1
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Wethekam LC, Moore JK. α-tubulin regulation by 5' introns in Saccharomyces cerevisiae. Genetics 2023; 225:iyad163. [PMID: 37675603 PMCID: PMC10697811 DOI: 10.1093/genetics/iyad163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 06/22/2023] [Accepted: 08/21/2023] [Indexed: 09/08/2023] Open
Abstract
Across eukaryotic genomes, multiple α- and β-tubulin genes require regulation to ensure sufficient production of tubulin heterodimers. Features within these gene families that regulate expression remain underexplored. Here, we investigate the role of the 5' intron in regulating α-tubulin expression in Saccharomyces cerevisiae. We find that the intron in the α-tubulin, TUB1, promotes α-tubulin expression and cell fitness during microtubule stress. The role of the TUB1 intron depends on proximity to the TUB1 promoter and sequence features that are distinct from the intron in the alternative α-tubulin isotype, TUB3. These results lead us to perform a screen to identify genes that act with the TUB1 intron. We identified several genes involved in chromatin remodeling, α/β-tubulin heterodimer assembly, and the spindle assembly checkpoint. We propose a model where the TUB1 intron promotes expression from the chromosomal locus and that this may represent a conserved mechanism for tubulin regulation under conditions that require high levels of tubulin production.
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Affiliation(s)
- Linnea C Wethekam
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
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2
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Caputo M, Martinelli I, Fini N, Gianferrari G, Simonini C, Trovato R, Santorelli FM, Tessa A, Mandrioli J, Zucchi E. A Variant in TBCD Associated with Motoneuronopathy and Corpus Callosum Hypoplasia: A Case Report. Int J Mol Sci 2023; 24:12386. [PMID: 37569761 PMCID: PMC10418765 DOI: 10.3390/ijms241512386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/26/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023] Open
Abstract
Mutations in the tubulin-specific chaperon D (TBCD) gene, involved in the assembly and disassembly of the α/β-tubulin heterodimers, have been reported in early-onset progressive neurodevelopment regression, with epilepsy and mental retardation. We describe a rare homozygous variant in TBCD, namely c.881G>A/p.Arg294Gln, in a young woman with a phenotype dominated by distal motorneuronopathy and mild mental retardation, with neuroimaging evidence of corpus callosum hypoplasia. The peculiar phenotype is discussed in light of the molecular interpretation, enriching the literature data on tubulinopathies generated from TBCD mutations.
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Affiliation(s)
- Maria Caputo
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
| | - Ilaria Martinelli
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
- Clinical and Experimental PhD Program, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Nicola Fini
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
| | - Giulia Gianferrari
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
| | - Cecilia Simonini
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
| | - Rosanna Trovato
- Molecular Medicine, IRCCS Fondazione Stella Maris, 56128 Pisa, Italy; (R.T.); (F.M.S.); (A.T.)
| | | | - Alessandra Tessa
- Molecular Medicine, IRCCS Fondazione Stella Maris, 56128 Pisa, Italy; (R.T.); (F.M.S.); (A.T.)
| | - Jessica Mandrioli
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
| | - Elisabetta Zucchi
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
- Neuroscience PhD Program, University of Modena and Reggio Emilia, 41125 Modena, Italy
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3
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Janakiraman V, Sudhan M, Alzahrani KJ, Alshammeri S, Ahmed SSSJ, Patil S. Dynamics of TUBB protein with five majorly occurring natural variants: a risk of cortical dysplasia. J Mol Model 2023; 29:100. [PMID: 36928665 DOI: 10.1007/s00894-023-05506-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 03/09/2023] [Indexed: 03/18/2023]
Abstract
Beta-tubulin (TUBB) protein is one of the components of the microtubule cytoskeleton that plays a critical role in the central nervous system. Genetic variants of TUBB cause cortical dysplasia, a developmental brain defect implicated in axonal guidance and the neuron migration. In this study, we assess pathogenic variants (Q15K, Y222F, M299V, V353I, and E401K) of TUBB protein and compared with non-pathogenic variant G235S to determine their impact on protein dynamic to cause cortical dysplasia. Among the analyzed variants, Q15K, Y222F, M299V, and E401K were noticed to have deleterious effect. Then, variant structures were modeled and their affinity with their known cofactor Guanosine-5'-triphosphate (GTP) was assessed which showed diverse binding energies ranged between (-7.436 to -6.950 kcal/mol) for the variants compared to wild-type (-7.428 kcal/mol). Finally, the molecular dynamics simulation of each variant was investigated which showed difference in trajectory between the pathogenic and non-pathogenic variant. Our analysis suggests change in amino acid residue of TUBB structure has notably affects the protein flexibility and their interactions with known cofactor. Overall, our findings provide insight on the relationship between TUBB variants and their structural dynamics that may cause diverse effects leading to cortical dysplasia.
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Affiliation(s)
- V Janakiraman
- Drug Discovery and Multi-Omics Laboratory, Faculty of Allied Health Sciences, Chettinad Hospital and Research Institute, Chettinad Academy of Research and Education, Kelambakkam, 603103, Tamil Nadu, India
| | - M Sudhan
- Drug Discovery and Multi-Omics Laboratory, Faculty of Allied Health Sciences, Chettinad Hospital and Research Institute, Chettinad Academy of Research and Education, Kelambakkam, 603103, Tamil Nadu, India
| | - Khalid J Alzahrani
- Department of Clinical Laboratories Sciences, College of Applied Medical Sciences, Taif University, P.O. Box 11099, Taif, 21944, Saudi Arabia
| | - Saleh Alshammeri
- Department of Optometry, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Shiek S S J Ahmed
- Drug Discovery and Multi-Omics Laboratory, Faculty of Allied Health Sciences, Chettinad Hospital and Research Institute, Chettinad Academy of Research and Education, Kelambakkam, 603103, Tamil Nadu, India.
| | - Shankargouda Patil
- College of Dental Medicine, Roseman University of Health Sciences, South Jordan, UT, USA
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4
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Pinho-Correia LM, Prokop A. Maintaining essential microtubule bundles in meter-long axons: a role for local tubulin biogenesis? Brain Res Bull 2023; 193:131-145. [PMID: 36535305 DOI: 10.1016/j.brainresbull.2022.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
Axons are the narrow, up-to-meter long cellular processes of neurons that form the biological cables wiring our nervous system. Most axons must survive for an organism's lifetime, i.e. up to a century in humans. Axonal maintenance depends on loose bundles of microtubules that run without interruption all along axons. The continued turn-over and the extension of microtubule bundles during developmental, regenerative or plastic growth requires the availability of α/β-tubulin heterodimers up to a meter away from the cell body. The underlying regulation in axons is poorly understood and hardly features in past and contemporary research. Here we discuss potential mechanisms, particularly focussing on the possibility of local tubulin biogenesis in axons. Current knowledge might suggest that local translation of tubulin takes place in axons, but far less is known about the post-translational machinery of tubulin biogenesis involving three chaperone complexes: prefoldin, CCT and TBC. We discuss functional understanding of these chaperones from a range of model organisms including yeast, plants, flies and mice, and explain what is known from human diseases. Microtubules across species depend on these chaperones, and they are clearly required in the nervous system. However, most chaperones display a high degree of functional pleiotropy, partly through independent functions of individual subunits outside their complexes, thus posing a challenge to experimental studies. Notably, we found hardly any studies that investigate their presence and function particularly in axons, thus highlighting an important gap in our understanding of axon biology and pathology.
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Affiliation(s)
- Liliana Maria Pinho-Correia
- The University of Manchester, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, Manchester, UK
| | - Andreas Prokop
- The University of Manchester, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, Manchester, UK.
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5
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Li G, Moore JK. Microtubule dynamics at low temperature: evidence that tubulin recycling limits assembly. Mol Biol Cell 2020; 31:1154-1166. [PMID: 32213119 PMCID: PMC7353160 DOI: 10.1091/mbc.e19-11-0634] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
How temperature specifically affects microtubule dynamics and how these lead to changes in microtubule networks in cells have not been established. We investigated these questions in budding yeast, an organism found in diverse environments and therefore predicted to exhibit dynamic microtubules across a broad temperature range. We measured the dynamics of GFP-labeled microtubules in living cells and found that lowering temperature from 37°C to 10°C decreased the rates of both polymerization and depolymerization, decreased the amount of polymer assembled before catastrophes, and decreased the frequency of microtubule emergence from nucleation sites. Lowering to 4°C caused rapid loss of almost all microtubule polymer. We provide evidence that these effects on microtubule dynamics may be explained in part by changes in the cofactor-dependent conformational dynamics of tubulin proteins. Ablation of tubulin-binding cofactors (TBCs) further sensitizes cells and their microtubules to low temperatures, and we highlight a specific role for TBCB/Alf1 in microtubule maintenance at low temperatures. Finally, we show that inhibiting the maturation cycle of tubulin by using a point mutant in β-tubulin confers hyperstable microtubules at low temperatures and rescues the requirement for TBCB/Alf1 in maintaining microtubule polymer at low temperatures. Together, these results reveal an unappreciated step in the tubulin cycle.
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Affiliation(s)
- Gabriella Li
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
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6
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Parker AL, Teo WS, Pandzic E, Vicente JJ, McCarroll JA, Wordeman L, Kavallaris M. β-tubulin carboxy-terminal tails exhibit isotype-specific effects on microtubule dynamics in human gene-edited cells. Life Sci Alliance 2018; 1. [PMID: 30079401 PMCID: PMC6070155 DOI: 10.26508/lsa.201800059] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
This study used human gene-edited cell models and image analysis to reveal that the tubulin C-terminal tails specifically regulate the dynamics of individual microtubules and coordinate microtubule behavior across the cell. Microtubules are highly dynamic structures that play an integral role in fundamental cellular functions. Different α- and β-tubulin isotypes are thought to confer unique dynamic properties to microtubules. The tubulin isotypes have highly conserved structures, differing mainly in their carboxy-terminal (C-terminal) tail sequences. However, little is known about the importance of the C-terminal tail in regulating and coordinating microtubule dynamics. We developed syngeneic human cell models using gene editing to precisely modify the β-tubulin C-terminal tail region while preserving the endogenous microtubule network. Fluorescent microscopy of live cells, coupled with advanced image analysis, revealed that the β-tubulin C-terminal tails differentially coordinate the collective and individual dynamic behavior of microtubules by affecting microtubule growth rates and explorative microtubule assembly in an isotype-specific manner. Furthermore, βI- and βIII-tubulin C-terminal tails differentially regulate the sensitivity of microtubules to tubulin-binding agents and the microtubule depolymerizing protein mitotic centromere-associated kinesin. The sequence of the β-tubulin tail encodes regulatory information that instructs and coordinates microtubule dynamics, thereby fine-tuning microtubule dynamics to support cellular functions.
