Browse
Submit Data
Databases
API
Help

Dataset Information

27 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Masking of the endoplasmic reticulum retention signals during assembly of the NMDA receptor.

ABSTRACT: NMDA receptors are glutamate-gated ion channels that play important roles in synaptic transmission and excitotoxicity. The functional NMDA receptor is thought to be a heterotetramer composed mainly of two NR1 and two NR2 subunits. Although it is generally accepted that only correctly assembled NMDA receptors can pass the ER quality control, the mechanism underlying this process is not well understood. Using truncated and chimeric NMDA receptor subunits expressed in heterologous cells and cortical neurons, we found that the third membrane domains (M3) of both NR1 and NR2B contain signals that cause the unassembled subunits to be retained in the ER. M3 of both NR1 and NR2B and, M4 of NR1, are necessary for masking ER retention signals found in M3. Thus, our data reveal a critical role of the membrane domains in the assembly of functional NMDA receptors.

SUBMITTER: Horak M

PROVIDER: S-EPMC6670593 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Masking of the endoplasmic reticulum retention signals during assembly of the NMDA receptor.

Horak Martin M Chang Kai K Wenthold Robert J RJ

The Journal of neuroscience : the official journal of the Society for Neuroscience 20080301 13

NMDA receptors are glutamate-gated ion channels that play important roles in synaptic transmission and excitotoxicity. The functional NMDA receptor is thought to be a heterotetramer composed mainly of two NR1 and two NR2 subunits. Although it is generally accepted that only correctly assembled NMDA receptors can pass the ER quality control, the mechanism underlying this process is not well understood. Using truncated and chimeric NMDA receptor subunits expressed in heterologous cells and cortica ...[more]

PMID: 18367616

Similar Datasets

Retention of NMDA receptor NR2 subunits in the lumen of endoplasmic reticulum in targeted NR1 knockout mice.

Project description:Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system, and the N-methyl-D-aspartate-selective glutamate receptor (NR) consisting of the NR1 subunit and an NR2 or NR3 subunit plays crucial roles in synaptic transmission, plasticity, and learning and memory. By using a knockout mouse strain, in which the NR1 gene deletion is primarily targeted to the CA1 pyramidal cells of the hippocampus, we investigated the in vivo effect of the loss of the NR1 subunit on the cellular expression and intracellular distribution of the NR2 subunits. The NR1 gene deletion had no apparent effect on the levels of NR2A or NR2B mRNA but led to severe reductions of NR2A and NR2B protein in dendrites of CA1 pyramidal cells. This reduced dendritic distribution of the NR2 subunits accompanied their robust accumulation in perikarya, where they were condensed in the lumen of the endoplasmic reticulum as electron-dense granules. These granules were also observed in CA1 pyramidal cells of the control mice but they were much fewer and contained no detectable levels of the NR2 subunit. The effect of the NR1 knockout on intracellular localization of the NR2 subunits was specific in that no such effect was observed for the GluR1 and PSD-95, two other major postsynaptic proteins. These results suggest that the NR1 subunit plays a crucial role in the release of the NR2 subunit from the endoplasmic reticulum in hippocampal pyramidal cells in vivo, and when the NR1 subunit is unavailable, the NR2 subunits are retained and aggregate into intracisternal granules.

| S-EPMC153645 | biostudies-literature

Interplay of substrate retention and export signals in endoplasmic reticulum quality control.

Project description:BACKGROUND: Endoplasmic reticulum (ER) quality control mechanisms are part of a comprehensive system to manage cell stress. The flux of molecules is monitored to retain folding intermediates and target misfolded molecules to ER-associated degradation (ERAD) pathways. The mechanisms of sorting remain unclear. While some proteins are retained statically, the classical model substrate CPY* is found in COPII transport vesicles, suggesting a retrieval mechanism for retention. However, its management can be even more dynamic. If ERAD is saturated under stress, excess CPY* traffics to the vacuole for degradation. These observations suggest that misfolded proteins might display different signals for their management. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report the existence of a functional ER exit signal in the pro-domain of CPY*. Compromising its integrity causes ER retention through exclusion from COPII vesicles. The signal co-exists with other signals used for retention and degradation. Physiologically, the export signal is important for stress tolerance. Disabling it converts a benign protein into one that is intrinsically cytotoxic. CONCLUSIONS/SIGNIFICANCE: These data reveal the remarkable interplay between opposing signals embedded within ERAD substrate molecules and the mechanisms that decipher them. Our findings demonstrate the diversity of mechanisms deployed for protein quality control and maintenance of protein homeostasis.

| S-EPMC2991357 | biostudies-literature

The Arabidopsis endoplasmic reticulum retention receptor functions in yeast.

