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Edward B Ziff

Publications and source records attributed to Edward B Ziff.

At least 19 recordsLinked to original sources
PubMed2006

Developmentally regulated, combinatorial RNA processing modulates AMPA receptor biogenesis.

The subunit composition determines AMPA receptor (AMPA-R) function and trafficking. Mechanisms underlying channel assembly are thus central to the efficacy and plasticity of glutamatergic synapses. We previously showed that RNA editing at the Q/R site of the GluR2 subunit contributes to the assembly of AMPA-R heteromers by attenuating formation of GluR2 homotetramers. Here we report that this function of the Q/R site depends on subunit contacts between adjacent ligand binding domains (LBDs). Changes of LBD interface contacts alter GluR2 assembly properties, forward traffic, and expression at synapses. Interestingly, developmentally regulated RNA editing within the LBD (at the R/G site) produces analogous effects. Our data reveal that editing to glycine reduces the self-assembly competence of this critical subunit and slows GluR2 maturation in the endoplasmic reticulum (ER). Therefore, RNA editing sites, located at strategic subunit interfaces, shape AMPA-R assembly and trafficking in a developmentally regulated manner.

Amino Acid Sequence↗
PubMed2006

Getting to synaptic complexes through systems biology.

Large numbers of synaptic components have been identified, but the effect so far on our understanding of synaptic function is limited. Now, network maps and annotated functions of individual components have been used in a systems biology approach to analyzing the function of NMDA receptor complexes at synapses, identifying biologically relevant modular networks within the complex.

Animals↗
PubMed2006

Identification of transcriptional regulators of neuropeptide FF gene expression.

Neuropeptide FF (NPFF) is an RF-amide peptide with pleiotropic functions in the mammalian central nervous system, including pain modulation, opiate interactions, cardiovascular regulation and neuroendocrine effects. To gain insights into the transcriptional mechanisms that regulate NPFF gene expression, we cloned and sequenced 9.8 and 1.5 kb of the mouse and rat NPFF 5'-flanking region, respectively. Regions with high sequence homology between mouse, rat and human were expected to have high probability to interact with regulatory proteins and were studied further. Electromobility shift assays revealed one region that may interact with the homeobox proteins Oct-1, PDX1, Pit-1 and MEIS and two consensus DRE sites that bind a nuclear protein, which was identified as the downstream regulatory element antagonistic modulator DREAM by supershift assays. The distribution of NPFF gene expression was examined in the mouse using in situ hybridization and RT-PCR. NPFF expression was also evident during mouse embryogenesis. A fixed transcription initiation site for the mouse NPFF gene was found. A novel splice variant with a retained intron of the NPFF gene was characterized. Chimeric luciferase reporter gene constructs for the mouse NPFF gene revealed a minimal promoter region and a region with transcriptional suppressor features. An NGF responsive area was found using mouse NPFF reporter gene constructs. We postulate that Oct-1, PDX1, Pit-1, MEIS and DREAM are likely transcriptional regulators of NPFF gene expression.

5' Flanking Region↗
PubMed2006

Membrane localization of membrane type 5 matrix metalloproteinase by AMPA receptor binding protein and cleavage of cadherins.

Matrix metalloproteinases (MMPs) have been proposed to remodel the extracellular environment of neurons. Here, we report that the metalloproteinase membrane-type 5 MMP (MT5-MMP) binds to AMPA receptor binding protein (ABP) and GRIP (glutamate receptor interaction protein), two related postsynaptic density (PSD) PDZ (postsynaptic density-95/Discs large/zona occludens-1) domain proteins that target AMPA receptors to synapses. The MT5-MMP C terminus binds ABP PDZ5 and the two proteins coimmunoprecipitated and colocalized in heterologous cells and neurons. MT5-MMP localized in filopodia at the tips of growth cones in young [2-5 d in vitro (DIV)] cultured embryonic hippocampal neurons, and at synapses in mature (21 DIV) neurons. Its enrichment in synaptosomes also indicated a synaptic localization in the mature brain. Deletion of the PDZ binding site impaired membrane trafficking of MT5-MMP, whereas exogenous ABP splice forms that are associated either with the plasma membrane or with the cytosol, respectively, colocalized with MT5-MMP in synaptic spines or recruited MT5-MMP to intracellular compartments. We show that endogenous MT5-MMP is found in cultured neurons and brain lysates in a proenzyme form that is activated by furin and degraded by auto-proteolysis. We also identify cadherins as MT5-MMP substrates. These results suggest that ABP directs MT5-MMP proteolytic activity to growth cones and synaptic sites in neurons, where it may regulate axon pathfinding or synapse remodeling through proteolysis of cadherins or other ECM or cell adhesion molecules.

