251
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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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252
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Rudd AK, Valls Cuevas JM, Devaraj NK. SNAP-Tag-Reactive Lipid Anchors Enable Targeted and Spatiotemporally Controlled Localization of Proteins to Phospholipid Membranes. J Am Chem Soc 2015; 137:4884-7. [DOI: 10.1021/jacs.5b00040] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Andrew K. Rudd
- Department
of Chemistry and
Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Joan M. Valls Cuevas
- Department
of Chemistry and
Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Neal K. Devaraj
- Department
of Chemistry and
Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
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253
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Schmidt H. Dynein motors: How AAA+ ring opening and closing coordinates microtubule binding and linker movement. Bioessays 2015; 37:532-43. [DOI: 10.1002/bies.201400215] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Helgo Schmidt
- Medical Research Council Laboratory of Molecular Biology; Division of Structural Studies; Cambridge UK
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254
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Hunn BHM, Cragg SJ, Bolam JP, Spillantini MG, Wade-Martins R. Impaired intracellular trafficking defines early Parkinson's disease. Trends Neurosci 2015; 38:178-88. [PMID: 25639775 PMCID: PMC4740565 DOI: 10.1016/j.tins.2014.12.009] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 12/17/2014] [Accepted: 12/24/2014] [Indexed: 12/13/2022]
Abstract
Parkinson's disease (PD) is an insidious and incurable neurodegenerative disease, and represents a significant cost to individuals, carers, and ageing societies. It is defined at post-mortem by the loss of dopamine neurons in the substantia nigra together with the presence of Lewy bodies and Lewy neurites. We examine here the role of α-synuclein and other cellular transport proteins implicated in PD and how their aberrant activity may be compounded by the unique anatomy of the dopaminergic neuron. This review uses multiple lines of evidence from genetic studies, human tissue, induced pluripotent stem cells, and refined animal models to argue that prodromal PD can be defined as a disease of impaired intracellular trafficking. Dysfunction of the dopaminergic synapse heralds trafficking impairment.
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Affiliation(s)
- Benjamin H M Hunn
- Oxford Parkinson's Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK; Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Stephanie J Cragg
- Oxford Parkinson's Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK; Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - J Paul Bolam
- Oxford Parkinson's Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK; Medical Research Council Anatomical Neuropharmacology Unit, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Maria-Grazia Spillantini
- Department of Clinical Neurosciences, University of Cambridge, The Clifford Allbutt Building, Hills Road, Cambridge CB2 0QH, UK
| | - Richard Wade-Martins
- Oxford Parkinson's Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK; Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK.
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255
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Lu W, Lakonishok M, Gelfand VI. Kinesin-1-powered microtubule sliding initiates axonal regeneration in Drosophila cultured neurons. Mol Biol Cell 2015; 26:1296-307. [PMID: 25657321 PMCID: PMC4454177 DOI: 10.1091/mbc.e14-10-1423] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Microtubule sliding drives initial axon regeneration in Drosophila neurons. Axotomy leads to fast calcium influx and subsequent microtubule reorganization. Kinesin-1 heavy chain drives the sliding of antiparallel microtubules to power axonal regrowth, and the JNK pathway promotes axonal regeneration by enhancing microtubule sliding. Understanding the mechanism underlying axon regeneration is of great practical importance for developing therapeutic treatment for traumatic brain and spinal cord injuries. Dramatic cytoskeleton reorganization occurs at the injury site, and microtubules have been implicated in the regeneration process. Previously we demonstrated that microtubule sliding by conventional kinesin (kinesin-1) is required for initiation of neurite outgrowth in Drosophila embryonic neurons and that sliding is developmentally down-regulated when neurite outgrowth is completed. Here we report that mechanical axotomy of Drosophila neurons in culture triggers axonal regeneration and regrowth. Regenerating neurons contain actively sliding microtubules; this sliding, like sliding during initial neurite outgrowth, is driven by kinesin-1 and is required for axonal regeneration. The injury induces a fast spike of calcium, depolymerization of microtubules near the injury site, and subsequent formation of local new microtubule arrays with mixed polarity. These events are required for reactivation of microtubule sliding at the initial stages of regeneration. Furthermore, the c-Jun N-terminal kinase pathway promotes regeneration by enhancing microtubule sliding in injured mature neurons.