Project description:Soluble proteins retained in the lumen of the endoplasmic reticulum (ER) contain a carboxyl-terminal tetrapeptide sequence that functions presumably to recycle these proteins from a subsequent compartment. Biochemical and genetic evidence indicate that the ERD2 gene product is the receptor for these ER retention signals. Here we report the identification of a cDNA clone from Arabidopsis thaliana (aERD2) similar in sequence and size to members of the ERD2 gene family. Southern and Northern blot analyses indicate that Arabidopsis contains a single aERD2 gene which is expressed at different levels in various plant tissues. A functional assay demonstrates that the Arabidopsis homologue, unlike the mammalian protein, can complement the lethal phenotype of the erd2 deletion mutant of Saccharomyces cerevisiae, indicating that this protein may have a similar function in plants. As the plant protein may have a binding specificity similar to the human Erd2 protein but can function in yeast, we suggest that the plant homologue is the functional link between yeast and animals.

| S-EPMC47997 | biostudies-other

NMDA receptor stimulation induces reversible fission of the neuronal endoplasmic reticulum.

Project description:With few exceptions the endoplasmic reticulum (ER) is considered a continuous system of endomembranes within which proteins and ions can move. We have studied dynamic structural changes of the ER in hippocampal neurons in primary culture and organotypic slices. Fluorescence recovery after photobleaching (FRAP) was used to quantify and model ER structural dynamics. Ultrastructure was assessed by electron microscopy. In live cell imaging experiments we found that, under basal conditions, the ER of neuronal soma and dendrites was continuous. The smooth and uninterrupted appearance of the ER changed dramatically after glutamate stimulation. The ER fragmented into isolated vesicles in a rapid fission reaction that occurred prior to overt signs of neuronal damage. ER fission was found to be independent of ER calcium levels. Apart from glutamate, the calcium ionophore ionomycin was able to induce ER fission. The N-methyl, D-aspartate (NMDA) receptor antagonist MK-801 inhibited ER fission induced by glutamate as well as by ionomycin. Fission was not blocked by either ifenprodil or kinase inhibitors. Interestingly, sub-lethal NMDA receptor stimulation caused rapid ER fission followed by fusion. Hence, ER fission is not strictly associated with cellular damage or death. Our results thus demonstrate that neuronal ER structure is dynamically regulated with important consequences for protein mobility and ER luminal calcium tunneling.

| S-EPMC2668765 | biostudies-other

Wnt signaling is regulated by endoplasmic reticulum retention.

Project description:Precise regulation of Wnt signaling is important in many contexts, as in development of the vertebrate forebrain, where excessive or ectopic Wnt signaling leads to severe brain defects. Mutation of the widely expressed oto gene causes loss of the anterior forebrain during mouse embryogenesis. Here we report that oto is the mouse ortholog of the gpi deacylase gene pgap1, and that the endoplasmic reticulum (ER)-resident Oto protein has a novel and deacylase-independent function during Wnt maturation. Oto increases the hydrophobicities of Wnt3a and Wnt1 by promoting the addition of glycophosphatidylinositol (gpi)-like anchors to these Wnts, which results in their retention in the ER. We also report that oto-deficient embryos exhibit prematurely robust Wnt activity in the Wnt1 domain of the early neural plate. We examine the effect of low oto expression on Wnt1 in vitro by knocking down endogenous oto expression in 293 and M14 melanoma cells using shRNA. Knockdown of oto results in increased Wnt1 secretion which is correlated with greatly enhanced canonical Wnt activity. These data indicate that oto deficiency increases Wnt signaling in vivo and in vitro. Finally, we address the mechanism of Oto-mediated Wnt retention under oto-abundant conditions, by cotransfecting Wnt1 with gpi-specific phospholipase D (GPI-PLD). The presence of GPI-PLD in the secretory pathway results in increased secretion of soluble Wnt1, suggesting that the gpi-like anchor lipids on Wnt1 mediate its retention in the ER. These data now provide a mechanistic framework for understanding the forebrain defects in oto mice, and support a role for Oto-mediated Wnt regulation during early brain development. Our work highlights a critical role for ER retention in regulating Wnt signaling in the mouse embryo, and gives insight into the notoriously inefficient secretion of Wnts.

