scholarly journals Tau directs intracellular trafficking by regulating the forces exerted by kinesin and dynein teams

2017 ◽  
Author(s):  
Abdullah R. Chaudhary ◽  
Florian Berger ◽  
Christopher L. Berger ◽  
Adam G. Hendricks
Keyword(s):  
Single Molecule ◽  
Intracellular Transport ◽  
Relative Activity ◽  
General Mechanism ◽  
Dependent Manner ◽  
Directional Bias ◽  
Associated Proteins ◽  
Bidirectional Transport ◽  
Balance Of Forces

AbstractOrganelles, proteins, and mRNA are transported bidirectionally along microtubules by plus-end directed kinesin and minus-end directed dynein motors. Microtubules are decorated by microtubule-associated proteins (MAPs) that organize the cytoskeleton, regulate microtubule dynamics and modulate the interaction between motor proteins and microtubules to direct intracellular transport. Tau is a neuronal MAP that stabilizes axonal microtubules and crosslinks them into bundles. Dysregulation of tau leads to a range of neurodegenerative diseases known as tauopathies including Alzheimer’s disease (AD). Tau reduces the processivity of kinesin and dynein by acting as an obstacle on the microtubule. Single-molecule assays indicate that kinesin-1 is more strongly inhibited than kinesin-2 or dynein, suggesting tau might act to spatially modulate the activity of specific motors. To investigate the role of tau in regulating bidirectional transport, we isolated phagosomes driven by kinesin-1, kinesin-2, and dynein and reconstituted their motility along microtubules. We find that tau biases bidirectional motility towards the microtubule minus-end in a dose-dependent manner. Optical trapping measurements show that tau increases the magnitude and frequency of forces exerted by dynein through inhibiting opposing kinesin motors. Mathematical modeling indicates that tau controls the directional bias of intracellular cargoes through differentially tuning the processivity of kinesin-1, kinesin-2, and dynein. Taken together, these results demonstrate that tau modulates motility in a motor-specific manner to direct intracellular transport, and suggests that dysregulation of tau might contribute to neurodegeneration by disrupting the balance of plus- and minus-end directed transport.Synopsis and Graphical Table of ContentsWe isolated endogenous cargoes, along with a complement of kinesin-1, kinesin-2, and dynein motors, and reconstituted their bidirectional motility in vitro. We find that tau, a microtubule-associated protein that stabilizes microtubules in neuronal axons, directs bidirectional cargoes towards the microtubule minus end by tuning the balance of forces exerted by kinesin and dynein teams. These results suggest a general mechanism for regulating the transport of intracellular cargoes through modulating the relative activity of opposing motor teams.

scholarly journals The mechanism of motor inhibition by microtubule-associated proteins

2020 ◽  
Author(s):  
Luke S Ferro ◽  
Lisa Eshun-Wilson ◽  
Mert Gölcük ◽  
Jonathan Fernandes ◽  
Teun Huijben ◽  
...  
Keyword(s):  
Binding Site ◽  
Single Molecule ◽  
Intracellular Transport ◽  
List Type ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Projection Domain ◽  
Electron Imaging

SUMMARYMicrotubule (MT)-associated proteins (MAPs) regulate intracellular transport by selectively recruiting or excluding kinesin and dynein motors from MTs. We used single-molecule and cryo-electron imaging to determine the mechanism of MAP-motor interactions in vitro. Unexpectedly, we found that the regulatory role of a MAP cannot be predicted based on whether it overlaps with the motor binding site or forms liquid condensates on the MT. Although the MT binding domain (MTBD) of MAP7 overlaps with the kinesin-1 binding site, tethering of kinesin-1 by the MAP7 projection domain supersedes this inhibition and results in biphasic regulation of kinesin-1 motility. Conversely, the MTBD of tau inhibits dynein motility without overlapping with the dynein binding site or by forming tau islands on the MT. Our results indicate that MAPs sort intracellular cargos moving in both directions, as neither dynein nor kinesin can walk on a MAP-coated MT without favorably interacting with that MAP.HIGHLIGHTSMAP7 binds to a novel site and can coexist with tau on the MT.Kinesin-1 motility is biphasically regulated by MAP7 accumulation on the microtubule.MT decoration of MAPs inhibits motors even when they do not block the motor binding site.Motors need to interact with a MAP to walk on MAP-decorated MTs

scholarly journals UBA1 and UBA2, Two Proteins That Interact with UBP1, a Multifunctional Effector of Pre-mRNA Maturation in Plants

