TorsinA and DYT1 dystonia: a synaptopathy?

2010 ◽  
Vol 38 (2) ◽  
pp. 452-456 ◽  
Author(s):  
Thomas T. Warner ◽  
Alassandra Granata ◽  
Giampietro Schiavo
Keyword(s):  
Nuclear Envelope ◽  
Early Onset ◽  
Secretory Pathway ◽  
Autosomal Dominant ◽  
Multiple Functions ◽  
Functional Roles ◽  
Aaa Atpase ◽  
Dyt1 Dystonia ◽  
C Terminus ◽  
Dyt1 Gene

DYT1 dystonia is an autosomal dominant movement disorder, characterized by early onset of involuntary sustained muscle contractions. It is caused by a 3-bp deletion in the DYT1 gene, which results in the deletion of a single glutamate residue in the C-terminus of the protein TA (torsinA). TA is a member of the AAA+ (ATPase associated with various cellular activities) family of chaperones with multiple functions in the cell. There is no evidence of neurodegeneration in DYT1 dystonia, which suggests that mutant TA leads to functional neuronal abnormalities, leading to dystonic movements. In recent years, different functional roles have been attributed to TA, including being a component of the cytoskeleton and the NE (nuclear envelope), and involvement in the secretory pathway and SV (synaptic vesicle) machinery. The aim of the present review is to summarize these findings and the different models proposed, which have contributed to our current understanding of the function of TA, and also to discuss the evidence implicating TA in SV function.

scholarly journals Expression of TorsinA in a heterologous yeast system reveals interactions with conserved lumenal domains of LINC and nuclear pore complexes

2018 ◽  
Author(s):  
Madeleine Chalfant ◽  
Karl W. Barber ◽  
Sapan Borah ◽  
David Thaller ◽  
C. Patrick Lusk
Keyword(s):  
Nuclear Envelope ◽  
Genetic Interaction ◽  
Spindle Pole ◽  
Nuclear Pore ◽  
Physical Interaction ◽  
Nuclear Pore Complexes ◽  
Gene Encoding ◽  
Aaa Atpase ◽  
Dyt1 Dystonia ◽  
Pore Complexes

ABSTRACTDYT1 dystonia is caused by an in-frame deletion of a glutamic acid codon in the gene encoding the AAA+ ATPase TorsinA. TorsinA localizes within the lumen of the nuclear envelope/ER and binds to a membrane-spanning co-factor, LAP1 or LULL1, to form an ATPase; the substrate(s) of TorsinA remain ill defined. Here we use budding yeast, which lack Torsins, to interrogate TorsinA function. We show that TorsinA accumulates at nuclear envelope embedded spindle pole bodies (SPBs) in a way that requires its oligomerization and the conserved SUN-domain protein, Mps3. TorsinA is released from SPBs upon expression of LAP1 and stabilized by LAP1 mutants incapable of stimulating TorsinA ATPase activity, suggesting the recapitulation of a TorsinA-substrate cycle. While the expression of TorsinA or TorsinA-ΔE impacts the fitness of strains expressing mps3 alleles, a genetic interaction with a conserved component of the nuclear pore complex, Pom152, is specific for TorsinA. This specificity is mirrored by a physical interaction between Pom152 and TorsinA, but not TorsinA-ΔE. These data suggest that TorsinA-nucleoporin interactions would be abrogated by TorsinA-ΔE, providing new experimental avenues to interrogate the molecular basis behind nuclear envelope herniations seen in cells lacking TorsinA function.

scholarly journals LULL1 Retargets TorsinA to the Nuclear Envelope Revealing an Activity That Is Impaired by the DYT1 Dystonia Mutation

2009 ◽  
Vol 20 (11) ◽  
pp. 2661-2672 ◽  
Author(s):  
Abigail B. Vander Heyden ◽  
Teresa V. Naismith ◽  
Erik L. Snapp ◽  
Didier Hodzic ◽  
Phyllis I. Hanson
Keyword(s):  
Nuclear Envelope ◽  
Membrane Structure ◽  
Wild Type ◽  
Nuclear Pores ◽  
Native Page ◽  
Aaa Atpase ◽  
Dyt1 Dystonia ◽  
Blue Native Page ◽  
Transient Interaction ◽  
Blue Native

