Disruption of the GluR2/GAPDH complex protects against ischemia-induced neuronal damage

Monomethyl fumarate attenuates lung Ischemia/Reperfusion injury by disrupting the GAPDH/Siah1 signaling cascade

Monomethyl fumarate (MMF), a potent anti-inflammatory agent used to treat multiple sclerosis, has demonstrated efficacy in various inflammatory and ischemia/reperfusion (IR) models; however, its impact on IR-induced acute lung injury (ALI) has not been explored. We investigated, for the first time, whether MMF attenuates lung IR injury through inhibition of the GAPDH/Siah1 signaling pathway. Rats were subjected to IR injury using an isolated perfused lung model, and proximity ligation assays were employed to evaluate the presence and distribution of the GAPDH/Siah1 complex. In vitro studies involved pretreating human primary alveolar epithelial cells (HPAECs) with MMF and/or inducing GAPDH overexpression or silencing, followed by exposure to hypoxia-reoxygenation. The findings revealed significantly reduced lung damage indicators, including edema, proinflammatory cytokines, oxidative stress and apoptosis, in MMF-treated rats. Notably, MMF treatment inhibited GAPDH/Siah1 complex formation and nuclear translocation, indicating that disruption of the GAPDH/Siah1 cascade was the primary cause of these improvements. Our in vitro studies on pretreated HPAECs corroborate these in vivo findings, further strengthening this interpretation. Our study results suggest that the protective effects of MMF against lung IR injury may be attributed, at least in part, to its ability to disrupt the GAPDH/Siah1 signaling cascade, thereby attenuating inflammatory and apoptotic responses. Given these encouraging results, MMF has emerged as a promising therapeutic candidate for the management of lung IR injury.

Development of a novel peptide to prevent entry of SARS-CoV-2 into lung and olfactory bulb cells of hACE2 expressing mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that has caused a global pandemic Coronavirus Disease 2019 (COVID-19). Currently, there are no effective treatments specifically for COVID-19 infection. The initial step in SARS-CoV-2 infection is attachment to the angiotensin-converting enzyme 2 (ACE2) on the cell surface. We have developed a protein peptide that effectively disrupts the binding between the SARS-CoV-2 spike protein and ACE2. When delivered by nasal spray, our peptide prevents SARS-CoV-2 spike protein from entering lung and olfactory bulb cells of mice expressing human ACE2. Our peptide represents a potential novel treatment and prophylaxis against COVID-19.

A Narrative Review on Axonal Neuroprotection in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) resulting in demyelination and neurodegeneration. The therapeutic strategy is now largely based on reducing inflammation with immunosuppressive drugs. Unfortunately, when disease progression is observed, no drug offers neuroprotection apart from its anti-inflammatory effect. In this review, we explore current knowledge on the assessment of neurodegeneration in MS and look at putative targets that might prove useful in protecting the axon from degeneration. Among them, Bruton's tyrosine kinase inhibitors, anti-apoptotic and antioxidant agents, sex hormones, statins, channel blockers, growth factors, and molecules preventing glutamate excitotoxicity have already been studied. Some of them have reached phase III clinical trials and carry a great message of hope for our patients with MS.

Constraint-induced movement therapy enhances AMPA receptor-dependent synaptic plasticity in the ipsilateral hemisphere following ischemic stroke

Constraint-induced movement therapy (CIMT) can promote the recovery of motor function in injured upper limbs following stroke, which may be associated with upregulation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) at synapses in the ipsilateral sensorimotor cortex in our previous study. However, AMPAR distribution is tightly regulated, and only AMPARs on the postsynaptic membrane can mediate synaptic transmission. We speculated that synaptic remodeling induced by movement-associated synaptic activity can promote functional recovery from stroke. To test this hypothesis, we compared AMPAR expression on the postsynaptic membrane surface in a rat model of ischemic stroke induced by middle cerebral artery occlusion (MCAO) with versus without CIMT, which consisted of daily running wheel training for 2 weeks starting on day 7 after MCAO. The results showed that CIMT increased the number of glutamate receptor (GluR)2-containing functional synapses in the ipsilateral sensorimotor cortex, and reduced non-GluR2 AMPARs in the ipsilateral sensorimotor cortex and hippocampal CA3 region. In addition, CIMT enhanced AMPAR expression on the surface of post-synaptic membrane in the ipsilateral sensorimotor cortex and hippocampus. Thus, CIMT promotes the recovery of motor function of injured upper limbs following stroke by enhancing AMPAR-mediated synaptic transmission in the ischemic hemisphere. These findings provide supporting evidence for the clinical value of CIMT for restoring limb movement in stroke patients. All experimental procedures and protocols were approved by the Department of Laboratory Animal Science of Fudan University, China (approval No. 201802173S) on March 3, 2018.