2002 ◽  
Vol 22 (12) ◽  
pp. 4346-4357 ◽  
Author(s):  
Mark H. L. Lambermon ◽  
Yu Fu ◽  
Dominika A. Wieczorek Kirk ◽  
Marcel Dupasquier ◽  
Witold Filipowicz ◽  
...  
Keyword(s):  
Steady State ◽  
Rna Binding ◽  
Rna Recognition Motif ◽  
Dependent Manner ◽  
Binding Domains ◽  
Mrna Maturation ◽  
Associated Proteins ◽  
Steady State Levels ◽  
Transient Overexpression

ABSTRACT Nicotiana plumbaginifolia UBP1 is an hnRNP-like protein associated with the poly(A)+ RNA in the cell nucleus. Consistent with a role in pre-mRNA processing, overexpression of UBP1 in N. plumabaginifolia protoplasts enhances the splicing of suboptimal introns and increases the steady-state levels of reporter mRNAs, even intronless ones. The latter effect of UBP1 is promoter specific and appears to be due to UBP1 binding to the 3′ untranslated region (3′-UTR) and protecting the mRNA from exonucleolytic degradation (M. H. L. Lambermon, G. G. Simpson, D. A. Kirk, M. Hemmings-Mieszczak, U. Klahre, and W. Filipowicz, EMBO J. 19:1638-1649, 2000). To gain more insight into UBP1 function in pre-mRNA maturation, we characterized proteins interacting with N. plumbaginifolia UBP1 and one of its Arabidopsis thaliana counterparts, AtUBP1b, by using yeast two-hybrid screens and in vitro pull-down assays. Two proteins, UBP1-associated proteins 1a and 2a (UBA1a and UBA2a, respectively), were identified in A. thaliana. They are members of two novel families of plant-specific proteins containing RNA recognition motif-type RNA-binding domains. UBA1a and UBA2a are nuclear proteins, and their recombinant forms bind RNA with a specificity for oligouridylates in vitro. As with UBP1, transient overexpression of UBA1a in protoplasts increases the steady-state levels of reporter mRNAs in a promoter-dependent manner. Similarly, overexpression of UBA2a increases the levels of reporter mRNAs, but this effect is promoter independent. Unlike UBP1, neither UBA1a nor UBA2a stimulates pre-mRNA splicing. These and other data suggest that UBP1, UBA1a, and UBA2a may act as components of a complex recognizing U-rich sequences in plant 3′-UTRs and contributing to the stabilization of mRNAs in the nucleus.

scholarly journals A Regulatory Circuit Mediating Convergence between Nurr1 Transcriptional Regulation and Wnt Signaling

2007 ◽  
Vol 27 (21) ◽  
pp. 7486-7496 ◽  
Author(s):  
Hirochika Kitagawa ◽  
William J. Ray ◽  
Helmut Glantschnig ◽  
Pascale V. Nantermet ◽  
Yuanjiang Yu ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Binding Pocket ◽  
Dependent Manner ◽  
Orphan Nuclear Receptor ◽  
Small Interfering Rnas ◽  
Regulatory Circuit ◽  
Midbrain Dopaminergic Neurons ◽  
Associated Proteins ◽  
Regulatory Convergence