TorsinA (TorA) is an AAA+ ATPase in the endoplasmic reticulum (ER) lumen that is mutated in early onset DYT1 dystonia. TorA is an essential protein in mice and is thought to function in the nuclear envelope (NE) despite localizing throughout the ER. Here, we report that transient interaction of TorA with the ER membrane protein LULL1 targets TorA to the NE. FRAP and Blue Native PAGE indicate that TorA is a stable, slowly diffusing oligomer in either the absence or presence of LULL1. Increasing LULL1 expression redistributes both wild-type and disease-mutant TorA to the NE, while decreasing LULL1 with shRNAs eliminates intrinsic enrichment of disease-mutant TorA in the NE. When concentrated in the NE, TorA displaces the nuclear membrane proteins Sun2, nesprin-2G, and nesprin-3 while leaving nuclear pores and Sun1 unchanged. Wild-type TorA also induces changes in NE membrane structure. Because SUN proteins interact with nesprins to connect nucleus and cytoskeleton, these effects suggest a new role for TorA in modulating complexes that traverse the NE. Importantly, once concentrated in the NE, disease-mutant TorA displaces Sun2 with reduced efficiency and does not change NE membrane structure. Together, our data suggest that LULL1 regulates the distribution and activity of TorA within the ER and NE lumen and reveal functional defects in the mutant protein responsible for DYT1 dystonia.

scholarly journals MLF2 modulates phase separated nuclear envelope condensates that provoke dual proteotoxicity

2021 ◽  
Author(s):  
Sarah M Prophet ◽  
Anthony J Rampello ◽  
Robert F Niescier ◽  
Juliana E Shaw ◽  
Anthony J Koleske ◽  
...  
Keyword(s):  
Phase Separation ◽  
Nuclear Envelope ◽  
Nuclear Pore ◽  
Disease Manifestation ◽  
Disease Etiology ◽  
Aaa Atpase ◽  
Dyt1 Dystonia ◽  
Chaperone Network ◽  
Neurological Movement Disorder

DYT1 dystonia is a highly debilitating neurological movement disorder arising from mutation in the AAA+ ATPase TorsinA. The hallmark of Torsin dysfunction is nuclear envelope blebbing resulting from defects in nuclear pore complex biogenesis. Whether blebs actively contribute to disease manifestation is presently unknown. We report that FG-nucleoporins in the bleb lumen undergo phase separation and contribute to DYT1 dystonia by provoking two proteotoxic insults. Short-lived ubiquitinated proteins that are normally rapidly degraded in healthy cells partition into the bleb lumen and become stabilized. Additionally, blebs selectively sequester a chaperone network composed of HSP70s and HSP40s. The composition of this chaperone network is altered by the bleb component MLF2. We further demonstrate that MLF2 is a catalyst of phase separation that suppresses the ectopic accumulation of FG-nucleoporins and modulates the selective properties and size of condensates in vitro. Our studies identify unprecedented, dual mechanisms of proteotoxicity in the context of liquid-liquid phase separation with direct implications for our understanding of disease etiology and treatment.

scholarly journals Expression of TorsinA in a heterologous yeast system reveals interactions with lumenal domains of LINC and nuclear pore complex components

2019 ◽  
Vol 30 (5) ◽  
pp. 530-541 ◽  
Author(s):  
Madeleine Chalfant ◽  
Karl W. Barber ◽  
Sapan Borah ◽  
David Thaller ◽  
C. Patrick Lusk
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Mammalian Cells ◽  
Spindle Pole ◽  
Nuclear Pore ◽  
Gene Encoding ◽  
Aaa Atpase ◽  
Dyt1 Dystonia ◽  
Physiological Relevance ◽  
Membrane Spanning

DYT1 dystonia is caused by an in-frame deletion of a glutamic acid codon in the gene encoding the AAA+ ATPase TorsinA (TorA). TorA localizes within the lumen of the nuclear envelope/endoplasmic reticulum and binds to a membrane-spanning cofactor, lamina associated polypeptide 1 (LAP1) or lumenal domain like LAP1 (LULL1), to form an ATPase; the substrate(s) of TorA remains ill-defined. Here we use budding yeast, which lack Torsins, to interrogate TorA function. We show that TorA accumulates at nuclear envelope-embedded spindle pole bodies (SPBs) in a way that requires its oligomerization and the SUN (Sad1 and UNc-84)-domain protein, Mps3. We further show that TorA physically interacts with human SUN1/2 within this system, supporting the physiological relevance of these interactions. Consistent with the idea that TorA acts on a SPB substrate, its binding to SPBs is modulated by the ATPase-stimulating activity of LAP1. TorA and TorA-ΔE reduce the fitness of cells expressing mps3 alleles, whereas TorA alone inhibits growth of cells lacking Pom152, a component of the nuclear pore complex. This genetic specificity is mirrored biochemically as TorA, but not TorA-ΔE, binds Pom152. Thus, TorA–nucleoporin interactions might be abrogated by TorA-ΔE, suggesting new experimental avenues to interrogate the molecular basis behind nuclear envelope herniations seen in mammalian cells lacking TorA function.

