The Experts below are selected from a list of 1422 Experts worldwide ranked by ideXlab platform
Evan Reid - One of the best experts on this subject based on the ideXlab platform.
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ESCRT-III-associated proteins and Spastin inhibit protrudin-dependent polarised membrane traffic
Cellular and Molecular Life Sciences, 2019Co-Authors: James W Connell, Rachel J. Allison, Catherine E. Rodger, Guy Pearson, Eliska Zlamalova, Evan ReidAbstract:Mutations in the gene encoding the microtubule severing ATPase Spastin are the most frequent cause of hereditary spastic paraplegia, a genetic condition characterised by length-dependent axonal degeneration. Here, we show that HeLa cells lacking Spastin and embryonic fibroblasts from a Spastin knock-in mouse model become highly polarised and develop cellular protrusions. In HeLa cells, this phenotype was rescued by wild-type Spastin, but not by forms unable to sever microtubules or interact with endosomal ESCRT-III proteins. Cells lacking the Spastin-interacting ESCRT-III-associated proteins IST1 or CHMP1B also developed protrusions. The protrusion phenotype required protrudin, a RAB-interacting protein that interacts with Spastin and localises to ER–endosome contact sites, where it promotes KIF5-dependent endosomal motility to protrusions. Consistent with this, the protrusion phenotype in cells lacking Spastin also required KIF5. Lack or mutation of Spastin resulted in functional consequences for receptor traffic of a pathway implicated in HSP, as Bone Morphogenetic Protein receptor distribution became polarised. Our results, therefore, identify a novel role for ESCRT-III proteins and Spastin in regulating polarised membrane traffic.
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BMP- and neuropilin 1-mediated motor axon navigation relies on Spastin alternative translation
Development (Cambridge England), 2018Co-Authors: Nicolas Jardin, Rachel Allison, Evan Reid, Jamilé Hazan, François Giudicelli, Daniel Ten Martín, Anaïs Vitrac, Stéphanie De Gois, Corinne Houart, Coralie FassierAbstract:Functional analyses of genes responsible for neurodegenerative disorders have unveiled crucial links between neurodegenerative processes and key developmental signalling pathways. Mutations in SPG4-encoding Spastin cause hereditary spastic paraplegia (HSP). Spastin is involved in diverse cellular processes that couple microtubule severing to membrane remodelling. Two main Spastin isoforms are synthesised from alternative translational start sites (M1 and M87). However, their specific roles in neuronal development and homeostasis remain largely unknown. To selectively unravel their neuronal function, we blocked Spastin synthesis from each initiation codon during zebrafish development and performed rescue analyses. The knockdown of each isoform led to different motor neuron and locomotion defects, which were not rescued by the selective expression of the other isoform. Notably, both morphant neuronal phenotypes were observed in a CRISPR/Cas9 Spastin mutant. We next showed that M1 Spastin, together with HSP proteins atlastin 1 and NIPA1, drives motor axon targeting by repressing BMP signalling, whereas M87 Spastin acts downstream of neuropilin 1 to control motor neuron migration. Our data therefore suggest that defective BMP and neuropilin 1 signalling may contribute to the motor phenotype in a vertebrate model of Spastin depletion.
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An ESCRT-Spastin interaction promotes fission of recycling tubules from the endosome
Journal of Cell Biology, 2013Co-Authors: Rachel Allison, James W Connell, Jamilé Hazan, Jennifer H. Lumb, Daniel Ten Martín, Coralie Fassier, Matthew N. J. Seaman, Evan ReidAbstract:Mechanisms coordinating endosomal degradation and recycling are poorly understood, as are the cellular roles of microtubule (MT) severing. We show that cells lacking the MT-severing protein Spastin had increased tubulation of and defective receptor sorting through endosomal tubular recycling compartments. Spastin required the ability to sever MTs and to interact with ESCRT-III (a complex controlling cargo degradation) proteins to regulate endosomal tubulation. Cells lacking IST1 (increased sodium tolerance 1), an endosomal sorting complex required for transport (ESCRT) component to which Spastin binds, also had increased endosomal tubulation. Our results suggest that inclusion of IST1 into the ESCRT complex allows recruitment of Spastin to promote fission of recycling tubules from the endosome. Thus, we reveal a novel cellular role for MT severing and identify a mechanism by which endosomal recycling can be coordinated with the degradative machinery. Spastin is mutated in the axonopathy hereditary spastic paraplegia. Zebrafish spinal motor axons depleted of Spastin or IST1 also had abnormal endosomal tubulation, so we propose this phenotype is important for axonal degeneration.