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Affiliation(s)
- Amelia L Parker
- Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, NSW, Australia 2031.,Australian Centre for NanoMedicine and ARC Centre of Excellence for Convergent BioNano Science and Technology, UNSW Sydney, NSW, Australia 2052.,School of Women's and Children's Health, Faculty of Medicine, UNSW Sydney, NSW, Australia 2052
| | - Wee Siang Teo
- Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, NSW, Australia 2031.,Australian Centre for NanoMedicine and ARC Centre of Excellence for Convergent BioNano Science and Technology, UNSW Sydney, NSW, Australia 2052.,School of Women's and Children's Health, Faculty of Medicine, UNSW Sydney, NSW, Australia 2052
| | - Elvis Pandzic
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, Lowy Cancer Research Centre, UNSW Sydney, NSW, Australia 2052
| | - Juan Jesus Vicente
- Department of Physiology and Biophysics, School of Medicine, University of Washington, Seattle, WA, USA 98195-7290
| | - Joshua A McCarroll
- Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, NSW, Australia 2031.,Australian Centre for NanoMedicine and ARC Centre of Excellence for Convergent BioNano Science and Technology, UNSW Sydney, NSW, Australia 2052.,School of Women's and Children's Health, Faculty of Medicine, UNSW Sydney, NSW, Australia 2052
| | - Linda Wordeman
- Department of Physiology and Biophysics, School of Medicine, University of Washington, Seattle, WA, USA 98195-7290
| | - Maria Kavallaris
- Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, NSW, Australia 2031.,Australian Centre for NanoMedicine and ARC Centre of Excellence for Convergent BioNano Science and Technology, UNSW Sydney, NSW, Australia 2052.,School of Women's and Children's Health, Faculty of Medicine, UNSW Sydney, NSW, Australia 2052
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7
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Francis JW, Goswami D, Novick SJ, Pascal BD, Weikum ER, Ortlund EA, Griffin PR, Kahn RA. Nucleotide Binding to ARL2 in the TBCD∙ARL2∙β-Tubulin Complex Drives Conformational Changes in β-Tubulin. J Mol Biol 2017; 429:3696-3716. [PMID: 28970104 DOI: 10.1016/j.jmb.2017.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 08/31/2017] [Accepted: 09/26/2017] [Indexed: 11/25/2022]
Abstract
Microtubules are highly dynamic tubulin polymers that are required for a variety of cellular functions. Despite the importance of a cellular population of tubulin dimers, we have incomplete information about the mechanisms involved in the biogenesis of αβ-tubulin heterodimers. In addition to prefoldin and the TCP-1 Ring Complex, five tubulin-specific chaperones, termed cofactors A-E (TBCA-E), and GTP are required for the folding of α- and β-tubulin subunits and assembly into heterodimers. We recently described the purification of a novel trimer, TBCD•ARL2•β-tubulin. Here, we employed hydrogen/deuterium exchange coupled with mass spectrometry to explore the dynamics of each of the proteins in the trimer. Addition of guanine nucleotides resulted in changes in the solvent accessibility of regions of each protein that led to predictions about each's role in tubulin folding. Initial testing of that model confirmed that it is ARL2, and not β-tubulin, that exchanges GTP in the trimer. Comparisons of the dynamics of ARL2 monomer to ARL2 in the trimer suggested that its protein interactions were comparable to those of a canonical GTPase with an effector. This was supported by the use of nucleotide-binding assays that revealed an increase in the affinity for GTP by ARL2 in the trimer. We conclude that the TBCD•ARL2•β-tubulin complex represents a functional intermediate in the β-tubulin folding pathway whose activity is regulated by the cycling of nucleotides on ARL2. The co-purification of guanine nucleotide on the β-tubulin in the trimer is also shown, with implications to modeling the pathway.
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Affiliation(s)
- Joshua W Francis
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Devrishi Goswami
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, United States
| | - Scott J Novick
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, United States
| | - Bruce D Pascal
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, United States
| | - Emily R Weikum
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Eric A Ortlund
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Patrick R Griffin
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, United States
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, United States.
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8
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Al-Bassam J. Revisiting the tubulin cofactors and Arl2 in the regulation of soluble αβ-tubulin pools and their effect on microtubule dynamics. Mol Biol Cell 2017; 28:359-363. [PMID: 28137948 PMCID: PMC5341719 DOI: 10.1091/mbc.e15-10-0694] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 11/22/2016] [Accepted: 12/01/2016] [Indexed: 12/12/2022] Open
Abstract
Soluble αβ-tubulin heterodimers are maintained at high concentration inside eukaryotic cells, forming pools that fundamentally drive microtubule dynamics. Five conserved tubulin cofactors and ADP ribosylation factor-like 2 regulate the biogenesis and degradation of αβ-tubulins to maintain concentrated soluble pools. Here I describe a revised model for the function of three tubulin cofactors and Arl2 as a multisubunit GTP-hydrolyzing catalytic chaperone that cycles to promote αβ-tubulin biogenesis and degradation. This model helps explain old and new data indicating these activities enhance microtubule dynamics in vivo via repair or removal of αβ-tubulins from the soluble pools.
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Affiliation(s)
- Jawdat Al-Bassam
- Molecular Cellular Biology, University of California, Davis, Davis, CA 95616
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9
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Disease mechanisms of X-linked retinitis pigmentosa due to RP2 and RPGR mutations. Biochem Soc Trans 2017; 44:1235-1244. [PMID: 27911705 DOI: 10.1042/bst20160148] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 08/16/2016] [Accepted: 08/18/2016] [Indexed: 01/24/2023]
Abstract
Photoreceptor degeneration is the prominent characteristic of retinitis pigmentosa (RP), a heterogeneous group of inherited retinal dystrophies resulting in blindness. Although abnormalities in many pathways can cause photoreceptor degeneration, one of the most important causes is defective protein transport through the connecting cilium, the structure that connects the biosynthetic inner segment with the photosensitive outer segment of the photoreceptors. The majority of patients with X-linked RP have mutations in the retinitis pigmentosa GTPase regulator (RPGR) or RP2 genes, the protein products of which are both components of the connecting cilium and associated with distinct mechanisms of protein delivery to the outer segment. RP2 and RPGR proteins are associated with severe diseases ranging from classic RP to atypical forms. In this short review, we will summarise current knowledge generated by experimental studies and knockout animal models, compare and discuss the prominent hypotheses about the two proteins' functions in retinal cell biology.
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10
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Weems A, McMurray M. The step-wise pathway of septin hetero-octamer assembly in budding yeast. eLife 2017; 6. [PMID: 28541184 PMCID: PMC5461111 DOI: 10.7554/elife.23689] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 05/24/2017] [Indexed: 01/22/2023] Open
Abstract
Septin proteins bind guanine nucleotides and form rod-shaped hetero-oligomers. Cells choose from a variety of available septins to assemble distinct hetero-oligomers, but the underlying mechanism was unknown. Using a new in vivo assay, we find that a stepwise assembly pathway produces the two species of budding yeast septin hetero-octamers: Cdc11/Shs1–Cdc12–Cdc3–Cdc10–Cdc10–Cdc3–Cdc12–Cdc11/Shs1. Rapid GTP hydrolysis by monomeric Cdc10 drives assembly of the core Cdc10 homodimer. The extended Cdc3 N terminus autoinhibits Cdc3 association with Cdc10 homodimers until prior Cdc3–Cdc12 interaction. Slow hydrolysis by monomeric Cdc12 and specific affinity of Cdc11 for transient Cdc12•GTP drive assembly of distinct trimers, Cdc11–Cdc12–Cdc3 or Shs1–Cdc12–Cdc3. Decreasing the cytosolic GTP:GDP ratio increases the incorporation of Shs1 vs Cdc11, which alters the curvature of filamentous septin rings. Our findings explain how GTP hydrolysis controls septin assembly, and uncover mechanisms by which cells construct defined septin complexes. DOI:http://dx.doi.org/10.7554/eLife.23689.001
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Affiliation(s)
- Andrew Weems
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, United States
| | - Michael McMurray
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, United States
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11
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McMurray MA. Coupling de novo protein folding with subunit exchange into pre-formed oligomeric protein complexes: the 'heritable template' hypothesis. Biomol Concepts 2017; 7:271-281. [PMID: 27875316 DOI: 10.1515/bmc-2016-0023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/11/2016] [Indexed: 11/15/2022] Open
Abstract
Despite remarkable advances in synthetic biology, the fact remains that it takes a living cell to make a new living cell. The information encoded in the genome is necessary to direct assembly of all cellular components, but it may not be sufficient. Some components (e.g. mitochondria) cannot be synthesized de novo, and instead require pre-existing templates, creating a fundamental continuity of life: if the template information is ever lost, the genomic code cannot suffice to ensure proper biogenesis. One type of information only incompletely encoded in the genome is the structures of macromolecular assemblies, which emerge from the conformations of the constituent molecules coupled with the ways in which these molecules interact. For many, if not most proteins, gene sequence is not the sole determinant of native conformation, particularly in the crowded cellular milieu. A partial solution to this problem lies in the functions of molecular chaperones, encoded by nearly all cellular genomes. Chaperones effectively restrict the ensemble of conformations sampled by polypeptides, promoting the acquisition of native, functional forms, but multiple proteins have evolved ways to achieve chaperone independence, perhaps by coupling folding with higher-order assembly. Here, I propose the existence of another solution: a novel mechanism of de novo folding in which the folding of specific proteins is templated by pre-folded molecules of a partner protein whose own folding also required similar templating. This hypothesis challenges prevailing paradigms by predicting that, in order to achieve a functional fold, some non-prion proteins require a seed passed down through generations.