Animals↗
PubMed2005

PICK1 interacts with ABP/GRIP to regulate AMPA receptor trafficking.

PICK1 and ABP/GRIP bind to the AMPA receptor (AMPAR) GluR2 subunit C terminus. Transfer of the receptor from ABP/GRIP to PICK1, facilitated by GluR2 S880 phosphorylation, may initiate receptor trafficking. Here we report protein interactions that regulate these steps. The PICK1 BAR domain interacts intermolecularly with the ABP/GRIP linker II region and intramolecularly with the PICK1 PDZ domain. Binding of PKCalpha or GluR2 to the PICK1 PDZ domain disrupts the intramolecular interaction and facilitates the PICK1 BAR domain association with ABP/GRIP. Interference with the PICK1-ABP/GRIP interaction impairs S880 phosphorylation of GluR2 by PKC and decreases the constitutive surface expression of GluR2, the NMDA-induced endocytosis of GluR2, and recycling of internalized GluR2. We suggest that the PICK1 interaction with ABP/GRIP is a critical step in controlling GluR2 trafficking.

Amino Acid Sequence↗
PubMed2004

Identification and verification of novel rodent postsynaptic density proteins.

The postsynaptic density (PSD) is a cellular structure specialized in receiving and transducing synaptic information. Here we describe the identification of 452 proteins isolated from biochemically purified PSD fractions of rat and mouse brains using nanoflow HPLC coupled to electrospray tandem mass spectrometry (LC-MS/MS). Fluorescence microscopy and Western blotting were used to verify that many of the novel proteins identified exhibit subcellular distributions consistent with those of PSD-localized proteins. In addition to identifying most previously described PSD components, we also detected proteins involved in signaling to the nucleus as well as regulators of ADP-ribosylation factor signaling, ubiquitination, RNA trafficking, and protein translation. These results suggest new mechanisms by which the PSD helps regulate synaptic strength and transmission.

Animals↗
PubMed2004

Bidirectional regulation of neuronal nitric-oxide synthase phosphorylation at serine 847 by the N-methyl-D-aspartate receptor.

At glutamatergic synapses, the scaffolding protein PSD95 links the neuronal isoform of nitric-oxide synthase (nNOS) to the N-methyl-d-aspartate (NMDA) receptor. Phosphorylation of nNOS at serine 847 (Ser(847)) by the calcium-calmodulin protein kinase II (CaMKII) inhibits nNOS activity, possibly by blocking the binding of Ca(2+)-CaM. Here we show that the NMDA mediates a novel bidirectional regulation of Ser(847) phosphorylation. nNOS phosphorylated at Ser(847) colocalizes with the NMDA receptor at spines of cultured hippocampal neurons. Treatment of neurons with 5 microm glutamate stimulated CaMKII phosphorylation of nNOS at Ser(847), whereas excitotoxic concentrations of glutamate, 100 and 500 microm, induced Ser(847)-PO(4) dephosphorylation by protein phosphatase 1. Strong NMDA receptor stimulation was likely to activate nNOS under these conditions because protein nitration to form nitrotyrosine, a marker of nNOS activity, correlated in individual neurons with Ser(847)-PO(4) dephosphorylation. Of particular note, stimulation with low glutamate that increased phosphorylation of nNOS at Ser(847) could be reversed by subsequent high glutamate treatment which induced dephosphorylation. The reversibility of NMDA receptor-induced phosphorylation at Ser(847) by different doses of glutamate suggests two mechanisms with opposite effects: 1). a time-dependent negative feedback induced by physiological concentrations of glutamate that limits nNOS activation and precludes the overproduction of NO; and 2). a pathological stimulation by high concentrations of glutamate that leads to unregulated nNOS activation and production of toxic levels of NO. These mechanisms may share pathways, respectively, with NMDA receptor-induced forms of synaptic plasticity and excitotoxicity.