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The AAA ATPase Spastin links microtubule severing to membrane modelling.
Biochimica et biophysica acta, 2011Co-Authors: Jennifer H. Lumb, James W Connell, Rachel Allison, Evan ReidAbstract:In 1999, mutations in the gene encoding the microtubule severing AAA ATPase Spastin were identified as a major cause of a genetic neurodegenerative condition termed hereditary spastic paraplegia (HSP). This finding stimulated intense study of the Spastin protein and over the last decade, a combination of cell biological, in vivo, in vitro and structural studies have provided important mechanistic insights into the cellular functions of the protein, as well as elucidating cell biological pathways that might be involved in axonal maintenance and degeneration. Roles for Spastin have emerged in shaping the endoplasmic reticulum and the abscission stage of cytokinesis, in which Spastin appears to couple membrane modelling to microtubule regulation by severing.
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the hereditary spastic paraplegia proteins nipa1 Spastin and spartin are inhibitors of mammalian bmp signalling
Human Molecular Genetics, 2009Co-Authors: Hilda T H Tsang, James W Connell, Thomas L Edwards, Paul J Luzio, Xinnan Wang, Rachel J Davies, Hannah J Durrington, Cahir J Okane, Evan ReidAbstract:The hereditary spastic paraplegias (HSPs) are genetic conditions characterized by distal axonopathy of the longest corticospinal tract axons, and so their study provides an important opportunity to understand mechanisms involved in axonal maintenance and degeneration. A group of HSP genes encode proteins that localize to endosomes. One of these is NIPA1 (non-imprinted in Prader-Willi/Angelman syndrome 1) and we have shown recently that its Drosophila homologue spichthyin inhibits bone morphogenic protein (BMP) signalling, although the relevance of this finding to the mammalian protein was not known. We show here that mammalian NIPA1 is also an inhibitor of BMP signalling. NIPA1 physically interacts with the type II BMP receptor (BMPRII) and we demonstrate that this interaction does not require the cytoplasmic tail of BMPRII. We show that the mechanism by which NIPA1 inhibits BMP signalling involves downregulation of BMP receptors by promoting their endocytosis and lysosomal degradation. Disease-associated mutant versions of NIPA1 alter the trafficking of BMPRII and are less efficient at promoting BMPRII degradation than wild-type NIPA1. In addition, we demonstrate that two other members of the endosomal group of HSP proteins, Spastin and spartin, are inhibitors of BMP signalling. Since BMP signalling is important for distal axonal function, we propose that dysregulation of BMP signalling could be a unifying pathological component in this endosomal group of HSPs, and perhaps of importance in other conditions in which distal axonal degeneration is found.
James W Connell - One of the best experts on this subject based on the ideXlab platform.
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ESCRT-III-associated proteins and Spastin inhibit protrudin-dependent polarised membrane traffic
Cellular and Molecular Life Sciences, 2019Co-Authors: James W Connell, Rachel J. Allison, Catherine E. Rodger, Guy Pearson, Eliska Zlamalova, Evan ReidAbstract:Mutations in the gene encoding the microtubule severing ATPase Spastin are the most frequent cause of hereditary spastic paraplegia, a genetic condition characterised by length-dependent axonal degeneration. Here, we show that HeLa cells lacking Spastin and embryonic fibroblasts from a Spastin knock-in mouse model become highly polarised and develop cellular protrusions. In HeLa cells, this phenotype was rescued by wild-type Spastin, but not by forms unable to sever microtubules or interact with endosomal ESCRT-III proteins. Cells lacking the Spastin-interacting ESCRT-III-associated proteins IST1 or CHMP1B also developed protrusions. The protrusion phenotype required protrudin, a RAB-interacting protein that interacts with Spastin and localises to ER–endosome contact sites, where it promotes KIF5-dependent endosomal motility to protrusions. Consistent with this, the protrusion phenotype in cells lacking Spastin also required KIF5. Lack or mutation of Spastin resulted in functional consequences for receptor traffic of a pathway implicated in HSP, as Bone Morphogenetic Protein receptor distribution became polarised. Our results, therefore, identify a novel role for ESCRT-III proteins and Spastin in regulating polarised membrane traffic.
