1
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Ugalde MV, Alecki C, Rizwan J, Le P, Jacob-Tomas S, Xu JM, Minotti S, Wu T, Durham H, Yeo G. Localized molecular chaperone synthesis maintains neuronal dendrite proteostasis. RESEARCH SQUARE 2023:rs.3.rs-3673702. [PMID: 38168440 PMCID: PMC10760236 DOI: 10.21203/rs.3.rs-3673702/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Proteostasis is maintained through regulated protein synthesis and degradation and chaperone-assisted protein folding. However, this is challenging in neuronal projections because of their polarized morphology and constant synaptic proteome remodeling. Using high-resolution fluorescence microscopy, we discovered that neurons localize a subset of chaperone mRNAs to their dendrites and use microtubule-based transport to increase this asymmetric localization following proteotoxic stress. The most abundant dendritic chaperone mRNA encodes a constitutive heat shock protein 70 family member (HSPA8). Proteotoxic stress also enhanced HSPA8 mRNA translation efficiency in dendrites. Stress-mediated HSPA8 mRNA localization to the dendrites was impaired by depleting fused in sarcoma-an amyotrophic lateral sclerosis-related protein-in cultured mouse motor neurons and expressing a pathogenic variant of heterogenous nuclear ribonucleoprotein A2/B1 in neurons derived from human induced pluripotent stem cells. These results reveal a crucial and unexpected neuronal stress response in which RNA-binding proteins increase the dendritic localization of HSPA8 mRNA to maintain proteostasis and prevent neurodegeneration.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Gene Yeo
- University of California, San Diego
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2
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Madan V, Albacete‐Albacete L, Jin L, Scaturro P, Watson JL, Muschalik N, Begum F, Boulanger J, Bauer K, Kiebler MA, Derivery E, Bullock SL. HEATR5B associates with dynein-dynactin and promotes motility of AP1-bound endosomal membranes. EMBO J 2023; 42:e114473. [PMID: 37872872 PMCID: PMC10690479 DOI: 10.15252/embj.2023114473] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 09/20/2023] [Accepted: 09/26/2023] [Indexed: 10/25/2023] Open
Abstract
The microtubule motor dynein mediates polarised trafficking of a wide variety of organelles, vesicles and macromolecules. These functions are dependent on the dynactin complex, which helps recruit cargoes to dynein's tail and activates motor movement. How the dynein-dynactin complex orchestrates trafficking of diverse cargoes is unclear. Here, we identify HEATR5B, an interactor of the adaptor protein-1 (AP1) clathrin adaptor complex, as a novel player in dynein-dynactin function. HEATR5B was recovered in a biochemical screen for proteins whose association with the dynein tail is augmented by dynactin. We show that HEATR5B binds directly to the dynein tail and dynactin and stimulates motility of AP1-associated endosomal membranes in human cells. We also demonstrate that the Drosophila HEATR5B homologue is an essential gene that selectively promotes dynein-based transport of AP1-bound membranes to the Golgi apparatus. As HEATR5B lacks the coiled-coil architecture typical of dynein adaptors, our data point to a non-canonical process orchestrating motor function on a specific cargo. We additionally show that HEATR5B promotes association of AP1 with endosomal membranes independently of dynein. Thus, HEATR5B co-ordinates multiple events in AP1-based trafficking.
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Affiliation(s)
- Vanesa Madan
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
- Present address:
AbcamCambridgeUK
| | - Lucas Albacete‐Albacete
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
| | - Li Jin
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
| | | | - Joseph L Watson
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
- Present address:
Department of BiochemistryUniversity of WashingtonSeattleWAUSA
| | - Nadine Muschalik
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
| | - Farida Begum
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
| | - Jérôme Boulanger
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
| | - Karl Bauer
- Biomedical Center, Department for Cell Biology, Medical FacultyLudwig‐Maximilians‐University of MunichMunichGermany
| | - Michael A Kiebler
- Biomedical Center, Department for Cell Biology, Medical FacultyLudwig‐Maximilians‐University of MunichMunichGermany
| | - Emmanuel Derivery
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
| | - Simon L Bullock
- Division of Cell BiologyMedical Research Council (MRC) Laboratory of Molecular BiologyCambridgeUK
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3
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Alecki C, Rizwan J, Le P, Jacob-Tomas S, Xu S, Minotti S, Wu T, Durham H, Yeo GW, Vera M. Localized synthesis of molecular chaperones sustains neuronal proteostasis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.03.560761. [PMID: 37873158 PMCID: PMC10592939 DOI: 10.1101/2023.10.03.560761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Neurons are challenged to maintain proteostasis in neuronal projections, particularly with the physiological stress at synapses to support intercellular communication underlying important functions such as memory and movement control. Proteostasis is maintained through regulated protein synthesis and degradation and chaperone-assisted protein folding. Using high-resolution fluorescent microscopy, we discovered that neurons localize a subset of chaperone mRNAs to their dendrites, particularly more proximal regions, and increase this asymmetric localization following proteotoxic stress through microtubule-based transport from the soma. The most abundant chaperone mRNA in dendrites encodes the constitutive heat shock protein 70, HSPA8. Proteotoxic stress in cultured neurons, induced by inhibiting proteasome activity or inducing oxidative stress, enhanced transport of Hspa8 mRNAs to dendrites and the percentage of mRNAs engaged in translation on mono and polyribosomes. Knocking down the ALS-related protein Fused in Sarcoma (FUS) and a dominant mutation in the heterogenous nuclear ribonucleoprotein A2/B1 (HNRNPA2B1) impaired stress-mediated localization of Hspa8 mRNA to dendrites in cultured murine motor neurons and human iPSC-derived neurons, respectively, revealing the importance of these RNA-binding proteins in maintaining proteostasis. These results reveal the increased dendritic localization and translation of the constitutive HSP70 Hspa8 mRNA as a crucial neuronal stress response to uphold proteostasis and prevent neurodegeneration.
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Affiliation(s)
- Celia Alecki
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Javeria Rizwan
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Phuong Le
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Suleima Jacob-Tomas
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Stella Xu
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Sandra Minotti
- Department of Neurology and Neurosurgery and Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Tad Wu
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Heather Durham
- Department of Neurology and Neurosurgery and Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Maria Vera
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
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4
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Subcellular spatial transcriptomics identifies three mechanistically different classes of localizing RNAs. Nat Commun 2022; 13:6355. [PMID: 36289223 PMCID: PMC9606379 DOI: 10.1038/s41467-022-34004-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 10/03/2022] [Indexed: 12/25/2022] Open
Abstract
Intracellular RNA localization is a widespread and dynamic phenomenon that compartmentalizes gene expression and contributes to the functional polarization of cells. Thus far, mechanisms of RNA localization identified in Drosophila have been based on a few RNAs in different tissues, and a comprehensive mechanistic analysis of RNA localization in a single tissue is lacking. Here, by subcellular spatial transcriptomics we identify RNAs localized in the apical and basal domains of the columnar follicular epithelium (FE) and we analyze the mechanisms mediating their localization. Whereas the dynein/BicD/Egl machinery controls apical RNA localization, basally-targeted RNAs require kinesin-1 to overcome a default dynein-mediated transport. Moreover, a non-canonical, translation- and dynein-dependent mechanism mediates apical localization of a subgroup of dynein-activating adaptor-encoding RNAs (BicD, Bsg25D, hook). Altogether, our study identifies at least three mechanisms underlying RNA localization in the FE, and suggests a possible link between RNA localization and dynein/dynactin/adaptor complex formation in vivo.
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5
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Vishal SS, Wijegunawardana D, Salaikumaran MR, Gopal PP. Sequence Determinants of TDP-43 Ribonucleoprotein Condensate Formation and Axonal Transport in Neurons. Front Cell Dev Biol 2022; 10:876893. [PMID: 35646935 PMCID: PMC9133736 DOI: 10.3389/fcell.2022.876893] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 04/21/2022] [Indexed: 11/17/2022] Open
Abstract
Mutations in TDP-43, a RNA-binding protein with multiple functions in RNA metabolism, cause amyotrophic lateral sclerosis (ALS), but it is uncertain how defects in RNA biology trigger motor neuron degeneration. TDP-43 is a major constituent of ribonucleoprotein (RNP) granules, phase separated biomolecular condensates that regulate RNA splicing, mRNA transport, and translation. ALS-associated TDP-43 mutations, most of which are found in the low complexity domain, promote aberrant liquid to solid phase transitions and impair the dynamic liquid-like properties and motility of RNP transport granules in neurons. Here, we perform a comparative analysis of ALS-linked mutations and TDP-43 variants in order to identify critical structural elements, aromatic and charged residues that are key determinants of TDP-43 RNP transport and condensate formation in neurons. We find that A315T and Q343R disease-linked mutations and substitutions of aromatic residues within the α-helical domain and LARKS, show the most severe defects in TDP-43 RNP granule transport and impair both anterograde and retrograde motility. F313L and F313-6L/Y substitutions of one or both phenylalanine residues in LARKS suggest the aromatic rings are important for TDP-43 RNP transport. Similarly, W334F/L substitutions of the tryptophan residue in the α-helical domain, impair TDP-43 RNP motility (W334L) or anterograde transport (W334F). We also show that R293A and R293K mutations, which disrupt the only RGG in the LCD, profoundly reduce long-range, directed transport and net velocity of TDP-43 RNP granules. In the disordered regions flanking the α-helical domain, we find that F283Y, F397Y or Y374F substitutions of conserved GF/G and SYS motifs, also impair anterograde and/or retrograde motility, possibly by altering hydrophobicity. Similarly, ALS-linked mutations in disordered regions distant from the α-helical domain also show anterograde transport deficits, consistent with previous findings, but these mutations are less severe than A315T and Q343R. Overall our findings demonstrate that the conserved α-helical domain, phenylalanine residues within LARKS and RGG motif are key determinants of TDP-43 RNP transport, suggesting they may mediate efficient recruitment of motors and adaptor proteins. These results offer a possible mechanism underlying ALS-linked TDP-43 defects in axonal transport and homeostasis.