Long-term depression induced by endogenous cannabinoids produces neuroprotection via astroglial CB1R after stroke in rodents

Ischemia not only activates cell death pathways but also triggers endogenous protective mechanisms. However, it is largely unknown what is the essence of the endogenous neuroprotective mechanisms induced by preconditioning. In this study we demonstrated that systemic injection of JZL195, a selective inhibitor of eCB clearance enzymes, induces in vivo long-term depression at CA3-CA1 synapses and at PrL-NAc synapses produces neuroprotection. JZL195-elicited long-term depression is blocked by AM281, the antagonist of cannabinoid 1 receptor (CB₁R) and is abolished in mice lacking cannabinoid CB₁ receptor (CB₁R) in astroglial cells, but is conserved in mice lacking CB₁R in glutamatergic or GABAergic neurons. Blocking the glutamate NMDA receptor and the synaptic trafficking of glutamate AMPA receptor abolishes both long-term depression and neuroprotection induced by JZL195. Mice lacking CB₁R in astroglia show decreased neuronal death following cerebral ischemia. Thus, an acute elevation of extracellular eCB following eCB clearance inhibition results in neuroprotection through long-term depression induction after sequential activation of astroglial CB₁R and postsynaptic glutamate receptors.

Phased Treatment Strategies for Cerebral Ischemia Based on Glutamate Receptors

Extracellular glutamate accumulation following cerebral ischemia leads to overactivation of glutamate receptors, thereby resulting in intracellular Ca²⁺ overload and excitotoxic neuronal injury. Multiple attempts have been made to counteract such effects by reducing glutamate receptor function, but none have been successful. In this minireview, we present the available evidence regarding the role of all types of ionotropic and metabotropic glutamate receptors in cerebral ischemia and propose phased treatment strategies based on glutamate receptors in both the acute and post-acute phases of cerebral ischemia, which may help realize the clinical application of glutamate receptor antagonists.

Disruption of the GluA2/GAPDH complex using TAT-GluA2NT1-3-2 peptide protects against AMPAR-mediated excitotoxicity after epilepsy

Excitotoxicity and neuronal death following epilepsy involve α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). It forms a protein complex with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and co-internalizes upon activation of AMPA receptors after epilepsy. Disruption of the GluA2/GAPDH complex with an interfering peptide, TAT-GluA2NT1-3-2, protects cells against AMPAR-mediated excitotoxicity, which have been identified in in-vitro and in-vivo models of brain ischemia. We postulated that disruption of the GluA2/GAPDH interaction with the TAT-GluA2NT1-3-2 peptide would also protect against AMPAR-induced neuronal injury in an in-vivo model of status epilepticus (SE). In the present study, we divided pilocarpine-induced SE Wistar rats into three main groups: the TAT-GluA2NT1-3-2 peptide group, the TAT-GluA2NT-scram peptide group, and the normal saline group, and injected different doses of peptides stereotaxically into the hippocampus of SE rats to investigate whether the GluA2/GAPDH interaction could be disrupted by our TAT-GluA2NT1-3-2 peptide and determine its most appropriate dose. Then, the dose was administered stereotaxically at different time points after SE to determine the best administration time of neuronal protection. We found that the TAT-GluA2NT1-3-2 peptide can disrupt the GluA2/GAPDH interaction and protects against epilepsy-induced neuronal damage. The GluA2/GAPDH interaction may be a novel therapeutic target for epilepsy.

Specific Alterations in Astrocyte Properties via the GluA2-GAPDH Complex Associated with Multiple Sclerosis

There is strong evidence indicating neuroinflammation is an important mediator in multiple sclerosis (MS), with astrogliosis playing a significant role in this process. Surprisingly, astrocytes exert paradoxical roles during disease development, but the mechanisms remain unknown. Previously, we have reported that administering an interfering peptide (GluA2-G-Gpep) which specifically disrupts the GluA2-GAPDH interaction rescued neurological symptoms in the EAE mouse model of MS. In this study, we validated that the GluA2-GAPDH complex was elevated in LPS-induced primary reactive astrocytes, and GluA2-G-Gpep treatment significantly reduced GFAP expression levels in both EAE mice and reactive astrocytes. Further in vivo and in vitro analyses revealed that GluA2-G-Gpep administration normalized EAAT1 and EAAT2 expression, rescued compromised blood-brain barrier integrity via AQP4, promoted actin reorganization and changed mitochondrial dynamics. These alterations may partially be explained by changes in the nuclear GAPDH and p53 transcription pathways. Our findings provide critical implications for understanding the astrocyte properties regulated by GluA2-GAPDH associated with MS, and insights for novel treatment options targeting at astrocytes.