ABSTRACT The orphan nuclear receptor Nurr1 is essential for the development and maintenance of midbrain dopaminergic neurons, the cells that degenerate during Parkinson's disease, by promoting the transcription of genes involved in dopaminergic neurotransmission. Since Nurr1 lacks a classical ligand-binding pocket, it is not clear which factors regulate its activity and how these factors are affected during disease pathogenesis. Since Wnt signaling via β-catenin promotes the differentiation of Nurr1+ dopaminergic precursors in vitro, we tested for functional interactions between these systems. We found that β-catenin and Nurr1 functionally interact at multiple levels. In the absence of β-catenin, Nurr1 is associated with Lef-1 in corepressor complexes. β-Catenin binds Nurr1 and disrupts these corepressor complexes, leading to coactivator recruitment and induction of Wnt- and Nurr1-responsive genes. We then identified KCNIP4/calsenilin-like protein as being responsive to concurrent activation by Nurr1 and β-catenin. Since KCNIP4 interacts with presenilins, the Alzheimer's disease-associated proteins that promote β-catenin degradation, we tested the possibility that KCNIP4 induction regulates β-catenin signaling. KCNIP4 induction limited β-catenin activity in a presenilin-dependent manner, thereby serving as a negative feedback loop; furthermore, Nurr1 inhibition of β-catenin activity was absent in PS1−/− cells or in the presence of small interfering RNAs specific to KCNIP4. These data describe regulatory convergence between Nurr1 and β-catenin, providing a mechanism by which Nurr1 could be regulated by Wnt signaling.

scholarly journals Utp9p Facilitates Msn5p-mediated Nuclear Reexport of Retrograded tRNAs in Saccharomyces cerevisiae

2009 ◽  
Vol 20 (23) ◽  
pp. 5007-5025 ◽  
Author(s):  
Manoja B.K. Eswara ◽  
Andrew T. McGuire ◽  
Jacqueline B. Pierce ◽  
Dev Mangroo
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Accumulation ◽  
Dependent Manner ◽  
Trna Synthetases ◽  
Trna Splicing ◽  
U3 Snorna ◽  
Aminoacyl Trna Synthetases ◽  
Associated Proteins ◽  
Export Receptors

Utp9p is a nucleolar protein that is part of a subcomplex containing several U3 snoRNA-associated proteins including Utp8p, which is a protein that shuttles aminoacyl-tRNAs from the nucleolus to the nuclear tRNA export receptors Los1p and Msn5p in Saccharomyces cerevisiae . Here we show that Utp9p is also an intranuclear component of the Msn5p-mediated nuclear tRNA export pathway. Depletion of Utp9p caused nuclear accumulation of mature tRNAs derived from intron-containing precursors, but not tRNAs made from intronless pre-tRNAs. Utp9p binds tRNA directly and saturably, and copurifies with Utp8p, Gsp1p, and Msn5p, but not with Los1p or aminoacyl-tRNA synthetases. Utp9p interacts directly with Utp8p, Gsp1p, and Msn5p in vitro. Furthermore, Gsp1p forms a complex with Msn5p and Utp9p in a tRNA-dependent manner. However, Utp9p does not shuttle between the nucleus and the cytoplasm. Because tRNA splicing occurs in the cytoplasm and the spliced tRNAs are retrograded back to the nucleus, we propose that Utp9p facilitates nuclear reexport of retrograded tRNAs. Moreover, the data suggest that Utp9p together with Utp8p translocate aminoacyl-tRNAs from the nucleolus to Msn5p and assist with formation of the Msn5p-tRNA-Gsp1p-GTP export complex.

scholarly journals Drosophila tubulin-binding cofactor B is required for microtubule network formation and for cell polarity

2012 ◽  
Vol 23 (18) ◽  
pp. 3591-3601 ◽  
Author(s):  
Alexandre D. Baffet ◽  
Béatrice Benoit ◽  
Jens Januschke ◽  
Jennifer Audo ◽  
Vanessa Gourhand ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Polarity ◽  
Intracellular Transport ◽  
Network Formation ◽  
Follicle Cells ◽  
Microtubule Network ◽  
Tubulin Binding ◽  
Associated Proteins ◽  
Dependent Cell