| S-EPMC2703784 | biostudies-literature

CDIP1-BAP31 complex transduces apoptotic signals from endoplasmic reticulum to mitochondria under endoplasmic reticulum stress.

Project description:Resolved endoplasmic reticulum (ER) stress response is essential for intracellular homeostatic balance, but unsettled ER stress can lead to apoptosis. Here, we show that a proapoptotic p53 target, CDIP1, acts as a key signal transducer of ER-stress-mediated apoptosis. We identify B-cell-receptor-associated protein 31 (BAP31) as an interacting partner of CDIP1. Upon ER stress, CDIP1 is induced and enhances an association with BAP31 at the ER membrane. We also show that CDIP1 binding to BAP31 is required for BAP31 cleavage upon ER stress and for BAP31-Bcl-2 association. The recruitment of Bcl-2 to the BAP31-CDIP1 complex, as well as CDIP1-dependent truncated Bid (tBid) and caspase-8 activation, contributes to BAX oligomerization. Genetic knockout of CDIP1 in mice leads to impaired response to ER-stress-mediated apoptosis. Altogether, our data demonstrate that the CDIP1/BAP31-mediated regulation of mitochondrial apoptosis pathway represents a mechanism for establishing an ER-mitochondrial crosstalk for ER-stress-mediated apoptosis signaling.

| S-EPMC3833439 | biostudies-literature

Mammalian endoplasmic reticulum stress sensor IRE1 signals by dynamic clustering.

Project description:Accumulation of misfolded proteins in the endoplasmic reticulum (ER) triggers the unfolded protein response (UPR), an intracellular signaling pathway that adjusts the protein folding capacity of the ER according to need. If homeostasis in the ER protein folding environment cannot be reestablished, cells commit to apoptosis. The ER-resident transmembrane kinase-endoribonuclease inositol-requiring enzyme 1 (IRE1) is the best characterized UPR signal transduction molecule. In yeast, Ire1 oligomerizes upon activation in response to an accumulation of misfolded proteins in the ER. Here we show that the salient mechanistic features of IRE1 activation are conserved: mammalian IRE1 oligomerizes in the ER membrane and oligomerization correlates with the onset of IRE1 phosphorylation and RNase activity. Moreover, the kinase/RNase module of human IRE1 activates cooperatively in vitro, indicating that formation of oligomers larger than four IRE1 molecules takes place upon activation. High-order IRE1 oligomerization thus emerges as a conserved mechanism of IRE1 signaling. IRE1 signaling attenuates after prolonged ER stress. IRE1 then enters a refractive state even if ER stress remains unmitigated. Attenuation includes dissolution of IRE1 clusters, IRE1 dephosphorylation, and decline in endoribonuclease activity. Thus IRE1 activity is governed by a timer that may be important in switching the UPR from the initially cytoprotective phase to the apoptotic mode.

| S-EPMC2941319 | biostudies-literature

Lynx1 shifts ?4?2 nicotinic receptor subunit stoichiometry by affecting assembly in the endoplasmic reticulum.