Evaluation of common housekeeping proteins under ischemic conditions and/or rt-PA treatment in bEnd.3 cells

Thrombolysis with recombinant tissue plasminogen activator (rt-PA) is the only pharmacological approved treatment for ischemic stroke, despite its associated increasing risk of hemorrhagic transformation. Since many of rt-PA effects in blood-brain barrier (BBB) are not well characterized, the study of protein changes in BBB cells after rt-PA administration may help to understand its adverse effects. Our aim was to analyze protein levels of four commonly used housekeeping proteins: β-Actin, α-Tubulin, GAPDH and HPRT in bEnd.3 endothelial cell line subjected to oxygen and glucose deprivation (OGD) conditions and rt-PA treatment to determine their reliability as Western blot loading controls. bEnd.3 monolayers were subjected to 2.5 h of OGD and reperfusion with/without 20 μg/ml of rt-PA. At 3, 6, 24 and 72 h post-OGD, protein levels were analyzed by Western blot using Stain-Free technology. OGD significantly decreased β-Actin, α-Tubulin, GAPDH and HPRT protein levels at 3, 6, 24 and 72 h post-OGD without significant rt-PA treatment effects except for the GAPDH levels increase in control condition at 3 h post-OGD. The present study clearly demonstrated that β-Actin, α-Tubulin, GAPDH and HPRT proteins are not suitable as loading controls for Western Blot analysis in bEnd.3 cells after OGD.

SIGNIFICANCE

We reported altered levels of β-Actin, α-Tubulin, GAPDH and HPRT housekeeping proteins in bEnd.3 endothelial cell line after an ischemic insult. Therefore, we demonstrated that these proteins are not suitable as loading controls for Western Blot analysis in our experimental conditions and we recommended the use of Stain-Free gels as an alternative to traditional housekeeping proteins normalization.

Disrupting GluA2-GAPDH Interaction Affects Axon and Dendrite Development

GluA2-containing AMPA receptors (AMPARs) play a critical role in various aspects of neurodevelopment. However, the molecular mechanisms underlying these processes are largely unknown. We report here that the interaction between GluA2 and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is necessary for neuron and cortical development. Using an interfering peptide (GluA2-G-Gpep) that specifically disrupts this interaction, we found that primary neuron cultures with peptide treatment displayed growth cone development deficits, impairment of axon formation, less dendritic arborization and lower spine protrusion density. Consistently, in vivo data with mouse brains from pregnant dams injected with GluA2-G-Gpep daily during embryonic day 8 to 19 revealed a reduction of cortical tract axon integrity and neuronal density in post-natal day 1 offspring. Disruption of GluA2-GAPDH interaction also impairs the GluA2-Plexin A4 interaction and reduces p53 acetylation in mice, both of which are possible mechanisms leading to the observed neurodevelopmental abnormalities. Furthermore, electrophysiological experiments indicate altered long-term potentiation (LTP) in hippocampal slices of offspring mice. Our results provide novel evidence that AMPARs, specifically the GluA2 subunit via its interaction with GAPDH, play a critical role in cortical neurodevelopment.

Quantitative proteomics analysis of zebrafish exposed to sub-lethal dosages of β-methyl-amino-L-alanine (BMAA)

The non-protein amino acid β-methylamino-L-alanine (BMAA) is a neurotoxin present in microalgae and shown to accumulate in the food web. BMAA has been linked to the complex neurodegenerative disorder of Guam and to increased incidents sporadic ALS. Two main neurotoxic routes are suggested; an excitotoxic by acting as an agonist towards glutamate receptors and a metabolic by misincorporating into cellular proteins. We have used zebrafish, an increasingly used model for neurodegenerative diseases, to further identify signaling components involved in BMAA-induced toxicity. Zebrafish embryos were exposed to sub-lethal dosages of BMAA and a label-free proteomics analysis was conducted on larvae 4 days post fertilization. The exposed larvae showed no developmental abnormalities, but a reduced heart rate and increased expression of GSK3 isoforms. Search towards a reviewed database containing 2968 entries identified 480 proteins. Only 17 of these were regulated 2-fold or more in the exposed larvae. Seven of these proteins could be associated to glutamate receptor signaling and recycling. The remaining nine have all been linked to disturbance in protein homeostasis, reactive oxygen species (ROS) development or neuronal cell death. We also found that BMAA influenced the endocannabinoid system by up-regulation of fatty acid amide hydrolase (FAAH) and that FAAH inhibitor URB597 reduced the BMAA effect on heart rate and GSK3 expression.

