Microtubule dynamics influence the retrograde biased motility of kinesin-4 motor teams in neuronal dendrites

Microtubules establish the directionality of intracellular transport by kinesins and dynein through polarized assembly, but it remains unclear how directed transport occurs along microtubules organized with mixed polarity. We investigated the ability of the plus-end directed kinesin-4 motor KIF21B to navigate mixed polarity microtubules in mammalian dendrites. Reconstitution assays with recombinant KIF21B and engineered microtubule bundles or extracted neuronal cytoskeletons indicate that nucleotide-independent microtubule binding regions of KIF21B modulate microtubule dynamics and promote directional switching on antiparallel microtubules. Optogenetic recruitment of KIF21B to organelles in live neurons induces unidirectional transport in axons but bi-directional transport with a net retrograde bias in dendrites. Removal of the secondary microtubule binding regions of KIF21B or dampening of microtubule dynamics with low concentrations of nocodazole eliminates retrograde bias in live dendrites. Further exploration of the contribution of microtubule dynamics in dendrites to directionality revealed plus-end-out microtubules to be more dynamic than plus-end-in microtubules, with nocodazole preferentially stabilizing the plus-end-out population. We propose a model in which both nucleotide-sensitive and insensitive microtubule binding sites of KIF21B motors contribute to the search and selection of stable plus-end-in microtubules within the mixed polarity microtubule arrays characteristic of mammalian dendrites to achieve net retrograde movement of KIF21B-bound cargos. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text]

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Kinesin-4 Motor Teams Effectively Navigate Dendritic Microtubule Arrays Through Track Switching and Regulation of Microtubule Dynamics

10.1101/2021.02.28.433181 ◽

2021 ◽

Author(s):

Erin M. Masucci ◽

Peter K. Relich ◽

Melike Lakadamyali ◽

E. Michael Ostap ◽

Erika L. F. Holzbaur

Keyword(s):

Binding Sites ◽

Intracellular Transport ◽

Microtubule Dynamics ◽

Directional Bias ◽

Microtubule Binding ◽

Directed Transport ◽

Binding Regions ◽

Mixed Polarity ◽

Directional Transport

Microtubules establish the directionality of intracellular transport by kinesins and dynein through their polarized assembly, but it remains unclear how directed transport occurs along microtubules organized with mixed polarity. We investigated the ability of the plus-end directed kinesin-4 motor KIF21B to navigate mixed polarity microtubules in mammalian dendrites. Reconstitution assays with recombinant KIF21B and engineered microtubule bundles or extracted neuronal cytoskeletons indicate that nucleotide-independent microtubule binding regions of KIF21B modulate microtubule dynamics and promote directional switching on antiparallel microtubules. Optogenetic recruitment of KIF21B to organelles in live neurons resulted in unidirectional transport in axons but bi-directional transport with a net retrograde bias in dendrites; microtubule dynamics and the secondary microtubule binding regions are required for this net directional bias. We propose a model in which cargo-bound KIF21B motors coordinate nucleotide-sensitive and insensitive microtubule binding sites to achieve net retrograde movement along the dynamic mixed polarity microtubule arrays of dendrites.

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Selection of the Optimal Critical Velocity for Sand Transport at Low Concentrations for Near-Horizontal Flow

10.4043/23075-ms ◽

2012 ◽

Cited By ~ 2

Author(s):

Byron F. Soepyan ◽

Selen Cremaschi ◽

Cem Sarica ◽

Hariprasad J. Subramani

Keyword(s):

Critical Velocity ◽

Horizontal Flow ◽

Sand Transport ◽

Low Concentrations ◽

Selection Of

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Low Concentrations of Propyzamide and Oryzalin Alter Microtubule Dynamics in Arabidopsis Epidermal Cells

Plant and Cell Physiology ◽

10.1093/pcp/pch300 ◽

2004 ◽

Vol 45 (9) ◽

pp. 1330-1334 ◽

Cited By ~ 88

Author(s):

Masayoshi Nakamura ◽

Kuniko Naoi ◽

Tsubasa Shoji ◽

Takashi Hashimoto

Keyword(s):

Epidermal Cells ◽

Microtubule Dynamics ◽

Low Concentrations

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Kinesin-1 tail autoregulation and microtubule-binding regions function in saltatory transport but not ooplasmic streaming

Development ◽

10.1242/dev.048645 ◽

2011 ◽

Vol 138 (6) ◽

pp. 1087-1092 ◽

Cited By ~ 14

Author(s):

P. Moua ◽

D. Fullerton ◽

L. R. Serbus ◽

R. Warrior ◽

W. M. Saxton

Keyword(s):

Microtubule Binding ◽

Binding Regions

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Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.6.123 ◽

2010 ◽

Vol 6 ◽

pp. 1079-1088 ◽

Cited By ~ 6

Author(s):

Peter C Griffiths ◽

David W Knight ◽

Ian R Morgan ◽

Amy Ford ◽

James Brown ◽

...

