scholarly journals Identification of secreted and cytosolic gelsolin in Drosophila.

1994 ◽  
Vol 125 (3) ◽  
pp. 607-616 ◽  
Author(s):  
M C Stella ◽  
H Schauerte ◽  
K L Straub ◽  
M Leptin
Keyword(s):  
Fat Body ◽  
Extracellular Fluid ◽  
Early Embryo ◽  
The Other ◽  
Cleavage Furrow ◽  
Secreted Protein ◽  
Differential Splicing ◽  
Contractile Ring ◽  
Dividing Cells

We have cloned the gene for Drosophila gelsolin. Two mRNAs are produced from this gene by differential splicing. The protein encoded by the longer mRNA has a signal peptide and its electrophoretic mobility when translated in vitro in the presence of microsomes is higher than when it is translated without microsomes. The protein translated from the shorter mRNA does not show this difference. This indicates that Drosophila like vertebrates has two forms of gelsolin, one secreted, the other cytoplasmic. The mRNA for both is present ubiquitously in the early embryo. Later, the cytoplasmic form is expressed in parts of the gut. The RNA for the secreted form is expressed in the fat body, and the secreted protein is abundant in extracellular fluid (hemolymph). The cytoplasmic form of gelsolin co-localizes with F-actin in the cortex of the cells in the embryo and in larval epithelia. However, during cellularization of the blastoderm it is reduced at the base of the cleavage furrow, a structure similar to the contractile ring in dividing cells.

scholarly journals The F-actin bundler α-actinin Ain1 is tailored for ring assembly and constriction during cytokinesis in fission yeast

2016 ◽  
Vol 27 (11) ◽  
pp. 1821-1833 ◽  
Author(s):  
Yujie Li ◽  
Jenna R. Christensen ◽  
Kaitlin E. Homa ◽  
Glen M. Hocky ◽  
Alice Fok ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Actin Filament ◽  
Actin Filaments ◽  
Biochemical Properties ◽  
Ring Formation ◽  
Cross Linking ◽  
Contractile Ring ◽  
Mixed Polarity ◽  
Dividing Cells

The actomyosin contractile ring is a network of cross-linked actin filaments that facilitates cytokinesis in dividing cells. Contractile ring formation has been well characterized in Schizosaccharomyces pombe, in which the cross-linking protein α-actinin SpAin1 bundles the actin filament network. However, the specific biochemical properties of SpAin1 and whether they are tailored for cytokinesis are not known. Therefore we purified SpAin1 and quantified its ability to dynamically bind and bundle actin filaments in vitro using a combination of bulk sedimentation assays and direct visualization by two-color total internal reflection fluorescence microscopy. We found that, while SpAin1 bundles actin filaments of mixed polarity like other α-actinins, SpAin1 has lower bundling activity and is more dynamic than human α-actinin HsACTN4. To determine whether dynamic bundling is important for cytokinesis in fission yeast, we created the less dynamic bundling mutant SpAin1(R216E). We found that dynamic bundling is critical for cytokinesis, as cells expressing SpAin1(R216E) display disorganized ring material and delays in both ring formation and constriction. Furthermore, computer simulations of initial actin filament elongation and alignment revealed that an intermediate level of cross-linking best facilitates filament alignment. Together our results demonstrate that dynamic bundling by SpAin1 is important for proper contractile ring formation and constriction.

scholarly journals PLK1 plays dual roles in centralspindlin regulation during cytokinesis

2019 ◽  
Vol 218 (4) ◽  
pp. 1250-1264 ◽  
Author(s):  
Ingrid E. Adriaans ◽  
Angika Basant ◽  
Bas Ponsioen ◽  
Michael Glotzer ◽  
Susanne M.A. Lens
Keyword(s):  
Small Gtpase ◽  
The Other ◽  
Aurora B ◽  
Cleavage Furrow ◽  
Contractile Ring ◽  
Dual Roles ◽  
Early Step ◽  
Rhoa Activation ◽  
Anaphase Onset ◽  
Spindle Midzone

Cytokinesis begins upon anaphase onset. An early step involves local activation of the small GTPase RhoA, which triggers assembly of an actomyosin-based contractile ring at the equatorial cortex. Here, we delineated the contributions of PLK1 and Aurora B to RhoA activation and cytokinesis initiation in human cells. Knock-down of PRC1, which disrupts the spindle midzone, revealed the existence of two pathways that can initiate cleavage furrow ingression. One pathway depends on a well-organized spindle midzone and PLK1, while the other depends on Aurora B activity and centralspindlin at the equatorial cortex and can operate independently of PLK1. We further show that PLK1 inhibition sequesters centralspindlin onto the spindle midzone, making it unavailable for Aurora B at the equatorial cortex. We propose that PLK1 activity promotes the release of centralspindlin from the spindle midzone through inhibition of PRC1, allowing centralspindlin to function as a regulator of spindle midzone formation and as an activator of RhoA at the equatorial cortex.

