Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Biosynthesis of the dystonia-associated AAA+ ATPase torsinA at the endoplasmic reticulum.

ABSTRACT: TorsinA is a widely expressed AAA(+) (ATPases associated with various cellular activities) ATPase of unknown function. Previous studies have described torsinA as a type II protein with a cleavable signal sequence, a single membrane spanning domain, and its C-terminus located in the ER (endoplasmic reticulum) lumen. However, in the present study we show that torsinA is not in fact an integral membrane protein. Instead we find that the mature protein associates peripherally with the ER membrane, most likely through an interaction with an integral membrane protein. Consistent with this model, we provide evidence that the signal peptidase complex cleaves the signal sequence of torsinA, and we show that the region previously suggested to form a transmembrane domain is translocated into the lumen of the ER. The finding that torsinA is a peripheral, and not an integral membrane protein as previously thought, has important implications for understanding the function of this novel ATPase.

SUBMITTER: Callan AC

PROVIDER: S-EPMC1820811 | biostudies-other | 2007 Jan

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

TorsinA participates in endoplasmic reticulum-associated degradation.

Project description:TorsinA is an AAA+ ATPase located within the lumen of the endoplasmic reticulum and nuclear envelope, with a mutant form causing early onset torsion dystonia (DYT1). Here we report a new function for torsinA in endoplasmic reticulum-associated degradation (ERAD). Retro-translocation and proteosomal degradation of a mutant cystic fibrosis transmembrane conductance regulator (CFTRΔF508) was inhibited by downregulation of torsinA or overexpression of mutant torsinA, and facilitated by increased torsinA. Retro-translocation of cholera toxin was also decreased by downregulation of torsinA. TorsinA associates with proteins implicated in ERAD, including Derlin-1, VIMP and p97. Further, torsinA reduces endoplasmic reticulum stress in nematodes overexpressing CFTRΔF508, and fibroblasts from DYT1 dystonia patients are more sensitive than controls to endoplasmic reticulum stress and less able to degrade mutant CFTR. Therefore, compromised ERAD function in the cells of DYT1 patients may increase sensitivity to endoplasmic reticulum stress with consequent alterations in neuronal function contributing to the disease state.

| S-EPMC3529909 | biostudies-literature

The AAA + ATPase TorsinA polymerizes into hollow helical tubes with 8.5 subunits per turn.

Project description:TorsinA is an ER-resident AAA + ATPase, whose deletion of glutamate E303 results in the genetic neuromuscular disease primary dystonia. TorsinA is an unusual AAA + ATPase that needs an external activator. Also, it likely does not thread a peptide substrate through a narrow central channel, in contrast to its closest structural homologs. Here, we examined the oligomerization of TorsinA to get closer to a molecular understanding of its still enigmatic function. We observe TorsinA to form helical filaments, which we analyzed by cryo-electron microscopy using helical reconstruction. The 4.4 Å structure reveals long hollow tubes with a helical periodicity of 8.5 subunits per turn, and an inner channel of ~ 4 nm diameter. We further show that the protein is able to induce tubulation of membranes in vitro, an observation that may reflect an entirely new characteristic of AAA + ATPases. We discuss the implications of these observations for TorsinA function.

| S-EPMC6646356 | biostudies-literature

A conserved AAA+ ATPase network regulates endoplasmic reticulum stress-induced transcription

Project description:In C. elegans cdc-48.2(-/-) mutant animals, ER stress-mediated expression of the UPR ckb-2::GFP reporter transgene is abolished. Here, we have used this phenotype in a genome-wide RNAi screen to identify genes involved in the CDC-48.2 mediated ER stress transcription. Combined with a comparative proteomic analysis, this approach has allowed us to identify the AAA+ ATPase RUVB-2 as a novel regulator of the ER stress response and a CDC-48 degradation target.

2015-09-30 | PXD000636 | Pride

Static retention of the lumenal monotopic membrane protein torsinA in the endoplasmic reticulum.

Project description:TorsinA is a membrane-associated enzyme in the endoplasmic reticulum (ER) lumen that is mutated in DYT1 dystonia. How it remains in the ER has been unclear. We report that a hydrophobic N-terminal domain (NTD) directs static retention of torsinA within the ER by excluding it from ER exit sites, as has been previously reported for short transmembrane domains (TMDs). We show that despite the NTD's physicochemical similarity to TMDs, it does not traverse the membrane, defining torsinA as a lumenal monotopic membrane protein and requiring a new paradigm to explain retention. ER retention and membrane association are perturbed by a subset of nonconservative mutations to the NTD, suggesting that a helical structure with defined orientation in the membrane is required. TorsinA preferentially enriches in ER sheets, as might be expected for a lumenal monotopic membrane protein. We propose that the principle of membrane-based protein sorting extends to monotopic membrane proteins, and identify other proteins including the monotopic lumenal enzyme cyclooxygenase 1 (prostaglandin H synthase 1) that share this mechanism of retention with torsinA.

| S-EPMC3160655 | biostudies-literature

Characterization of human torsinA and its dystonia-associated mutant form.