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Affiliation(s)
- Sonali S. Vishal
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States
| | | | | | - Pallavi P. Gopal
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, CT, United States
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6
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Abstract
Microtubules are essential cytoskeletal elements found in all eukaryotic cells. The structure and composition of microtubules regulate their function, and the dynamic remodeling of the network by posttranslational modifications and microtubule-associated proteins generates diverse populations of microtubules adapted for various contexts. In the cardiomyocyte, the microtubules must accommodate the unique challenges faced by a highly contractile, rigidly structured, and long-lasting cell. Through their canonical trafficking role and positioning of mRNA, proteins, and organelles, microtubules regulate essential cardiomyocyte functions such as electrical activity, calcium handling, protein translation, and growth. In a more specialized role, posttranslationally modified microtubules form load-bearing structures that regulate myocyte mechanics and mechanotransduction. Modified microtubules proliferate in cardiovascular diseases, creating stabilized resistive elements that impede cardiomyocyte contractility and contribute to contractile dysfunction. In this review, we highlight the most exciting new concepts emerging from recent studies into canonical and noncanonical roles of cardiomyocyte microtubules.
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Affiliation(s)
- Keita Uchida
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
| | - Emily A Scarborough
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
| | - Benjamin L Prosser
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
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7
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Cui H, Ali MY, Goyal P, Zhang K, Loh JY, Trybus KM, Solmaz SR. Coiled-coil registry shifts in the F684I mutant of Bicaudal D result in cargo-independent activation of dynein motility. Traffic 2021; 21:463-478. [PMID: 32378283 DOI: 10.1111/tra.12734] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 04/29/2020] [Accepted: 05/01/2020] [Indexed: 11/28/2022]
Abstract
The dynein adaptor Drosophila Bicaudal D (BicD) is auto-inhibited and activates dynein motility only after cargo is bound, but the underlying mechanism is elusive. In contrast, we show that the full-length BicD/F684I mutant activates dynein processivity even in the absence of cargo. Our X-ray structure of the C-terminal domain of the BicD/F684I mutant reveals a coiled-coil registry shift; in the N-terminal region, the two helices of the homodimer are aligned, whereas they are vertically shifted in the wild-type. One chain is partially disordered and this structural flexibility is confirmed by computations, which reveal that the mutant transitions back and forth between the two registries. We propose that a coiled-coil registry shift upon cargo-binding activates BicD for dynein recruitment. Moreover, the human homolog BicD2/F743I exhibits diminished binding of cargo adaptor Nup358, implying that a coiled-coil registry shift may be a mechanism to modulate cargo selection for BicD2-dependent transport pathways.
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Affiliation(s)
- Heying Cui
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, USA
| | - M Yusuf Ali
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, USA
| | - Puja Goyal
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, USA
| | - Kaiqi Zhang
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, USA
| | - Jia Ying Loh
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, USA
| | - Kathleen M Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, USA
| | - Sozanne R Solmaz
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, USA
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8
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Turner-Bridger B, Caterino C, Cioni JM. Molecular mechanisms behind mRNA localization in axons. Open Biol 2020; 10:200177. [PMID: 32961072 PMCID: PMC7536069 DOI: 10.1098/rsob.200177] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 09/01/2020] [Indexed: 12/12/2022] Open
Abstract
Messenger RNA (mRNA) localization allows spatiotemporal regulation of the proteome at the subcellular level. This is observed in the axons of neurons, where mRNA localization is involved in regulating neuronal development and function by orchestrating rapid adaptive responses to extracellular cues and the maintenance of axonal homeostasis through local translation. Here, we provide an overview of the key findings that have broadened our knowledge regarding how specific mRNAs are trafficked and localize to axons. In particular, we review transcriptomic studies investigating mRNA content in axons and the molecular principles underpinning how these mRNAs arrived there, including cis-acting mRNA sequences and trans-acting proteins playing a role. Further, we discuss evidence that links defective axonal mRNA localization and pathological outcomes.
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Affiliation(s)
- Benita Turner-Bridger
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, UK
| | - Cinzia Caterino
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy
| | - Jean-Michel Cioni
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy
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9
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Bhaskar V, Jia M, Chao JA. A Single-Molecule RNA Mobility Assay to Identify Proteins that Link RNAs to Molecular Motors. Methods Mol Biol 2020; 2166:269-282. [PMID: 32710415 DOI: 10.1007/978-1-0716-0712-1_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
mRNA transport and localization is a key aspect of posttranscriptional gene regulation. While the transport of many mRNAs is thought to occur through the recruitment of molecular motors, it has been a challenge to identify RNA-binding proteins (RBPs) that directly interact with motors by conventional assays. In order to identify RBPs and their specific domains that are responsible for recruiting a motor to transport granules, we have developed a single-molecule RNA mobility assay that enables quantifying the effect of a tethered RBP on the movement of an RNA. We demonstrate that tethering of RNAs to myosin or kinesin through their well-characterized interacting proteins results in quantitative differences in RNA mobility. This methodology provides a framework for identifying RBPs that mediate associations with motors.
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Affiliation(s)
- Varun Bhaskar
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Min Jia
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Jeffrey A Chao
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
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10
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Will L, Portegies S, van Schelt J, van Luyk M, Jaarsma D, Hoogenraad CC. Dynein activating adaptor BICD2 controls radial migration of upper-layer cortical neurons in vivo. Acta Neuropathol Commun 2019; 7:162. [PMID: 31655624 PMCID: PMC6815425 DOI: 10.1186/s40478-019-0827-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/03/2019] [Indexed: 01/19/2023] Open
Abstract
For the proper organization of the six-layered mammalian neocortex it is required that neurons migrate radially from their place of birth towards their designated destination. The molecular machinery underlying this neuronal migration is still poorly understood. The dynein-adaptor protein BICD2 is associated with a spectrum of human neurological diseases, including malformations of cortical development. Previous studies have shown that knockdown of BICD2 interferes with interkinetic nuclear migration in radial glial progenitor cells, and that Bicd2-deficient mice display an altered laminar organization of the cerebellum and the neocortex. However, the precise in vivo role of BICD2 in neocortical development remains unclear. By comparing cell-type specific conditional Bicd2 knock-out mice, we found that radial migration in the cortex predominantly depends on BICD2 function in post-mitotic neurons. Neuron-specific Bicd2 cKO mice showed severely impaired radial migration of late-born upper-layer neurons. BICD2 depletion in cortical neurons interfered with proper Golgi organization, and neuronal maturation and survival of cortical plate neurons. Single-neuron labeling revealed a specific role of BICD2 in bipolar locomotion. Rescue experiments with wildtype and disease-related mutant BICD2 constructs revealed that a point-mutation in the RAB6/RANBP2-binding-domain, associated with cortical malformation in patients, fails to restore proper cortical neuron migration. Together, these findings demonstrate a novel, cell-intrinsic role of BICD2 in cortical neuron migration in vivo and provide new insights into BICD2-dependent dynein-mediated functions during cortical development.
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11
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Goldman CH, Neiswender H, Veeranan-Karmegam R, Gonsalvez GB. The Egalitarian binding partners Dynein light chain and Bicaudal-D act sequentially to link mRNA to the Dynein motor. Development 2019; 146:dev.176529. [PMID: 31391195 DOI: 10.1242/dev.176529] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 07/15/2019] [Indexed: 01/24/2023]
Abstract
A conserved mechanism of polarity establishment is the localization of mRNA to specific cellular regions. Although it is clear that many mRNAs are transported along microtubules, much less is known about the mechanism by which these mRNAs are linked to microtubule motors. The RNA binding protein Egalitarian (Egl) is necessary for localization of several mRNAs in Drosophila oocytes and embryos. Egl also interacts with Dynein light chain (Dlc) and Bicaudal-D (BicD). The role of Dlc and BicD in mRNA localization has remained elusive. Both proteins are required for oocyte specification, as is Egl. Null alleles in these genes result in an oogenesis block. In this report, we used an shRNA-depletion strategy to overcome the oogenesis block. Our findings reveal that the primary function of Dlc is to promote Egl dimerization. Loss of dimerization compromises the ability of Egl to bind RNA. Consequently, Egl is not bound to cargo, and is not able to efficiently associate with BicD and the Dynein motor. Our results therefore identify the key molecular steps required for assembling a localization-competent mRNP.