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12
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Miyake N, Fukai R, Ohba C, Chihara T, Miura M, Shimizu H, Kakita A, Imagawa E, Shiina M, Ogata K, Okuno-Yuguchi J, Fueki N, Ogiso Y, Suzumura H, Watabe Y, Imataka G, Leong HY, Fattal-Valevski A, Kramer U, Miyatake S, Kato M, Okamoto N, Sato Y, Mitsuhashi S, Nishino I, Kaneko N, Nishiyama A, Tamura T, Mizuguchi T, Nakashima M, Tanaka F, Saitsu H, Matsumoto N. Biallelic TBCD Mutations Cause Early-Onset Neurodegenerative Encephalopathy. Am J Hum Genet 2016; 99:950-961. [PMID: 27666374 DOI: 10.1016/j.ajhg.2016.08.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/09/2016] [Indexed: 01/01/2023] Open
Abstract
We describe four families with affected siblings showing unique clinical features: early-onset (before 1 year of age) progressive diffuse brain atrophy with regression, postnatal microcephaly, postnatal growth retardation, muscle weakness/atrophy, and respiratory failure. By whole-exome sequencing, we identified biallelic TBCD mutations in eight affected individuals from the four families. TBCD encodes TBCD (tubulin folding co-factor D), which is one of five tubulin-specific chaperones playing a pivotal role in microtubule assembly in all cells. A total of seven mutations were found: five missense mutations, one nonsense, and one splice site mutation resulting in a frameshift. In vitro cell experiments revealed the impaired binding between most mutant TBCD proteins and ARL2, TBCE, and β-tubulin. The in vivo experiments using olfactory projection neurons in Drosophila melanogaster indicated that the TBCD mutations caused loss of function. The wide range of clinical severity seen in this neurodegenerative encephalopathy may result from the residual function of mutant TBCD proteins. Furthermore, the autopsied brain from one deceased individual showed characteristic neurodegenerative findings: cactus and somatic sprout formations in the residual Purkinje cells in the cerebellum, which are also seen in some diseases associated with mitochondrial impairment. Defects of microtubule formation caused by TBCD mutations may underlie the pathomechanism of this neurodegenerative encephalopathy.
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13
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Chen K, Koe CT, Xing ZB, Tian X, Rossi F, Wang C, Tang Q, Zong W, Hong WJ, Taneja R, Yu F, Gonzalez C, Wu C, Endow S, Wang H. Arl2- and Msps-dependent microtubule growth governs asymmetric division. J Cell Biol 2016; 212:661-76. [PMID: 26953351 PMCID: PMC4792071 DOI: 10.1083/jcb.201503047] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 02/10/2016] [Indexed: 12/18/2022] Open
Abstract
Drosophila Arl2 governs neuroblast asymmetric cell division through regulation of microtubule growth and localization of Msps to centrosomes. Asymmetric division of neural stem cells is a fundamental strategy to balance their self-renewal and differentiation. It is long thought that microtubules are not essential for cell polarity in asymmetrically dividing Drosophila melanogaster neuroblasts (NBs; neural stem cells). Here, we show that Drosophila ADP ribosylation factor like-2 (Arl2) and Msps, a known microtubule-binding protein, control cell polarity and spindle orientation of NBs. Upon arl2 RNA intereference, Arl2-GDP expression, or arl2 deletions, microtubule abnormalities and asymmetric division defects were observed. Conversely, overactivation of Arl2 leads to microtubule overgrowth and depletion of NBs. Arl2 regulates microtubule growth and asymmetric division through localizing Msps to the centrosomes in NBs. Moreover, Arl2 regulates dynein function and in turn centrosomal localization of D-TACC and Msps. Arl2 physically associates with tubulin cofactors C, D, and E. Arl2 functions together with tubulin-binding cofactor D to control microtubule growth, Msps localization, and NB self-renewal. Therefore, Arl2- and Msps-dependent microtubule growth is a new paradigm regulating asymmetric division of neural stem cells.
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Affiliation(s)
- Keng Chen
- Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore 169857 National University of Singapore Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456
| | - Chwee Tat Koe
- Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore 169857 National University of Singapore Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456
| | - Zhanyuan Benny Xing
- Department of Cell Biology, Duke University, Duke University Medical Center, Durham, NC 27710
| | - Xiaolin Tian
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112
| | - Fabrizio Rossi
- Institute for Research in Biomedicine Barcelona, 08028 Barcelona, Spain
| | - Cheng Wang
- Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore 169857
| | - Quan Tang
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117604
| | - Wenhui Zong
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117604
| | - Wan Jin Hong
- Institute of Molecular and Cell Biology, Singapore 138673
| | - Reshma Taneja
- National University of Singapore Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
| | - Fengwei Yu
- Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore 169857 National University of Singapore Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117604
| | - Cayetano Gonzalez
- Institute for Research in Biomedicine Barcelona, 08028 Barcelona, Spain Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
| | - Chunlai Wu
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112
| | - Sharyn Endow
- Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore 169857 Department of Cell Biology, Duke University, Duke University Medical Center, Durham, NC 27710
| | - Hongyan Wang
- Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore 169857 National University of Singapore Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
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14
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Nithianantham S, Le S, Seto E, Jia W, Leary J, Corbett KD, Moore JK, Al-Bassam J. Tubulin cofactors and Arl2 are cage-like chaperones that regulate the soluble αβ-tubulin pool for microtubule dynamics. eLife 2015. [PMID: 26208336 PMCID: PMC4574351 DOI: 10.7554/elife.08811] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Microtubule dynamics and polarity stem from the polymerization of
αβ-tubulin heterodimers. Five conserved tubulin cofactors/chaperones
and the Arl2 GTPase regulate α- and β-tubulin assembly into
heterodimers and maintain the soluble tubulin pool in the cytoplasm, but their
physical mechanisms are unknown. Here, we reconstitute a core tubulin chaperone
consisting of tubulin cofactors TBCD, TBCE, and Arl2, and reveal a cage-like
structure for regulating αβ-tubulin. Biochemical assays and electron
microscopy structures of multiple intermediates show the sequential binding of
αβ-tubulin dimer followed by tubulin cofactor TBCC onto this chaperone,
forming a ternary complex in which Arl2 GTP hydrolysis is activated to alter
αβ-tubulin conformation. A GTP-state locked Arl2 mutant inhibits
ternary complex dissociation in vitro and causes severe defects in microtubule
dynamics in vivo. Our studies suggest a revised paradigm for tubulin cofactors and
Arl2 functions as a catalytic chaperone that regulates soluble
αβ-tubulin assembly and maintenance to support microtubule
dynamics. DOI:http://dx.doi.org/10.7554/eLife.08811.001 Cells contain a network of protein filaments called microtubules. These filaments are
involved in many biological processes; for example, they help cells keep the right
shape, and they help to transport proteins and other materials inside cells. Two proteins called α-tubulin and β-tubulin are the building blocks of
microtubules. The filaments are very dynamic structures that can rapidly change
length as individual tubulin units are either added or removed to the filament ends.
Several proteins known as tubulin cofactors and an enzyme called Arl2 help to build a
vast pool of tubulin units that are able attach to the microtubules. These
units—called αβ-tubulin—are formed by α-tubulin
and β-tubulin binding to each other, but it not clear exactly what roles the
tubulin cofactors and Arl2 play in this process. Nithianantham et al. used a combination of microscopy and biochemical techniques to
study how the tubulin cofactors and Arl2 are organised, and their role in the
assembly of microtubules in yeast. The experiments show that Arl2 and two tubulin
cofactors associate with each other to form a stable ‘complex’ that has
a cage-like structure. A molecule of αβ-tubulin binds to the complex,
followed by another cofactor called TBCC. This activates the enzyme activity of Arl2,
which releases the energy needed to alter the shape of the αβ-tubulin.
Nithianantham et al. also found that yeast cells with a mutant form of Arl2 that
lacked enzyme activity had problems forming microtubules. Together, these findings show that the tubulin cofactors and Arl2 form a complex that
regulates the assembly and maintenance of αβ-tubulin. The next
challenge is to understand how this regulation influences the way that microtubules
grow and shrink inside cells. DOI:http://dx.doi.org/10.7554/eLife.08811.002
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Affiliation(s)
- Stanley Nithianantham
- Department of Molecular Cellular Biology, University of California, Davis, Davis, United States
| | - Sinh Le
- Department of Molecular Cellular Biology, University of California, Davis, Davis, United States
| | - Elbert Seto
- Department of Molecular Cellular Biology, University of California, Davis, Davis, United States
| | - Weitao Jia
- Department of Molecular Cellular Biology, University of California, Davis, Davis, United States
| | - Julie Leary
- Department of Molecular Cellular Biology, University of California, Davis, Davis, United States
| | - Kevin D Corbett
- Ludwig Institute for Cancer Research, University of California, San Diego, San Diego, United States
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States
| | - Jawdat Al-Bassam
- Department of Molecular Cellular Biology, University of California, Davis, Davis, United States
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15
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Gonçalves J, Tavares A, Carvalhal S, Soares H. Revisiting the tubulin folding pathway: new roles in centrosomes and cilia. Biomol Concepts 2015; 1:423-34. [PMID: 25962015 DOI: 10.1515/bmc.2010.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Centrosomes and cilia are critical eukaryotic organelles which have been in the spotlight in recent years given their implication in a myriad of cellular and developmental processes. Despite their recognized importance and intense study, there are still many open questions about their biogenesis and function. In the present article, we review the existing data concerning members of the tubulin folding pathway and related proteins, which have been identified at centrosomes and cilia and were shown to have unexpected roles in these structures.
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16
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Serna M, Carranza G, Martín-Benito J, Janowski R, Canals A, Coll M, Zabala JC, Valpuesta JM. The structure of the complex between α-tubulin, TBCE and TBCB reveals a tubulin dimer dissociation mechanism. J Cell Sci 2015; 128:1824-34. [PMID: 25908846 DOI: 10.1242/jcs.167387] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 03/16/2015] [Indexed: 11/20/2022] Open
Abstract
Tubulin proteostasis is regulated by a group of molecular chaperones termed tubulin cofactors (TBC). Whereas tubulin heterodimer formation is well-characterized biochemically, its dissociation pathway is not clearly understood. Here, we carried out biochemical assays to dissect the role of the human TBCE and TBCB chaperones in α-tubulin-β-tubulin dissociation. We used electron microscopy and image processing to determine the three-dimensional structure of the human TBCE, TBCB and α-tubulin (αEB) complex, which is formed upon α-tubulin-β-tubulin heterodimer dissociation by the two chaperones. Docking the atomic structures of domains of these proteins, including the TBCE UBL domain, as we determined by X-ray crystallography, allowed description of the molecular architecture of the αEB complex. We found that heterodimer dissociation is an energy-independent process that takes place through a disruption of the α-tubulin-β-tubulin interface that is caused by a steric interaction between β-tubulin and the TBCE cytoskeleton-associated protein glycine-rich (CAP-Gly) and leucine-rich repeat (LRR) domains. The protruding arrangement of chaperone ubiquitin-like (UBL) domains in the αEB complex suggests that there is a direct interaction of this complex with the proteasome, thus mediating α-tubulin degradation.