scholarly journals Localization of the signal of dystonia-associated protein torsinA near the Golgi apparatus in cultured central neurons

2019 ◽  
Author(s):  
Sadahiro Iwabuchi ◽  
Hiroyuki Kawano ◽  
N. Charles Harata
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Nuclear Envelope ◽  
Autosomal Dominant ◽  
Wild Type ◽  
Glutamic Acid Residue ◽  
Dyt1 Dystonia ◽  
Central Neurons ◽  
Endogenous Level ◽  
Abnormal Posture

ABSTRACTA single in-frame deletion of a codon for a glutamic acid residue within the TOR1A gene is linked to the autosomal-dominant movement disorder DYT1 dystonia, a condition characterized by involuntary muscle contractions that cause abnormal posture. This gene encodes the protein torsinA, and the functions of both wild-type and mutant (ΔE-torsinA) forms remain poorly understood. Previous studies based on overexpression systems indicated that wild-type torsinA resides mainly in the endoplasmic reticulum but that ΔE-torsinA is localized to the nuclear envelope or intracellular inclusions. This mutation-associated mis-localization has been proposed to underlie at least a part of the pathophysiology of DYT1 dystonia. However, the subcellular localization of torsinA has not been extensively studied when expressed at the endogenous level. Here we report an immunocytochemical analysis of torsinA proteins in cultured mouse neurons from a ΔE-torsinA knock-in model of DYT1 dystonia, where torsinA proteins are not upregulated. In all examined neurons of wild-type, heterozygous and homozygous mice, torsinA signal was found mainly near the Golgi apparatus, and only weakly in the endoplasmic reticulum and nuclear envelope. These results suggest that, in the absence of overexpression, torsinA proteins are localized near the Golgi apparatus and may influence cellular function involving the organelle.

scholarly journals The C-terminal helix 9 motif in rat cannabinoid receptor type 1 regulates axonal trafficking and surface expression

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Alexandra Fletcher-Jones ◽  
Keri L Hildick ◽  
Ashley J Evans ◽  
Yasuko Nakamura ◽  
Kevin A Wilkinson ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Secretory Pathway ◽  
Cannabinoid Receptor ◽  
Surface Expression ◽  
Surface Polarity ◽  
Time Resolved ◽  
Surface Stability ◽  
C Terminus ◽  
Time Resolved Imaging ◽  
Dual Mechanism

Cannabinoid type one receptor (CB1R) is only stably surface expressed in axons, where it downregulates neurotransmitter release. How this tightly regulated axonal surface polarity is established and maintained is unclear. To address this question, we used time-resolved imaging to determine the trafficking of CB1R from biosynthesis to mature polarised localisation in cultured rat hippocampal neurons. We show that the secretory pathway delivery of CB1R is axonally biased and that surface expressed CB1R is more stable in axons than in dendrites. This dual mechanism is mediated by the CB1R C-terminus and involves the Helix 9 (H9) domain. Removal of the H9 domain increases secretory pathway delivery to dendrites and decreases surface stability. Furthermore, CB1RΔH9 is more sensitive to agonist-induced internalisation and less efficient at downstream signalling than CB1RWT. Together, these results shed new light on how polarity of CB1R is mediated and indicate that the C-terminal H9 domain plays key roles in this process.

scholarly journals Ykt6 membrane-to-cytosol cycling regulates exosomal Wnt secretion

2018 ◽  
Author(s):  
Karen Linnemannstöns ◽  
Pradhipa Karuna M ◽  
Leonie Witte ◽  
Jeanette Clarissa Kittel ◽  
Adi Danieli ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Wnt Signaling ◽  
Signaling Pathways ◽  
Long Range ◽  
Protein Trafficking ◽  
Secretory Pathway ◽  
Multivesicular Bodies ◽  
Phosphorylation Sites ◽  
Wnt Proteins ◽  
C Terminus

