzymes, we speculate that these two path-ways may cooperate together to influence AMPA receptor-mediated synaptic transmission. In this regard, it would be ofgreat interest to determine whether iPLA2 systems are impli-cated in the development of physiological processes whichare known to require up-regulation of AMPA receptor phos-phorylation by PKC enzymes[21]. Assuming, for example,that iPLA2 contributes with PKC to the phosphorylation ofAMPA receptors during long-term potentiation, we shouldthen expect iPLA2 inhibitors to occlude LTP formation inhippocampal slices. However, this notion is complicated byreports that many PLA2 isoforms (iPLA2�, iPLA2� andcPLA2�) are expressed in the brain[12], and further inves-tigations will be required to determine which isoforms arei byP
that,i hG 2/3s pre-v n ofG ro-t ep-t enth uingp cee entso cantv so-m e,A d byr log-i t thisp cul-t kadeo ion.I tionw ure( esi tiono hedo
sultsh LA
2eceptor properties.
To further characterize the mechanisms responsiblhosphorylation of AMPA receptor subunits by cPLA2 and
PLA2 inhibitors, the effects of compounds known to inct with phosphorylation/dephosphorylation reactions w
ested. First, since AMPA receptor subunits are sensitihosphatase enzymes[20], the question arises as to whet
acilitation of AMPA receptor phosphorylation by cPLA2 andPLA2 inhibitors could result from interactions with thenzymes. However, this possibility seems unlikely givenlockade of phosphatase activities with okadaic acido effect on phosphorylation enhancement elicited by P2
nhibitors. Nevertheless, the fact that BEL- and AACOCnduced changes in GluR subunit phosphorylation calocked by a cell-permeable PKC inhibitor strongly sest that iPLA2 and cPLA2 may regulate AMPA receptoroperties by interacting with PKC activity in rat brains. Tecent finding that the purinoceptor-mediated associatioPKC, a neuron-specific subtype of PKC, with the plaembrane is shortened by BEL and AACOCF3[25] is sup-ortive of such modulatory roles by PLA2 enzymes. On thther hand, it has been discovered that iPLA2 and cPLA2nzymes are differentially distributed within cell compents[12,17], suggesting that both inhibitors could existinct actions on receptors, depending on their localiza
n neurons (intracellular versus membrane receptors). Aiderable body of evidence also indicates that PLA2-inducedhanges in the phospholipid environment of membranemportant for regulating AMPA receptor conformation[13],nd we cannot exclude the possibility that PLA2 inhibitors
mplicated in the phosphorylation of AMPA receptorsKC.We have also underscored in the present investigation
n contrast to iPLA2, cPLA2 activity does not interact witluR1 phosphorylation, but can instead influence GluR
ubunit phosphorylation. From a functional perspective,ious studies have demonstrated that phosphorylatioluR2 subunit, through interaction with PDZ-binding p
eins, is sufficient to mediate internalization of AMPA recors[21]. Thus, the present finding that AACOCF3 treatmeightened GluR2/3 phosphorylation raises the intrigossibility that cPLA2 could eventually influence the surfaxpression of AMPA receptors in neurons. Here, experimn frozen-thawed brain sections failed to detect signifiariations in AMPA receptor levels in crude synaptoal fractions, indicating that over a short period of timACOCF3-induced phosphorylation is not accompanie
eceptor internalization. However, due to the unphysiocal nature of the preparation used, we cannot rule ouossibility, and studies in organotypic hippocampal slice
ures are currently being conducted to evaluate if blocf cPLA2 activity alters AMPA receptor surface express
n fact, initial studies on glutamate receptor phosphorylaith this system indicate that, following long-term expos
i.e. 12 h), both BEL and AACOCF3 could elicit changn AMPA receptor phosphorylation as well as redistribuf GluR subunits in synaptosomal P2 fractions (unpublisbservations).
Independently of the mechanisms involved, these reave interesting implications regarding the potential of P2
56 C. Menard et al. / Neuroscience Letters 389 (2005) 51–56
enzymes in neurodegenerative diseases[1,6]. As far asthe cPLA2 system is concerned, it has been observed thatAACOCF3-treated and cPLA2 knockout mice are more resis-tant to neuronal death after ischemic insult[19]. Our resultsdescribed here strongly suggest a regulatory role of cPLA2in the phosphorylation of AMPA receptor GluR2/3 subunits,which have been identified as contributors of post-ischemicneurodegeneration[10]. The pathological significance ofthese findings is further reinforced by the observations thatcPLA2 activity is altered in the brain during schizophrenia[18], epilepsy[2] and Alzheimer’s disease[14].
Acknowledgements
This research was supported by grants from the Natu-ral Sciences and Engineering Research Council (NSERC) ofCanada to G.M. C.M. is the recipient of a studentship fromNSERC. The authors thank Ovid Da Silva for editing thismanuscript.
