scholarly journals The role of motor proteins in endosomal sorting

2011 ◽  
Vol 39 (5) ◽  
pp. 1179-1184 ◽  
Author(s):  
Sylvie D. Hunt ◽  
David J. Stephens
Keyword(s):  
Membrane Trafficking ◽  
Spatial Organization ◽  
Motor Proteins ◽  
Cytoplasmic Dynein ◽  
Endosomal Sorting ◽  
Microtubule Motors ◽  
Complex Motor ◽  
Microtubule Motor ◽  
Endosomal System ◽  
And Control

Microtubule motor proteins play key roles in the spatial organization of intracellular organelles as well as the transfer of material between them. This is well illustrated both by the vectorial transfer of biosynthetic cargo from the endoplasmic reticulum to the Golgi apparatus as well as the sorting of secretory and endocytic cargo in the endosomal system. Roles have been described for dynein and kinesin motors in each of these steps. Cytoplasmic dynein is a highly complex motor comprising multiple subunits that provide functional specialization. The family of human kinesins includes over 40 members. This complexity provides immense functional diversity, yet little is known of the specific requirements and functions of individual motors during discrete membrane trafficking steps. In the present paper, we describe some of the latest findings in this area that seek to define the mechanisms of recruitment and control of activity of microtubule motors in spatial organization and cargo trafficking through the endosomal network.

scholarly journals Dynactin is required for bidirectional organelle transport

2003 ◽  
Vol 160 (3) ◽  
pp. 297-301 ◽  
Author(s):  
Sean W. Deacon ◽  
Anna S. Serpinskaya ◽  
Patricia S. Vaughan ◽  
Monica Lopez Fanarraga ◽  
Isabelle Vernos ◽  
...  
Keyword(s):  
Cell Types ◽  
Cytoplasmic Dynein ◽  
Opposite Polarity ◽  
Model System ◽  
Organelle Transport ◽  
Transport Activity ◽  
Microtubule Motors ◽  
Microtubule Motor ◽  
Dynactin Complex ◽  
Binding Subunit

Kinesin II is a heterotrimeric plus end–directed microtubule motor responsible for the anterograde movement of organelles in various cell types. Despite substantial literature concerning the types of organelles that kinesin II transports, the question of how this motor associates with cargo organelles remains unanswered. To address this question, we have used Xenopus laevis melanophores as a model system. Through analysis of kinesin II–mediated melanosome motility, we have determined that the dynactin complex, known as an anchor for cytoplasmic dynein, also links kinesin II to organelles. Biochemical data demonstrates that the putative cargo-binding subunit of Xenopus kinesin II, Xenopus kinesin II–associated protein (XKAP), binds directly to the p150Glued subunit of dynactin. This interaction occurs through aa 530–793 of XKAP and aa 600–811 of p150Glued. These results reveal that dynactin is required for transport activity of microtubule motors of opposite polarity, cytoplasmic dynein and kinesin II, and may provide a new mechanism to coordinate their activities.

scholarly journals Microtubule-organizing center formation at telomeres induces meiotic telomere clustering

2013 ◽  
Vol 200 (4) ◽  
pp. 385-395 ◽  
Author(s):  
Masashi Yoshida ◽  
Satoshi Katsuyama ◽  
Kazuki Tateho ◽  
Hiroto Nakamura ◽  
Junpei Miyoshi ◽  
...  
Keyword(s):  
Chromosome Pairing ◽  
Light Chain ◽  
Homologous Chromosome ◽  
Cytoplasmic Dynein ◽  
Dynein Light Chain ◽  
Microtubule Organizing Center ◽  
Homologous Chromosome Pairing ◽  
Microtubule Motors ◽  
Microtubule Motor ◽  
Organizing Center

During meiosis, telomeres cluster and promote homologous chromosome pairing. Telomere clustering requires the interaction of telomeres with the nuclear membrane proteins SUN (Sad1/UNC-84) and KASH (Klarsicht/ANC-1/Syne homology). The mechanism by which telomeres gather remains elusive. In this paper, we show that telomere clustering in fission yeast depends on microtubules and the microtubule motors, cytoplasmic dynein, and kinesins. Furthermore, the γ-tubulin complex (γ-TuC) is recruited to SUN- and KASH-localized telomeres to form a novel microtubule-organizing center that we termed the “telocentrosome.” Telocentrosome formation depends on the γ-TuC regulator Mto1 and on the KASH protein Kms1, and depletion of either Mto1 or Kms1 caused severe telomere clustering defects. In addition, the dynein light chain (DLC) contributes to telocentrosome formation, and simultaneous depletion of DLC and dynein also caused severe clustering defects. Thus, the telocentrosome is essential for telomere clustering. We propose that telomere-localized SUN and KASH induce telocentrosome formation and that subsequent microtubule motor-dependent aggregation of telocentrosomes via the telocentrosome-nucleated microtubules causes telomere clustering.