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Affiliation(s)
- Chandler H Goldman
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
| | - Hannah Neiswender
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
| | - Rajalakshmi Veeranan-Karmegam
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
| | - Graydon B Gonsalvez
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
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12
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Inberg S, Meledin A, Kravtsov V, Iosilevskii Y, Oren-Suissa M, Podbilewicz B. Lessons from Worm Dendritic Patterning. Annu Rev Neurosci 2019; 42:365-383. [PMID: 30939099 DOI: 10.1146/annurev-neuro-072116-031437] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The structural and functional properties of neurons have intrigued scientists since the pioneering work of Santiago Ramón y Cajal. Since then, emerging cutting-edge technologies, including light and electron microscopy, electrophysiology, biochemistry, optogenetics, and molecular biology, have dramatically increased our understanding of dendritic properties. This advancement was also facilitated by the establishment of different animal model organisms, from flies to mammals. Here we describe the emerging model system of a Caenorhabditis elegans polymodal neuron named PVD, whose dendritic tree follows a stereotypical structure characterized by repeating candelabra-like structural units. In the past decade, progress has been made in understanding PVD's functions, morphogenesis, regeneration, and aging, yet many questions still remain.
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Affiliation(s)
- Sharon Inberg
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel;
| | - Anna Meledin
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel;
| | - Veronika Kravtsov
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel;
| | - Yael Iosilevskii
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel;
| | - Meital Oren-Suissa
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Benjamin Podbilewicz
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel;
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13
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Single-molecule analysis of endogenous β-actin mRNA trafficking reveals a mechanism for compartmentalized mRNA localization in axons. Proc Natl Acad Sci U S A 2018; 115:E9697-E9706. [PMID: 30254174 PMCID: PMC6187124 DOI: 10.1073/pnas.1806189115] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
De novo protein synthesis in neuronal axons plays important roles in neural circuit formation, maintenance, and disease. Key to the selectivity of axonal protein synthesis is whether an mRNA is present at the right place to be translated, but the mechanisms behind axonal mRNA localization remain poorly understood. In this work, we quantitatively analyze the link between axonal β-actin mRNA trafficking and its localization patterns. By developing a single-molecule approach to live-image β-actin mRNAs in axons, we explore the biophysical drivers behind β-actin mRNA motion and uncover a mechanism for generating increased density at the axon tip by differences in motor protein-driven transport speeds. These results provide mechanistic insight into the control of local translation through mRNA trafficking. During embryonic nervous system assembly, mRNA localization is precisely regulated in growing axons, affording subcellular autonomy by allowing controlled protein expression in space and time. Different sets of mRNAs exhibit different localization patterns across the axon. However, little is known about how mRNAs move in axons or how these patterns are generated. Here, we couple molecular beacon technology with highly inclined and laminated optical sheet microscopy to image single molecules of identified endogenous mRNA in growing axons. By combining quantitative single-molecule imaging with biophysical motion models, we show that β-actin mRNA travels mainly as single copies and exhibits different motion-type frequencies in different axonal subcompartments. We find that β-actin mRNA density is fourfold enriched in the growth cone central domain compared with the axon shaft and that a modicum of directed transport is vital for delivery of mRNA to the axon tip. Through mathematical modeling we further demonstrate that directional differences in motor-driven mRNA transport speeds are sufficient to generate β-actin mRNA enrichment at the growth cone. Our results provide insight into how mRNAs are trafficked in axons and a mechanism for generating different mRNA densities across axonal subcompartments.
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14
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McClintock MA, Dix CI, Johnson CM, McLaughlin SH, Maizels RJ, Hoang HT, Bullock SL. RNA-directed activation of cytoplasmic dynein-1 in reconstituted transport RNPs. eLife 2018; 7:36312. [PMID: 29944118 PMCID: PMC6056234 DOI: 10.7554/elife.36312] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/19/2018] [Indexed: 12/19/2022] Open
Abstract
Polarised mRNA transport is a prevalent mechanism for spatial control of protein synthesis. However, the composition of transported ribonucleoprotein particles (RNPs) and the regulation of their movement are poorly understood. We have reconstituted microtubule minus end-directed transport of mRNAs using purified components. A Bicaudal-D (BicD) adaptor protein and the RNA-binding protein Egalitarian (Egl) are sufficient for long-distance mRNA transport by the dynein motor and its accessory complex dynactin, thus defining a minimal transport-competent RNP. Unexpectedly, the RNA is required for robust activation of dynein motility. We show that a cis-acting RNA localisation signal promotes the interaction of Egl with BicD, which licenses the latter protein to recruit dynein and dynactin. Our data support a model for BicD activation based on RNA-induced occupancy of two Egl-binding sites on the BicD dimer. Scaffolding of adaptor protein assemblies by cargoes is an attractive mechanism for regulating intracellular transport. In our cells, tiny molecular motors transport the components necessary for life’s biological processes from one location to another. They do so by loading their cargo, and burning up chemical fuel to carry it along pathways made of filaments. For example, one such motor, called dynein, can move molecules of messenger RNA (mRNA) to specific locations within the cell. There, the mRNA will be used as a template to create proteins, which will operate at exactly the right place. Transporting mRNA in this way is critical in processes such as embryonic development and the formation of memories; yet, this mechanism is still poorly understood. Previous work suggested that the mRNA is simply a passenger of the dynein motor, but McClintock et al. asked if this is really the case. Instead, could mRNA regulate its own sorting by controlling the activity of dynein? Studying mRNA trafficking within the complex molecular environment of a cell is challenging, so mRNA transporting machinery was recreated in the laboratory. Only the proteins necessary to build a working system were included in the experiments. In addition to the filaments, the components included dynein and a complex of proteins known as dynactin, which allows the motor to move together with a protein called BICD2. A protein named Egalitarian was used to link the mRNA to BICD2. By filming fluorescently labelled proteins and mRNAs, McClintock et al. discovered that mRNA strongly promotes the movement of the dynein motor. A structured section in the mRNA acts as a docking area for two copies of Egalitarian. This activates BICD2, which then binds to dynein and dynactin, thereby completing the transport machinery. According to these results, the mRNA directs the assembly of the system that will carry it within the cell. Viruses such as HIV and herpesvirus hijack dynein motors to have their genetic information moved around a cell in order to propagate infection. Understanding precisely how mRNA is transported may help to develop new strategies to fight these viruses.
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Affiliation(s)
- Mark A McClintock
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Carly I Dix
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Christopher M Johnson
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Stephen H McLaughlin
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Rory J Maizels
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Ha Thi Hoang
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Simon L Bullock
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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15
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Perez-Pepe M, Fernández-Alvarez AJ, Boccaccio GL. Life and Work of Stress Granules and Processing Bodies: New Insights into Their Formation and Function. Biochemistry 2018; 57:2488-2498. [PMID: 29595960 DOI: 10.1021/acs.biochem.8b00025] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The dynamic formation of stress granules (SGs), processing bodies (PBs), and related RNA organelles regulates diverse cellular processes, including the coordination of functionally connected messengers, the translational regulation at the synapse, and the control of viruses and retrotransposons. Recent studies have shown that pyruvate kinase and other enzymes localize in SGs and PBs, where they become protected from stress insults. These observations may have implications for enzyme regulation and metabolic control exerted by RNA-based organelles. The formation of these cellular bodies is governed by liquid-liquid phase separation (LLPS) processes, and it needs to be strictly controlled to prevent pathogenic aggregation. The intracellular concentration of key metabolites, such as ATP and sterol derivatives, may influence protein solubility, thus affecting the dynamics of liquid organelles. LLPS in vitro depends on the thermal diffusion of macromolecules, which is limited inside cells, where the condensation and dissolution of membrane-less organelles are helped by energy-driven processes. The active transport by the retrograde motor dynein helps SG assembly, whereas the anterograde motor kinesin mediates SG dissolution; a tug of war between these two molecular motors allows transient SG formation. There is evidence that the efficiency of dynein-mediated transport increases with the number of motor molecules associated with the cargo. The dynein-dependent transport may be influenced by cargo size as larger cargos can load a larger number of motors. We propose a model based on this emergent property of dynein motors, which would be collectively stronger during SG condensation and weaker during SG breakdown, thus allowing kinesin-mediated dispersion.