References
[1] C. Bate, R. Veerhuis, P. Eikelenboom, A. Williams, Neurones treatedwith cyclooxygenase-1 inhibitors are resistant to amyloid-beta1-42,
lipidnesis,
har-s ofrs in
ry
ofectsRes.
ieseu-rd. 4
tn J.
tion-a tondent
[9] J.M. Henley, Subcellular localization and molecular pharmacology ofdistinct populations of [3H]-AMPA binding sites in rat hippocampus,Br. J. Pharmacol. 115 (2) (1995) 295–301.
[10] S.S. Jayakar, M. Dikshit, AMPA receptor regulation mechanisms:future target for safer neuroprotective drugs, Int. J. Neurosci. 114(6) (2004) 695–734.
[11] S.S. Kim, D.K. Kim, Y.H. Suh, Cerebral cortical phospholipase A2activity of senescence-accelerated mouse is increased in an age-dependent manner, Neurosci. Res. 29 (3) (1997) 269–272.
[12] G.R. Kinsey, B.S. Cummings, C.S. Beckett, G. Saavedra, W. Zhang,J. McHowat, R.G. Schnellmann, Identification and distribution ofendoplasmic reticulum iPLA2, Biochem. Biophys. Res. Commun.327 (1) (2005) 287–293.
[13] I. Kudo, M. Murakami, Phospholipases A2 enzymes, ProstaglandinsOther Lipid Mediat. 68–69 (2002) 3–58.
[15] G. Massicotte, Modification of glutamate receptors by phospholipaseA2: its role in adaptive neural plasticity, Cell Mol. Life Sci. 57 (11)(2000) 1542–1550.
[16] C. Menard, B. Valastro, M.A. Martel, E. Chartier, A. Marineau,M. Baudry, G. Massicotte, AMPA receptor phosphorylation is selec-tively regulated by constitutive phospholipase A2 and 5-lipoxygenaseactivities, Hippocampus 15 (3) (2005) 370–380.
[17] W.Y. Ong, T.L. Sandhya, L.A. Horrocks, A.A. Farooqui, Distribu-tion of cytoplasmic phospholipase A2 in the normal rat brain, J.Hirnforsch. 39 (3) (1999) 391–400.
NeuroReport 14 (16) (2003) 2099–2103.[2] N.G. Bazan, B. Tu, E.B. Rodriguez de Turco, What synaptic
signaling tells us about seizure-induced damage and epileptogeProg. Brain Res. 135 (2002) 175–185.
[3] X. Bi, J. Chen, S. Dang, R.J. Wenthold, G. Tocco, M. Baudry, Cacterization of calpain-mediated proteolysis of GluR1 subunitalpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptorat brain, J. Neurochem. 68 (4) (1997) 1484–1494.
[7] S. Fujita, Y. Ikegaya, N. Nishiyama, N. Matsuki, Ca2+-independenphospholipase A2 inhibitor impairs spatial memory of mice, JpPharmacol. 83 (2000) 277–278.
[8] S. Grewal, J. Smith, S. Ponnambalam, J. Walker, Stimuladependent recruitment of cytosolic phospholipase A2-alphEA.hy.926 endothelial cell membranes leads to calcium-indepeassociation, Eur. J. Biochem. 271 (1) (2004) 69–77.
19] A. Sapirstein, J.V. Bonventre, Phospholipases A2 in ischemictoxic brain injury, Neurochem. Res. 25 (5) (2000) 745–753.
20] G.L. Snyder, S. Galdi, A.A. Fienberg, P. Allen, A.C. Nairn, P. Gregard, Regulation of AMPA receptor dephosphorylation by glutamreceptor agonists, Neuropharmacology 45 (6) (2003) 703–713
21] I. Song, R.L. Huganir, Regulation of AMPA receptors during syntic plasticity, Trends Neurosci. 25 (11) (2002) 578–588.
22] F. St-Gelais, C. Menard, P. Congar, L.-E. Trudeau, G. Macotte, Postsynaptic injection of calcium-independent phospholA2 inhibitors selectively increases AMPA receptor-mediated syntransmission, Hippocampus 14 (3) (2004) 319–325.
23] G.Y. Sun, J. Xu, M.D. Jensen, A. Simonyi, Phospholipase A2 incentral nervous system: implications for neurodegenerative disJ. Lipid Res. 45 (2004) 205–213.
24] R. Tapia, F. Pena, C. Arias, Neurotoxic and synaptic effectokadaic acid, an inhibitor of protein phosphatases, Neurochem24 (11) (1999) 1423–1430.
25] K. Yagi, Y. Shirai, M. Hirai, N. Sakai, N. Saito, Phospholipaseproducts retain a neuron specific� isoform of PKC on the plasmmembrane through the C1 domain—a molecular mechanism fotained enzyme activity, Neurochem. Int. 45 (2004) 39–47.
26] H.C. Yang, M. Mosior, C.A. Johnson, Y. Chen, E.A. Dennis, Grospecific assays that distinguish between the four major typmammalian phospholipase A2, Anal. Biochem. 269 (1999) 278–
