Contribution of cytoplasm viscoelastic properties to mitotic spindle positioning

Cells are filled with macromolecules and polymer networks that set scale-dependent viscous and elastic properties to the cytoplasm. Although the role of these parameters in molecular diffusion, reaction kinetics and cellular biochemistry is being increasingly recognized, their contributions to the motion and positioning of larger organelles, such as mitotic spindles for cell division remain unknown. Here, using magnetic tweezers to displace and rotate mitotic spindles in living embryos, we uncovered that the cytoplasm matrix can impart viscoelastic reactive forces that move spindles, or passive objects with similar size, back to their original position. These forces are independent of cytoskeletal force generators, yet reach hundreds of piconewtons and scale with cytoplasm crowding. Spindle motion causes the cytoplasm to shear and rearrange, dissipating elastic energy and limiting spindle recoils with functional implications for asymmetric and oriented divisions. These findings suggest that bulk cytoplasm material properties may constitute important control elements for the regulation of division positioning and cellular organization.

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The Kip3-Like Kinesin KipB Moves along Microtubules and Determines Spindle Position during Synchronized Mitoses in Aspergillus nidulans Hyphae

Eukaryotic Cell ◽

10.1128/ec.3.3.632-645.2004 ◽

2004 ◽

Vol 3 (3) ◽

pp. 632-645 ◽

Cited By ~ 42

Author(s):

Patricia E. Rischitor ◽

Sven Konzack ◽

Reinhard Fischer

Keyword(s):

Aspergillus Nidulans ◽

Fluorescent Protein ◽

Temperature Sensitive ◽

Mitotic Spindles ◽

Spindle Positioning ◽

High Concentrations ◽

Synthetically Lethal ◽

Green Fluorescent ◽

Spindle Position

ABSTRACT Kinesins are motor proteins which are classified into 11 different families. We identified 11 kinesin-like proteins in the genome of the filamentous fungus Aspergillus nidulans. Relatedness analyses based on the motor domains grouped them into nine families. In this paper, we characterize KipB as a member of the Kip3 family of microtubule depolymerases. The closest homologues of KipB are Saccharomyces cerevisiae Kip3 and Schizosaccharomyces pombe Klp5 and Klp6, but sequence similarities outside the motor domain are very low. A disruption of kipB demonstrated that it is not essential for vegetative growth. kipB mutant strains were resistant to high concentrations of the microtubule-destabilizing drug benomyl, suggesting that KipB destabilizes microtubules. kipB mutations caused a failure of spindle positioning in the cell, a delay in mitotic progression, an increased number of bent mitotic spindles, and a decrease in the depolymerization of cytoplasmic microtubules during interphase and mitosis. Meiosis and ascospore formation were not affected. Disruption of the kipB gene was synthetically lethal in combination with the temperature-sensitive mitotic kinesin motor mutation bimC4, suggesting an important but redundant role of KipB in mitosis. KipB localized to cytoplasmic, astral, and mitotic microtubules in a discontinuous pattern, and spots of green fluorescent protein moved along microtubules toward the plus ends.

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Exploring secondary interactions and the role of temperature in moisture-contaminated polymer networks through molecular simulations

Soft Matter ◽

10.1039/d0sm02009e ◽

2021 ◽

Vol 17 (10) ◽

pp. 2942-2956

Author(s):

Rishabh D. Guha ◽

Ogheneovo Idolor ◽

Katherine Berkowitz ◽

Melissa Pasquinelli ◽

Landon R. Grace

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Temperature Variation ◽

Polymer Networks ◽

Molecular Simulations ◽

Effect Of Temperature ◽

Secondary Interactions ◽

Dynamics Simulations ◽

Secondary Bonding

We investigated the effect of temperature variation on the secondary bonding interactions between absorbed moisture and epoxies with different morphologies using molecular dynamics simulations.

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Functional interaction between dynein light chain and intermediate chain is required for mitotic spindle positioning

Molecular Biology of the Cell ◽

10.1091/mbc.e11-01-0075 ◽

2011 ◽

Vol 22 (15) ◽

pp. 2690-2701 ◽

Cited By ~ 23

Author(s):

Melissa D. Stuchell-Brereton ◽

Amanda Siglin ◽

Jun Li ◽

Jeffrey K. Moore ◽

Shubbir Ahmed ◽

...

Keyword(s):

Light Chain ◽

Direct Evidence ◽

Retrograde Transport ◽

Cytoplasmic Dynein ◽

Dynein Light Chain ◽

Spindle Positioning ◽

Dynein Motor ◽

Intermediate Chains ◽

Activator Complex

Cytoplasmic dynein is a large multisubunit complex involved in retrograde transport and the positioning of various organelles. Dynein light chain (LC) subunits are conserved across species; however, the molecular contribution of LCs to dynein function remains controversial. One model suggests that LCs act as cargo-binding scaffolds. Alternatively, LCs are proposed to stabilize the intermediate chains (ICs) of the dynein complex. To examine the role of LCs in dynein function, we used Saccharomyces cerevisiae, in which the sole function of dynein is to position the spindle during mitosis. We report that the LC8 homologue, Dyn2, localizes with the dynein complex at microtubule ends and interacts directly with the yeast IC, Pac11. We identify two Dyn2-binding sites in Pac11 that exert differential effects on Dyn2-binding and dynein function. Mutations disrupting Dyn2 elicit a partial loss-of-dynein phenotype and impair the recruitment of the dynein activator complex, dynactin. Together these results indicate that the dynein-based function of Dyn2 is via its interaction with the dynein IC and that this interaction is important for the interaction of dynein and dynactin. In addition, these data provide the first direct evidence that LC occupancy in the dynein motor complex is important for function.