Enzyme Complexes Important for the Glutamate-Glutamine Cycle

Transient multienzyme and/or multiprotein complexes (metabolons) direct substrates toward specific pathways and can significantly influence the metabolism of glutamate and glutamine in the brain. Glutamate is the primary excitatory neurotransmitter in brain. This neurotransmitter has essential roles in normal brain function including learning and memory. Metabolism of glutamate involves the coordinated activity of astrocytes and neurons and high affinity transporter proteins that are selectively distributed on these cells. This chapter describes known and possible metabolons that affect the metabolism of glutamate and related compounds in the brain, as well as some factors that can modulate the association and dissociation of such complexes, including protein modifications by acylation reactions (e.g., acetylation, palmitoylation, succinylation, SUMOylation, etc.) of specific residues. Development of strategies to modulate transient multienzyme and/or enzyme-protein interactions may represent a novel and promising therapeutic approach for treatment of diseases involving dysregulation of glutamate metabolism.

Involvement of GluR2 up-regulation in neuroprotection by electroacupuncture pretreatment via cannabinoid CB1 receptor in mice

We investigated whether glutamate receptor subunit 2 (GluR2) is involved in EA pretreatment-induced neuroprotection via cannabinoid CB1 receptors (CB1R) after global cerebral ischemia in mice. Two hours after electric acupuncture (EA) pretreatment, global cerebral ischemia (GCI) was induced by bilateral common carotid artery occlusion (BCCAO) for 20 min. The GluR2 expression was examined in the hippocampus after reperfusion. Cell survival, neuronal apoptosis, the Bax/Bcl-2 ratio and neurological scores were evaluated at 24 h after BCCAO in the presence or absence of the GluR2 inhibitor. Furthermore, the GluR2 was determined in the presence and absence of CB1R inhibitor. Our results showed EA pretreatment enhanced expression of GluR2 in the hippocampus 2 h after reperfusion. Moreover, EA pretreatment improved neurological outcome, promoted cell survival, inhibited neuronal apoptosis, and decreased the Bax/Bcl-2 ratio after reperfusion. GluR2 knockdown by GluR2 siRNA effectively reversed the beneficial effects of EA pretreatment. Furthermore, CB1R siRNA and two CB1R antagonists blocked the elevation of GluR2 expression by EA pretreatment, whereas the two CB1R agonists up-regulated GluR2 expression as EA pretreatment. In conclusion, GluR2 up-regulation is involved in neuroprotection of EA pretreatment against GCI through CB1R, suggesting that GluR2 may be a novel target for stroke intervention.

Blocking GluR2-GAPDH ameliorates experimental autoimmune encephalomyelitis

OBJECTIVE

Multiple sclerosis (MS) is the most common disabling neurological disease of young adults. The pathophysiological mechanism of MS remains largely unknown and no cure is available. Current clinical treatments for MS modulate the immune system, with the rationale that autoimmunity is at the core of MS pathophysiology.

METHODS

Experimental autoimmune encephalitis (EAE) was induced in mice with MOG35-55 and clinical scoring was performed to monitor signs of paralysis. EAE mice were injected intraperitoneally with TAT-fusion peptides daily from day 10 until day 30 after immunization, and their effects were measured at day 17 or day 30.

RESULTS

We report a novel target for the development of MS therapy, which aimed at blocking glutamate-mediated neurotoxicity through targeting the interaction between the AMPA (2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl) propanoic acid) receptor and an interacting protein. We found that protein complex composed of the GluR2 subunit of AMPA receptors and GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was present at significantly higher levels in postmortem tissue from MS patients and in EAE mice, an animal model for MS. Next, we developed a peptide that specifically disrupts the GluR2 -GAPDH complex. This peptide greatly improves neurological function in EAE mice, reduces neuron death, rescues demyelination, increases oligodendrocyte survival, and reduces axonal damage in the spinal cords of EAE mice. More importantly, our peptide has no direct suppressive effect on naive T-cell responses or basal neurotransmission.