Protein trafficking in the secretory pathway, for example the secretion of Wnt proteins, requires tight regulation. These ligands activate Wnt signaling pathways and are crucially involved in development and disease. Wnt is transported to the plasma membrane by its cargo receptor Evi, where Wnt/Evi complexes are endocytosed and sorted onto exosomes for long-range secretion. However, the trafficking steps within the endosomal compartment are not fully understood. The promiscuous SNARE Ykt6 folds into an auto-inhibiting conformation in the cytosol, but a portion associates with membranes by its farnesylated and palmitoylated C-terminus. Here, we demonstrate that membrane detachment of Ykt6 is essential for exosomal Wnt secretion. We identified conserved phosphorylation sites within the SNARE domain of Ykt6, which block Ykt6 cycling from the membrane to the cytosol. In Drosophila, Ykt6-RNAi mediated block of Wg secretion is rescued by wildtype but not phosphomimicking Ykt6. The latter accumulates at membranes, while wildtype Ykt6 regulates Wnt trafficking between the plasma membrane and multivesicular bodies. Taken together, we show that a regulatory switch in Ykt6 fine-tunes sorting of Wnts in endosomes.

scholarly journals Pkd1 mutation has no apparent effects on peroxisome structure or lipid metabolism

2021 ◽  
Author(s):  
Takeshi Terabayashi ◽  
Luis F Menezes ◽  
Fang Zhou ◽  
Hongyi Cai ◽  
Peter J Walter ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Autosomal Dominant ◽  
Acid Metabolism ◽  
Acid Oxidation ◽  
Peroxisome Biogenesis ◽  
Polycystic Kidney ◽  
Imaging Studies ◽  
C Terminus ◽  
Autosomal Dominant Polycystic Kidney ◽  
Mutant Cells

AbstractBackgroundMultiple studies of tissue and cell samples from patients and pre-clinical models of autosomal dominant polycystic kidney disease report abnormal mitochondrial function and morphology and suggest metabolic reprogramming is an intrinsic feature of this disease. Peroxisomes interact with mitochondria physically and functionally, and congenital peroxisome biogenesis disorders can cause various phenotypes, including mitochondrial defects, metabolic abnormalities and renal cysts. We hypothesized that a peroxisomal defect might contribute to the metabolic and mitochondrial impairments observed in autosomal dominant polycystic kidney disease.MethodsUsing control and Pkd1-/- kidney epithelial cells, we investigated peroxisome abundance, biogenesis and morphology by immunoblotting, immunofluorescent and live cell imaging of peroxisome-related proteins and assayed peroxisomal specific β-oxidation. We further analyzed fatty acid composition by mass spectrometry in kidneys of Pkd1fl/fl; Ksp-Cre mice. We also evaluated peroxisome lipid metabolism in published metabolomics datasets of Pkd1 mutant cells and kidneys. Lastly, we investigated if the C-terminus or full-length polycystin-1 co-localize with peroxisome markers by imaging studies.ResultsPeroxisome abundance, morphology and peroxisome-related protein expression in Pkd1-/- cells were normal, suggesting preserved peroxisome biogenesis. Peroxisomal β-oxidation was not impaired in Pkd1-/- cells, and there was no obvious accumulation of very long chain fatty acids in kidneys of mutant mice. Re-analysis of published datasets provide little evidence of peroxisomal abnormalities in independent sets of Pkd1 mutant cells and cystic kidneys, while providing further evidence of mitochondrial fatty acid oxidation defects. Imaging studies with either full length polycystin-1 or its C-terminus, a fragment previously shown to go to the mitochondria, showed minimal co-localization with peroxisome markers.ConclusionsOur studies showed that loss of Pkd1 does not disrupt peroxisome biogenesis nor peroxisome-dependent fatty acid metabolism.Key points-While mitochondrial abnormalities and fatty acid oxidation impairment have been reported in ADPKD, no studies have investigated if peroxisome dysfunction contributes to these defects.-We investigated peroxisome morphology, biogenesis and function in cell and animal models of ADPKD and investigated whether polycystin-1 co-localized with peroxisome proteins.-Our studies show that loss of Pkd1 does not disrupt peroxisome biogenesis nor peroxisome-dependent fatty acid metabolism.

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