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An ESCRT-Spastin interaction promotes fission of recycling tubules from the endosome
Journal of Cell Biology, 2013Co-Authors: Rachel Allison, James W Connell, Jamilé Hazan, Jennifer H. Lumb, Daniel Ten Martín, Coralie Fassier, Matthew N. J. Seaman, Evan ReidAbstract:Mechanisms coordinating endosomal degradation and recycling are poorly understood, as are the cellular roles of microtubule (MT) severing. We show that cells lacking the MT-severing protein Spastin had increased tubulation of and defective receptor sorting through endosomal tubular recycling compartments. Spastin required the ability to sever MTs and to interact with ESCRT-III (a complex controlling cargo degradation) proteins to regulate endosomal tubulation. Cells lacking IST1 (increased sodium tolerance 1), an endosomal sorting complex required for transport (ESCRT) component to which Spastin binds, also had increased endosomal tubulation. Our results suggest that inclusion of IST1 into the ESCRT complex allows recruitment of Spastin to promote fission of recycling tubules from the endosome. Thus, we reveal a novel cellular role for MT severing and identify a mechanism by which endosomal recycling can be coordinated with the degradative machinery. Spastin is mutated in the axonopathy hereditary spastic paraplegia. Zebrafish spinal motor axons depleted of Spastin or IST1 also had abnormal endosomal tubulation, so we propose this phenotype is important for axonal degeneration.
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mutations in the er shaping protein reticulon 2 cause the axon degenerative disorder hereditary spastic paraplegia type 12
Journal of Clinical Investigation, 2012Co-Authors: Gladys Montenegro, Adriana P Rebelo, James W Connell, Rachel Allison, Carla Babalini, Michela Daloia, Pasqua Montieri, Hiroyuki Ishiura, Rebecca Schule, Justin PriceAbstract:: Hereditary spastic paraplegias (HSPs) are a group of genetically heterogeneous neurodegenerative conditions. They are characterized by progressive spastic paralysis of the legs as a result of selective, length-dependent degeneration of the axons of the corticospinal tract. Mutations in 3 genes encoding proteins that work together to shape the ER into sheets and tubules - receptor accessory protein 1 (REEP1), atlastin-1 (ATL1), and Spastin (SPAST) - have been found to underlie many cases of HSP in Northern Europe and North America. Applying Sanger and exome sequencing, we have now identified 3 mutations in reticulon 2 (RTN2), which encodes a member of the reticulon family of prototypic ER-shaping proteins, in families with spastic paraplegia 12 (SPG12). These autosomal dominant mutations included a complete deletion of RTN2 and a frameshift mutation predicted to produce a highly truncated protein. Wild-type reticulon 2, but not the truncated protein potentially encoded by the frameshift allele, localized to the ER. RTN2 interacted with Spastin, and this interaction required a hydrophobic region in Spastin that is involved in ER localization and that is predicted to form a curvature-inducing/sensing hairpin loop domain. Our results directly implicate a reticulon protein in axonopathy, show that this protein participates in a network of interactions among HSP proteins involved in ER shaping, and further support the hypothesis that abnormal ER morphogenesis is a pathogenic mechanism in HSP.
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The AAA ATPase Spastin links microtubule severing to membrane modelling.