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Affiliation(s)
- Marina Serna
- Departamento de Estructura de Macromoléculas, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
| | - Gerardo Carranza
- Departamento de Biología Molecular, Facultad de Medicina, IDIVAL-Universidad de Cantabria, Santander 39011, Spain
| | - Jaime Martín-Benito
- Departamento de Estructura de Macromoléculas, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
| | - Robert Janowski
- Departamento de Biología Estructural y Computacional, Institute for Research in Biomedicine (IRB-Barcelona), Barcelona 08028, Spain Departamento de Biología Estructural, Institut de Biologia Molecular de Barcelona (IBMB-CSIC), Barcelona 08028, Spain
| | - Albert Canals
- Departamento de Biología Estructural y Computacional, Institute for Research in Biomedicine (IRB-Barcelona), Barcelona 08028, Spain Departamento de Biología Estructural, Institut de Biologia Molecular de Barcelona (IBMB-CSIC), Barcelona 08028, Spain
| | - Miquel Coll
- Departamento de Biología Estructural y Computacional, Institute for Research in Biomedicine (IRB-Barcelona), Barcelona 08028, Spain Departamento de Biología Estructural, Institut de Biologia Molecular de Barcelona (IBMB-CSIC), Barcelona 08028, Spain
| | - Juan Carlos Zabala
- Departamento de Biología Molecular, Facultad de Medicina, IDIVAL-Universidad de Cantabria, Santander 39011, Spain
| | - José María Valpuesta
- Departamento de Estructura de Macromoléculas, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
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17
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Johnson CR, Weems AD, Brewer JM, Thorner J, McMurray MA. Cytosolic chaperones mediate quality control of higher-order septin assembly in budding yeast. Mol Biol Cell 2015; 26:1323-44. [PMID: 25673805 PMCID: PMC4454179 DOI: 10.1091/mbc.e14-11-1531] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Septin hetero-oligomers polymerize into cytoskeletal filaments with essential functions in many eukaryotic cell types. Mutations within the oligomerization interface that encompasses the GTP-binding pocket of a septin (its "G interface") cause thermoinstability of yeast septin hetero-oligomer assembly, and human disease. When coexpressed with its wild-type counterpart, a G interface mutant is excluded from septin filaments, even at moderate temperatures. We show that this quality control mechanism is specific to G interface mutants, operates during de novo septin hetero-oligomer assembly, and requires specific cytosolic chaperones. Chaperone overexpression lowers the temperature permissive for proliferation of cells expressing a G interface mutant as the sole source of a given septin. Mutations that perturb the septin G interface retard release from these chaperones, imposing a kinetic delay on the availability of nascent septin molecules for higher-order assembly. Un-expectedly, the disaggregase Hsp104 contributes to this delay in a manner that does not require its "unfoldase" activity, indicating a latent "holdase" activity toward mutant septins. These findings provide new roles for chaperone-mediated kinetic partitioning of non-native proteins and may help explain the etiology of septin-linked human diseases.
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Affiliation(s)
- Courtney R Johnson
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Andrew D Weems
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Jennifer M Brewer
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Jeremy Thorner
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Michael A McMurray
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
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18
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Bellouze S, Schäfer MK, Buttigieg D, Baillat G, Rabouille C, Haase G. Golgi fragmentation in pmn mice is due to a defective ARF1/TBCE cross-talk that coordinates COPI vesicle formation and tubulin polymerization. Hum Mol Genet 2014; 23:5961-75. [DOI: 10.1093/hmg/ddu320] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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19
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Tian G, Cowan NJ. Tubulin-specific chaperones: components of a molecular machine that assembles the α/β heterodimer. Methods Cell Biol 2014; 115:155-71. [PMID: 23973072 DOI: 10.1016/b978-0-12-407757-7.00011-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The tubulin heterodimer consists of one α- and one β-tubulin polypeptide. Neither protein can partition to the native state or assemble into polymerization competent heterodimers without the concerted action of a series of chaperone proteins including five tubulin-specific chaperones (TBCs) termed TBCA-TBCE. TBCA and TBCB bind to and stabilize newly synthesized quasi-native β- and α-tubulin polypeptides, respectively, following their generation via multiple rounds of ATP-dependent interaction with the cytosolic chaperonin. There is free exchange of β-tubulin between TBCA and TBCD, and of α-tubulin between TBCB and TBCE, resulting in the formation of TBCD/β and TBCE/α, respectively. The latter two complexes interact, forming a supercomplex (TBCE/α/TBCD/β). Discharge of the native α/β heterodimer occurs via interaction of the supercomplex with TBCC, which results in the triggering of TBC-bound β-tubulin (E-site) GTP hydrolysis. This reaction acts as a switch for disassembly of the supercomplex and the release of E-site GDP-bound heterodimer, which becomes polymerization competent following spontaneous exchange with GTP. The tubulin-specific chaperones thus function together as a tubulin assembly machine, marrying the α- and β-tubulin subunits into a tightly associated heterodimer. The existence of this evolutionarily conserved pathway explains why it has never proved possible to isolate α- or β-tubulin as stable independent entities in the absence of their cognate partners, and implies that each exists and is maintained in the heterodimer in a nonminimal energy state. Here, we describe methods for the purification of recombinant TBCs as biologically active proteins following their expression in a variety of host/vector systems.
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Affiliation(s)
- Guoling Tian
- Department of Biochemistry and Molecular Pharmacology, New York University Langone Medical Center, New York, New York, USA
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20
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Andre J, Kerry L, Qi X, Hawkins E, Drizyte K, Ginger ML, McKean PG. An alternative model for the role of RP2 protein in flagellum assembly in the African trypanosome. J Biol Chem 2013; 289:464-75. [PMID: 24257747 PMCID: PMC3879569 DOI: 10.1074/jbc.m113.509521] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The tubulin cofactor C domain-containing protein TbRP2 is a basal body (centriolar) protein essential for axoneme formation in the flagellate protist Trypanosoma brucei, the causal agent of African sleeping sickness. Here, we show how TbRP2 is targeted and tethered at mature basal bodies and provide novel insight into TbRP2 function. Regarding targeting, understanding how several hundred proteins combine to build a microtubule axoneme is a fundamental challenge in eukaryotic cell biology. We show that basal body localization of TbRP2 is mediated by twinned, N-terminal TOF (TON1, OFD1, and FOP) and LisH motifs, motifs that otherwise facilitate localization of only a few conserved proteins at microtubule-organizing centers in animals, plants, and flagellate protists. Regarding TbRP2 function, there is a debate as to whether the flagellar assembly function of specialized, centriolar tubulin cofactor C domain-containing proteins is processing tubulin, the major component of axonemes, or general vesicular trafficking in a flagellum assembly context. Here we report that TbRP2 is required for the recruitment of T. brucei orthologs of MKS1 and MKS6, proteins that, in animal cells, are part of a complex that assembles at the base of the flagellum to regulate protein composition and cilium function. We also identify that TbRP2 is detected by YL1/2, an antibody classically used to detect α-tubulin. Together, these data suggest a general processing role for TbRP2 in trypanosome flagellum assembly and challenge the notion that TbRP2 functions solely in assessing tubulin “quality” prior to tubulin incorporation into the elongating axoneme.
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Affiliation(s)
- Jane Andre
- From the Faculty of Health and Medicine, Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YQ, United Kingdom
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21
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Gombos L, Neuner A, Berynskyy M, Fava LL, Wade RC, Sachse C, Schiebel E. GTP regulates the microtubule nucleation activity of γ-tubulin. Nat Cell Biol 2013; 15:1317-27. [PMID: 24161932 DOI: 10.1038/ncb2863] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Accepted: 09/19/2013] [Indexed: 12/25/2022]
Abstract
Both subunits of αβ-tubulin that comprise the core components of microtubules bind GTP. GTP binding to α-tubulin has a structural role, whereas β-tubulin binds and hydrolyses GTP to regulate microtubule dynamics. γ-tubulin, another member of the tubulin superfamily that seeds microtubule nucleation at microtubule-organizing centres, also binds GTP; however, the importance of this association remains elusive. To address the role of GTP binding to γ-tubulin, we systematically mutagenized the GTP contact residues in the yeast γ-tubulin Tub4. Tub4(GTP)-mutant proteins that exhibited greatly reduced GTP affinity still assembled into the small γ-tubulin complex. However, tub4(GTP) mutants were no longer viable, and had defects in interaction between γ-tubulin and αβ-tubulin, decreased microtubule nucleation and defects in microtubule organization. In vitro and in vivo data show that only γ-tubulin loaded with GTP nucleates microtubules. Our results suggest that GTP recruitment to γ-tubulin enhances its interaction with αβ-tubulin similarly to GTP recruitment to β-tubulin.
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Affiliation(s)
- Linda Gombos
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), ZMBH-DKFZ Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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22
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Mori R, Toda T. The dual role of fission yeast Tbc1/cofactor C orchestrates microtubule homeostasis in tubulin folding and acts as a GAP for GTPase Alp41/Arl2. Mol Biol Cell 2013; 24:1713-24, S1-8. [PMID: 23576550 PMCID: PMC3667724 DOI: 10.1091/mbc.e12-11-0792] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 02/22/2013] [Accepted: 03/29/2013] [Indexed: 11/11/2022] Open
Abstract
Supplying the appropriate amount of correctly folded α/β-tubulin heterodimers is critical for microtubule dynamics. Formation of assembly-competent heterodimers is remarkably elaborate at the molecular level, in which the α- and β-tubulins are separately processed in a chaperone-dependent manner. This sequential step is performed by the tubulin-folding cofactor pathway, comprising a specific set of regulatory proteins: cofactors A-E. We identified the fission yeast cofactor: the orthologue of cofactor C, Tbc1. In addition to its roles in tubulin folding, Tbc1 acts as a GAP in regulating Alp41/Arl2, a highly conserved small GTPase. Of interest, the expression of GDP- or GTP-bound Alp41 showed the identical microtubule loss phenotype, suggesting that continuous cycling between these forms is important for its functions. In addition, we found that Alp41 interacts with Alp1(D), the orthologue of cofactor D, specifically when in the GDP-bound form. Intriguingly, Alp1(D) colocalizes with microtubules when in excess, eventually leading to depolymerization, which is sequestered by co-overproducing GDP-bound Alp41. We present a model of the final stages of the tubulin cofactor pathway that includes a dual role for both Tbc1 and Alp1(D) in opposing regulation of the microtubule.