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Affiliation(s)
- Marcelo Perez-Pepe
- Instituto Leloir and Instituto de Investigaciones Bioquı́micas de Buenos Aires (IIBBA)-CONICET , Buenos Aires , Argentina
| | - Ana J Fernández-Alvarez
- Instituto Leloir and Instituto de Investigaciones Bioquı́micas de Buenos Aires (IIBBA)-CONICET , Buenos Aires , Argentina
| | - Graciela L Boccaccio
- Instituto Leloir and Instituto de Investigaciones Bioquı́micas de Buenos Aires (IIBBA)-CONICET , Buenos Aires , Argentina
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16
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Co-translational control of protein complex formation: a fundamental pathway of cellular organization? Biochem Soc Trans 2018; 46:197-206. [PMID: 29432142 DOI: 10.1042/bst20170451] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 12/10/2017] [Accepted: 01/08/2018] [Indexed: 12/16/2022]
Abstract
Analyses of proteomes from a large number of organisms throughout the domains of life highlight the key role played by multiprotein complexes for the implementation of cellular function. While the occurrence of multiprotein assemblies is ubiquitous, the understanding of pathways that dictate the formation of quaternary structure remains enigmatic. Interestingly, there are now well-established examples of protein complexes that are assembled co-translationally in both prokaryotes and eukaryotes, and indications are that the phenomenon is widespread in cells. Here, we review complex assembly with an emphasis on co-translational pathways, which involve interactions of nascent chains with other nascent or mature partner proteins, respectively. In prokaryotes, such interactions are promoted by the polycistronic arrangement of mRNA and the associated co-translation of functionally related cell constituents in order to enhance otherwise diffusion-dependent processes. Beyond merely stochastic events, however, co-translational complex formation may be sensitive to subunit availability and allow for overall regulation of the assembly process. We speculate how co-translational pathways may constitute integral components of quality control systems to ensure the correct and complete formation of hundreds of heterogeneous assemblies in a single cell. Coupling of folding of intrinsically disordered domains with co-translational interaction of binding partners may furthermore enhance the efficiency and fidelity with which correct conformation is attained. Co-translational complex formation may constitute a fundamental pathway of cellular organization, with profound importance for health and disease.
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17
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Abstract
The last past decade has witnessed a revolution in our appreciation of transcriptome complexity and regulation. This remarkable expansion in our knowledge largely originates from the advent of high-throughput methodologies, and the consecutive discovery that up to 90% of eukaryotic genomes are transcribed, thus generating an unanticipated large range of noncoding RNAs (Hangauer et al., 15(4):112, 2014). Besides leading to the identification of new noncoding RNA species, transcriptome-wide studies have uncovered novel layers of posttranscriptional regulatory mechanisms controlling RNA processing, maturation or translation, and each contributing to the precise and dynamic regulation of gene expression. Remarkably, the development of systems-level studies has been accompanied by tremendous progress in the visualization of individual RNA molecules in single cells, such that it is now possible to image RNA species with a single-molecule resolution from birth to translation or decay. Monitoring quantitatively, with unprecedented spatiotemporal resolution, the fate of individual molecules has been key to understanding the molecular mechanisms underlying the different steps of RNA regulation. This has also revealed biologically relevant, intracellular and intercellular heterogeneities in RNA distribution or regulation. More recently, the convergence of imaging and high-throughput technologies has led to the emergence of spatially resolved transcriptomic techniques that provide a means to perform large-scale analyses while preserving spatial information. By generating transcriptome-wide data on single-cell RNA content, or even subcellular RNA distribution, these methodologies are opening avenues to a wide range of network-level studies at the cell and organ-level, and promise to strongly improve disease diagnostic and treatment.In this introductory chapter, we highlight how recently developed technologies aiming at detecting and visualizing RNA molecules have contributed to the emergence of entirely new research fields, and to dramatic progress in our understanding of gene expression regulation.
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Affiliation(s)
- Caroline Medioni
- Université Côte d'Azur, CNRS, Inserm, iBV, Parc Valrose, 06100, Nice, France
| | - Florence Besse
- Université Côte d'Azur, CNRS, Inserm, iBV, Parc Valrose, 06100, Nice, France.
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18
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Trovisco V, Belaya K, Nashchekin D, Irion U, Sirinakis G, Butler R, Lee JJ, Gavis ER, St Johnston D. bicoid mRNA localises to the Drosophila oocyte anterior by random Dynein-mediated transport and anchoring. eLife 2016; 5. [PMID: 27791980 PMCID: PMC5125753 DOI: 10.7554/elife.17537] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 10/25/2016] [Indexed: 01/17/2023] Open
Abstract
bicoid mRNA localises to the Drosophila oocyte anterior from stage 9 of oogenesis onwards to provide a local source for Bicoid protein for embryonic patterning. Live imaging at stage 9 reveals that bicoid mRNA particles undergo rapid Dynein-dependent movements near the oocyte anterior, but with no directional bias. Furthermore, bicoid mRNA localises normally in shot2A2, which abolishes the polarised microtubule organisation. FRAP and photo-conversion experiments demonstrate that the RNA is stably anchored at the anterior, independently of microtubules. Thus, bicoid mRNA is localised by random active transport and anterior anchoring. Super-resolution imaging reveals that bicoid mRNA forms 110-120 nm particles with variable RNA content, but constant size. These particles appear to be well-defined structures that package the RNA for transport and anchoring.
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Affiliation(s)
- Vítor Trovisco
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Katsiaryna Belaya
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Dmitry Nashchekin
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Uwe Irion
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - George Sirinakis
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Richard Butler
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
| | - Jack J Lee
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Elizabeth R Gavis
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Daniel St Johnston
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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19
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Salogiannis J, Reck-Peterson SL. Hitchhiking: A Non-Canonical Mode of Microtubule-Based Transport. Trends Cell Biol 2016; 27:141-150. [PMID: 27665063 DOI: 10.1016/j.tcb.2016.09.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 08/29/2016] [Accepted: 09/02/2016] [Indexed: 01/01/2023]
Abstract
The long-range movement of organelles, vesicles, and macromolecular complexes by microtubule-based transport is crucial for cell growth and survival. The canonical view of intracellular transport is that each cargo directly recruits molecular motors via cargo-specific adaptor molecules. Recently, a new paradigm called 'hitchhiking' has emerged: some cargos can achieve motility by interacting with other cargos that have already recruited molecular motors. In this way, cargos are co-transported together and their movements are directly coupled. Cargo hitchhiking was discovered in fungi. However, the observation that organelle dynamics are coupled in mammalian cells suggests that this paradigm may be evolutionarily conserved. We review here the data for hitchhiking and discuss the biological significance of this non-canonical mode of microtubule-based transport.
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Affiliation(s)
- John Salogiannis
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA; Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Samara L Reck-Peterson
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA; Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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20
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Arora GK, Tran SL, Rizzo N, Jain A, Welte MA. Temporal control of bidirectional lipid-droplet motion in Drosophila depends on the ratio of kinesin-1 and its co-factor Halo. J Cell Sci 2016; 129:1416-28. [PMID: 26906417 DOI: 10.1242/jcs.183426] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/15/2016] [Indexed: 12/27/2022] Open
Abstract
During bidirectional transport, individual cargoes move continuously back and forth along microtubule tracks, yet the cargo population overall displays directed net transport. How such transport is controlled temporally is not well understood. We analyzed this issue for bidirectionally moving lipid droplets in Drosophila embryos, a system in which net transport direction is developmentally controlled. By quantifying how the droplet distribution changes as embryos develop, we characterize temporal transitions in net droplet transport and identify the crucial contribution of the previously identified, but poorly characterized, transacting regulator Halo. In particular, we find that Halo is transiently expressed; rising and falling Halo levels control the switches in global distribution. Rising Halo levels have to pass a threshold before net plus-end transport is initiated. This threshold level depends on the amount of the motor kinesin-1: the more kinesin-1 is present, the more Halo is needed before net plus-end transport commences. Because Halo and kinesin-1 are present in common protein complexes, we propose that Halo acts as a rate-limiting co-factor of kinesin-1.
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Affiliation(s)
- Gurpreet K Arora
- Department of Biology, University of Rochester, Rochester, NY, USA
| | - Susan L Tran
- Department of Biology, University of Rochester, Rochester, NY, USA Department of Biology, Brandeis University, Waltham, MA, USA
| | - Nicholas Rizzo
- Department of Biology, University of Rochester, Rochester, NY, USA
| | - Ankit Jain
- Department of Biology, Brandeis University, Waltham, MA, USA
| | - Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY, USA Department of Biology, Brandeis University, Waltham, MA, USA
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21
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Cianfrocco MA, DeSantis ME, Leschziner AE, Reck-Peterson SL. Mechanism and regulation of cytoplasmic dynein. Annu Rev Cell Dev Biol 2015; 31:83-108. [PMID: 26436706 DOI: 10.1146/annurev-cellbio-100814-125438] [Citation(s) in RCA: 152] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Until recently, dynein was the least understood of the cytoskeletal motors. However, a wealth of new structural, mechanistic, and cell biological data is shedding light on how this complicated minus-end-directed, microtubule-based motor works. Cytoplasmic dynein-1 performs a wide array of functions in most eukaryotes, both in interphase, in which it transports organelles, proteins, mRNAs, and viruses, and in mitosis and meiosis. Mutations in dynein or its regulators are linked to neurodevelopmental and neurodegenerative diseases. Here, we begin by providing a synthesis of recent data to describe the current model of dynein's mechanochemical cycle. Next, we discuss regulators of dynein, with particular focus on those that directly interact with the motor to modulate its recruitment to microtubules, initiate cargo transport, or activate minus-end-directed motility.