Biochimica et biophysica acta, 2011Co-Authors: Jennifer H. Lumb, James W Connell, Rachel Allison, Evan ReidAbstract:In 1999, mutations in the gene encoding the microtubule severing AAA ATPase Spastin were identified as a major cause of a genetic neurodegenerative condition termed hereditary spastic paraplegia (HSP). This finding stimulated intense study of the Spastin protein and over the last decade, a combination of cell biological, in vivo, in vitro and structural studies have provided important mechanistic insights into the cellular functions of the protein, as well as elucidating cell biological pathways that might be involved in axonal maintenance and degeneration. Roles for Spastin have emerged in shaping the endoplasmic reticulum and the abscission stage of cytokinesis, in which Spastin appears to couple membrane modelling to microtubule regulation by severing.
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the hereditary spastic paraplegia proteins nipa1 Spastin and spartin are inhibitors of mammalian bmp signalling
Human Molecular Genetics, 2009Co-Authors: Hilda T H Tsang, James W Connell, Thomas L Edwards, Paul J Luzio, Xinnan Wang, Rachel J Davies, Hannah J Durrington, Cahir J Okane, Evan ReidAbstract:The hereditary spastic paraplegias (HSPs) are genetic conditions characterized by distal axonopathy of the longest corticospinal tract axons, and so their study provides an important opportunity to understand mechanisms involved in axonal maintenance and degeneration. A group of HSP genes encode proteins that localize to endosomes. One of these is NIPA1 (non-imprinted in Prader-Willi/Angelman syndrome 1) and we have shown recently that its Drosophila homologue spichthyin inhibits bone morphogenic protein (BMP) signalling, although the relevance of this finding to the mammalian protein was not known. We show here that mammalian NIPA1 is also an inhibitor of BMP signalling. NIPA1 physically interacts with the type II BMP receptor (BMPRII) and we demonstrate that this interaction does not require the cytoplasmic tail of BMPRII. We show that the mechanism by which NIPA1 inhibits BMP signalling involves downregulation of BMP receptors by promoting their endocytosis and lysosomal degradation. Disease-associated mutant versions of NIPA1 alter the trafficking of BMPRII and are less efficient at promoting BMPRII degradation than wild-type NIPA1. In addition, we demonstrate that two other members of the endosomal group of HSP proteins, Spastin and spartin, are inhibitors of BMP signalling. Since BMP signalling is important for distal axonal function, we propose that dysregulation of BMP signalling could be a unifying pathological component in this endosomal group of HSPs, and perhaps of importance in other conditions in which distal axonal degeneration is found.
Craig Blackstone - One of the best experts on this subject based on the ideXlab platform.
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Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through escrt iii
Journal of Cell Biology, 2019Co-Authors: Chilun Chang, Aubrey V Weigel, Maria S Ioannou, Amalia H Pasolli, Shan C Xu, David Peale, Gleb Shtengel, Harald F Hess, Melanie Freeman, Craig BlackstoneAbstract:Lipid droplets (LDs) are neutral lipid storage organelles that transfer lipids to various organelles including peroxisomes. Here, we show that the hereditary spastic paraplegia protein M1 Spastin, a membrane-bound AAA ATPase found on LDs, coordinates fatty acid (FA) trafficking from LDs to peroxisomes through two interrelated mechanisms. First, M1 Spastin forms a tethering complex with peroxisomal ABCD1 to promote LD–peroxisome contact formation. Second, M1 Spastin recruits the membrane-shaping ESCRT-III proteins IST1 and CHMP1B to LDs via its MIT domain to facilitate LD-to-peroxisome FA trafficking, possibly through IST1- and CHMP1B-dependent modifications in LD membrane morphology. Furthermore, LD-to-peroxisome FA trafficking mediated by M1 Spastin is required to relieve LDs of lipid peroxidation. M1 Spastin’s dual roles in tethering LDs to peroxisomes and in recruiting ESCRT-III components to LD–peroxisome contact sites for FA trafficking may underlie the pathogenesis of diseases associated with defective FA metabolism in LDs and peroxisomes.