Microtubules (MTs) are essential for cell division, shape, intracellular transport, and polarity. MT stability is regulated by many factors, including MT-associated proteins and proteins controlling the amount of free tubulin heterodimers available for polymerization. Tubulin-binding cofactors are potential key regulators of free tubulin concentration, since they are required for α-β–tubulin dimerization in vitro. In this paper, we show that mutation of the Drosophila tubulin-binding cofactor B (dTBCB) affects the levels of both α- and β-tubulins and dramatically destabilizes the MT network in different fly tissues. However, we find that dTBCB is dispensable for the early MT-dependent steps of oogenesis, including cell division, and that dTBCB is not required for mitosis in several tissues. In striking contrast, the absence of dTBCB during later stages of oogenesis causes major defects in cell polarity. We show that dTBCB is required for the polarized localization of the axis-determining mRNAs within the oocyte and for the apico-basal polarity of the surrounding follicle cells. These results establish a developmental function for the dTBCB gene that is essential for viability and MT-dependent cell polarity, but not cell division.

Toll-like receptor 2/6 stimulation promotes angiogenesis via GM-CSF as a potential strategy for immune defense and tissue regeneration

Blood ◽  
2010 ◽  
Vol 115 (12) ◽  
pp. 2543-2552 ◽  
Author(s):  
Karsten Grote ◽  
Harald Schuett ◽  
Gustavo Salguero ◽  
Christina Grothusen ◽  
Joanna Jagielska ◽  
...  
Keyword(s):  
Tissue Regeneration ◽  
Immune Defense ◽  
General Mechanism ◽  
Endothelial Cell Proliferation ◽  
Dependent Manner ◽  
Gm Csf ◽  
Potential Strategy ◽  
And Migration

AbstractToll-like receptors (TLRs) are known primarily as pathogen recognition receptors of the innate immunity, initiating inflammatory pathways to organize the immune defense. More recently, an involvement of TLRs in various physiologic and pathologic processes has been reported. Because many of these processes implicate angiogenesis, we here elucidated the role of a TLR2/6-dependent pathway on angiogenesis using the TLR2/6 agonist macrophage-activating lipopeptide of 2 kDa (MALP-2), a common bacterial lipopeptide. In vivo and in vitro Matrigel assays demonstrated that MALP-2 promoted angiogenesis in a TLR2/6-dependent manner. Moreover, MALP-2 induced endothelial cell proliferation and migration and a strong secretion of granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF release in response to MALP-2 from isolated vascular segments was completely prevented when the endothelium was removed. MALP-2 containing Matrigel implants exhibited vascular structures as well as CD45+ cells. MALP-2 induced migration of leukocytes and likewise GM-CSF release, particularly from the monocyte population. Inhibition of GM-CSF by siRNA or antibodies suppressed MALP-2-induced angiogenesis in vitro and in vivo. These results clearly identified a TLR2/6-dependent induction of angiogenesis by the bacterial lipopeptide MALP-2, which is mediated by GM-CSF. This might represent a general mechanism to enhance or restore blood flow and recruit immune cells for pathogen defense and tissue regeneration.

scholarly journals MAP7 recruits kinesin-1 to microtubules to direct organelle transport

2019 ◽  
Author(s):  
Abdullah R. Chaudhary ◽  
Hailong Lu ◽  
Elena B. Krementsova ◽  
Carol S. Bookwalter ◽  
Kathleen M. Trybus ◽  
...  
Keyword(s):  
Single Molecule ◽  
Organelle Transport ◽  
Microtubule Associated Proteins ◽  
Microtubule Polymerization ◽  
Binding Rate ◽  
Associated Proteins ◽  
Bidirectional Transport ◽  
Directed Motility ◽  
Clear Shift