Project description:Deletion of a single glutamate in torsinA correlates with early-onset dystonia, the most severe form of a neurological disorder characterized by uncontrollable muscle contractions. TorsinA is targeted to the ER (endoplasmic reticulum) in eukaryotic cells. We investigated the processing and membrane association of torsinA and the dystonia-associated Glu-deletion mutant (torsinAdeltaE). We found that the signal sequence of torsinA (residues 1-20 from the 40 amino-acid long N-terminal hydrophobic region) is cleaved in Drosophila S2 cells, as shown by the N-terminal sequencing after partial protein purification. TorsinA is not secreted from S2 cells. Consistently, sodium carbonate extraction and Triton X-114 treatment showed that torsinA is associated with the ER membrane in CHO (Chinese-hamster ovary) cells. In contrast, a variant of torsinA that contains the native signal sequence without the hydrophobic region Ile24-Pro40 does not associate with the membranes in CHO cells, and a truncated torsinA without the 40 N-terminal amino acids is secreted in the S2 culture. Thus the 20-amino-acid-long hydrophobic segment in torsinA, which remains at the N-terminus after signal-peptide cleavage, is responsible for the membrane anchoring of torsinA. TorsinAdeltaE showed similar cleavage of the 20 N-terminal amino acids and membrane association properties similar to wild-type torsinA but, unlike the wild-type, torsinAdeltaE was not secreted in the S2 culture even after deletion of the membrane-anchoring segment. This indicates that the dystonia-associated mutation produces a structurally distinct, possibly misfolded, form of torsinA, which cannot be properly processed in the secretory pathway of eukaryotic cells.

| S-EPMC1223590 | biostudies-other

Cholinergic dysregulation produced by selective inactivation of the dystonia-associated protein torsinA.

Project description:DYT1 dystonia, a common and severe primary dystonia, is caused by a 3-bp deletion in TOR1A which encodes torsinA, a protein found in the endoplasmic reticulum. Several cellular functions are altered by the mutant protein, but at a systems level the link between these and the symptoms of the disease is unclear. The most effective known therapy for DYT1 dystonia is the use of anticholinergic drugs. Previous studies have revealed that in mice, transgenic expression of human mutant torsinA under a non-selective promoter leads to abnormal function of striatal cholinergic neurons. To investigate what pathological role torsinA plays in cholinergic neurons, we created a mouse model in which the Dyt1 gene, the mouse homolog of TOR1A, is selectively deleted in cholinergic neurons (ChKO animals). These animals do not have overt dystonia, but do have subtle motor abnormalities. There is no change in the number or size of striatal cholinergic cells or striatal acetylcholine content, uptake, synthesis, or release in ChKO mice. There are, however, striking functional abnormalities of striatal cholinergic cells, with paradoxical excitation in response to D2 receptor activation and loss of muscarinic M2/M4 receptor inhibitory function. These effects are specific for cholinergic interneurons, as recordings from nigral dopaminergic neurons revealed normal responses. Amphetamine stimulated dopamine release was also unaltered. These results demonstrate a cell-autonomous effect of Dyt1 deletion on striatal cholinergic function. Therapies directed at modifying the function of cholinergic neurons may prove useful in the treatment of the human disorder.

| S-EPMC3392411 | biostudies-literature

Liver cytochrome P450 3A endoplasmic reticulum-associated degradation: a major role for the p97 AAA ATPase in cytochrome P450 3A extraction into the cytosol.

Project description:The CYP3A subfamily of hepatic cytochromes P450, being engaged in the metabolism and clearance of >50% of clinically relevant drugs, can significantly influence therapeutics and drug-drug interactions. Our characterization of CYP3A degradation has indicated that CYPs 3A incur ubiquitin-dependent proteasomal degradation (UPD) in an endoplasmic reticulum (ER)-associated degradation (ERAD) process. Cytochromes P450 are monotopic hemoproteins N-terminally anchored to the ER membrane with their protein bulk readily accessible to the cytosolic proteasome. Given this topology, it was unclear whether they would require the AAA-ATPase p97 chaperone complex that retrotranslocates/dislocates ubiquitinated ER-integral and luminal proteins into the cytosol for proteasomal delivery. To assess the in vivo relevance of this p97-CYP3A association, we used lentiviral shRNAs to silence p97 (80% mRNA and 90% protein knockdown relative to controls) in sandwich-cultured rat hepatocytes. This extensive hepatic p97 knockdown remarkably had no effect on cellular morphology, ER stress, and/or apoptosis, despite the well recognized strategic p97 roles in multiple important cellular processes. However, such hepatic p97 knockdown almost completely abrogated CYP3A extraction into the cytosol, resulting in a significant accumulation of parent and ubiquitinated CYP3A species that were firmly ER-tethered. Little detectable CYP3A accumulated in the cytosol, even after concomitant inhibition of proteasomal degradation, thereby documenting a major role of p97 in CYP3A extraction and delivery to the 26 S proteasome during its UPD/ERAD. Intriguingly, the accumulated parent CYP3A was functionally active, indicating that p97 can regulate physiological CYP3A content and thus influence its clinically relevant function.

| S-EPMC3030383 | biostudies-other

SBF-1 exerts strong anticervical cancer effect through inducing endoplasmic reticulum stress-associated cell death via targeting sarco/endoplasmic reticulum Ca(2+)-ATPase 2.