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Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through escrt iii
bioRxiv, 2019Co-Authors: Chilun Chang, Aubrey V Weigel, Maria S Ioannou, Amalia H Pasolli, Shan C Xu, David Peale, Gleb Shtengel, Harald F Hess, Melanie Freeman, Craig BlackstoneAbstract:Abstract Lipid droplets (LDs) are neutral lipid storage organelles that transfer lipids to various organelles including peroxisomes. Here, we show that the hereditary spastic paraplegia protein M1 Spastin, a membrane-bound AAA ATPase found on LDs, coordinates fatty acid (FA) trafficking from LDs to peroxisomes through two inter-related mechanisms. First, M1 Spastin forms a tethering complex with peroxisomal ABCD1 to promote LD-peroxisome contact formation. Second, M1 Spastin recruits the membrane-shaping ESCRT-III proteins IST1 and CHMP1B to LDs via its MIT domain to facilitate LD-to-peroxisome FA trafficking, possibly through IST1 and CHMP1B modifying LD membrane morphology. Furthermore, M1 Spastin, IST1 and CHMP1B are all required to relieve LDs of lipid peroxidation. M1 Spastin’s dual roles in tethering LDs to peroxisomes and in recruiting ESCRT-components to LD-peroxisome contact sites for FA trafficking may help explain the pathogenesis of diseases associated with defective FA metabolism in LDs and peroxisomes.
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SPG20 protein spartin is recruited to midbodies by ESCRT-III protein Ist1 and participates in cytokinesis
Molecular biology of the cell, 2010Co-Authors: Benoît Renvoisé, Rell L Parker, Joanna C. Bakowska, Dong Yang, James H. Hurley, Craig BlackstoneAbstract:Hereditary spastic paraplegias (HSPs, SPG1-46) are inherited neurological disorders characterized by lower extremity spastic weakness. Loss-of-function SPG20 gene mutations cause an autosomal recessive HSP known as Troyer syndrome. The SPG20 protein spartin localizes to lipid droplets and endosomes, and it interacts with tail interacting protein 47 (TIP47) as well as the ubiquitin E3 ligases atrophin-1-interacting protein (AIP)4 and AIP5. Spartin harbors a domain contained within microtubule-interacting and trafficking molecules (MIT) at its N-terminus, and most proteins with MIT domains interact with specific ESCRT-III proteins. Using yeast two-hybrid and in vitro surface plasmon resonance assays, we demonstrate that the spartin MIT domain binds with micromolar affinity to the endosomal sorting complex required for transport (ESCRT)-III protein increased sodium tolerance (Ist)1 but not to ESCRT-III proteins charged multivesicular body proteins 1-7. Spartin colocalizes with Ist1 at the midbody, and depletion of Ist1 in cells by small interfering RNA significantly decreases the number of cells where spartin is present at midbodies. Depletion of spartin does not affect Ist1 localization to midbodies but markedly impairs cytokinesis. A structure-based amino acid substitution in the spartin MIT domain (F24D) blocks the spartin-Ist1 interaction. Spartin F24D does not localize to the midbody and acts in a dominant-negative manner to impair cytokinesis. These data suggest that Ist1 interaction is important for spartin recruitment to the midbody and that spartin participates in cytokinesis.
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hereditary spastic paraplegia proteins reep1 Spastin and atlastin 1 coordinate microtubule interactions with the tubular er network
Journal of Clinical Investigation, 2010Co-Authors: Seong H. Park, Rell L Parker, Craig BlackstoneAbstract:Hereditary spastic paraplegias (HSPs; SPG1–45) are inherited neurological disorders characterized by lower extremity spastic weakness. More than half of HSP cases result from autosomal dominant mutations in atlastin-1 (also known as SPG3A), receptor expression enhancing protein 1 (REEP1; SPG31), or Spastin (SPG4). The atlastin-1 GTPase interacts with Spastin, a microtubule-severing ATPase, as well as with the DP1/Yop1p and reticulon families of ER-shaping proteins, and SPG3A caused by atlastin-1 mutations has been linked pathogenically to abnormal ER morphology. Here we investigated SPG31 by analyzing the distribution, interactions, and functions of REEP1. We determined that REEP1 is structurally related to the DP1/Yop1p family of ER-shaping proteins and localizes to the ER in cultured rat cerebral cortical neurons, where it colocalizes with Spastin and atlastin-1. Upon overexpression in COS7 cells, REEP1 formed protein complexes with atlastin-1 and Spastin within the tubular ER, and these interactions required hydrophobic hairpin domains in each of these proteins. REEP proteins were required for ER network formation in vitro, and REEP1 also bound microtubules and promoted ER alignment along the microtubule cytoskeleton in COS7 cells. A SPG31 mutant REEP1 lacking the C-terminal cytoplasmic region did not interact with microtubules and disrupted the ER network. These data indicate that the HSP proteins atlastin-1, Spastin, and REEP1 interact within the tubular ER membrane in corticospinal neurons to coordinate ER shaping and microtubule dynamics. Thus, defects in tubular ER shaping and network interactions with the microtubule cytoskeleton seem to be the predominant pathogenic mechanism of HSP.