scholarly journals mDia2 Induces the Actin Scaffold for the Contractile Ring and Stabilizes Its Position during Cytokinesis in NIH 3T3 Cells

2008 ◽  
Vol 19 (5) ◽  
pp. 2328-2338 ◽  
Author(s):  
Sadanori Watanabe ◽  
Yoshikazu Ando ◽  
Shingo Yasuda ◽  
Hiroshi Hosoya ◽  
Naoki Watanabe ◽  
...  
Keyword(s):  
Rna Interference ◽  
Mammalian Cell ◽  
Equatorial Region ◽  
Cleavage Furrow ◽  
3T3 Cells ◽  
Contractile Ring ◽  
Binucleate Cells ◽  
Dividing Cells ◽  
Nih 3T3 ◽  
Nih 3T3 Cells

mDia proteins are mammalian homologues of Drosophila diaphanous and belong to the formin family proteins that catalyze actin nucleation and polymerization. Although formin family proteins of nonmammalian species such as Drosophila diaphanous are essential in cytokinesis, whether and how mDia proteins function in cytokinesis remain unknown. Here we depleted each of the three mDia isoforms in NIH 3T3 cells by RNA interference and examined this issue. Depletion of mDia2 selectively increased the number of binucleate cells, which was corrected by coexpression of RNAi-resistant full-length mDia2. mDia2 accumulates in the cleavage furrow during anaphase to telophase, and concentrates in the midbody at the end of cytokinesis. Depletion of mDia2 induced contraction at aberrant sites of dividing cells, where contractile ring components such as RhoA, myosin, anillin, and phosphorylated ERM accumulated. Treatment with blebbistatin suppressed abnormal contraction, corrected localization of the above components, and revealed that the amount of F-actin at the equatorial region during anaphase/telophase was significantly decreased with mDia2 RNAi. These results demonstrate that mDia2 is essential in mammalian cell cytokinesis and that mDia2-induced F-actin forms a scaffold for the contractile ring and maintains its position in the middle of a dividing cell.

scholarly journals Rab1 interacts with GOLPH3 and controls Golgi structure and contractile ring constriction during cytokinesis in Drosophila melanogaster

Open Biology ◽  
2017 ◽  
Vol 7 (1) ◽  
pp. 160257 ◽  
Author(s):  
Stefano Sechi ◽  
Anna Frappaolo ◽  
Roberta Fraschini ◽  
Luisa Capalbo ◽  
Marco Gottardo ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Membrane Trafficking ◽  
Molecular Mechanisms ◽  
Super Resolution ◽  
Cleavage Furrow ◽  
Contractile Ring ◽  
Cog Complex ◽  
Dividing Cells ◽  
Ring Constriction ◽  
Phosphatidylinositol 4

Cytokinesis requires a tight coordination between actomyosin ring constriction and new membrane addition along the ingressing cleavage furrow. However, the molecular mechanisms underlying vesicle trafficking to the equatorial site and how this process is coupled with the dynamics of the contractile apparatus are poorly defined. Here we provide evidence for the requirement of Rab1 during cleavage furrow ingression in cytokinesis. We demonstrate that the gene omelette ( omt ) encodes the Drosophila orthologue of human Rab1 and is required for successful cytokinesis in both mitotic and meiotic dividing cells of Drosophila melanogaster . We show that Rab1 protein colocalizes with the conserved oligomeric Golgi (COG) complex Cog7 subunit and the phosphatidylinositol 4-phosphate effector GOLPH3 at the Golgi stacks. Analysis by transmission electron microscopy and 3D-SIM super-resolution microscopy reveals loss of normal Golgi architecture in omt mutant spermatocytes indicating a role for Rab1 in Golgi formation. In dividing cells, Rab1 enables stabilization and contraction of actomyosin rings. We further demonstrate that GTP-bound Rab1 directly interacts with GOLPH3 and controls its localization at the Golgi and at the cleavage site . We propose that Rab1, by associating with GOLPH3, controls membrane trafficking and contractile ring constriction during cytokinesis.