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Affiliation(s)
- Risa Mori
- Cell Regulation Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3LY, United Kingdom
| | - Takashi Toda
- Cell Regulation Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3LY, United Kingdom
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23
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Ataullakhanov FI, Melnik KS, Butylin AA. Molecular self-organization and multiple equilibrium systems. Biophysics (Nagoya-shi) 2013. [DOI: 10.1134/s0006350913010028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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24
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East MP, Bowzard JB, Dacks JB, Kahn RA. ELMO domains, evolutionary and functional characterization of a novel GTPase-activating protein (GAP) domain for Arf protein family GTPases. J Biol Chem 2012; 287:39538-53. [PMID: 23014990 DOI: 10.1074/jbc.m112.417477] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human family of ELMO domain-containing proteins (ELMODs) consists of six members and is defined by the presence of the ELMO domain. Within this family are two subclassifications of proteins, based on primary sequence conservation, protein size, and domain architecture, deemed ELMOD and ELMO. In this study, we used homology searching and phylogenetics to identify ELMOD family homologs in genomes from across eukaryotic diversity. This demonstrated not only that the protein family is ancient but also that ELMOs are potentially restricted to the supergroup Opisthokonta (Metazoa and Fungi), whereas proteins with the ELMOD organization are found in diverse eukaryotes and thus were likely the form present in the last eukaryotic common ancestor. The segregation of the ELMO clade from the larger ELMOD group is consistent with their contrasting functions as unconventional Rac1 guanine nucleotide exchange factors and the Arf family GTPase-activating proteins, respectively. We used unbiased, phylogenetic sorting and sequence alignments to identify the most highly conserved residues within the ELMO domain to identify a putative GAP domain within the ELMODs. Three independent but complementary assays were used to provide an initial characterization of this domain. We identified a highly conserved arginine residue critical for both the biochemical and cellular GAP activity of ELMODs. We also provide initial evidence of the function of human ELMOD1 as an Arf family GAP at the Golgi. These findings provide the basis for the future study of the ELMOD family of proteins and a new avenue for the study of Arf family GTPases.
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Affiliation(s)
- Michael P East
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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25
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Fabrizio JJ, Aqeel N, Cote J, Estevez J, Jongoy M, Mangal V, Tema W, Rivera A, Wnukowski J, Bencosme Y. Mulet (mlt) encodes a tubulin-binding cofactor E-like homolog required for spermatid individualization in Drosophila melanogaster. Fly (Austin) 2012; 6:261-72. [PMID: 22885996 DOI: 10.4161/fly.21533] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Spermatogenesis in all animal species occurs within a syncytium. Only at the very end of spermatogenesis are individual sperm cells resolved from this syncytium in a process known as individualization. Individualization in Drosophila begins as a membrane-cytoskeletal complex known as the individualization complex (IC) assembles around the sperm heads and proceeds down the flagella, removing cytoplasm from between the sperm tails and shrink-wrapping each spermatid into its own plasma membrane as it travels. The mulet (mlt) mutation results in severely disrupted ICs, indicating that the mlt gene product is required for individualization. Inverse PCR followed by cycle sequencing maps all known P-insertion alleles of mlt to two overlapping genes, CG12214 (the Drosophila tubulin-binding cofactor E-like homolog) and KCNQ (a large voltage-gated potassium channel). However, since the alleles of mlt map to the 5'-UTR of CG12214 and since CG12214 is contained within an intron of KCNQ, it was hypothesized that mlt and CG12214 are allelic. Indeed, CG12214 mutant testes exhibited severely disrupted ICs and were indistinguishable from mlt mutant testes, thus further suggesting allelism. To test this hypothesis, alleles of mlt were crossed to CG12214 in order to generate trans-heterozygous males. Testes from all trans-heterozygous combinations revealed severely disrupted ICs and were also indistinguishable from mlt mutant testes, indicating that mlt and CG12214 fail to complement one another and are thus allelic. In addition, complementation testing against null alleles of KCNQ verified that the observed individualization defect is not caused by a disruption of KCNQ. Finally, since a population of spermatid-associated microtubules known to disappear prior to movement of the IC abnormally persists during individualization in CG12214 mutant testes, this work implicates TBCE-like in the removal of these microtubules prior to IC movement. Taken together, these results identify mlt as CG12214 and suggest that the removal of microtubules by TBCE-like is a necessary pre-requisite for proper coordinated movement of the IC.
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Affiliation(s)
- James J Fabrizio
- Biology Department, Division of Natural Sciences, College of Mount Saint Vincent, Riverdale, NY, USA.
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26
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Schwarz N, Novoselova TV, Wait R, Hardcastle AJ, Cheetham ME. The X-linked retinitis pigmentosa protein RP2 facilitates G protein traffic. Hum Mol Genet 2011; 21:863-73. [PMID: 22072390 DOI: 10.1093/hmg/ddr520] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The X-linked retinitis pigmentosa protein RP2 is a GTPase activating protein (GAP) for the small GTPase Arl3 and both proteins are implicated in the traffic of proteins to the primary cilia. Here, we show that RP2 can facilitate the traffic of the Gβ subunit of transducin (Gβ1). Glutathione S-transferase (GST)-RP2 pulled down Gβ from retinal lysates and the interaction was specific to Gβ1, as Gβ3 or Gβ5L did not bind RP2. RP2 did not appear to interact with the Gβ:Gγ heterodimer, in contrast Gγ1 competed with RP2 for Gβ binding. Overexpression of Gβ1 in SK-N-SH cells led to a cytoplasmic accumulation of Gβ1, while co-expression of RP2 or Gγ1 with Gβ1 restored membrane association of Gβ1. Furthermore, RP2 small interfering RNA in ARPE19 cells resulted in a reduction in Gβ1 membrane association that was rescued by Gγ1 overexpression. The interaction of RP2 with Gβ1 required RP2 N-terminal myristolyation and the co-factor C (TBCC) homology domain. The interaction was also disrupted by the pathogenic mutation R118H, which blocks Arl3 GAP activity. Interestingly, Arl3-Q71L competed with Gβ1 for RP2 binding, suggesting that Arl3-GTP binding by RP2 would release Gβ1. RP2 also stimulated the association of Gβ1 with Rab11 vesicles. Collectively, the data support a role for RP2 in facilitating the membrane association and traffic of Gβ1, potentially prior to the formation of the obligate Gβ:Gγ heterodimer. Combined with other recent evidence, this suggests that RP2 may co-operate with Arl3 and its effectors in the cilia-associated traffic of G proteins.
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Affiliation(s)
- Nele Schwarz
- UCL Institute of Ophthalmology, London EC1V 9EL, UK
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27
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Szolajska E, Chroboczek J. Faithful chaperones. Cell Mol Life Sci 2011; 68:3307-22. [PMID: 21655914 PMCID: PMC3181412 DOI: 10.1007/s00018-011-0740-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 05/19/2011] [Accepted: 05/23/2011] [Indexed: 12/01/2022]
Abstract
This review describes the properties of some rare eukaryotic chaperones that each assist in the folding of only one target protein. In particular, we describe (1) the tubulin cofactors, (2) p47, which assists in the folding of collagen, (3) α-hemoglobin stabilizing protein (AHSP), (4) the adenovirus L4-100 K protein, which is a chaperone of the major structural viral protein, hexon, and (5) HYPK, the huntingtin-interacting protein. These various-sized proteins (102–1,190 amino acids long) are all involved in the folding of oligomeric polypeptides but are otherwise functionally unique, as they each assist only one particular client. This raises a question regarding the biosynthetic cost of the high-level production of such chaperones. As the clients of faithful chaperones are all abundant proteins that are essential cellular or viral components, it is conceivable that this necessary metabolic expenditure withstood evolutionary pressure to minimize biosynthetic costs. Nevertheless, the complexity of the folding pathways in which these chaperones are involved results in error-prone processes. Several human disorders associated with these chaperones are discussed.
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Affiliation(s)
- Ewa Szolajska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02106 Warsaw, Poland
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28
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Tian G, Thomas S, Cowan NJ. Effect of TBCD and its regulatory interactor Arl2 on tubulin and microtubule integrity. Cytoskeleton (Hoboken) 2011; 67:706-14. [PMID: 20740604 DOI: 10.1002/cm.20480] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Assembly of the α/β tubulin heterodimer requires the participation of a series of chaperone proteins (TBCA-E) that function downstream of the cytosolic chaperonin (CCT) as a heterodimer assembly machine. TBCD and TBCE are also capable of acting in a reverse reaction in which they disrupt native heterodimers. Homologs of TBCA-E exist in all eukaryotes, and the amino acid sequences of α- and β-tubulin isotypes are rigidly conserved among vertebrates. However, the efficiency with which TBCD effects tubulin disruption in vivo depends on its origin: bovine (but not human) TBCD efficiently destroys tubulin and microtubules upon overexpression in cultured cells. Here we show that recombinant bovine TBCD is produced in HeLa cells as a stoichiometric cocomplex with β-tubulin, consistent with its behavior in vitro and in vivo. In contrast, expression of human TBCD using the same host/vector system results in the generation of TBCD that is not complexed with β-tubulin. We show that recombinant human TBCD functions indistinguishably from its nonrecombinant bovine counterpart in in vitro CCT-driven folding reactions, in tubulin disruption reactions, and in tubulin GTPase activating protein assays in which TBCD and TBCC stimulate GTP hydrolysis by β-tubulin at a heterodimer concentration far below that required for polymerization into microtubules. We conclude that bovine and human TBCD have functionally identical roles in de novo tubulin heterodimer assembly, and show that the inability of human TBCD to disrupt microtubule integrity upon overexpression in vivo can be overcome by siRNA-mediated suppression of expression of the TBCD regulator Arl2 (ADP ribosylation factor-like protein).