Keyword(s):

Molecular Recognition ◽

Neutron Scattering ◽

Spin Echo ◽

Inelastic Neutron ◽

Gelation Mechanism ◽

Regular Structures ◽

Low Concentrations ◽

Wide Range ◽

History Of ◽

Selection Of

Understanding the gelation of liquids by low molecular weight solutes at low concentrations gives an insight into many molecular recognition phenomena and also offers a simple route to modifying the physical properties of the liquid. Bis-(α,β-dihydroxy ester)s are shown here to gel thermoreversibly a wide range of solvents, raising interesting questions as to the mechanism of gelation. At gelator concentrations of 5–50 mg ml−1, gels were successfully formed in acetone, ethanol/water mixtures, toluene, cyclohexane and chloroform (the latter, albeit at a higher gelator concentration). A range of neutron techniques – in particular small-angle neutron scattering (SANS) – have been employed to probe the structure of a selection of these gels. The universality of gelation in a range of solvent types suggests the gelation mechanism is a feature of the bis-(α,β-dihydroxy ester) motif, with SANS demonstrating the presence of regular structures in the 30–40 Å range. A correlation between the apparent rodlike character of the structures formed and the polarity of the solvent is evident. Preliminary spin-echo neutron scattering studies (SESANS) indicated the absence of any larger scale structures. Inelastic neutron spectroscopy (INS) studies demonstrated that the solvent is largely unaffected by gelation, but does reveal insights into the thermal history of the samples. Further neutron studies of this kind (particularly SESANS and INS) are warranted, and it is hoped that this work will stimulate others to pursue this line of research.

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Yeast Kinetochores Do Not Stabilize Stu2p-dependent Spindle Microtubule Dynamics

Molecular Biology of the Cell ◽

10.1091/mbc.e03-03-0180 ◽

2003 ◽

Vol 14 (10) ◽

pp. 4181-4195 ◽

Cited By ~ 61

Author(s):

Chad G. Pearson ◽

Paul S. Maddox ◽

Ted R. Zarzar ◽

E.D. Salmon ◽

Kerry Bloom

Keyword(s):

Chromosome Segregation ◽

Live Cell Imaging ◽

Cell Imaging ◽

Regulatory Mechanism ◽

Metaphase Plate ◽

Microtubule Dynamics ◽

Spindle Microtubule ◽

Microtubule Binding ◽

Microtubule Stabilization ◽

Kinetochore Function

The interaction of kinetochores with dynamic microtubules during mitosis is essential for proper centromere motility, congression to the metaphase plate, and subsequent anaphase chromosome segregation. Budding yeast has been critical in the discovery of proteins necessary for this interaction. However, the molecular mechanism for microtubule–kinetochore interactions remains poorly understood. Using live cell imaging and mutations affecting microtubule binding proteins and kinetochore function, we identify a regulatory mechanism for spindle microtubule dynamics involving Stu2p and the core kinetochore component, Ndc10p. Depleting cells of the microtubule binding protein Stu2p reduces kinetochore microtubule dynamics. Centromeres remain under tension but lack motility. Thus, normal microtubule dynamics are not required to maintain tension at the centromere. Loss of the kinetochore (ndc10-1, ndc10-2, and ctf13-30) does not drastically affect spindle microtubule turnover, indicating that Stu2p, not the kinetochore, is the foremost governor of microtubule dynamics. Disruption of kinetochore function with ndc10-1 does not affect the decrease in microtubule turnover in stu2 mutants, suggesting that the kinetochore is not required for microtubule stabilization. Remarkably, a partial kinetochore defect (ndc10-2) suppresses the decreased spindle microtubule turnover in the absence of Stu2p. These results indicate that Stu2p and Ndc10p differentially function in controlling kinetochore microtubule dynamics necessary for centromere movements.