INTERPRETATION

The GluR2 -GAPDH complex represents a novel therapeutic target for the development of medications for MS that work through a different mechanism than existing treatments.

Pivotal role of cerebral interleukin-23 during immunologic injury in delayed cerebral ischemia in mice

BACKGROUND

Interleukin-23 (IL-23) is required for T helper 17 (Th17) cell responses and IL-17 production in ischemic stroke. We previously showed that the IL-23/IL-17 axis aggravates immune injury after cerebral infarction in mice. However, IL-23 might activate other cytokines and transcription factor forkhead box P3 (Foxp3) production in cerebral ischemia. We aimed to determine whether IL-23p19 knockdown prevents cerebral ischemic injury by reducing ischemic-induced inflammation.

METHODS

Ischemic stroke models were established by permanent middle cerebral arterial occlusion (pMCAO) in male C57BL/6 mice. In vivo gene knockdown was achieved by intravenous delivery of lentiviral vectors (LVs) encoding IL-23p19 short hairpin RNA (LV-IL-23p19 shRNA). Enzyme-linked immunoassay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR) confirmed inhibitory efficiency. Behavioral deficits were evaluated by adhesive-removal somatic-sensory test. Brain infarct volume was measured at day 5 after pMCAO by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Expression of IL-17, IL-4, interferon (IFN)-γ and Foxp3 in ischemic brain tissues were detected by qRT-PCR and Western blotting, respectively. Additionally, immunohistochemical staining located cytokines in ischemic brain tissues.

RESULTS

RNA interference knockdown of IL-23p19 resulted in improved neurological function and reduced infarct volume. IL-23p19 knockdown suppressed IL-17 gene and protein expression. Moreover, IL-23p19 deficiency enhanced IFN-γ and Foxp3 expressions in delayed cerebral ischemic mice, and did not impact IL-4 expression. Immunohistochemical staining showed that IL-17, IL-4, IFN-γ and Foxp3-positive cells were located around ischemic lesions of the ipsilateral hemisphere.

CONCLUSIONS

IL-23p19 knockdown prevents delayed cerebral ischemic injury by dampening the ischemia-induced inflammation, and is a promising approach for clinically managing ischemic stroke.

"Moonlighting" GAPDH Protein Localizes with AMPA Receptor GluA2 and L1 Axonal Cell Adhesion Molecule at Fiber Cell Borders in the Lens

PURPOSE

The canonical role of glyceraldehyde phosphate dehydrogenase (GAPDH) is as an enzyme in glycolysis. GAPDH is also a principal "moonlighting" protein with additional roles at diverse sites in a variety of cells. Surface GAPDH on mammalian, yeast, and bacterial cells acts as a receptor and also mediates cell contacts. In neurons, extracellular GAPDH localizes at synapses. Two GAPDH binding partners at synapses are α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptor (AMPA) GluA2 subunit at dendritic spines and L1 cell adhesion molecule at pre-synaptic membranes, and both proteins are also expressed in lenses. Fiber cell membrane protrusions and dendritic spines have similar size, shape, and spacing, contain F-actin, and express clathrin/AP-2 Adaptor at their surfaces linked with Tyr-phosphatase STEP-regulated endocytosis of AMPA/GluA2 receptors. AMPA receptors work with NMDA (N-methyl-d-aspartate) and GABA (γ-aminobutyric acid) receptors, calcium calmodulin kinase II (CaMKIIα), channel proteins, STEP, and ephrin receptors, which are also expressed in lenses. In neurons, coordinate AMPA/GluA2 receptor endocytosis with GAPDH is linked with disease. GAPDH was previously characterized as a fiber cell membrane protein and shown to decrease substantially in interior fiber cells in human age-related cataract. Here, we examined GAPDH spatial expression in healthy lenses in two vertebrate species.

METHODS

In situ methods were used to examine GAPDH expression in lenses of healthy young adult rabbits and chickens. Immunoblots were used to detect L1 in lenses.

RESULTS

The present study demonstrated that GAPDH is present at fiber cell borders in adult rabbit and chicken lenses with evidence of focal concentrations along the fiber cell perimeter, and overlapped with detection of p-Tyr-GluA2, L1, STEP, actin and clathrin. We observed that L1-140 kDa was the prominent form in lens.