Project description:Cervical cancer is one of the most common carcinomas in the genital system. In the present study, we report that SBF-1, a synthetic steroidal glycoside, has a strong antigrowth activity against human cervical cancer cells in vitro and in vivo. SBF-1 suppressed the growth, migration and colony formation of HeLa cells. In addition, severe endoplasmic reticulum (ER) stress was triggered by SBF-1, and 4-phenyl-butyric acid, a chemical chaperone, partially reversed SBF-1-induced cell death. To uncover the target protein of SBF-1, the compound was labeled with biotin. The biotin-labeled SBF-1 bound to sarco/ER Ca(2+)-ATPase 2 (SERCA2) and colocalized with SERCA2 in HeLa cells. Moreover, SBF-1 inhibited SERCA activity, depleted ER Ca2+ and increased cytosolic Ca2+ levels. 1,2-Bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, a chelator of Ca2+, partially blocked SBF-1-induced ER stress and growth inhibition. Importantly, knockdown of SERCA2 increased the sensitivity of HeLa cells to SBF-1-induced ER stress and cell death, whereas overexpression of SERCA2 decreased this sensitivity. Furthermore, SBF-1 induced growth suppression and apoptosis in HeLa xenografts, which is closely related to the induction of ER stress and inhibition of SERCA activity. Finally, SERCA2 expression was elevated in human cervical cancer tissues (n=299) and lymph node metastasis (n=8), as compared with normal cervix tissues (n=23), with a positive correlation with clinical stages. In all, these results suggest that SBF-1 disrupts Ca2+ homeostasis and causes ER stress-associated cell death through directly binding to SERCA2 and inhibiting SERCA activity. Our findings also indicate that SERCA2 is a potential therapeutic target for human cervical cancer.

| S-EPMC4649847 | biostudies-literature

The endoplasmic reticulum P5A-ATPase is a transmembrane helix dislocase.

Project description:Organelle identity depends on protein composition. How mistargeted proteins are selectively recognized and removed from organelles is incompletely understood. Here, we found that the orphan P5A-adenosine triphosphatase (ATPase) transporter ATP13A1 (Spf1 in yeast) directly interacted with the transmembrane segment (TM) of mitochondrial tail-anchored proteins. P5A-ATPase activity mediated the extraction of mistargeted proteins from the endoplasmic reticulum (ER). Cryo-electron microscopy structures of Saccharomyces cerevisiae Spf1 revealed a large, membrane-accessible substrate-binding pocket that alternately faced the ER lumen and cytosol and an endogenous substrate resembling an α-helical TM. Our results indicate that the P5A-ATPase could dislocate misinserted hydrophobic helices flanked by short basic segments from the ER. TM dislocation by the P5A-ATPase establishes an additional class of P-type ATPase substrates and may correct mistakes in protein targeting or topogenesis.

| S-EPMC8053355 | biostudies-literature

Access of torsinA to the inner nuclear membrane is activity dependent and regulated in the endoplasmic reticulum.

Project description:TorsinA (also known as torsin-1A) is a membrane-embedded AAA+ ATPase that has an important role in the nuclear envelope lumen. However, most torsinA is localized in the peripheral endoplasmic reticulum (ER) lumen where it has a slow mobility that is incompatible with free equilibration between ER subdomains. We now find that nuclear-envelope-localized torsinA is present on the inner nuclear membrane (INM) and ask how torsinA reaches this subdomain. The ER system contains two transmembrane proteins, LAP1 and LULL1 (also known as TOR1AIP1 and TOR1AIP2, respectively), that reversibly co-assemble with and activate torsinA. Whereas LAP1 localizes on the INM, we show that LULL1 is in the peripheral ER and does not enter the INM. Paradoxically, interaction between torsinA and LULL1 in the ER targets torsinA to the INM. Native gel electrophoresis reveals torsinA oligomeric complexes that are destabilized by LULL1. Mutations in torsinA or LULL1 that inhibit ATPase activity reduce the access of torsinA to the INM. Furthermore, although LULL1 binds torsinA in the ER lumen, its effect on torsinA localization requires cytosolic-domain-mediated oligomerization. These data suggest that LULL1 oligomerizes to engage and transiently disassemble torsinA oligomers, and is thereby positioned to transduce cytoplasmic signals to the INM through torsinA.

| S-EPMC4540951 | 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