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Affiliation(s)
- Michael A Cianfrocco
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093;
| | - Morgan E DeSantis
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093;
| | - Andres E Leschziner
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093;
| | - Samara L Reck-Peterson
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093;
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22
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Welte MA. As the fat flies: The dynamic lipid droplets of Drosophila embryos. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1156-85. [PMID: 25882628 DOI: 10.1016/j.bbalip.2015.04.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/31/2015] [Accepted: 04/06/2015] [Indexed: 01/09/2023]
Abstract
Research into lipid droplets is rapidly expanding, and new cellular and organismal roles for these lipid-storage organelles are continually being discovered. The early Drosophila embryo is particularly well suited for addressing certain questions in lipid-droplet biology and combines technical advantages with unique biological phenomena. This review summarizes key features of this experimental system and the techniques available to study it, in order to make it accessible to researchers outside this field. It then describes the two topics most heavily studied in this system, lipid-droplet motility and protein sequestration on droplets, discusses what is known about the molecular players involved, points to open questions, and compares the results from Drosophila embryo studies to what it is known about lipid droplets in other systems.
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Affiliation(s)
- Michael A Welte
- Department of Biology University of Rochester, RC Box 270211, 317 Hutchison Hall, Rochester, NY 14627, USA.
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23
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In the right place at the right time: visualizing and understanding mRNA localization. Nat Rev Mol Cell Biol 2014; 16:95-109. [PMID: 25549890 DOI: 10.1038/nrm3918] [Citation(s) in RCA: 379] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The spatial regulation of protein translation is an efficient way to create functional and structural asymmetries in cells. Recent research has furthered our understanding of how individual cells spatially organize protein synthesis, by applying innovative technology to characterize the relationship between mRNAs and their regulatory proteins, single-mRNA trafficking dynamics, physiological effects of abrogating mRNA localization in vivo and for endogenous mRNA labelling. The implementation of new imaging technologies has yielded valuable information on mRNA localization, for example, by observing single molecules in tissues. The emerging movements and localization patterns of mRNAs in morphologically distinct unicellular organisms and in neurons have illuminated shared and specialized mechanisms of mRNA localization, and this information is complemented by transgenic and biochemical techniques that reveal the biological consequences of mRNA mislocalization.
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24
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Vollmeister E, Schipper K, Feldbrügge M. Microtubule-dependent mRNA transport in the model microorganismUstilago maydis. RNA Biol 2014; 9:261-8. [DOI: 10.4161/rna.19432] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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25
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Niedner A, Edelmann FT, Niessing D. Of social molecules: The interactive assembly of ASH1 mRNA-transport complexes in yeast. RNA Biol 2014; 11:998-1009. [PMID: 25482892 PMCID: PMC4615550 DOI: 10.4161/rna.29946] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Asymmetric, motor-protein dependent transport of mRNAs and subsequent localized translation is an important mechanism of gene regulation. Due to the high complexity of such motile particles, our mechanistic understanding of mRNA localization is limited. Over the last two decades, ASH1 mRNA localization in budding yeast has served as comparably simple and accessible model system. Recent advances have helped to draw an increasingly clear picture on the molecular mechanisms governing ASH1 mRNA localization from its co-transcriptional birth to its delivery at the site of destination. These new insights help to better understand the requirement of initial nuclear mRNPs, the molecular basis of specific mRNA-cargo recognition via cis-acting RNA elements, the different stages of RNP biogenesis and reorganization, as well as activation of the motile activity upon cargo binding. We discuss these aspects in context of published findings from other model organisms.
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Affiliation(s)
- Annika Niedner
- a Institute of Structural Biology; Helmholtz Zentrum München - German Center for Environmental Health ; Neuherberg , Germany
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26
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mRNA transport meets membrane traffic. Trends Genet 2014; 30:408-17. [DOI: 10.1016/j.tig.2014.07.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/09/2014] [Accepted: 07/09/2014] [Indexed: 02/07/2023]
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27
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Mutations in cytoplasmic dynein and its regulators cause malformations of cortical development and neurodegenerative diseases. Biochem Soc Trans 2014; 41:1605-12. [PMID: 24256262 DOI: 10.1042/bst20130188] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Neurons are highly specialized for the processing and transmission of electrical signals and use cytoskeleton-based motor proteins to transport different vesicles and cellular materials. Abnormalities in intracellular transport are thought to be a critical factor in the degeneration and death of neurons in both the central and peripheral nervous systems. Several recent studies describe disruptive mutations in the minus-end-directed microtubule motor cytoplasmic dynein that are directly linked to human motor neuropathies, such as SMA (spinal muscular atrophy) and axonal CMT (Charcot-Marie-Tooth) disease or malformations of cortical development, including lissencephaly, pachygyria and polymicrogyria. In addition, genetic defects associated with these and other neurological disorders have been found in multifunctional adaptors that regulate dynein function, including the dynactin subunit p150(Glued), BICD2 (Bicaudal D2), Lis-1 (lissencephaly 1) and NDE1 (nuclear distribution protein E). In the present paper we provide an overview of the disease-causing mutations in dynein motors and regulatory proteins that lead to a broad phenotypic spectrum extending from peripheral neuropathies to cerebral malformations.
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28
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Bicaudal d family adaptor proteins control the velocity of Dynein-based movements. Cell Rep 2014; 8:1248-56. [PMID: 25176647 DOI: 10.1016/j.celrep.2014.07.052] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 06/08/2014] [Accepted: 07/28/2014] [Indexed: 01/19/2023] Open
Abstract
Cargo transport along microtubules is driven by the collective function of microtubule plus- and minus-end-directed motors (kinesins and dyneins). How the velocity of cargo transport is driven by opposing teams of motors is still poorly understood. Here, we combined inducible recruitment of motors and adaptors to Rab6 secretory vesicles with detailed tracking of vesicle movements to investigate how changes in the transport machinery affect vesicle motility. We find that the velocities of kinesin-based vesicle movements are slower and more homogeneous than those of dynein-based movements. We also find that Bicaudal D (BICD) adaptor proteins can regulate dynein-based vesicle motility. BICD-related protein 1 (BICDR-1) accelerates minus-end-directed vesicle movements and affects Rab6 vesicle distribution. These changes are accompanied by reduced axonal outgrowth in neurons, supporting their physiological importance. Our study suggests that adaptor proteins can modulate the velocity of dynein-based motility and thereby control the distribution of transport carriers.
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29
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Terawaki SI, Ootsuka H, Higuchi Y, Wakamatsu K. Crystallographic characterization of the C-terminal coiled-coil region of mouse Bicaudal-D1 (BICD1). ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2014; 70:1103-6. [PMID: 25084392 DOI: 10.1107/s2053230x1401276x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 06/01/2014] [Indexed: 01/11/2023]
Abstract
Bicaudal-D1 (BICD1) is an α-helical coiled-coil protein which is evolutionarily conserved from Drosophila to mammals and facilitates the attachment of specific cargo factors to the dynein motor complex. The C-terminal coiled-coil region (CC3) of BICD1 plays an important role in sorting cargo, linking proteins such as the small GTPase Rab6 and the nuclear pore complex component Ran-binding protein 2 (RanBP2) to the dynein motor complex. This report describes the crystallization and X-ray data collection of the BICD1 CC3 region, as well as the preparation of the complex of BICD1 CC3 with a constitutively active mutant of Rab6. The crystals of the BICD1 CC3 region belonged to space group C2, with unit-cell parameters a = 59.0, b = 36.8, c = 104.3 Å, α = γ = 90, β = 99.8°. The X-ray diffraction data set was collected to 1.50 Å resolution.
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Affiliation(s)
- Shin-ichi Terawaki
- Faculty of Gunma University, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
| | - Hiroki Ootsuka
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
| | - Yoshiki Higuchi
- Department of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Kaori Wakamatsu
- Faculty of Gunma University, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
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30
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Hain D, Langlands A, Sonnenberg HC, Bailey C, Bullock SL, Müller HAJ. The Drosophila MAST kinase Drop out is required to initiate membrane compartmentalisation during cellularisation and regulates dynein-based transport. Development 2014; 141:2119-30. [PMID: 24803657 PMCID: PMC4011086 DOI: 10.1242/dev.104711] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cellularisation of the Drosophila syncytial blastoderm embryo into the polarised blastoderm epithelium provides an excellent model with which to determine how cortical plasma membrane asymmetry is generated during development. Many components of the molecular machinery driving cellularisation have been identified, but cell signalling events acting at the onset of membrane asymmetry are poorly understood. Here we show that mutations in drop out (dop) disturb the segregation of membrane cortical compartments and the clustering of E-cadherin into basal adherens junctions in early cellularisation. dop is required for normal furrow formation and controls the tight localisation of furrow canal proteins and the formation of F-actin foci at the incipient furrows. We show that dop encodes the single Drosophila homologue of microtubule-associated Ser/Thr (MAST) kinases. dop interacts genetically with components of the dynein/dynactin complex and promotes dynein-dependent transport in the embryo. Loss of dop function reduces phosphorylation of Dynein intermediate chain, suggesting that dop is involved in regulating cytoplasmic dynein activity through direct or indirect mechanisms. These data suggest that Dop impinges upon the initiation of furrow formation through developmental regulation of cytoplasmic dynein.