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Anandamide and 2-AG are endogenously present within the laterodorsal tegmental nucleus: Functional implications for a role of eCBs in arousal

Brain Research ◽

10.1016/j.brainres.2017.04.003 ◽

2017 ◽

Vol 1665 ◽

pp. 74-79 ◽

Cited By ~ 2

Author(s):

Neeraj Soni ◽

Bala Krishna Prabhala ◽

Ved Mehta ◽

Osman Mirza ◽

Kristi Anne Kohlmeier

Keyword(s):

Laterodorsal Tegmental Nucleus ◽

Tegmental Nucleus ◽

Functional Implications

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Interaction between Poly(ADP-ribose) and NuMA Contributes to Mitotic Spindle Pole Assembly

Molecular Biology of the Cell ◽

10.1091/mbc.e09-06-0477 ◽

2009 ◽

Vol 20 (21) ◽

pp. 4575-4585 ◽

Cited By ~ 58

Author(s):

Paul Chang ◽

Margaret Coughlin ◽

Timothy J. Mitchison

Keyword(s):

Binding Proteins ◽

Magnetic Beads ◽

Spindle Pole ◽

Covalent Modification ◽

Mitotic Spindles ◽

Spindle Poles ◽

Tankyrase 1 ◽

Mitotic Spindle Pole

Poly(ADP-ribose) (pADPr), made by PARP-5a/tankyrase-1, localizes to the poles of mitotic spindles and is required for bipolar spindle assembly, but its molecular function in the spindle is poorly understood. To investigate this, we localized pADPr at spindle poles by immuno-EM. We then developed a concentrated mitotic lysate system from HeLa cells to probe spindle pole assembly in vitro. Microtubule asters assembled in response to centrosomes and Ran-GTP in this system. Magnetic beads coated with pADPr, extended from PARP-5a, also triggered aster assembly, suggesting a functional role of the pADPr in spindle pole assembly. We found that PARP-5a is much more active in mitosis than interphase. We used mitotic PARP-5a, self-modified with pADPr chains, to capture mitosis-specific pADPr-binding proteins. Candidate binding proteins included the spindle pole protein NuMA previously shown to bind to PARP-5a directly. The rod domain of NuMA, expressed in bacteria, bound directly to pADPr. We propose that pADPr provides a dynamic cross-linking function at spindle poles by extending from covalent modification sites on PARP-5a and NuMA and binding noncovalently to NuMA and that this function helps promote assembly of exactly two poles.

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Exploring the Role of Supramolecular Associations in Mechanical Toughening of Interpenetrating Polymer Networks

Macromolecules ◽

10.1021/acs.macromol.5b01752 ◽

2015 ◽

Vol 48 (19) ◽

pp. 7146-7155 ◽

Cited By ~ 15

Author(s):

Seyedali Monemian ◽

LaShanda T. J. Korley

Keyword(s):

Polymer Networks ◽

Interpenetrating Polymer Networks ◽

Supramolecular Associations

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LPS inhibits fasted plasma ghrelin levels in rats: role of IL-1 and PGs and functional implications

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00533.2005 ◽

2006 ◽

Vol 291 (4) ◽

pp. G611-G620 ◽

Cited By ~ 56

Author(s):

Lixin Wang ◽

Nicole R. Basa ◽

Almaas Shaikh ◽

Andrew Luckey ◽

David Heber ◽

...

Keyword(s):

Blood Glucose ◽

Gastric Emptying ◽

Food Intake ◽

Intravenous Injection ◽

Plasma Levels ◽

Inhibitory Action ◽

Functional Implications ◽

Urocortin 1 ◽

Fasted Rats

LPS injected intraperitoneally decreases fasted plasma levels of ghrelin at 3 h postinjection in rats. We characterized the inhibitory action of LPS on plasma ghrelin and whether exogenous ghrelin restores LPS-induced suppression of food intake and gastric emptying in fasted rats. Plasma ghrelin and insulin and blood glucose were measured after intraperitoneal injection of LPS, intravenous injection of IL-1β and urocortin 1, and in response to LPS under conditions of blockade of IL-1 or CRF receptors by subcutaneous injection of IL-1 receptor antagonist (IL-1Ra) or astressin B, respectively, and prostaglandin (PG) synthesis by intraperitoneal indomethacin. Food intake and gastric emptying were measured after intravenous injection of ghrelin at 5 h postintraperitoneal LPS injection. LPS inhibited the elevated fasted plasma ghrelin levels by 47.6 ± 4.9%, 58.9 ± 3.3%, 74.4 ± 2.7%, and 48.9 ± 8.7% at 2, 3, 5, and 7 h postinjection, respectively, and values returned to preinjection levels at 24 h. Insulin levels were negatively correlated to those of ghrelin, whereas there was no significant correlation between glucose and ghrelin. IL-1Ra and indomethacin prevented the first 3-h decline in ghrelin levels induced by LPS, whereas astressin B did not. IL-1β inhibited plasma ghrelin levels, whereas urocortin 1 had no influence. Ghrelin injected intravenously prevented an LPS-induced 87% reduction of gastric emptying and 61% reduction of food intake. These data showed that IL-1 and PG pathways are part of the early mechanisms by which LPS suppresses fasted plasma ghrelin and that exogenous ghrelin can normalize LPS-induced-altered digestive functions.

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