scholarly journals PLK1 plays dual roles in centralspindlin regulation during cytokinesis

2018 ◽  
Author(s):  
Ingrid E. Adriaans ◽  
Angika Basant ◽  
Bas Ponsioen ◽  
Michael Glotzer ◽  
Susanne M. A. Lens
Keyword(s):  
Small Gtpase ◽  
Human Cells ◽  
The Other ◽  
Aurora B ◽  
Cleavage Furrow ◽  
Contractile Ring ◽  
Dual Roles ◽  
Local Activation ◽  
Rhoa Activation ◽  
Spindle Midzone

AbstractCytokinesis starts in anaphase with the formation of an actomyosin-based contractile ring at the equatorial cortex, which is governed by the local activation of the small GTPase RhoA. Here we delineated the contributions of PLK1 and Aurora B to RhoA activation and cytokinesis initiation in human cells. Knock-down of PRC1, which disrupts the spindle midzone, revealed the existence of two pathways that can initiate cleavage furrow ingression. One pathway depends on a well-organized spindle midzone and PLK1, while the other depends on Aurora B activity and centralspindlin oligomerization at the equatorial cortex and can operate independently of PLK1. We further show that PLK1 inhibition sequesters centralspindlin onto the spindle midzone making it unavailable for Aurora B-dependent oligomerization at the equatorial cortex. We propose that PLK1 activity promotes the release of centralspindlin from the spindle midzone through inhibition of PRC1, allowing centralspindlin to function as a regulator of spindle midzone formation and as an activator of RhoA at the equatorial cortex.

scholarly journals On the embryonic cell division beyond the contractile ring mechanism: experimental and computational investigation of effects of vitelline confinement, temperature and egg size

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1490 ◽  
Author(s):  
Evgeny Gladilin ◽  
Roland Eils ◽  
Leonid Peshkin
Keyword(s):  
Cell Division ◽  
Egg Size ◽  
Early Embryo ◽  
Embryonic Cell ◽  
Vitelline Membrane ◽  
Imaging Data ◽  
Contractile Ring ◽  
Dividing Cells ◽  
Vitelline Envelope ◽  
Effects Of Temperature

Embryonic cell division is a mechanical process which is predominantly driven by contraction of the cleavage furrow and response of the remaining cellular matter. While most previous studies focused on contractile ring mechanisms of cytokinesis, effects of environmental factors such as pericellular vitelline membrane and temperature on the mechanics of dividing cells were rarely studied. Here, we apply a model-based analysis to the time-lapse imaging data of two species (Saccoglossus kowalevskiiandXenopus laevis) with relatively large eggs, with the goal of revealing the effects of temperature and vitelline envelope on the mechanics of the first embryonic cell division. We constructed a numerical model of cytokinesis to estimate the effects of vitelline confinement on cellular deformation and to predict deformation of cellular contours. We used the deviations of our computational predictions from experimentally observed cell elongation to adjust variable parameters of the contractile ring model and to quantify the contribution of other factors (constitutive cell properties, spindle polarization) that may influence the mechanics and shape of dividing cells. We find that temperature affects the size and rate of dilatation of the vitelline membrane surrounding fertilized eggs and show that in native (not artificially devitellinized) egg cells the effects of temperature and vitelline envelope on mechanics of cell division are tightly interlinked. In particular, our results support the view that vitelline membrane fulfills an important role of micromechanical environment around the early embryo the absence or improper function of which under moderately elevated temperature impairs normal development. Furthermore, our findings suggest the existence of scale-dependent mechanisms that contribute to cytokinesis in species with different egg size, and challenge the view of mechanics of embryonic cell division as a scale-independent phenomenon.

Some observations on the determination of extracellular fluid volume of jejunal tissue using [3H]inulin and [14C]inulin

1977 ◽  
Vol 55 (3) ◽  
pp. 389-393 ◽  
Author(s):  
P. K. Dinda ◽  
I. T. Beck ◽  
M. Beck
Keyword(s):  
Water Content ◽  
Extracellular Fluid ◽  
Progressive Increase ◽  
Fluid Volume ◽  
The Other ◽  
Total Water Content ◽  
Total Water ◽  
Tissue Water ◽  
Rate Of Increase