CONCLUSIONS

Our findings indicate investigations into GAPDH "moonlighting" activities similar to its role in cell-cell interactions at neuron surfaces are warranted in the lens.

A dopamine D2 receptor-DISC1 protein complex may contribute to antipsychotic-like effects

Current antipsychotic drugs primarily target dopamine D2 receptors (D2Rs), in conjunction with other receptors such as those for serotonin. However, these drugs have serious side effects such as extrapyramidal symptoms (EPS) and diabetes. Identifying a specific D2R signaling pathway that could be targeted for antipsychotic effects, without inducing EPS, would be a significant improvement in the treatment of schizophrenia. We report here that the D2R forms a protein complex with Disrupted in Schizophrenia 1 (DISC1) that facilitates D2R-mediated glycogen synthase kinase (GSK)-3 signaling and inhibits agonist-induced D2R internalization. D2R-DISC1 complex levels are increased in conjunction with decreased GSK-3α/β (Ser21/9) phosphorylation in both postmortem brain tissue from schizophrenia patients and in Disc1-L100P mutant mice, an animal model with behavioral abnormalities related to schizophrenia. Administration of an interfering peptide that disrupts the D2R-DISC1 complex successfully reverses behaviors relevant to schizophrenia but does not induce catalepsy, a strong predictor of EPS in humans.

P38 MAPK inhibition protects against glutamate neurotoxicity and modifies NMDA and AMPA receptor subunit expression

NMDA and AMPA receptors are thought to be responsible for Ca(++) influx during glutamate-induced excitotoxicity and, therefore, hippocampal neuronal death. We assessed whether excitotoxicity induced by neonatal treatment with monosodium glutamate in rats at postnatal age of 1, 3, 5, and 7 modifies the hippocampal expression of the NMDAR subunit NR1 and the AMPAR subunits GluR1/GluR2 at postnatal days 8, 10, 12, and 14. We also assessed the involvement of MAPK signaling by using the p38 inhibitor SB203580. Our results showed that monosodium glutamate induces neuronal death and alters the expression of the subunits evaluated in the hippocampus at all ages studied, which could be prevented by SB203580 treatment.Furthermore, expression of the NRSF gene silencing factor also increased in response to excitotoxicity, suggesting a relationship in suppressing GluR2-expression, which was regulated by the p38-MAPK pathway inhibitor SB203580. This result suggests that selectively blocking the pro-death signaling pathway may reduce neuronal death in some neurodegenerative diseases in which these neurotoxic processes are present and produce major clinical benefits in the treatment of these pathologies.

Ligand-gated ion channel interacting proteins and their role in neuroprotection

Ion channel receptors are a vital component of nervous system signaling, allowing rapid and direct conversion of a chemical neurotransmitter message to an electrical current. In recent decades, it has become apparent that ionotropic receptors are regulated by protein-protein interactions with other ion channels, G-protein coupled receptors and intracellular proteins. These other proteins can also be modulated by these interactions with ion channel receptors. This bidirectional functional cross-talk is important for critical cellular functions such as excitotoxicity in pathological and disease states like stroke, and for the basic dynamics of activity-dependent synaptic plasticity. Protein interactions with ion channel receptors can therefore increase the computational capacity of neuronal signaling cascades and also represent a novel target for therapeutic intervention in neuropsychiatric disease. This review will highlight some examples of ion channel receptor interactions and their potential clinical utility for neuroprotection.

Disruption of the nuclear p53-GAPDH complex protects against ischemia-induced neuronal damage

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is conventionally considered a critical enzyme that involves in glycolysis for energy production. Recent previous studies have suggested that GAPDH is important in glutamate-induced neuronal excitotoxicity, while accumulated evidence also demonstrated that GAPDH nuclear translocation plays a critical role in cell death. However, the molecular mechanisms underlying this process remain largely unknown. In this study, we showed that GAPDH translocates to the nucleus in a Siah1-dependent manner upon glutamate stimulation. The nuclear GAPDH forms a protein complex with p53 and enhances p53 expression and phosphorylation. Disruption of the GAPDH-p53 interaction with an interfering peptide blocks glutamate-induced cell death and GAPDH-mediated up-regulation of p53 expression and phosphorylation. Furthermore, administration of the interfering peptide in vivo protects against ischemia-induced cell death in rats subjected to tMCAo. Our data suggest that the nuclear p53-GAPDH complex is important in regulating glutamate-mediated neuronal death and could serve as a potential therapeutic target for ischemic stroke treatment.