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Lack of spartin protein in Troyer syndrome: a loss-of-function disease mechanism?
Archives of neurology, 2008Co-Authors: Joanna C. Bakowska, Heng Wang, Baozhong Xin, Charlotte J. Sumner, Craig BlackstoneAbstract:Background Hereditary spastic paraplegias (SPG1-SPG33) are characterized by progressive spastic weakness of the lower limbs. A nucleotide deletion (1110delA) in the ( SPG20 ; OMIM275900) spartin gene is the origin of autosomal recessive Troyer syndrome. This mutation is predicted to cause premature termination of the spartin protein. However, it remains unknown whether this truncated spartin protein is absent or is present and partially functional in patients. Objective To determine whether the truncated spartin protein is present or absent in cells derived from patients with Troyer syndrome. Design Case report. Setting Academic research. Patients We describe a new family with Troyer syndrome due to the 1110delA mutation. Main Outcome Measures We cultured primary fibroblasts and generated lymphoblasts from affected individuals, carriers, and control subjects and subjected these cells to immunoblot analyses. Results Spartin protein is undetectable in several cell lines derived from patients with Troyer syndrome. Conclusions Our data suggest that Troyer syndrome results from complete loss of spartin protein rather than from the predicted partly functional fragment. This may reflect increased protein degradation or impaired translation.
Christopher M Sanderson - One of the best experts on this subject based on the ideXlab platform.
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endogenous spartin spg20 is recruited to endosomes and lipid droplets and interacts with the ubiquitin e3 ligases aip4 and aip5
Biochemical Journal, 2009Co-Authors: Thomas L Edwards, James W Connell, Christopher M Sanderson, Paul J Luzio, Virginia E Clowes, Hilda T H Tsang, Evan ReidAbstract:The HSPs (hereditary spastic paraplegias) are genetic conditions in which there is distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that, at steady state, endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 [atrophin-interacting protein 4; WWP2 (WW domain-containing E3 ubiquitin protein ligase 2] and AIP5 (WWP1). Surprisingly, the PPXY motif, AIP4 and AIP5 are not required for spartin's ubiquitination, and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Endogenous spartin (SPG20) is recruited to endosomes and lipid droplets and interacts with the ubiquitin E3 ligases AIP4 and AIP5.
Biochemical Journal, 2009Co-Authors: Thomas L Edwards, James W Connell, Christopher M Sanderson, J. Paul Luzio, Virginia E Clowes, Hilda T H Tsang, Evan ReidAbstract:The hereditary spastic paraplegias (HSPs) are genetic conditions exhibiting distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that at steady state endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 (WWP2) and AIP5 (WWP1). Surprisingly, neither the PPXY motif, AIP4 nor AIP5 are required for spartin's ubiquitination and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Endogenous spartin (SPG20) is recruited to endosomes and lipid droplets and interacts with the ubiquitin E3 ligases AIP4 and AIP5.