Microtubule-associated proteins (MAPs) play well-characterized roles in regulating microtubule polymerization, dynamics, and organization. In addition, MAPs control trans-port along microtubules by regulating the motility of kinesin and dynein. MAP7 (ensconsin, E-MAP-115) is a ubiquitous MAP that organizes the microtubule cytoskeleton in mitosis and neuronal branching. MAP7 also promotes the interaction of kinesin-1 with microtubules. We expressed and purified full-length kinesin-1 and MAP7 in Sf9 cells. In single-molecule motiity assays, MAP7 recruits kinesin-1 to microtubules, increasing the frequency of both diffusive and processive runs. Optical trapping assays on beads transported by single and teams of kinesin-1 motors indicate that MAP7 increases the relative binding rate of kinesin-1 and the number of motors simultaneously engaged in ensembles. To examine the role of MAP7 in regulating bidirectional transport, we isolated late phagosomes along with their native set of kinesin-1, kinesin-2, and dynein motors. Bidirectional cargoes exhibit a clear shift towards plus-end directed motility on MAP7-decorated microtubules due to increased forces exerted by kinesin teams. Collectively, our results indicate that MAP7 enhances kinesin-1 recruitment to microtubules and targets organelle transport to the plus end.

scholarly journals The C-terminal actin binding domain of talin forms an asymmetric catch bond with F-actin

2020 ◽  
Author(s):  
Leanna M. Owen ◽  
Nick A. Bax ◽  
William I. Weis ◽  
Alexander R. Dunn
Keyword(s):  
Single Molecule ◽  
Optical Trap ◽  
Focal Adhesions ◽  
Actin Binding ◽  
Cell Periphery ◽  
Dependent Manner ◽  
Dimerization Domain ◽  
Catch Bond ◽  
Cellular Cytoskeleton

AbstractFocal adhesions (FAs) are large, integrin-based adhesion complexes that link cells to the extracellular matrix (ECM). Previous work demonstrates that FAs form only when and where they are necessary to transmit force between the cellular cytoskeleton and the ECM, but how this occurs remains poorly understood. Talin is a 270 kDa adapter protein that links integrins to filamentous (F)-actin and recruits additional components during FA assembly in a force-dependent manner. Cell biological and developmental data demonstrate that the third, and C-terminal, F-actin binding site (ABS3) of talin is required for normal FA formation. However, ABS3 binds F-actin only weakly in in vitro, biochemical assays. We used a single-molecule optical trap assay to examine how and whether ABS3 binds F-actin under physiologically relevant, pN mechanical loads. We find that ABS3 forms a directional catch bond with F-actin when force is applied towards the pointed end of the actin filament, with binding lifetimes more than 100-fold longer than when force is applied towards the barbed end. Long-lived bonds to F-actin under load require the ABS3 C-terminal dimerization domain, whose cleavage is known to regulate focal adhesion turnover. Our results support a mechanism in which talin ABS3 preferentially binds and orients actin filaments with barbed ends facing the cell periphery, thus nucleating long-range order in the actin cytoskeleton. We suggest that talin ABS3 may function as a molecular AND gate that allows FA growth only when sufficient integrin density, F-actin polarization, and mechanical tension are simultaneously present.

scholarly journals Characterization of small molecule induced changes in Parkinson’s-related trafficking via the Nedd4 ubiquitin signaling cascade

2020 ◽  
Author(s):  
A. Katherine Hatstat ◽  
Hannah D. Ahrendt ◽  
Matthew W. Foster ◽  
Leland Mayne ◽  
M. Arthur Moseley ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Side Chain ◽  
Dependent Manner ◽  
Associated Proteins ◽  
Molecular Mechanism Of Action ◽  
Trafficking Defects ◽  
Induced Changes ◽  
Early Onset Parkinson’S Disease

SummaryThe benzdiimidazole NAB2 rescues α-synuclein-associated trafficking defects associated with early onset Parkinson’s disease in a Nedd4-dependent manner. Despite identification of E3 ubiquitin ligase Nedd4 as a putative target of NAB2, its molecular mechanism of action has not been elucidated. As such, the effect of NAB2 on Nedd4 activity and specificity was interrogated through biochemical, biophysical, and proteomic analyses. NAB2 was found to bind Nedd4 (KDapp = 42 nM), but this binding is side chain mediated and does not alter its conformation or ubiquitination kinetics in vitro. Nedd4 co-localizes with trafficking organelles, and NAB2 exposure did not alter its colocalization. Ubiquitin-enrichment coupled proteomics revealed that NAB2 stimulates ubiquitination of trafficking and transport associated proteins, most likely through modulating the substrate specificity of Nedd4, providing a putative protein network involved in the NAB2 mechanism.