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Affiliation(s)
- Daniel Hain
- Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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31
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CK2 activates kinesin via induction of a conformational change. Proc Natl Acad Sci U S A 2014; 111:7000-5. [PMID: 24782540 DOI: 10.1073/pnas.1321419111] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kinesin is the canonical plus-end microtubule motor and has been the focus of intense study since its discovery in 1985. We previously demonstrated a time-dependent inactivation of kinesin in vitro that was fully reversible by the addition of purified casein kinase 2 (CK2) and showed that this inactivation/reactivation pathway was relevant in cells. Here we show that kinesin inactivation results from a conformational change that causes the neck linker to be positioned closer to the motor domain. Furthermore, we show that treatment of kinesin with CK2 prevents and reverses this repositioning. Finally, we demonstrate that CK2 treatment facilitates ADP dissociation from the motor, resulting in a nucleotide-free state that promotes microtubule binding. Thus, we propose that kinesin inactivation results from neck-linker repositioning and that CK2-mediated reactivation results from CK2's dual ability to reverse this repositioning and to promote ADP release.
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Soundararajan HC, Bullock SL. The influence of dynein processivity control, MAPs, and microtubule ends on directional movement of a localising mRNA. eLife 2014; 3:e01596. [PMID: 24737859 PMCID: PMC3985186 DOI: 10.7554/elife.01596] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Many cellular constituents travel along microtubules in association with multiple copies of motor proteins. How the activity of these motors is regulated during cargo sorting is poorly understood. In this study, we address this issue using a novel in vitro assay for the motility of localising Drosophila mRNAs bound to native dynein-dynactin complexes. High precision tracking reveals that individual RNPs within a population undergo either diffusive, or highly processive, minus end-directed movements along microtubules. RNA localisation signals stimulate the processive movements, with regulation of dynein-dynactin’s activity rather than its total copy number per RNP, responsible for this effect. Our data support a novel mechanism for multi-motor translocation based on the regulation of dynein processivity by discrete cargo-associated features. Studying the in vitro responses of RNPs to microtubule-associated proteins (MAPs) and microtubule ends provides insights into how an RNA population could navigate the cytoskeletal network and become anchored at its destination in cells. DOI:http://dx.doi.org/10.7554/eLife.01596.001 For a cell to do its job, the different components inside it need to be moved to different locations. This is achieved by an elaborate cellular transport system. To move a component to where it needs to be, motor proteins bind to it, often with the assistance of other ‘accessory’ proteins. This cargo-motor complex then moves along a network of tracks within the cell. Viruses also exploit this transport system in order to be trafficked to specific parts of the cell during their life cycles. Many cargos are moved along microtubule tracks. Multiple microtubule motor proteins often attach to the same cargo, but it is unclear how they work together during transport. Previous studies have attempted to address this issue by attaching motor proteins to artificial cargoes, such as synthetic beads. However, these experiments did not include some of the accessory proteins that are thought to play a role during transport within the living cell. Soundararajan and Bullock have now examined how complexes containing multiple motors bound to accessory proteins move molecules of messenger RNA to specific sites within cells. By visualising fruit fly mRNA moving along microtubules attached to a glass surface, the transport process can be studied in detail. It appears that the complexes travel using one of two methods: they either diffuse along the microtubules, which they can do in either direction, or they power themselves along the microtubules, which they can only do in one direction. Although previous experiments with artificial cargos suggested that the number of motors in the complex determines the likelihood of one-way traffic, it appears that one or more accessory proteins are actually in control during mRNA transport. Soundararajan and Bullock also documented how the mRNA-motor complexes react to roadblocks and dead-ends on the microtubule highway. Rather than letting go of the microtubule upon such an encounter, the complexes can reverse back down the track. This behaviour may help them to find a new route to their destination. DOI:http://dx.doi.org/10.7554/eLife.01596.002
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Dynein-dependent transport of nanos RNA in Drosophila sensory neurons requires Rumpelstiltskin and the germ plasm organizer Oskar. J Neurosci 2013; 33:14791-800. [PMID: 24027279 DOI: 10.1523/jneurosci.5864-12.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Intracellular mRNA localization is a conserved mechanism for spatially regulating protein production in polarized cells, such as neurons. The mRNA encoding the translational repressor Nanos (Nos) forms ribonucleoprotein (RNP) particles that are dendritically localized in Drosophila larval class IV dendritic arborization (da) neurons. In nos mutants, class IV da neurons exhibit reduced dendritic branching complexity, which is rescued by transgenic expression of wild-type nos mRNA but not by a localization-compromised nos derivative. While localization is essential for nos function in dendrite morphogenesis, the mechanism underlying the transport of nos RNP particles was unknown. We investigated the mechanism of dendritic nos mRNA localization by analyzing requirements for nos RNP particle motility in class IV da neuron dendrites through live imaging of fluorescently labeled nos mRNA. We show that dynein motor machinery components mediate transport of nos mRNA in proximal dendrites. Two factors, the RNA-binding protein Rumpelstiltskin and the germ plasm protein Oskar, which are required for diffusion/entrapment-mediated localization of nos during oogenesis, also function in da neurons for formation and transport of nos RNP particles. Additionally, we show that nos regulates neuronal function, most likely independent of its dendritic localization and function in morphogenesis. Our results reveal adaptability of localization factors for regulation of a target transcript in different cellular contexts.
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34
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Dix CI, Soundararajan HC, Dzhindzhev NS, Begum F, Suter B, Ohkura H, Stephens E, Bullock SL. Lissencephaly-1 promotes the recruitment of dynein and dynactin to transported mRNAs. ACTA ACUST UNITED AC 2013; 202:479-94. [PMID: 23918939 PMCID: PMC3734092 DOI: 10.1083/jcb.201211052] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lissencephaly-1 promotes the interaction of dynein with dynactin and facilitates motor complex association with mRNA cargos. Microtubule-based transport mediates the sorting and dispersal of many cellular components and pathogens. However, the mechanisms by which motor complexes are recruited to and regulated on different cargos remain poorly understood. Here we describe a large-scale biochemical screen for novel factors associated with RNA localization signals mediating minus end–directed mRNA transport during Drosophila development. We identified the protein Lissencephaly-1 (Lis1) and found that minus-end travel distances of localizing transcripts are dramatically reduced in lis1 mutant embryos. Surprisingly, given its well-documented role in regulating dynein mechanochemistry, we uncovered an important requirement for Lis1 in promoting the recruitment of dynein and its accessory complex dynactin to RNA localization complexes. Furthermore, we provide evidence that Lis1 levels regulate the overall association of dynein with dynactin. Our data therefore reveal a critical role for Lis1 within the mRNA localization machinery and suggest a model in which Lis1 facilitates motor complex association with cargos by promoting the interaction of dynein with dynactin.
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Affiliation(s)
- Carly I Dix
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
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35
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Gumy LF, Katrukha EA, Kapitein LC, Hoogenraad CC. New insights into mRNA trafficking in axons. Dev Neurobiol 2013; 74:233-44. [PMID: 23959656 DOI: 10.1002/dneu.22121] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 07/17/2013] [Accepted: 08/12/2013] [Indexed: 12/13/2022]
Abstract
In recent years, it has been demonstrated that mRNAs localize to axons of young and mature central and peripheral nervous system neurons in culture and in vivo. Increasing evidence is supporting a fundamental role for the local translation of these mRNAs in neuronal function by regulating axon growth, maintenance and regeneration after injury. Although most mRNAs found in axons are abundant transcripts and not restricted to the axonal compartment, they are sequestered into transport ribonucleoprotein particles and their axonal localization is likely the result of specific targeting rather than passive diffusion. It has been reported that long-distance mRNA transport requires microtubule-dependent motors, but the molecular mechanisms underlying the sorting and trafficking of mRNAs into axons have remained elusive. This review places particular emphasis on motor-dependent transport of mRNAs and presents a mathematical model that describes how microtubule-dependent motors can achieve targeted trafficking in axons. A future challenge will be to systematically explore how the numerous axonal mRNAs and RNA-binding proteins regulate different aspects of specific axonal mRNA trafficking during development and after regeneration.