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Affiliation(s)
- Guoling Tian
- Department of Biochemistry, NYU Langone Medical Center, 550 First Avenue, New York, New York 10016, USA
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Aylett CH, Löwe J, Amos LA. New Insights into the Mechanisms of Cytomotive Actin and Tubulin Filaments. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 292:1-71. [DOI: 10.1016/b978-0-12-386033-0.00001-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Abstract
The Arf-like (Arl) small GTPases have a diverse range of functions in the eukaryotic cell. Metazoan Arl2 acts as a regulator of microtubule biogenesis, binding to the tubulin-specific chaperone cofactor D. Arl2 also has a mitochondrial function through its interactions with BART and ANT-1, the only member of the Ras superfamily to be found in this organelle to date. In the present study, we describe characterization of the Arl2 orthologue in the protozoan parasite Trypanosoma brucei. Modulation of TbARL2 expression in bloodstream form parasites by RNA interference (RNAi) causes inhibition of cleavage furrow formation, resulting in a severe defect in cytokinesis and the accumulation of multinucleated cells. RNAi of TbARL2 also results in loss of acetylated alpha-tubulin but not of total -tubulin from cellular microtubules. While overexpression of TbARL2(myc) also leads to a defect in cytokinesis, an excess of untagged protein has no effect on cell division, demonstrating the importance of the extreme C-terminus in correct function. TbARL2 overexpressing cells (either myc-tagged or untagged) have an increase in acetylated -tubulin. Our data indicate that Arl2 has a fundamentally conserved role in trypanosome microtubule biogenesis that correlates with -tubulin acetylation.
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Hage-Sleiman R, Herveau S, Matera EL, Laurier JF, Dumontet C. Tubulin binding cofactor C (TBCC) suppresses tumor growth and enhances chemosensitivity in human breast cancer cells. BMC Cancer 2010; 10:135. [PMID: 20384997 PMCID: PMC2859754 DOI: 10.1186/1471-2407-10-135] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 04/12/2010] [Indexed: 12/22/2022] Open
Abstract
Background Microtubules are considered major therapeutic targets in patients with breast cancer. In spite of their essential role in biological functions including cell motility, cell division and intracellular transport, microtubules have not yet been considered as critical actors influencing tumor cell aggressivity. To evaluate the impact of microtubule mass and dynamics on the phenotype and sensitivity of breast cancer cells, we have targeted tubulin binding cofactor C (TBCC), a crucial protein for the proper folding of α and β tubulins into polymerization-competent tubulin heterodimers. Methods We developed variants of human breast cancer cells with increased content of TBCC. Analysis of proliferation, cell cycle distribution and mitotic durations were assayed to investigate the influence of TBCC on the cell phenotype. In vivo growth of tumors was monitored in mice xenografted with breast cancer cells. The microtubule dynamics and the different fractions of tubulins were studied by time-lapse microscopy and lysate fractionation, respectively. In vitro sensitivity to antimicrotubule agents was studied by flow cytometry. In vivo chemosensitivity was assayed by treatment of mice implanted with tumor cells. Results TBCC overexpression influenced tubulin fraction distribution, with higher content of nonpolymerizable tubulins and lower content of polymerizable dimers and microtubules. Microtubule dynamicity was reduced in cells overexpressing TBCC. Cell cycle distribution was altered in cells containing larger amounts of TBCC with higher percentage of cells in G2-M phase and lower percentage in S-phase, along with slower passage into mitosis. While increased content of TBCC had little effect on cell proliferation in vitro, we observed a significant delay in tumor growth with respect to controls when TBCC overexpressing cells were implanted as xenografts in vivo. TBCC overexpressing variants displayed enhanced sensitivity to antimicrotubule agents both in vitro and in xenografts. Conclusion These results underline the essential role of fine tuned regulation of tubulin content in tumor cells and the major impact of dysregulation of tubulin dimer content on tumor cell phenotype and response to chemotherapy. A better understanding of how the microtubule cytoskeleton is dysregulated in cancer cells would greatly contribute to a better understanding of tumor cell biology and characterisation of resistant phenotypes.
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Affiliation(s)
- Rouba Hage-Sleiman
- Inserm U590, Laboratoire de Cytologie Analytique, Université Lyon 1, 69008 Lyon, France.
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Fedyanina OS. The alp1-1315 mutation of the tubulin-folding cofactor D gene delays the mitosis initiation in cdc25-22 mutant cells of Schizosaccharomyces pombe. RUSS J GENET+ 2010. [DOI: 10.1134/s1022795410030051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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TBCCD1, a new centrosomal protein, is required for centrosome and Golgi apparatus positioning. EMBO Rep 2010; 11:194-200. [PMID: 20168327 DOI: 10.1038/embor.2010.5] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 12/18/2009] [Accepted: 01/04/2010] [Indexed: 01/02/2023] Open
Abstract
In animal cells the centrosome is positioned at the cell centre in close association with the nucleus. The mechanisms responsible for this are not completely understood. Here, we report the first characterization of human TBCC-domain containing 1 (TBCCD1), a protein related to tubulin cofactor C. TBCCD1 localizes at the centrosome and at the spindle midzone, midbody and basal bodies of primary and motile cilia. Knockdown of TBCCD1 in RPE-1 cells caused the dissociation of the centrosome from the nucleus and disorganization of the Golgi apparatus. TBCCD1-depleted cells are larger, less efficient in primary cilia assembly and their migration is slower in wound-healing assays. However, the major microtubule-nucleating activity of the centrosome is not affected by TBCCD1 silencing. We propose that TBCCD1 is a key regulator of centrosome positioning and consequently of internal cell organization.
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Lundin VF, Leroux MR, Stirling PC. Quality control of cytoskeletal proteins and human disease. Trends Biochem Sci 2010; 35:288-97. [PMID: 20116259 DOI: 10.1016/j.tibs.2009.12.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Revised: 12/22/2009] [Accepted: 12/23/2009] [Indexed: 11/25/2022]
Abstract
Actins and tubulins are abundant cytoskeletal proteins that support diverse cellular processes. Owing to the unique properties of these filament-forming proteins, an intricate cellular machinery consisting minimally of the chaperonin CCT, prefoldin, phosducin-like proteins, and tubulin cofactors has evolved to facilitate their biogenesis. More recent evidence also suggests that regulated degradation pathways exist for actin (via TRIM32) and tubulin (via parkin or cofactor E-like). Collectively, these pathways maintain the quality control of cytoskeletal proteins ('proteostasis'), ensuring the appropriate function of microfilaments and microtubules. Here, we focus on the molecular mechanisms of the quality control of actin and tubulin, and discuss emerging links between cytoskeletal proteostasis and human diseases.
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Affiliation(s)
- Victor F Lundin
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
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Veltel S, Wittinghofer A. RPGR and RP2: targets for the treatment of X-linked retinitis pigmentosa? Expert Opin Ther Targets 2009; 13:1239-51. [PMID: 19702441 DOI: 10.1517/14728220903225016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Retinitis pigmentosa is the most important hereditary eye disease and there is currently no cure available. Although mutations were found in more than 40 genes in patients with retinitis pigmentosa, only two genes have thus far been found to be responsible for one of the most severe forms of the disease, X-linked retinitis pigmentosa. In this review, we highlight the current knowledge about the two gene products RPGR and RP2 and try to link genetic data from patients with functional data on the corresponding proteins. Based on the fact that recent gene therapeutic approaches for eye diseases are at a very promising stage, we discuss the potential of RPGR and RP2 as drug targets to treat retinitis pigmentosa.
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Affiliation(s)
- Stefan Veltel
- Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto Hahn-Street 11, 44227 Dortmund, Germany
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36
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Beghin A, Belin S, Sleiman RH, Brunet Manquat S, Goddard S, Tabone E, Jordheim LP, Treilleux I, Poupon MF, Diaz JJ, Dumontet C. ADP ribosylation factor like 2 (Arl2) regulates breast tumor aggressivity in immunodeficient mice. PLoS One 2009; 4:e7478. [PMID: 19829707 PMCID: PMC2759505 DOI: 10.1371/journal.pone.0007478] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 09/02/2009] [Indexed: 11/19/2022] Open
Abstract
We have previously reported that ADP ribosylation factor like 2 (Arl2), a small GTPase, content influences microtubule dynamics and cell cycle distribution in breast tumor cells, as well as the degree and distribution of phosphorylated P53. Here we show, in two different human breast adenocarcinoma models, that Arl2 content has a major impact on breast tumor cell aggressivity both in vitro and in vivo. Cells with reduced content of Arl2 displayed reduced contact inhibition, increased clonogenic or cluster formation as well as a proliferative advantage over control cells in an in vitro competition assay. These cells also caused larger tumors in SCID mice, a phenotype which was mimicked by the in vivo administration of siRNA directed against Arl2. Cells with increased Arl2 content displayed reduced aggressivity, both in vitro and in vivo, with enhanced necrosis and were also found to contain increased PP2A phosphatase activity. A rt-PCR analysis of fresh human tumor breast samples suggested that low Arl2 expression was associated with larger tumor size and greater risk of lymph node involvement at diagnosis. These data underline the role of Arl2, a small GTPase, as an important regulator of breast tumor cell aggressivity, both in vitro and in vivo.
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Affiliation(s)
- Anne Beghin
- Inserm, U590, Lyon, France
- Université Lyon 1, ISPB, Lyon, France
| | - Stéphane Belin
- CNRS, Centre de Génétique Moléculaire et Cellulaire, UMR 5534, Villeurbanne, France
| | | | | | - Sophie Goddard
- Centre Léon Bérard, Service Anatomie-Cytologie Pathologiques, Lyon, France
| | - Eric Tabone
- Centre Léon Bérard, Service Anatomie-Cytologie Pathologiques, Lyon, France
| | | | - Isabelle Treilleux
- Centre Léon Bérard, Service Anatomie-Cytologie Pathologiques, Lyon, France
| | | | - Jean-Jacques Diaz
- CNRS, Centre de Génétique Moléculaire et Cellulaire, UMR 5534, Villeurbanne, France
| | - Charles Dumontet
- Inserm, U590, Lyon, France
- Université Lyon 1, ISPB, Lyon, France
- * E-mail:
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Mayya V, Lundgren DH, Hwang SI, Rezaul K, Wu L, Eng JK, Rodionov V, Han DK. Quantitative phosphoproteomic analysis of T cell receptor signaling reveals system-wide modulation of protein-protein interactions. Sci Signal 2009; 2:ra46. [PMID: 19690332 DOI: 10.1126/scisignal.2000007] [Citation(s) in RCA: 302] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Protein phosphorylation events during T cell receptor (TCR) signaling control the formation of complexes among proteins proximal to the TCR, the activation of kinase cascades, and the activation of transcription factors; however, the mode and extent of the influence of phosphorylation in coordinating the diverse phenomena associated with T cell activation are unclear. Therefore, we used the human Jurkat T cell leukemia cell line as a model system and performed large-scale quantitative phosphoproteomic analyses of TCR signaling. We identified 10,665 unique phosphorylation sites, of which 696 showed TCR-responsive changes. In addition, we analyzed broad trends in phosphorylation data sets to uncover underlying mechanisms associated with T cell activation. We found that, upon stimulation of the TCR, phosphorylation events extensively targeted protein modules involved in all of the salient phenomena associated with T cell activation: patterning of surface proteins, endocytosis of the TCR, formation of the F-actin cup, inside-out activation of integrins, polarization of microtubules, production of cytokines, and alternative splicing of messenger RNA. Further, case-by-case analysis of TCR-responsive phosphorylation sites on proteins belonging to relevant functional modules together with network analysis allowed us to deduce that serine-threonine (S-T) phosphorylation modulated protein-protein interactions (PPIs) in a system-wide fashion. We also provide experimental support for this inference by showing that phosphorylation of tubulin on six distinct serine residues abrogated PPIs during the assembly of microtubules. We propose that modulation of PPIs by stimulus-dependent changes in S-T phosphorylation state is a widespread phenomenon applicable to many other signaling systems.