scholarly journals The Interaction of Neurofilaments with the Microtubule Motor Cytoplasmic Dynein

2004 ◽  
Vol 15 (11) ◽  
pp. 5092-5100 ◽  
Author(s):  
Oliver I. Wagner ◽  
Jennifer Ascaño ◽  
Mariko Tokito ◽  
Jean-Francois Leterrier ◽  
Paul A. Janmey ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Specific Interaction ◽  
Cytoplasmic Dynein ◽  
Live Cells ◽  
Slow Axonal Transport ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microtubule Motors ◽  
Microtubule Motor ◽  
Physical Interactions

Neurofilaments are synthesized in the cell body of neurons and transported outward along the axon via slow axonal transport. Direct observation of neurofilaments trafficking in live cells suggests that the slow outward rate of transport is due to the net effects of anterograde and retrograde microtubule motors pulling in opposition. Previous studies have suggested that cytoplasmic dynein is required for efficient neurofilament transport. In this study, we examine the interaction of neurofilaments with cytoplasmic dynein. We used fluid tapping mode atomic force microscopy to visualize single neurofilaments, microtubules, dynein/dynactin, and physical interactions between these neuronal components. AFM images suggest that neurofilaments act as cargo for dynein, associating with the base of the motor complex. Yeast two-hybrid and affinity chromatography assays confirm this hypothesis, indicating that neurofilament subunit M binds directly to dynein IC. This interaction is blocked by monoclonal antibodies directed either to NF-M or to dynein. Together these data suggest that a specific interaction between neurofilament subunit M and cytoplasmic dynein is involved in the saltatory bidirectional motility of neurofilaments undergoing axonal transport in the neuron.

membrane traffic: Microtubule motor cycles and kinectin

1996 ◽  
Vol 54 ◽  
pp. 732-733
Author(s):  
Michael P. Sheetz
Keyword(s):  
Membrane Traffic ◽  
Growth Conditions ◽  
Cytoplasmic Dynein ◽  
Microtubule Motors ◽  
Transport Cycle ◽  
Microtubule Motor ◽  
Associated Proteins ◽  
The Many ◽  
Dependent Transport

Although membrane traffic can occur in the absence of microtubules, the rapid metabolism of many eucaryotic cells requires that vesicular organelles are actively transported. Microtubule-dependent transport is particularly robust in actively growing cells and the volume of membrane transported increases dramatically in going from static to growth conditions. Both inward and outward movement are regulated simultaneously implying coordinate activation of both motors or a transport cycle. Relatively large complexes of the microtubule motors and associated proteins are responsible for powering the movements (reviewed in Vallee and Sheetz, 1996). Of the many motors that have been described, kinesin and cytoplasmic dynein are the most abundant and have been the focus of these studies. Included in the microtubule motor complexes are motor receptors and activating factors. A membranous motor receptor, kinectin, was identified on the basis of its interaction with kinesin (Toyoshima et al., 1992). An antibody to kinectin blocks both kinesin binding to organelles and kinesin-dependent motility of those organelles (Kumar et al., 1995).

Microtubule-Dependent Vesicle Transport: Modulation of Channel and Transporter Activity in Liver and Kidney

1998 ◽  
Vol 78 (4) ◽  
pp. 1109-1129 ◽  
Author(s):  
SARAH F. HAMM-ALVAREZ ◽  
MICHAEL P. SHEETZ
Keyword(s):  
Membrane Trafficking ◽  
Plasma Membranes ◽  
Motor Proteins ◽  
Cytoplasmic Dynein ◽  
Vesicle Transport ◽  
Directed Movement ◽  
Liver And Kidney ◽  
Transport Modulation ◽  
In Cells

Hamm-Alvarez, Sarah F., and Michael P. Sheetz. Microtubule-Dependent Vesicle Transport: Modulation of Channel and Transporter Activity in Liver and Kidney. Physiol. Rev. 78: 1109–1129, 1998. — Microtubule-based vesicle transport driven by kinesin and cytoplasmic dynein motor proteins facilitates several membrane-trafficking steps including elements of endocytosis and exocytosis in many different cell types. Most early studies on the role of microtubule-dependent vesicle transport in membrane trafficking focused either on neurons or on simple cell lines. More recently, other work has considered the role of microtubule-based vesicle transport in other physiological systems, including kidney and liver. Investigation of the role of microtubule-based vesicle transport in membrane trafficking in cells of the kidney and liver suggests a major role for microtubule-based vesicle transport in the rapid and directed movement of ion channels and transporters to and from the apical plasma membranes, events essential for kidney and liver function and homeostasis. This review discusses the evidence supporting a role for microtubule-based vesicle transport and the motor proteins, kinesin and cytoplasmic dynein, in different aspects of membrane trafficking in cells of the kidney and liver, with emphasis on those functions such as maintenance of ion channel and transporter composition in apical membranes that are specialized functions of these organs. Evidence that defects in microtubule-based transport contribute to diseases of the kidney and liver is also discussed.