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Bacterial Microtubules Exhibit Polarized Growth, Mixed-Polarity Bundling, and Destabilization by GTP Hydrolysis

10.1101/112987 ◽

2017 ◽

Author(s):

César Díaz-Celis ◽

Viviana I. Risca ◽

Felipe Hurtado ◽

Jessica K. Polka ◽

Scott D. Hansen ◽

...

Keyword(s):

Molecular Motors ◽

Intracellular Transport ◽

Complex Dynamics ◽

Critical Concentration ◽

Polarized Growth ◽

Gtp Hydrolysis ◽

Filament Dynamics ◽

Mixed Polarity ◽

Self Association

AbstractBacteria of the genusProsthecobacterexpress homologs of eukaryotic α-and β-tubulin, called BtubA and BtubB, that have been observed to assemble into bacterial microtubules (bMTs). ThebtubABgenes likely entered theProsthecobacterlineage via horizontal gene transfer and may derive from an early ancestor of the modern eukaryotic microtubule (MT). Previous biochemical studies revealed that BtubA/B polymerization is GTP-dependent and reversible and that BtubA/B folding does not require chaperones. To better understand bMT behavior and gain insight into the evolution of microtubule dynamics, we characterizedin vitrobMT assembly using a combination of polymerization kinetics assays, and microscopy. Like eukaryotic microtubules, bMTs exhibit polarized growth with different assembly rates at each end. GTP hydrolysis stimulated by bMT polymerization drives a stochastic mechanism of bMT disassembly that occurs via polymer breakage. We also observed treadmilling (continuous addition and loss of subunits at opposite ends) of bMT fragments. Unlike MTs, polymerization of bMTs requires KCl, which reduces the critical concentration for BtubA/B assembly and induces bMTs to form stable mixed-orientation bundles in the absence of any additional bMT-binding proteins. Our results suggest that at potassium concentrations resembling that inside the cytoplasm ofProsthecobacter, bMT stabilization through self-association may be a default behavior. The complex dynamics we observe in both stabilized and unstabilized bMTs may reflect common properties of an ancestral eukaryotic tubulin polymer.ImportanceMicrotubules are polymers within all eukaryotic cells that perform critical functions: they segregate chromosomes in cell division, organize intracellular transport by serving as tracks for molecular motors, and support the flagella that allow sperm to swim. These functions rely on microtubules remarkable range of tunable dynamic behaviors. Recently discovered bacterial microtubules composed of an evolutionarily related protein are evolved from a missing link in microtubule evolution, the ancestral eukaryotic tubulin polymer. Using microscopy and biochemical approaches to characterize bacterial microtubules, we observed that they exhibit complex and structurally polarized dynamic behavior like eukaryotic microtubules, but differ in how they self-associate into bundles and become destabilized. Our results demonstrate the diversity of mechanisms that microtubule-like filaments employ to promote filament dynamics and monomer turnover.

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Screening of Amazonian bacillus strains for lipase production using glycerol as substrate

ScientiaTec ◽

10.35819/scientiatec.v7i03.2560 ◽

2020 ◽

Vol 7 (03) ◽

Author(s):

Giandra Volpato ◽

Victória Furtado Migliavacca ◽

Bruna Coelho de Andrade ◽

Júlio Xandro Heck ◽

Marco Antônio Záchia Ayub

Keyword(s):

Organic Synthesis ◽

Culture Medium ◽

Lipolytic Activity ◽

Gum Arabic ◽

Lipase Production ◽

Culture Conditions ◽

Search And Selection ◽

Triton X ◽

Potential Use ◽

Selection Of

The industrial application of lipolytic enzymes has been studied mainly due to the ability of these enzymes in catalyze reactions of synthesis and their stability in various organic solvents. One possibility is the use of lipase the organic synthesis, taking advantage as the generation of waste and difficult recovery of sub bioproducts. In this work, we carried out a selection of eighty-four isolates of Bacillus amazonian for lipase production, of which 30 strains showed lipolytic activity. The study of the culture conditions was performed through a Plackett-Burman experimental design using the strain that presented the highest lipolytic activity in a culture medium using glycerol as substrate. The studied conditions were: concentration of soybean oil, olive oil, triton X-100, gum arabic, glycerol, and (NH4)2SO4, pH, temperature and concentration of inoculums. The best result obtained were 27 U/L in 48 h of cultivation by Bacillus circulans BL53. This work shows that the search and selection of microorganism with lipolytic activities can facilitate the discovery of new lipases, with potential use as by-product surplus.

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