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Affiliation(s)
- Laura F Gumy
- Division of Cell Biology, University of Utrecht, Padualaan 8, 3584CH, Utrecht, The Netherlands
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36
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Single-molecule reconstitution of mRNA transport by a class V myosin. Nat Struct Mol Biol 2013; 20:952-7. [PMID: 23812374 PMCID: PMC3735863 DOI: 10.1038/nsmb.2614] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/14/2013] [Indexed: 12/27/2022]
Abstract
Molecular motors are instrumental in mRNA localization, which provides spatial and temporal control of protein expression and function. To obtain mechanistic insight into how a class V myosin transports mRNA, we performed single-molecule in vitro assays on messenger ribonucleoprotein (mRNP) complexes reconstituted from purified proteins and a localizing mRNA found in budding yeast. mRNA is required to form a stable, processive transport complex on actin--an elegant mechanism to ensure that only cargo-bound motors are motile. Increasing the number of localizing elements ('zip codes') on the mRNA, or configuring the track to resemble actin cables, enhanced run length and event frequency. In multi-zip-code mRNPs, motor separation distance varied during a run, thus showing the dynamic nature of the transport complex. Building the complexity of single-molecule in vitro assays is necessary to understand how these complexes function within cells.
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37
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Bicaudal-D uses a parallel, homodimeric coiled coil with heterotypic registry to coordinate recruitment of cargos to dynein. Genes Dev 2013; 27:1233-46. [PMID: 23723415 DOI: 10.1101/gad.212381.112] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cytoplasmic dynein is the major minus end-directed microtubule motor in eukaryotes. However, there is little structural insight into how different cargos are recognized and linked to the motor complex. Here we describe the 2.2 Å resolution crystal structure of a cargo-binding region of the dynein adaptor Bicaudal-D (BicD), which reveals a parallel coiled-coil homodimer. We identify a shared binding site for two cargo-associated proteins-Rab6 and the RNA-binding protein Egalitarian (Egl)-within a region of the BicD structure with classical, homotypic core packing. Structure-based mutagenesis in Drosophila provides evidence that occupancy of this site drives association of BicD with dynein, thereby coupling motor recruitment to cargo availability. The structure also contains a region in which, remarkably, the same residues in the polypeptide sequence have different heptad registry in each chain. In vitro and in vivo analysis of a classical Drosophila dominant mutation reveals that this heterotypic region regulates the recruitment of dynein to BicD. Our results support a model in which the heterotypic segment is part of a molecular switch that promotes release of BicD autoinhibition following cargo binding to the neighboring, homotypic coiled-coil region. Overall, our data reveal a pivotal role of a highly asymmetric coiled-coil domain in coordinating the assembly of cargo-motor complexes.
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38
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Gagnon JA, Kreiling JA, Powrie EA, Wood TR, Mowry KL. Directional transport is mediated by a Dynein-dependent step in an RNA localization pathway. PLoS Biol 2013; 11:e1001551. [PMID: 23637574 PMCID: PMC3640089 DOI: 10.1371/journal.pbio.1001551] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/19/2013] [Indexed: 12/15/2022] Open
Abstract
In vivo imaging of subcellular RNA localization in Xenopus oocytes reveals domains of transport directionality mediated by distinct molecular motors, with dynein providing a directional cue for polarized transport. Cytoplasmic RNA localization is a key biological strategy for establishing polarity in a variety of organisms and cell types. However, the mechanisms that control directionality during asymmetric RNA transport are not yet clear. To gain insight into this crucial process, we have analyzed the molecular machinery directing polarized transport of RNA to the vegetal cortex in Xenopus oocytes. Using a novel approach to measure directionality of mRNA transport in live oocytes, we observe discrete domains of unidirectional and bidirectional transport that are required for vegetal RNA transport. While kinesin-1 appears to promote bidirectional transport along a microtubule array with mixed polarity, dynein acts first to direct unidirectional transport of RNA towards the vegetal cortex. Thus, vegetal RNA transport occurs through a multistep pathway with a dynein-dependent directional cue. This provides a new framework for understanding the mechanistic basis of cell and developmental polarity. Like traffic on highways, molecular cargos are transported within cells on tracks that are collectively referred to as cytoskeletal networks. RNA molecules are one such cargo, and in many species, the localization of RNAs in egg cells or oocytes is essential for establishing the first asymmetries that are necessary for proper embryo development. RNAs can be actively transported by molecular motors that move cargos along the cytoskeletal tracks, but how such motors are capable of directing cargos to specific destinations within the cell is not yet known. Here we show that two motors, dynein and kinesin—known to carry out transport in opposite directions—are both directly involved in RNA localization in frog oocytes. To understand how these motors can promote directional cargo transport, we developed a system to monitor RNA transport in live oocytes. We find that the motor acting first in the pathway, dynein, is responsible for unidirectional transport. Bidirectional transport, mediated by kinesin, occurs subsequently on cytoskeletal tracks of opposing polarity near the RNA's final destination. Our results suggest a new model for directional transport comprising an initial directional cue that dominates over a later nondirectional step, acting to refine the ultimate cargo distribution.
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Affiliation(s)
- James A. Gagnon
- Department of Molecular Biology, Cell Biology & Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Jill A. Kreiling
- Department of Molecular Biology, Cell Biology & Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Erin A. Powrie
- Department of Molecular Biology, Cell Biology & Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Timothy R. Wood
- Department of Molecular Biology, Cell Biology & Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Kimberly L. Mowry
- Department of Molecular Biology, Cell Biology & Biochemistry, Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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39
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Cody NA, Iampietro C, Lécuyer E. The many functions of mRNA localization during normal development and disease: from pillar to post. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 2:781-96. [DOI: 10.1002/wdev.113] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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40
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Abstract
Directed transport of the mRNA binding protein, zipcode binding protein1 (ZBP1), into developing axons is believed to play an important role in mRNA localization and local protein synthesis. The role of molecular motors in this process is unclear. We elucidated a role for myosin Va (MyoVa) to modulate the axonal localization and transport of ZBP1 in axons. Using cultured rat hippocampal neurons, ZBP1 colocalized with MyoVa in axons and growth cones. Interaction of MyoVa with ZBP1 was evident by coimmunoprecipitation of endogenous and overexpressed proteins. Inhibition of MyoVa function with the globular tail domain (GTD) of MyoVa protein or short hairpin RNA led to an accumulation of ZBP1 in axons. Live cell imaging of mCherryZBP1 in neurons expressing GTD showed an increase in the number of motile particles, run length, and stimulated anterograde moving ZBP1 particles, suggesting that MyoVa controls availability of ZBP1 for microtubule-dependent transport. These findings suggest a novel regulatory role for MyoVa in the transport of ZBP1 within axons.
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41
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Blower MD. Molecular insights into intracellular RNA localization. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 302:1-39. [PMID: 23351709 DOI: 10.1016/b978-0-12-407699-0.00001-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Localization of mRNAs to specific destinations within a cell or an embryo is important for local control of protein synthesis. mRNA localization is well known to function in very large and polarized cells such as neurons, and to facilitate embryonic patterning during early development. However, recent genome-wide studies have revealed that mRNA localization is more widely utilized than previously thought to control gene expression. Not only can transcripts be localized asymmetrically within the cytoplasm, they are often also localized to symmetrically distributed organelles. Recent genetic, cytological, and biochemical studies have begun to provide molecular insight into how cells select RNAs for transport, move them to specific destinations, and control their translation. This chapter will summarize recent insights into the mechanisms and function of RNA localization with a specific emphasis on molecular insights into each step in the mRNA localization process.
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Affiliation(s)
- Michael D Blower
- Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA, USA.
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42
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Medioni C, Mowry K, Besse F. Principles and roles of mRNA localization in animal development. Development 2012; 139:3263-76. [PMID: 22912410 DOI: 10.1242/dev.078626] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Intracellular targeting of mRNAs has long been recognized as a means to produce proteins locally, but has only recently emerged as a prevalent mechanism used by a wide variety of polarized cell types. Localization of mRNA molecules within the cytoplasm provides a basis for cell polarization, thus underlying developmental processes such as asymmetric cell division, cell migration, neuronal maturation and embryonic patterning. In this review, we describe and discuss recent advances in our understanding of both the regulation and functions of RNA localization during animal development.
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Affiliation(s)
- Caroline Medioni
- Institute of Biology Valrose, University of Nice-Sophia Antipolis/UMR7277 CNRS/UMR1091 INSERM, Parc Valrose, 06108 Nice Cedex 2, France
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43
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Splinter D, Razafsky DS, Schlager MA, Serra-Marques A, Grigoriev I, Demmers J, Keijzer N, Jiang K, Poser I, Hyman AA, Hoogenraad CC, King SJ, Akhmanova A. BICD2, dynactin, and LIS1 cooperate in regulating dynein recruitment to cellular structures. Mol Biol Cell 2012; 23:4226-41. [PMID: 22956769 PMCID: PMC3484101 DOI: 10.1091/mbc.e12-03-0210] [Citation(s) in RCA: 185] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study dissects the recruitment of dynein and dynactin to cargo by a conserved motor adaptor BICD2. It is shown that dynein, dynactin, and BICD2 form a triple complex in vitro and in vivo. Investigation of the properties of this complex by direct visualization of dynein in live cells shows that BICD2-induced dynein transport requires LIS1. Cytoplasmic dynein is the major microtubule minus-end–directed cellular motor. Most dynein activities require dynactin, but the mechanisms regulating cargo-dependent dynein–dynactin interaction are poorly understood. In this study, we focus on dynein–dynactin recruitment to cargo by the conserved motor adaptor Bicaudal D2 (BICD2). We show that dynein and dynactin depend on each other for BICD2-mediated targeting to cargo and that BICD2 N-terminus (BICD2-N) strongly promotes stable interaction between dynein and dynactin both in vitro and in vivo. Direct visualization of dynein in live cells indicates that by itself the triple BICD2-N–dynein–dynactin complex is unable to interact with either cargo or microtubules. However, tethering of BICD2-N to different membranes promotes their microtubule minus-end–directed motility. We further show that LIS1 is required for dynein-mediated transport induced by membrane tethering of BICD2-N and that LIS1 contributes to dynein accumulation at microtubule plus ends and BICD2-positive cellular structures. Our results demonstrate that dynein recruitment to cargo requires concerted action of multiple dynein cofactors.