Project description:Glycosylphosphatidylinositol-anchored neurotoxin-like receptor binding proteins, such as lynx modulators, are topologically positioned to exert pharmacological effects by binding to the extracellular portion of nAChRs. These actions are generally thought to proceed when both lynx and the nAChRs are on the plasma membrane. Here, we demonstrate that lynx1 also exerts effects on ?4?2 nAChRs within the endoplasmic reticulum. Lynx1 affects assembly of nascent ?4 and ?2 subunits and alters the stoichiometry of the receptor population that reaches the plasma membrane. Additionally, these data suggest that lynx1 shifts nAChR stoichiometry to low sensitivity (?4)3(?2)2 pentamers primarily through this interaction in the endoplasmic reticulum, rather than solely via direct modulation of activity on the plasma membrane. To our knowledge, these data represent the first test of the hypothesis that a lynx family member, or indeed any glycosylphosphatidylinositol-anchored protein, could act within the cell to alter assembly of a multisubunit protein.

| S-EPMC4223341 | biostudies-literature

A plant-specific calreticulin is a key retention factor for a defective brassinosteroid receptor in the endoplasmic reticulum.

Project description:Mammalian calreticulin (CRT) is a multifunctional Ca(2+)-binding protein involved in more than 40 cellular processes in various subcellular compartments, such as Ca(2+) storage and protein folding in the endoplasmic reticulum (ER). CRT homologues were discovered in plants almost 15 years ago, and recent studies revealed that many plant species contain 2 or more CRTs that are members of 2 distinct families, the CRT1/2 family and the plant-specific CRT3 family. However, little is known about their physiological functions. Here we report ebs2 (EMS-mutagenized bri1 suppressor 2) as an allele-specific suppressor of bri1-9, a dwarf Arabidopsis mutant caused by retention of a defective brassinosteroid receptor in the ER. EBS2 encodes the Arabidopsis CRT3 that interacts with ER-localized bri1-9 in a glycan-dependent manner. Loss-of-function ebs2 mutations compromise ER retention of bri1-9 and suppress its dwarfism, whereas EBS2 over-expression enhances its dwarf phenotype. In contrast, mutations of 2 other CRTs or their membrane-localized homologues calnexins had little effect on bri1-9. A domain-swapping experiment revealed that the positively charged C-terminal tail of CRT3 is crucial for its "bri1-9-retainer" function. Our study revealed not only a functional role for a plant-specific CRT, but also functional diversity among the 3 Arabidopsis CRT paralogues.

| S-EPMC2726391 | biostudies-literature

A Metabotropic-Like Flux-Independent NMDA Receptor Regulates Ca2+ Exit from Endoplasmic Reticulum and Mitochondrial Membrane Potential in Cultured Astrocytes.

Project description:Astrocytes were long thought to be only structural cells in the CNS; however, their functional properties support their role in information processing and cognition. The ionotropic glutamate N-methyl D-aspartate (NMDA) receptor (NMDAR) is critical for CNS functions, but its expression and function in astrocytes is still a matter of research and debate. Here, we report immunofluorescence (IF) labeling in rat cultured cortical astrocytes (rCCA) of all NMDAR subunits, with phenotypes suggesting their intracellular transport, and their mRNA were detected by qRT-PCR. IF and Western Blot revealed GluN1 full-length synthesis, subunit critical for NMDAR assembly and transport, and its plasma membrane localization. Functionally, we found an iCa2+ rise after NMDA treatment in Fluo-4-AM labeled rCCA, an effect blocked by the NMDAR competitive inhibitors D(-)-2-amino-5-phosphonopentanoic acid (APV) and Kynurenic acid (KYNA) and dependent upon GluN1 expression as evidenced by siRNA knock down. Surprisingly, the iCa2+ rise was not blocked by MK-801, an NMDAR channel blocker, or by extracellular Ca2+ depletion, indicating flux-independent NMDAR function. In contrast, the IP3 receptor (IP3R) inhibitor XestosponginC did block this response, whereas a Ryanodine Receptor inhibitor did so only partially. Furthermore, tyrosine kinase inhibition with genistein enhanced the NMDA elicited iCa2+ rise to levels comparable to those reached by the gliotransmitter ATP, but with different population dynamics. Finally, NMDA depleted the rCCA mitochondrial membrane potential (m??) measured with JC-1. Our results demonstrate that rCCA express NMDAR subunits which assemble into functional receptors that mediate a metabotropic-like, non-canonical, flux-independent iCa2+ increase.

| S-EPMC4425671 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data