Animals↗
PubMed2003

AMPA receptor tetramerization is mediated by Q/R editing.

AMPA-type glutamate receptors (AMPARs) play a major role in excitatory synaptic transmission and plasticity. Channel properties are largely dictated by their composition of the four subunits, GluR1-4 (or A-D). Here we show that AMPAR assembly and subunit stoichiometry are determined by RNA editing in the pore loop. We demonstrate that editing at the GluR2 Q/R site regulates AMPAR assembly at the step of tetramerization. Specifically, edited R subunits are largely unassembled and ER retained, whereas unedited Q subunits readily tetramerize and traffic to synapses. This assembly mechanism restricts the number of the functionally critical R subunits in AMPAR tetramers. Therefore, a single amino acid residue affects channel composition and, in turn, controls ion conduction through the majority of AMPARs in the brain.

Amino Acid Sequence↗
PubMed2003

Intracellular membrane targeting and suppression of Ser880 phosphorylation of glutamate receptor 2 by the linker I-set II domain of AMPA receptor-binding protein.

AMPA receptor-binding protein (ABP) is a multi-postsynaptic density-95/discs large/zona occludens (PDZ) protein that binds to the glutamate receptor 2/3 (GluR2/3) subunits of the AMPA receptor and is implicated in receptor membrane anchorage. A palmitoylated form of ABP localizes to spine heads, whereas a nonpalmitoylated form is found in intracellular clusters. Here, we investigate intracellular cluster formation by ABP and the ability of ABP to associate with GluR2 while in these clusters. We show that ABP interacts with intracellular membranes via the ABP linker I (LI)-set II (SII) subdomain, a region consisting of ABP linker 1 and PDZ4, -5, and -6. This suggests that cluster formation results from LI-SII ABP association with the membrane of a vesicular structure. We present evidence that ABP can self-associate at intracellular membrane surfaces via interactions involving SII. ABP in such membrane clusters can bind and retain GluR2 that has trafficked endocytotically from the plasma membrane. Phosphorylation of GluR2 at serine 880, proximal to the ABP binding site, has been implicated by others in the release of ABP from GluR2 and the mobilization of AMPA receptors for trafficking. We show that binding of GluR2 to ABP blocks phosphorylation of serine 880. This suggests that ABP can stabilize its own association with GluR2. We discuss a model in which ABP can form a protein scaffold at a vesicular membrane that is capable of binding GluR2, leading to formation of an intracellular AMPA receptor pool. Receptors in such a pool may contribute to receptor endocytotic and exocytotic trafficking and recycling.

Adaptor Proteins, Signal Transducing↗
PubMed2003

NMDA receptor regulation of nNOS phosphorylation and induction of neuron death.

Stimulation of NMDA receptors activates neuronal nitric oxide synthase (nNOS) and the production of nitric oxide (NO). Dephosphorylation of nNOS increases nNOS enzymatic activity. We have examined the regulation of nNOS phosphorylation in rat cortical neurons following NMDA receptor activation. We show that nNOS is constitutively phosphorylated and that NMDA receptor activation decreases the level of nNOS phosphorylation by a mechanism that is blocked specifically by NMDA receptor antagonists and inhibitors of the Ca2+-regulated phosphatases calcineurin and PP1/PP2A. Using quantitative digital microscopy, we show that NMDA receptor activation induces the accumulation of nitrotyrosine, a measure of nNOS activity, and TdT-mediated fluorescein-dUTP nick end labeling (TUNEL) positivity, a measure of cell death. A calcineurin inhibitor blocked the increase in both TUNEL and nitrotyrosine positivity. Notably, TUNEL was increased in those neurons that were most strongly positive for nitrotyrosine. We conclude that NMDA receptor activation induces death of neurons by a cell autonomous pathway involving nNOS dephosphorylation by a calcineurin-dependent mechanism.