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Affiliation(s)
- Wen Lu
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Margot Lakonishok
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
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256
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Chen GY, Arginteanu DFJ, Hancock WO. Processivity of the kinesin-2 KIF3A results from rear head gating and not front head gating. J Biol Chem 2015; 290:10274-94. [PMID: 25657001 DOI: 10.1074/jbc.m114.628032] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Indexed: 01/12/2023] Open
Abstract
The kinesin-2 family motor KIF3A/B works together with dynein to bidirectionally transport intraflagellar particles, melanosomes, and neuronal vesicles. Compared with kinesin-1, kinesin-2 is less processive, and its processivity is more sensitive to load, suggesting that processivity may be controlled by different gating mechanisms. We used stopped-flow and steady-state kinetics experiments, along with single-molecule and multimotor assays to characterize the entire kinetic cycle of a KIF3A homodimer that exhibits motility similar to that of full-length KIF3A/B. Upon first encounter with a microtubule, the motor rapidly exchanges both mADP and mATP. When adenosine 5'-[(β,γ)-imido]triphosphate was used to entrap the motor in a two-head-bound state, exchange kinetics were unchanged, indicating that rearward strain in the two-head-bound state does not alter nucleotide binding to the front head. A similar lack of front head gating was found when intramolecular strain was enhanced by shortening the neck linker domain from 17 to 14 residues. In single-molecule assays in ADP, the motor dissociates at 2.1 s(-1), 20-fold slower than the stepping rate, demonstrating the presence of rear head gating. In microtubule pelleting assays, the KD(Mt) is similar in ADP and ATP. The data and accompanying simulations suggest that, rather than KIF3A processivity resulting from strain-dependent regulation of nucleotide binding (front head gating), the motor spends a significant fraction of its hydrolysis cycle in a low affinity state but dissociates only slowly from this state. This work provides a mechanism to explain differences in the load-dependent properties of kinesin-1 and kinesin-2.
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Affiliation(s)
- Geng-Yuan Chen
- From the Department of Biomedical Engineering Pennsylvania State University University Park, Pennsylvania 16802
| | - David F J Arginteanu
- From the Department of Biomedical Engineering Pennsylvania State University University Park, Pennsylvania 16802
| | - William O Hancock
- From the Department of Biomedical Engineering Pennsylvania State University University Park, Pennsylvania 16802
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257
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Abstract
We review studies that quantify newly discovered forces from single enzymatic reactions. These forces arise from the conversion of chemical energy to kinetic energy, which can be harnessed to direct diffusion of the enzyme up a concentration gradient of substrate, a novel phenomenon of molecular chemotaxis. When immobilized, enzymes can move fluid around them and perform directional pumping in microfluidic chambers. Because of the extensive array of enzymes in biological cells, we also develop three new hypotheses: that enzymatic self diffusion can assist in organizing signaling pathways in cells, can assist in pumping of fluid in cells, and can impose biologically significant forces on organelles, which will be manifested as stochastic motion not explained by thermal forces or myosin II. Such mechanochemical phenomena open up new directions in research in mechanobiology in which all enzymes, in addition to their primary function as catalysts for reactions, may have secondary functions as initiators of mechanosensitive transduction pathways.
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Affiliation(s)
- Peter J Butler
- Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA
| | - Krishna K Dey
- Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA
| | - Ayusman Sen
- Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA
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258
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Norris SR, Soppina V, Dizaji AS, Schimert KI, Sept D, Cai D, Sivaramakrishnan S, Verhey KJ. A method for multiprotein assembly in cells reveals independent action of kinesins in complex. ACTA ACUST UNITED AC 2014; 207:393-406. [PMID: 25365993 PMCID: PMC4226728 DOI: 10.1083/jcb.201407086] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A new system for generating cellular protein assemblies of defined spacing and composition reveals that kinesin motors located near each other function independently rather than cooperatively and are influenced primarily by the characteristics of the microtubule track on which they are moving. Teams of processive molecular motors are critical for intracellular transport and organization, yet coordination between motors remains poorly understood. Here, we develop a system using protein components to generate assemblies of defined spacing and composition inside cells. This system is applicable to studying macromolecular complexes in the context of cell signaling, motility, and intracellular trafficking. We use the system to study the emergent behavior of kinesin motors in teams. We find that two kinesin motors in complex act independently (do not help or hinder each other) and can alternate their activities. For complexes containing a slow kinesin-1 and fast kinesin-3 motor, the slow motor dominates motility in vitro but the fast motor can dominate on certain subpopulations of microtubules in cells. Both motors showed dynamic interactions with the complex, suggesting that motor–cargo linkages are sensitive to forces applied by the motors. We conclude that kinesin motors in complex act independently in a manner regulated by the microtubule track.
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Affiliation(s)
- Stephen R Norris
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Virupakshi Soppina
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Aslan S Dizaji
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Kristin I Schimert
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - David Sept
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Dawen Cai
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Sivaraj Sivaramakrishnan
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Kristen J Verhey
- Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 Department of Biophysics, Department of Cell and Developmental Biology, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
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