Evaluation of Novel S-Allyl Derivatives of 6-Mercapto-Purine against B-CLL: Combining the Effects of Different Compounds in A Single Molecule.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3437-3437
Author(s):  
Fabian David Arditti ◽  
Mordechai Shtalrid ◽  
Lucette Bassous ◽  
Lev Shvidel ◽  
Alain Berrebi ◽  
...  
Keyword(s):  
Single Molecule ◽  
Conflicts Of Interest ◽  
Annexin V ◽  
Daily Basis ◽  
High Reactivity ◽  
In Vitro Assays ◽  
Dependent Manner ◽  
Purine Analogs

Abstract Abstract 3437 Poster Board III-325 Previously, we have shown that Allicin, the highly active compound of freshly crushed garlic, produced by the reaction of the enzyme Alliinase with its substrate Alliin, induced the apoptotic killing of B-CLL cells in vitro. In addition, we also reported that generation of Allicin in situ on the surface of B-CLL cells by targeting Alliinase to the cell surface of the CD20+ cells by Rituximab, resulted in the eradication of primary B-CLL in a human-mouse chimeric model, denoting the marked anti-CLL potential of combining these two different molecules, with different mechanism of action, into a single drug entity (Arditti et al., Mol Cancer Ther 2005;4(2)325-331). Indeed, monotherapeutic approaches, even if effective, are usually not sufficient to fully eradicate B-CLL and the most effective therapeutic protocols require the utilization of more than one agent. With this in mind, we took advantage of the high reactivity of Allicin, with SH-containing compounds, and created novel chimeric compounds by the combination of Allicin with 6-Mercapto-Purine (6MP) and 6MP-riboside (6MPR), both SH-containing purine analogs used for decades for the treatment of hematologic malignancies. The resulting novel compounds, S-Allyl-6MP (SA-6MP) and S-Allyl-6MPR (SA-6MPR), were examined against primary B-CLL cells obtained from the peripheral blood of patients at Binnet stage C. In our in vitro assays, Annexin-V staining indicated that SA-6MP acted in a dose dependent manner, inducing the apoptotic death of 37.9% and 95.2% of plated CD19+CD5+ B-CLL cells (10.9% in untreated cells) incubated for 16 h at 37 °C in the presence of 50 uM or 100 uM, respectively. As expected, the original 6MP compound had no impact on the viability of plated B-CLL cells (9.7% and 8.7%) at doses of up to 150 uM. In preliminary in vivo experiments, we compared the anti-BCLL activity of SA-6MP with that of SA-6MPR and the original 6MP compound on primary B-CLL cells from 5 different patients (Binnet stage C) in a human-SCID/Beige mouse model. Following the engraftment of the human B-CLL cells, mice were treated with i.p. injections of 2.5 mg/kg body weight of SA-6MP, SA-6MPR, or 6MP on a daily basis throughout 7 consecutive days, after which, the engraftment of primary B-CLL cells was examined by the recovery of CD45+CD19+CD5+ from injected mice. An additional group of mice injected with vehicle (1% DMSO) was also examined as a control. In close similarity to our in vitro results, engraftment of primary B-CLL cells was considerably reduced following treatment with SA-6MP (>90% reduction), as compared with treatment with the original 6MP drug. In addition, the chimeric riboside 6MP derivative, SA-6MPR, induced a potent anti-BCLL effect comparable to that of SA-6MP. In summary, our results in vitro and in vivo suggests that combining the pro-apoptotic effects of Allicin with the antiproliferative effects of 6MP or 6MPR is superior to the effect of either of the purine analogs alone. This approach may be evaluated at first instance in B-CLL patients with refractory disease. Disclosures No relevant conflicts of interest to declare.

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