Animals↗
PubMed2002

AMPA receptors do the electric slide.

How the synapse is organized and how its organization changes during events that result in long-term changes in synaptic efficacy is the subject of intense study. Various anchoring proteins work in concert to organize the postsynaptic side of the membrane, and the interactions of these proteins can be altered by synaptic activity. DeSouza and Ziff discuss the evidence that the reversible palmitoylation of the postsynaptic density protein PSD-95 may result in the movement of AMPA-type glutamate receptors into and out of lipid raft domains, ultimately controlling AMPA receptor accumulation at the postsynaptic membrane.

Glutamic Acid↗
PubMed2002

Association of the AMPA receptor-related postsynaptic density proteins GRIP and ABP with subsets of glutamate-sensitive neurons in the rat retina.

We used specific antibodies against two postsynaptic density proteins, GRIP (glutamate receptor interacting protein) and ABP (AMPA receptor-binding protein), to study their distribution in the rat retina. In the central nervous system, it has been shown that both proteins bind strongly to the AMPA glutamate receptor (GluR) 2/3 subunits, but not other GluRs, through a set of three PDZ domains. Western blots detected a single GRIP protein that was virtually identical in retina and brain, whereas retinal ABP corresponded to only one of three ABP peptides found in brain. The retinal distributions of GluR2/3, GRIP, and ABP immunoreactivity (IR) were similar but not identical. GluR2/3 immunoreactivity (IR) was abundant in both plexiform layers and in large perikarya. ABP IR was concentrated in large perikarya but was sparse in the plexiform layers, whereas GRIP IR was relatively more abundant in the plexiform layers than in perikarya. Immunolabel for these three antibodies consisted of puncta < or = 0.2 microm in diameter. The cellular localization of GRIP and ABP IR was examined by double labeling subclasses of retinal neuron with characteristic marker proteins, e.g., calbindin. GRIP, ABP, and GluR2/3 IR were detected in horizontal cells, dopaminergic and glycinergic AII amacrine cells and large ganglion cells. Immunolabel was absent in rod bipolar and weak or absent in cholinergic amacrine cells. By using the tyramide method of signal amplification, a colocalization of GluR2/3 was found with either GRIP or ABP in horizontal cell terminals, and perikarya of amacrine and ganglion cells. Our results show that ABP and GRIP colocalize with GluR2/3 in particular subsets of retinal neuron, as was previously established for certain neurons in the brain.

Animals↗
PubMed2002

RNA editing at arg607 controls AMPA receptor exit from the endoplasmic reticulum.

AMPA-receptor (AMPAR) transport to synapses plays a critical role in the modulation of synaptic strength. We show that the functionally critical GluR2 subunit stably resides in an intracellular pool in the endoplasmic reticulum (ER). GluR2 in this pool is extensively complexed with GluR3 but not with GluR1, which is mainly confined to the cell surface. Mutagenesis revealed that elements in the C terminus including the PDZ motif are required for GluR2 forward-transport from the ER. Surprisingly, ER retention of GluR2 is controlled by Arg607 at the Q/R-editing site. Reversion to Gln (R607Q) resulted in rapid release from the pool and elevated surface expression of GluR2 in neurons. Therefore, Arg607 is a central regulator. In addition to channel gating, it also controls ER exit and may thereby ensure the availability of GluR2 for assembly into AMPARs.

Amidohydrolases↗
PubMed2002

Differential palmitoylation directs the AMPA receptor-binding protein ABP to spines or to intracellular clusters.