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Affiliation(s)
- Viveka Mayya
- Department of Cell Biology, University of Connecticut Health Center, Farmington, 06030, USA
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38
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The microtubule network and neuronal morphogenesis: Dynamic and coordinated orchestration through multiple players. Mol Cell Neurosci 2009; 43:15-32. [PMID: 19660553 DOI: 10.1016/j.mcn.2009.07.012] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2009] [Accepted: 07/27/2009] [Indexed: 11/24/2022] Open
Abstract
Nervous system function and plasticity rely on the complex architecture of neuronal networks elaborated during development, when neurons acquire their specific and complex shape. During neuronal morphogenesis, the formation and outgrowth of functionally and structurally distinct axons and dendrites require a coordinated and dynamic reorganization of the microtubule cytoskeleton involving numerous regulators. While most of these factors act directly on microtubules to stabilize them or promote their assembly, depolymerization or fragmentation, others are now emerging as essential regulators of neuronal differentiation by controlling tubulin availability and modulating microtubule dynamics. In this review, we recapitulate how the microtubule network is actively regulated during the successive phases of neuronal morphogenesis, and what are the specific roles of the various microtubule-regulating proteins in that process. We then describe the specific signaling pathways and inter-regulations that coordinate the different activities of these proteins to sustain neuronal development in response to environmental cues.
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Abstract
Nucleoside diphosphate kinases (NDPK) are encoded by the NME genes, also called NM23. They catalyze the transfer of gamma-phosphate from nucleoside triphosphates to nucleoside diphosphates by a ping-pong mechanism involving the formation of a high energy phospho-histidine intermediate [1, 2]. Besides their known functions in the control of intracellular nucleotide homeostasis, they are involved in multiple physiological and pathological cellular processes such as differentiation, development, metastastic dissemination or cilia functions. Over the past 15 years, ten human genes have been discovered encoding partial, full length, and/or tandemly repeated Nm23/NDPK domains, with or without N-or C-terminal extensions and/or additional domains. These genes encode proteins exhibiting different functions at various tissular and subcellular localizations. Most of these genes appear late in evolution with the emergence of the vertebrate lineage. This review summarizes the present knowledge on these multitalented proteins.
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40
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Boissan M, Dabernat S, Peuchant E, Schlattner U, Lascu I, Lacombe ML. The mammalian Nm23/NDPK family: from metastasis control to cilia movement. Mol Cell Biochem 2009; 329:51-62. [PMID: 19387795 DOI: 10.1007/s11010-009-0120-7] [Citation(s) in RCA: 155] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 04/02/2009] [Indexed: 01/12/2023]
Abstract
Nucleoside diphosphate kinases (NDPK) are encoded by the NME genes, also called NM23. They catalyze the transfer of gamma-phosphate from nucleoside triphosphates to nucleoside diphosphates by a ping-pong mechanism involving the formation of a high energy phospho-histidine intermediate [1, 2]. Besides their known functions in the control of intracellular nucleotide homeostasis, they are involved in multiple physiological and pathological cellular processes such as differentiation, development, metastastic dissemination or cilia functions. Over the past 15 years, ten human genes have been discovered encoding partial, full length, and/or tandemly repeated Nm23/NDPK domains, with or without N-or C-terminal extensions and/or additional domains. These genes encode proteins exhibiting different functions at various tissular and subcellular localizations. Most of these genes appear late in evolution with the emergence of the vertebrate lineage. This review summarizes the present knowledge on these multitalented proteins.
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Affiliation(s)
- Mathieu Boissan
- INSERM UMRS_938, UMPC Université Paris 06, 75012 Paris, France
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41
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McMurray MA, Thorner J. Reuse, replace, recycle. Specificity in subunit inheritance and assembly of higher-order septin structures during mitotic and meiotic division in budding yeast. Cell Cycle 2009; 8:195-203. [PMID: 19164941 DOI: 10.4161/cc.8.2.7381] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Septins are guanine nucleotide-binding proteins that form hetero-oligomeric complexes, which assemble into filaments and higher-order structures at sites of cell division and morphogenesis in eukaryotes. Dynamic changes in the organization of septin-containing structures occur concomitantly with progression through the mitotic cell cycle and during cell differentiation. Septins also undergo stage-specific post-translational modifications, which have been implicated in regulating their dynamics, in some cases via purported effects on septin turnover. In our recent study, the fate of two of the five septins expressed in mitotic cells of budding yeast (Saccharomyces cerevisiae) was tracked using two complementary fluorescence-based methods for pulse-chase analysis. During mitotic growth, previously-made molecules of both septins (Cdc10 and Cdc12) persisted through multiple successive divisions and were incorporated equivalently with newly synthesized molecules into hetero-oligomers and higher-order structures. Similarly, in cells undergoing meiosis and the developmental program of sporulation, pre-existing copies of Cdc10 were incorporated into new structures. In marked contrast, Cdc12 was irreversibly excluded from septin complexes and replaced by another septin, Spr3. Here, we discuss the broader implications of these results and related findings with regard to how septin dynamics is coordinated with the mitotic cell cycle and in the yeast life cycle, and how these observations may relate to control of the dynamics of other complex multi-subunit assemblies.
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Affiliation(s)
- Michael A McMurray
- Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California; Berkeley, California 94720-3202, USA
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42
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Fedyanina OS, Book AJ, Grishchuk EL. Tubulin heterodimers remain functional for one cell cycle after the inactivation of tubulin-folding cofactor D in fission yeast cells. Yeast 2009; 26:235-47. [PMID: 19330768 PMCID: PMC5705012 DOI: 10.1002/yea.1663] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Tubulin-folding cofactor D plays a major role in the formation of functional tubulin heterodimers, the subunits of microtubules (MTs) that are essential for cell division. Previous work has suggested that, in Schizosaccharomyces pombe, cofactor D function is required during G(1) or S phases of the cell cycle, and when it fails to function due to the temperature-sensitive mutation alp1-t1, cells are unable to segregate their chromosomes in the subsequent mitosis. Here we report that another mutation in the cofactor D gene, alp1-1315, causes failures in either the first or second mitosis in cells synchronized in G(1) or G(2) phases, respectively. Other results, however, suggest that the kinetics of viability loss in these mutants does not depend on progression through the cell cycle. When cofactor D function is perturbed in cells blocked in G(2), cytoplasmic MTs appear normal for 2-3 h but thereafter they disintegrate quickly, so that only a few short MTs remain. These residual MTs are, however, stably maintained, suggesting that they do not require active cofactor D function. The abrupt disassembly of MT cytoskeleton at restrictive temperature in non-cycling cofactor D mutant cells strongly suggests that the life-span of folded tubulin dimers might be downregulated. Indeed, this period is significantly shorter than the previously determined dissociation time of bovine tubulins in vitro. The death of mutant cells occurs inevitably after 2-3 h at restrictive temperature in the following mitosis, and is explained by the idea that MT structures formed in the absence of cofactor D cannot support normal cell division.
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Fanarraga ML, Villegas JC, Carranza G, Castaño R, Zabala JC. Tubulin cofactor B regulates microtubule densities during microglia transition to the reactive states. Exp Cell Res 2008; 315:535-41. [PMID: 19038251 DOI: 10.1016/j.yexcr.2008.10.045] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Revised: 10/21/2008] [Accepted: 10/31/2008] [Indexed: 10/21/2022]
Abstract
Microglia are highly dynamic cells of the CNS that continuously survey the welfare of the neural parenchyma and play key roles modulating neurogenesis and neuronal cell death. In response to injury or pathogen invasion parenchymal microglia transforms into a more active cell that proliferates, migrates and behaves as a macrophage. The acquisition of these extra skills implicates enormous modifications of the microtubule and actin cytoskeletons. Here we show that tubulin cofactor B (TBCB), which has been found to contribute to various aspects of microtubule dynamics in vivo, is also implicated in microglial cytoskeletal changes. We find that TBCB is upregulated in post-lesion reactive parenchymal microglia/macrophages, in interferon treated BV-2 microglial cells, and in neonate amoeboid microglia where the microtubule densities are remarkably low. Our data demonstrate that upon TBCB downregulation both, after microglia differentiation to the ramified phenotype in vivo and in vitro, or after TBCB gene silencing, microtubule densities are restored in these cells. Taken together these observations support the view that TBCB functions as a microtubule density regulator in microglia during activation, and provide an insight into the understanding of the complex mechanisms controlling microtubule reorganization during microglial transition between the amoeboid, ramified, and reactive phenotypes.
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Affiliation(s)
- M L Fanarraga
- Departamentos de Biología Molecular, Universidad de Cantabria, IFIMAV. Herrera Oria s/n. 39011, Santander, Spain.
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Kosmaoglou M, Schwarz N, Bett JS, Cheetham ME. Molecular chaperones and photoreceptor function. Prog Retin Eye Res 2008; 27:434-49. [PMID: 18490186 PMCID: PMC2568879 DOI: 10.1016/j.preteyeres.2008.03.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Molecular chaperones facilitate and regulate protein conformational
change within cells. This encompasses many fundamental cellular processes:
including the correct folding of nascent chains; protein transport and
translocation; signal transduction and protein quality control. Chaperones are,
therefore, important in several forms of human disease, including
neurodegeneration. Within the retina, the highly specialized photoreceptor cell
presents a fascinating paradigm to investigate the specialization of molecular
chaperone function and reveals unique chaperone requirements essential to
photoreceptor function. Mutations in several photoreceptor proteins lead to
protein misfolding mediated neurodegeneration. The best characterized of these
are mutations in the molecular light sensor, rhodopsin, which cause autosomal
dominant retinitis pigmentosa. Rhodopsin biogenesis is likely to require
chaperones, while rhodopsin misfolding involves molecular chaperones in quality
control and the cellular response to protein aggregation. Furthermore, the
specialization of components of the chaperone machinery to photoreceptor
specific roles has been revealed by the identification of mutations in molecular
chaperones that cause inherited retinal dysfunction and degeneration. These
chaperones are involved in several important cellular pathways and further
illuminate the essential and diverse roles of molecular
chaperones.