The Biochemical journal, 2009Co-Authors: Thomas L Edwards, James W Connell, Christopher M Sanderson, J. Paul Luzio, Virginia E Clowes, Hilda T H Tsang, Evan ReidAbstract:The HSPs (hereditary spastic paraplegias) are genetic conditions in which there is distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that, at steady state, endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 [atrophin-interacting protein 4; ITCH (itchy E3 ubiquitin protein ligase homologue] [corrected] and AIP5 (WWP1). Surprisingly, the PPXY motif, AIP4 and AIP5 are not required for spartin's ubiquitination, and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Spastin and atlastin two proteins mutated in autosomal dominant hereditary spastic paraplegia are binding partners
Human Molecular Genetics, 2006Co-Authors: Christopher M Sanderson, James W Connell, Thomas L Edwards, Nicholas A Bright, Simon Duley, Amanda Thompson, Paul J Luzio, Evan ReidAbstract:The pure hereditary spastic paraplegias (HSPs) are a group of conditions in which there is progressive length-dependent degeneration of the distal ends of the corticospinal tract axons, resulting in spastic paralysis of the legs. Pure HSPs are most frequently inherited in an autosomal dominant pattern and are commonly caused by mutations in either the SPG4 gene Spastin or in the SPG3A gene atlastin. To identify binding partners for Spastin, we carried out a yeast two-hybrid screen on a brain cDNA library, using Spastin as bait. Remarkably, nearly all of the positive interacting prey clones coded for atlastin. We have verified the physiological relevance of this interaction using co-immunoprecipitation, GST-pull down and intracellular co-localisation experiments. We show that the Spastin domain required for binding to atlastin lies within the N-terminal 80 residues of the protein, a region that is only present in the predominantly cytoplasmic full-length Spastin isoform. These data suggest that Spastin and atlastin function in the same biochemical pathway and that it is the cytoplasmic function of Spastin which is important for the pathogenesis of HSP. They also provide further evidence for a physiological and pathological role for Spastin in membrane dynamics.
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Spastin and atlastin, two proteins mutated in autosomal-dominant hereditary spastic paraplegia, are binding partners
Human Molecular Genetics, 2005Co-Authors: Christopher M Sanderson, James W Connell, Thomas L Edwards, Nicholas A Bright, Simon Duley, Amanda Thompson, J. Paul Luzio, Evan ReidAbstract:The pure hereditary spastic paraplegias (HSPs) are a group of conditions in which there is a progressive length-dependent degeneration of the distal ends of the corticospinal tract axons, resulting in spastic paralysis of the legs. Pure HSPs are most frequently inherited in an autosomal-dominant pattern and are commonly caused by mutations either in the SPG4 gene Spastin or in the SPG3A gene atlastin. To identify binding partners for Spastin, we carried out a yeast two-hybrid screen on a brain cDNA library, using Spastin as bait. Remarkably, nearly all of the positive interacting prey clones coded for atlastin. We have verified the physiological relevance of this interaction using co-immunoprecipitation, glutathione S-transferase pull-down and intracellular co-localization experiments. We show that the Spastin domain required for binding to atlastin lies within the N-terminal 80 residues of the protein, a region that is only present in the predominantly cytoplasmic, full-length Spastin isoform. These data suggest that Spastin and atlastin function in the same biochemical pathway and that it is the cytoplasmic function of Spastin which is important for the pathogenesis of HSP. They also provide further evidence for a physiological and pathological role of Spastin in membrane dynamics.
Thomas L Edwards - One of the best experts on this subject based on the ideXlab platform.
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the hereditary spastic paraplegia proteins nipa1 Spastin and spartin are inhibitors of mammalian bmp signalling
Human Molecular Genetics, 2009Co-Authors: Hilda T H Tsang, James W Connell, Thomas L Edwards, Paul J Luzio, Xinnan Wang, Rachel J Davies, Hannah J Durrington, Cahir J Okane, Evan ReidAbstract:The hereditary spastic paraplegias (HSPs) are genetic conditions characterized by distal axonopathy of the longest corticospinal tract axons, and so their study provides an important opportunity to understand mechanisms involved in axonal maintenance and degeneration. A group of HSP genes encode proteins that localize to endosomes. One of these is NIPA1 (non-imprinted in Prader-Willi/Angelman syndrome 1) and we have shown recently that its Drosophila homologue spichthyin inhibits bone morphogenic protein (BMP) signalling, although the relevance of this finding to the mammalian protein was not known. We show here that mammalian NIPA1 is also an inhibitor of BMP signalling. NIPA1 physically interacts with the type II BMP receptor (BMPRII) and we demonstrate that this interaction does not require the cytoplasmic tail of BMPRII. We show that the mechanism by which NIPA1 inhibits BMP signalling involves downregulation of BMP receptors by promoting their endocytosis and lysosomal degradation. Disease-associated mutant versions of NIPA1 alter the trafficking of BMPRII and are less efficient at promoting BMPRII degradation than wild-type NIPA1. In addition, we demonstrate that two other members of the endosomal group of HSP proteins, Spastin and spartin, are inhibitors of BMP signalling. Since BMP signalling is important for distal axonal function, we propose that dysregulation of BMP signalling could be a unifying pathological component in this endosomal group of HSPs, and perhaps of importance in other conditions in which distal axonal degeneration is found.