Long-term changes in excitatory synapse strength are thought to reflect changes in synaptic abundance of AMPA receptors mediated by receptor trafficking. AMPA receptor-binding protein (ABP) and glutamate receptor-interacting protein (GRIP) are two similar PDZ (postsynaptic density 95/Discs large/zona occludens 1) proteins that interact with glutamate receptors 2 and 3 (GluR2 and GluR3) subunits. Both proteins have proposed roles during long-term potentiation and long-term depression in the delivery and anchorage of AMPA receptors at synapses. Here we report a variant of ABP-L (seven PDZ form of ABP) called pABP-L that is palmitoylated at a cysteine residue at position 11 within a novel 18 amino acid N-terminal leader sequence encoded through differential splicing. In cultured hippocampal neurons, nonpalmitoylated ABP-L localizes with internal GluR2 pools expressed from a Sindbis virus vector, whereas pABP-L is membrane targeted and associates with surface-localized GluR2 receptors at the plasma membrane in spines. Mutation of Cys-11 to alanine blocks the palmitoylation of pABP-L and targets the protein to intracellular clusters, confirming that targeting the protein to spines is dependent on palmitoylation. Non-palmitoylated GRIP is primarily intracellular, but a chimera with the pABP-L N-terminal palmitoylation sequence linked to the body of the GRIP protein is targeted to spines. We suggest that pABP-L and ABP-L provide, respectively, synaptic and intracellular sites for the anchorage of AMPA receptors during receptor trafficking to and from the synapse.

Adaptor Proteins, Signal Transducing↗
PubMed2002

NSF ATPase and alpha-/beta-SNAPs disassemble the AMPA receptor-PICK1 complex.

AMPA receptor (AMPAR) trafficking is crucial for synaptic plasticity that may be important for learning and memory. NSF and PICK1 bind the AMPAR GluR2 subunit and are involved in trafficking of AMPARs. Here, we show that GluR2, PICK1, NSF, and alpha-/beta-SNAPs form a complex in the presence of ATPgammaS. Similar to SNARE complex disassembly, NSF ATPase activity disrupts PICK1-GluR2 interactions in this complex. Alpha- and beta-SNAP have differential effects on this reaction. SNAP overexpression in hippocampal neurons leads to corresponding changes in AMPAR trafficking by acting on GluR2-PICK1 complexes. This demonstrates that the previously reported synaptic stabilization of AMPARs by NSF involves disruption of GluR2-PICK1 interactions. Furthermore, we are reporting a non-SNARE substrate for NSF disassembly activity.

Adenosine Triphosphatases↗
PubMed2002

Ca2+-dependent formation of a dynamin-synaptophysin complex: potential role in synaptic vesicle endocytosis.

Synaptophysin is a synaptic vesicle (SV) protein of unknown function. Here we show that a repeated sequence in the cytoplasmic tail of synaptophysin mediates the formation of a protein complex containing the GTPase dynamin. The formation of this complex requires a high Ca(2+) concentration, suggesting that it occurs preferentially at the sites of SV exocytosis. Coimmunoprecipitation of a dynamin-synaptophysin complex from brain extracts is promoted by dissociation of vesicle-associated membrane protein 2 from synaptophysin. This finding suggests that dynamin only associates with synaptophysin in vivo after vesicle-associated membrane protein 2 (VAMP2) enters the SNARE complex. GTP binding releases dynamin from synaptophysin, possibly serving to regulate dynamin selfassembly during endocytosis. Our results suggest that synaptophysin plays a role in SV recycling by recruiting dynamin to the vesicle membrane.

Amino Acid Sequence↗
PubMed2002

Receptor trafficking and the plasticity of excitatory synapses.

Newly discovered features of the trafficking of AMPA receptors to and from the postsynaptic membrane of excitatory synapses are now bringing the mechanisms of synaptic plasticity into focus. Recent advances, including the existence of slots, anchors, transport factors and pathways for activity-dependent control, have elucidated the role of the individual AMPA receptor subunits and their binding partners. The latest views describe how subunit type dictates the assembly of heteromeric receptors, and how these heteromers interact with the receptor trafficking machinery and synaptic anchorage factors. Moreover, phosphorylation may play an important role in receptor transport and synaptic turnover.

Animals↗