scholarly journals Bidirectional Translocation of Neurofilaments along Microtubules Mediated in Part by Dynein/Dynactin

2000 ◽  
Vol 11 (10) ◽  
pp. 3495-3508 ◽  
Author(s):  
Jagesh V. Shah ◽  
Lisa A. Flanagan ◽  
Paul A. Janmey ◽  
Jean-François Leterrier
Keyword(s):  
Spinal Cord ◽  
Molecular Motors ◽  
Motor Proteins ◽  
Motor Complex ◽  
Microtubule Motors ◽  
Microtubule Motor ◽  
Cytoskeletal Elements

Neuronal cytoskeletal elements such as neurofilaments, F-actin, and microtubules are actively translocated by an as yet unidentified mechanism. This report describes a novel interaction between neurofilaments and microtubule motor proteins that mediates the translocation of neurofilaments along microtubules in vitro. Native neurofilaments purified from spinal cord are transported along microtubules at rates of 100-1000 nm/s to both plus and minus ends. This motion requires ATP and is partially inhibited by vanadate, consistent with the activity of neurofilament-bound molecular motors. Motility is in part mediated by the dynein/dynactin motor complex and several kinesin-like proteins. This reconstituted motile system suggests how slow net movement of cytoskeletal polymers may be achieved by alternating activities of fast microtubule motors.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

scholarly journals Novel and Converging Ways of NOX2 and SOD3 in Trafficking and Redox Signaling in Macrophages

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 172
Author(s):  
Steen Vang Petersen ◽  
Nanna Bach Poulsen ◽  
Cecilie Linneberg Matthiesen ◽  
Frederik Vilhardt
Keyword(s):  
Hydrogen Peroxide ◽  
Membrane Trafficking ◽  
Spatial Organization ◽  
Redox Signaling ◽  
Small Gtpase ◽  
Paracrine Signaling ◽  
Tissue Macrophage ◽  
Storage Vesicles ◽  
Superoxide Dismutase 3 ◽  
Macrophage Populations

Macrophages and related tissue macrophage populations use the classical NADPH oxidase (NOX2) for the regulated production of superoxide and derived oxidants for pathogen combat and redox signaling. With an emphasis on macrophages, we discuss how sorting into secretory storage vesicles, agonist-responsive membrane trafficking, and segregation into sphingolipid and cholesterol-enriched microdomains (lipid rafts) determine the subcellular distribution and spatial organization of NOX2 and superoxide dismutase-3 (SOD3). We discuss how inflammatory activation of macrophages, in part through small GTPase Rab27A/B regulation of the secretory compartments, mediates the coalescence of these two proteins on the cell surface to deliver a focalized hydrogen peroxide output. In interplay with membrane-embedded oxidant transporters and redox sensitive target proteins, this arrangement allows for the autocrine and paracrine signaling, which govern macrophage activation states and transcriptional programs. By discussing examples of autocrine and paracrine redox signaling, we highlight why formation of spatiotemporal microenvironments where produced superoxide is rapidly converted to hydrogen peroxide and conveyed immediately to reach redox targets in proximal vicinity is required for efficient redox signaling. Finally, we discuss the recent discovery of macrophage-derived exosomes as vehicles of NOX2 holoenzyme export to other cells.

scholarly journals Bringing the Virus Back Home: Media Representations of Ukrainian Labour Migrants in a Time of Pandemic

2021 ◽  
pp. 088832542110187
Author(s):  
Alexander Tymczuk
Keyword(s):  
Spatial Organization ◽  
Frame Analysis ◽  
Media Representations ◽  
Potential Danger ◽  
Economic Resource ◽  
Clear Cut ◽  
And Control ◽  
Globalized World ◽  
The Way

In a globalized world where mobility and movement is at its essence, the movement of viruses paradoxically causes a preoccupation with boundaries, containment, and control over borders, and thus keeping the “dangerous” outside separated from the “safe” inside. Through a qualitative thematic and frame analysis of news articles published on 12 Ukrainian news sites, I found that Ukrainian labour migrants conceptually constitute a challenge to such a clear-cut spatial organization in a time of a pandemic. Labour migrants are part of the national “we,” but their presence in the dangerous outside excludes them from the “imagined immunity.” This ambiguity is evident in the way labour migrants were portrayed during the first months of the outbreak in Ukraine. Initially, Ukrainian labour migrants were depicted as a potential danger, and then blamed for bringing the virus back home. However, the framing of the labour migrants as a danger is only part of the story, and the image of a scapegoat was eventually replaced with images of an economic resource and a victim. Thus, Ukrainian labour migrants have been the object of vilification, heroization, as well as empathy during the various phases of the outbreak. I would argue that these shifting frames are connected to the ambiguous conceptualization of Ukrainian labour migrants in general.

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