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Affiliation(s)
- Daniël Splinter
- Department of Cell Biology, Erasmus Medical Centre, 3000 CA Rotterdam, Netherlands Department of Neuroscience, Erasmus Medical Centre, 3000 CA Rotterdam, The Netherlands
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44
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Jansen RP, Niessing D. Assembly of mRNA-protein complexes for directional mRNA transport in eukaryotes--an overview. Curr Protein Pept Sci 2012; 13:284-93. [PMID: 22708485 PMCID: PMC3474952 DOI: 10.2174/138920312801619493] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 01/10/2012] [Accepted: 01/20/2012] [Indexed: 12/11/2022]
Abstract
At all steps from transcription to translation, RNA-binding proteins play important roles in determining mRNA function. Initially it was believed that for the vast majority of transcripts the role of RNA-binding proteins is limited to general functions such as splicing and translation. However, work from recent years showed that members of this class of proteins also recognize several mRNAs via cis-acting elements for their incorporation into large motor-containing particles. These particles are transported to distant subcellular sites, where they become subsequently translated. This process, called mRNA localization, occurs along microtubules or actin filaments, and involves kinesins, dyneins, as well as myosins. Although mRNA localization has been detected in a large number of organisms from fungi to humans, the underlying molecular machineries are not well understood. In this review we will outline general principles of mRNA localization and highlight three examples, for which a comparably large body of information is available. The first example is She2p/She3p-dependent localization of ASH1 mRNA in budding yeast. It is particularly well suited to highlight the interdependence between different steps of mRNA localization. The second example is Staufen-dependent localization of oskar mRNA in the Drosophila embryo, for which the importance of nuclear events for cytoplasmic localization and translational control has been clearly demonstrated. The third example summarizes Egalitarian/Bicaudal D-dependent mRNA transport events in the oocyte and embryo of Drosophila. We will highlight general themes and differences, point to similarities in other model systems, and raise open questions that might be answered in the coming years.
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Affiliation(s)
- Ralf-Peter Jansen
- Interfaculty Institute for Biochemistry, University of Tübingen, Tübingen, Germany
| | - Dierk Niessing
- Institute of Structural Biology, Helmholtz Zentrum München–German Research Center for Environmental Health, München, Germany
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-University, München, Germany
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45
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Conservation of the RNA Transport Machineries and Their Coupling to Translation Control across Eukaryotes. Comp Funct Genomics 2012; 2012:287852. [PMID: 22666086 PMCID: PMC3361156 DOI: 10.1155/2012/287852] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 02/09/2012] [Indexed: 01/03/2023] Open
Abstract
Restriction of proteins to discrete subcellular regions is a common mechanism to establish cellular asymmetries and depends on a coordinated program of mRNA localization and translation control. Many processes from the budding of a yeast to the establishment of metazoan embryonic axes and the migration of human neurons, depend on this type of cell polarization. How factors controlling transport and translation assemble to regulate at the same time the movement and translation of transported mRNAs, and whether these mechanisms are conserved across kingdoms is not yet entirely understood. In this review we will focus on some of the best characterized examples of mRNA transport machineries, the "yeast locasome" as an example of RNA transport and translation control in unicellular eukaryotes, and on the Drosophila Bic-D/Egl/Dyn RNA localization machinery as an example of RNA transport in higher eukaryotes. This focus is motivated by the relatively advanced knowledge about the proteins that connect the localizing mRNAs to the transport motors and the many well studied proteins involved in translational control of specific transcripts that are moved by these machineries. We will also discuss whether the core of these RNA transport machineries and factors regulating mRNA localization and translation are conserved across eukaryotes.
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46
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Abstract
Microtubule-based mRNA transport participates in the establishment of cell asymmetries. An in vitro reconstitution assay demonstrates that localization signals present in an mRNA influence motor copy number on single RNA molecule cargoes, ultimately leading to highly polarized distributions of transcripts.
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47
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Amrute-Nayak M, Bullock SL. Single-molecule assays reveal that RNA localization signals regulate dynein-dynactin copy number on individual transcript cargoes. Nat Cell Biol 2012; 14:416-23. [PMID: 22366687 PMCID: PMC3343632 DOI: 10.1038/ncb2446] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 01/24/2012] [Indexed: 11/13/2022]
Abstract
Subcellular localization of mRNAs by cytoskeletal motors plays critical roles in the spatial control of protein function1. However, optical limitations of studying mRNA transport in vivo mean that there is little mechanistic insight into how transcripts are packaged and linked to motors, and how the movement of mRNA:motor complexes on the cytoskeleton is orchestrated. Here, we have reconstituted transport of mRNPs containing specific RNAs in vitro. We show directly that mRNAs that are either apically localized or non-localized in Drosophila embryos associate with the dynein motor and move bidirectionally on individual microtubules, with localizing mRNPs exhibiting a strong minus-end-directed bias. Single-molecule fluorescence measurements reveal that RNA localization signals increase the average number of dynein and dynactin components recruited to individual mRNPs. We find that, surprisingly, individual RNA molecules are present in motile mRNPs in vitro and present evidence that this is also the case in vivo. Thus, RNA oligomerization is not obligatory for transport. Our findings lead to a model in which RNA localization signals produce highly polarized distributions of transcript populations through modest changes in motor copy number on single mRNA molecules.
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Affiliation(s)
- Mamta Amrute-Nayak
- Cell Biology Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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48
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Shahbabian K, Chartrand P. Control of cytoplasmic mRNA localization. Cell Mol Life Sci 2012; 69:535-52. [PMID: 21984598 PMCID: PMC11115051 DOI: 10.1007/s00018-011-0814-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 08/09/2011] [Accepted: 09/01/2011] [Indexed: 12/17/2022]
Abstract
mRNA localization is a mechanism used by various organisms to control the spatial and temporal production of proteins. This process is a highly regulated event that requires multiple cis- and trans-acting elements that mediate the accurate localization of target mRNAs. The intrinsic nature of localization elements, together with their interaction with different RNA-binding proteins, establishes control mechanisms that can oversee the transcript from its birth in the nucleus to its specific final destination. In this review, we aim to summarize the different mechanisms of mRNA localization, with a particular focus on the various control mechanisms that affect the localization of mRNAs in the cytoplasm.
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Affiliation(s)
- Karen Shahbabian
- Department of Biochemistry, Université de Montréal, 2900 Edouard-Montpetit, Montréal, Qc Canada
| | - Pascal Chartrand
- Department of Biochemistry, Université de Montréal, 2900 Edouard-Montpetit, Montréal, Qc Canada
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49
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An intracellular transmission control protocol: assembly and transport of ribonucleoprotein complexes. Curr Opin Cell Biol 2012; 24:202-10. [PMID: 22278045 DOI: 10.1016/j.ceb.2011.12.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 12/21/2011] [Accepted: 12/27/2011] [Indexed: 12/31/2022]
Abstract
Initially assumed to be a special feature of highly polarized eukaryotic cells, recent evidence suggests that mRNA localization coupled with local translation is a widespread strategy for spatial restriction of protein synthesis within cells. Genome-wide analyses and live imaging approaches have shed new light on the prevalence and the mechanistic details of this phenomenon. Here we review some of the recent findings that have emerged from research from the RNA localization field, from the birth of mRNAs in the nucleus, to their delivery at specific sites within the cytoplasm.
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50
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Microtubule-based motor-mediated mRNA localization in Drosophila oocytes and embryos. Biochem Soc Trans 2012; 39:1197-201. [PMID: 21936788 DOI: 10.1042/bst0391197] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
RNA localization coupled to translational repression is a general mechanism for creating structural and functional asymmetry within the cell. While there are many possible ways to target an mRNA to its destination, a large fraction of the studied transcripts undertake active transport mediated by cytoskeletal elements (microtubules and actin filaments) and associated mechanoenzymes. Among the best-studied model systems of RNA localization are the oocyte and the early embryo of Drosophila melanogaster, for which many well-characterized tools have been developed to study this cell biological phenomenon in a dynamic, developing system in its in vivo context. In the present paper, we review the current evidence and models explaining the different modes of RNA localization that depend on active transport within cells.
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