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Affiliation(s)
- Maria Kosmaoglou
- Division of Molecular and Cellular Neuroscience, UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1 V 9EL, UK
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The retinitis pigmentosa 2 gene product is a GTPase-activating protein for Arf-like 3. Nat Struct Mol Biol 2008; 15:373-80. [DOI: 10.1038/nsmb.1396] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2007] [Accepted: 01/28/2008] [Indexed: 11/09/2022]
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46
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Sellin ME, Holmfeldt P, Stenmark S, Gullberg M. Op18/Stathmin counteracts the activity of overexpressed tubulin-disrupting proteins in a human leukemia cell line. Exp Cell Res 2008; 314:1367-77. [PMID: 18262179 DOI: 10.1016/j.yexcr.2007.12.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 12/21/2007] [Accepted: 12/27/2007] [Indexed: 11/30/2022]
Abstract
Op18/stathmin (Op18) is a phosphorylation-regulated and differentially expressed microtubule-destabilizing protein in animal cells. Op18 regulates tubulin monomer-polymer partitioning of the interphase microtubule system and forms complexes with tubulin heterodimers. Recent reports have shown that specific tubulin-folding cofactors and related proteins may disrupt tubulin heterodimers. We therefore investigated whether Op18 protects unpolymerized tubulin from such disruptive activities. Our approach was based on inducible overexpression of two tubulin-disrupting proteins, namely TBCE, which is required for tubulin biogenesis, and E-like, which has been proposed to regulate tubulin turnover and microtubule stability. Expression of either of these proteins was found to cause a rapid degradation of both alpha-tubulin and beta-tubulin subunits of unpolymerized, but not polymeric, tubulin heterodimers. We found that depletion of Op18 by means of RNA interference increased the susceptibility of tubulin to TBCE or E-like mediated disruption, while overexpressed Op18 exerted a tubulin-protective effect. Tubulin protection was shown to depend on Op18 levels, binding affinity, and the partitioning between tubulin monomers and polymers. Hence, the present study reveals that Op18 at physiologically relevant levels functions to preserve the integrity of tubulin heterodimers, which may serve to regulate tubulin turnover rates.
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Affiliation(s)
- Mikael E Sellin
- Department of Molecular Biology, Umeå University, Umeå, Sweden.
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47
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Cunningham LA, Kahn RA. Cofactor D functions as a centrosomal protein and is required for the recruitment of the gamma-tubulin ring complex at centrosomes and organization of the mitotic spindle. J Biol Chem 2008; 283:7155-65. [PMID: 18171676 DOI: 10.1074/jbc.m706753200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Microtubules are highly dynamic structures, composed of alpha/beta-tubulin heterodimers. Biosynthesis of the functional dimer involves the participation of several chaperones, termed cofactors A-E, that act on folding intermediates downstream of the cytosolic chaperonin CCT (1, 2). We show that cofactor D is also a centrosomal protein and that overexpression of either the full-length protein or either of two centrosome localization domains leads to the loss of anchoring of the gamma-tubulin ring complex and of nucleation of microtubule growth at centrosomes. In contrast, depletion of cofactor D by short interfering RNA results in mitotic spindle defects. Because none of these changes in cofactor D activity produced a change in the levels of alpha-or beta-tubulin, we conclude that these newly discovered functions for cofactor D are distinct from its previously described role in tubulin folding. Thus, we describe a new role for cofactor D at centrosomes that is important to its function in polymerization of tubulin and organization of the mitotic spindle.
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Affiliation(s)
- Leslie A Cunningham
- Department of Biochemistry and the Biochemistry, Cell, and Developmental Biology Program, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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48
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Shultz T, Shmuel M, Hyman T, Altschuler Y. Beta-tubulin cofactor D and ARL2 take part in apical junctional complex disassembly and abrogate epithelial structure. FASEB J 2007; 22:168-82. [PMID: 17704193 DOI: 10.1096/fj.06-7786com] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In epithelial cells, the apical junctional complex (AJC), composed of tight junctions (TJs) and adherens junctions (AJs), maintains cell-surface polarity by forming a fence that prevents lateral movement and diffusion of proteins and lipids between the apical and basolateral PM and holds the epithelial monolayer intact through cell-cell contacts. Disassembly of this complex is a prime event in development and cell transformation. Maintenance of the AJC has been shown to involve mainly the actin cytoskeleton. Recent findings also point to the involvement of the microtubule (MT) system. Here we show the first evidence that in polarized epithelial MDCK cells, ARF-like protein 2 (ARL2) and beta-tubulin cofactor D, known to be involved in MT dynamics, have a role in disassembly of the AJC followed by cell dissociation from the epithelial monolayer, which is not dependent on MT depolymerization. In addition, we show that beta-tubulin cofactor D is partially localized to the lateral PM through its 15 C-terminal amino acids and intact MTs. ARL2 inhibited beta-tubulin cofactor D-dependent cell dissociation from the monolayer and AJC disassembly. To our knowledge, this is the first evidence that beta-tubulin cofactor D plays a role in cells independent of its presumed role in folding tubulin heterodimers. We conclude that ARL2 and beta-tubulin cofactor D participate in AJC disassembly and epithelial depolarization.
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Affiliation(s)
- Tamar Shultz
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Israel
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49
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Stephan A, Vaughan S, Shaw MK, Gull K, McKean PG. An essential quality control mechanism at the eukaryotic basal body prior to intraflagellar transport. Traffic 2007; 8:1323-30. [PMID: 17645436 DOI: 10.1111/j.1600-0854.2007.00611.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Constructing a eukaryotic cilium/flagellum is a demanding task requiring the transport of proteins from their cytoplasmic synthesis site into a spatially and environmentally distinct cellular compartment. The clear potential hazard is that import of aberrant proteins could seriously disable cilia/flagella assembly or turnover processes. Here, we reveal that tubulin protein destined for incorporation into axonemal microtubules interacts with a tubulin cofactor C (TBCC) domain-containing protein that is specifically located at the mature basal body transitional fibres. RNA interference-mediated ablation of this protein results in axonemal microtubule defects but no effect on other microtubule populations within the cell. Bioinformatics analysis indicates that this protein belongs to a clade of flagellum-specific TBCC-like proteins that includes the human protein, XRP2, mutations which lead to certain forms of the hereditary eye disease retinitis pigmentosa. Taken with other observations regarding the role of transitional fibres in cilium/flagellum assembly, we suggest that a localized protein processing capacity embedded at transitional fibres ensures the 'quality' of tubulin imported into the cilium/flagellum, and further, that loss of a ciliary/flagellar quality control capability may underpin a number of human genetic disorders.
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Affiliation(s)
- Angela Stephan
- Biomedical Sciences Unit, Department of Biological Sciences, Lancaster University, Lancaster, LA1 4YQ, UK
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50
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Keays DA, Tian G, Poirier K, Huang GJ, Siebold C, Cleak J, Oliver PL, Fray M, Harvey RJ, Molnár Z, Piñon MC, Dear N, Valdar W, Brown SD, Davies KE, Rawlins JNP, Cowan NJ, Nolan P, Chelly J, Flint J. Mutations in alpha-tubulin cause abnormal neuronal migration in mice and lissencephaly in humans. Cell 2007; 128:45-57. [PMID: 17218254 PMCID: PMC1885944 DOI: 10.1016/j.cell.2006.12.017] [Citation(s) in RCA: 324] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 07/25/2006] [Accepted: 12/18/2006] [Indexed: 02/06/2023]
Abstract
The development of the mammalian brain is dependent on extensive neuronal migration. Mutations in mice and humans that affect neuronal migration result in abnormal lamination of brain structures with associated behavioral deficits. Here, we report the identification of a hyperactive N-ethyl-N-nitrosourea (ENU)-induced mouse mutant with abnormalities in the laminar architecture of the hippocampus and cortex, accompanied by impaired neuronal migration. We show that the causative mutation lies in the guanosine triphosphate (GTP) binding pocket of α-1 tubulin (Tuba1) and affects tubulin heterodimer formation. Phenotypic similarity with existing mouse models of lissencephaly led us to screen a cohort of patients with developmental brain anomalies. We identified two patients with de novo mutations in TUBA3, the human homolog of Tuba1. This study demonstrates the utility of ENU mutagenesis in the mouse as a means to discover the basis of human neurodevelopmental disorders.
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Affiliation(s)
- David A. Keays
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Guoling Tian
- Department of Biochemistry, New York University Medical Center, New York, NY10016, USA
| | - Karine Poirier
- Institut Cochin, INSERM Unité 567, CNRS UMR 8104, Université René Descartes – Paris 5, Faculté de Médecine René Descartes, Paris, F-75014, France
| | - Guo-Jen Huang
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Christian Siebold
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - James Cleak
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Peter L. Oliver
- MRC Functional Genetics Unit, South Parks Road, Oxford, OX1 3QX, UK
| | - Martin Fray
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - Robert J. Harvey
- Department of Pharmacology, The School of Pharmacy, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | - Zoltán Molnár
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford, OX1 3QX, UK
| | - Maria C. Piñon
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford, OX1 3QX, UK
| | - Neil Dear
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - William Valdar
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Steve D.M. Brown
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - Kay E. Davies
- MRC Functional Genetics Unit, South Parks Road, Oxford, OX1 3QX, UK
| | - J. Nicholas P. Rawlins
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, OX1 3UD, UK
| | - Nicholas J. Cowan
- Department of Biochemistry, New York University Medical Center, New York, NY10016, USA
| | - Patrick Nolan
- MRC Mammalian Genetics Unit, Harwell, Didcot, OX11 0RD, Oxfordshire, UK
| | - Jamel Chelly
- Institut Cochin, INSERM Unité 567, CNRS UMR 8104, Université René Descartes – Paris 5, Faculté de Médecine René Descartes, Paris, F-75014, France
| | - Jonathan Flint
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
- Corresponding author
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