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endogenous spartin spg20 is recruited to endosomes and lipid droplets and interacts with the ubiquitin e3 ligases aip4 and aip5
Biochemical Journal, 2009Co-Authors: Thomas L Edwards, James W Connell, Christopher M Sanderson, Paul J Luzio, Virginia E Clowes, Hilda T H Tsang, Evan ReidAbstract:The HSPs (hereditary spastic paraplegias) are genetic conditions in which there is distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that, at steady state, endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 [atrophin-interacting protein 4; WWP2 (WW domain-containing E3 ubiquitin protein ligase 2] and AIP5 (WWP1). Surprisingly, the PPXY motif, AIP4 and AIP5 are not required for spartin's ubiquitination, and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Endogenous spartin (SPG20) is recruited to endosomes and lipid droplets and interacts with the ubiquitin E3 ligases AIP4 and AIP5.
Biochemical Journal, 2009Co-Authors: Thomas L Edwards, James W Connell, Christopher M Sanderson, J. Paul Luzio, Virginia E Clowes, Hilda T H Tsang, Evan ReidAbstract:The hereditary spastic paraplegias (HSPs) are genetic conditions exhibiting distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that at steady state endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 (WWP2) and AIP5 (WWP1). Surprisingly, neither the PPXY motif, AIP4 nor AIP5 are required for spartin's ubiquitination and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Endogenous spartin (SPG20) is recruited to endosomes and lipid droplets and interacts with the ubiquitin E3 ligases AIP4 and AIP5.
The Biochemical journal, 2009Co-Authors: Thomas L Edwards, James W Connell, Christopher M Sanderson, J. Paul Luzio, Virginia E Clowes, Hilda T H Tsang, Evan ReidAbstract:The HSPs (hereditary spastic paraplegias) are genetic conditions in which there is distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that, at steady state, endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 [atrophin-interacting protein 4; ITCH (itchy E3 ubiquitin protein ligase homologue] [corrected] and AIP5 (WWP1). Surprisingly, the PPXY motif, AIP4 and AIP5 are not required for spartin's ubiquitination, and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Spastin and atlastin two proteins mutated in autosomal dominant hereditary spastic paraplegia are binding partners
Human Molecular Genetics, 2006Co-Authors: Christopher M Sanderson, James W Connell, Thomas L Edwards, Nicholas A Bright, Simon Duley, Amanda Thompson, Paul J Luzio, Evan ReidAbstract:The pure hereditary spastic paraplegias (HSPs) are a group of conditions in which there is progressive length-dependent degeneration of the distal ends of the corticospinal tract axons, resulting in spastic paralysis of the legs. Pure HSPs are most frequently inherited in an autosomal dominant pattern and are commonly caused by mutations in either the SPG4 gene Spastin or in the SPG3A gene atlastin. To identify binding partners for Spastin, we carried out a yeast two-hybrid screen on a brain cDNA library, using Spastin as bait. Remarkably, nearly all of the positive interacting prey clones coded for atlastin. We have verified the physiological relevance of this interaction using co-immunoprecipitation, GST-pull down and intracellular co-localisation experiments. We show that the Spastin domain required for binding to atlastin lies within the N-terminal 80 residues of the protein, a region that is only present in the predominantly cytoplasmic full-length Spastin isoform. These data suggest that Spastin and atlastin function in the same biochemical pathway and that it is the cytoplasmic function of Spastin which is important for the pathogenesis of HSP. They also provide further evidence for a physiological and pathological role for Spastin in membrane dynamics.