The objective of the present study was to examine the nature of equilibration of [3H]-inulin and [14C]inulin in the jejunal tissue in vitro. Rings of everted hamster jejunum were incubated at 37 °C in Krebs Ringer bicarbonate solution containing 10 mM glucose, tracer amounts of [14C]inulin, and tracer amounts of [3H]inulin from one of the two lots (lot X and lot Y) tested. The incubations were carried out for 5, 10, 20, 30, 45, or 60 min. One lot of [3H]inulin (lot X) provided an estimate of the extracellular (EC) fluid volume which, at all periods of incubation, was comparable with that provided by the [14C]inulin. In contrast, the estimate of EC fluid volume obtained from the other lot of [3H]inulin (lot Y) was consistently higher than that obtained from the [14C]inulin and increased linearly with the period of incubation. Because, with [3H]inulin of lot Y, the calculated intracellular (IC) fluid volume decreased linearly with the period of incubation, and because this was not the case with the [14C]inulin or with the [3H]inulin of lot X, it would appear that [3H]inulin of lot Y failed to equilibrate within the tissue water, while the other lot of [3H]inulin (lot X), as well as [14C]inulin, did. Although the EC fluid volume obtained from [14C]inulin (as well as that from [3H]inulin of lot X) increased progressively, the rate of increase during the first 30 min was considerably higher than that during the last 30 min of incubation. The progressive increase in the [14C]inulin space, however, was accompanied by a corresponding increase in the total water content as well as in the calculated IC fluid content of the tissue. Since the IC fluid volume as percentage of total water content after 5 min of incubation was not significantly different from that after 60 min of incubation, it would appear that [14C]inulin equilibrates within the EC fluid after 5 min, and that the progressive increase in the calculated EC fluid volume is the result of a corresponding increase in the EC fluid (containing [14C]inulin) content of the tissue.

scholarly journals Biochemical and biological properties of cortexillin III, a component of Dictyostelium DGAP1–cortexillin complexes

2014 ◽  
Vol 25 (13) ◽  
pp. 2026-2038 ◽  
Author(s):  
Xiong Liu ◽  
Shi Shu ◽  
Shuhua Yu ◽  
Duck-Yeon Lee ◽  
Grzegorz Piszczek ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Growth ◽  
Leading Edge ◽  
Biological Properties ◽  
Negative Regulator ◽  
Cleavage Furrow ◽  
Motile Cells ◽  
Dividing Cells

Cortexillins I–III are members of the α-actinin/spectrin subfamily of Dictyostelium calponin homology proteins. Unlike recombinant cortexillins I and II, which form homodimers as well as heterodimers in vitro, we find that recombinant cortexillin III is an unstable monomer but forms more stable heterodimers when coexpressed in Escherichia coli with cortexillin I or II. Expressed cortexillin III also forms heterodimers with both cortexillin I and II in vivo, and the heterodimers complex in vivo with DGAP1, a Dictyostelium GAP protein. Binding of cortexillin III to DGAP1 requires the presence of either cortexillin I or II; that is, cortexillin III binds to DGAP1 only as a heterodimer, and the heterodimers form in vivo in the absence of DGAP1. Expressed cortexillin III colocalizes with cortexillins I and II in the cortex of vegetative amoebae, the leading edge of motile cells, and the cleavage furrow of dividing cells. Colocalization of cortexillin III and F-actin may require the heterodimer/DGAP1 complex. Functionally, cortexillin III may be a negative regulator of cell growth, cytokinesis, pinocytosis, and phagocytosis, as all are enhanced in cortexillin III–null cells.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

1973 ◽  
Vol 29 (02) ◽  
pp. 490-498 ◽  
Author(s):  
Hiroh Yamazaki ◽  
Itsuro Kobayashi ◽  
Tadahiro Sano ◽  
Takio Shimamoto
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
The Other ◽  
Endothelial Surface ◽  
Important Interaction ◽  
Blood Coagulability ◽  
The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

ALDOSTERONE STIMULATION IN VITRO

1965 ◽  
Vol 50 (2) ◽  
pp. 301-309 ◽  
Author(s):  
Jürg Müller
Keyword(s):  
Ammonium Chloride ◽  
Human Urine ◽  
Incubation Medium ◽  
The Other ◽  
Ammonium Ions ◽  
Response Curves ◽  
Urine Extract ◽  
Similar Dose ◽  
Aldosterone Production

ABSTRACT An extract of human urine, which was previously shown to stimulate aldosterone production by rat adrenal sections, was further purified. Evidence was obtained that its aldosterone-stimulating effect was due to the presence of ammonium ions. Addition of ammonium chloride and of urine extract to the incubation medium caused identical increases in aldosterone production in vitro. In addition to ammonium ions, rubidium and caesium ions also stimulated aldosterone production up to 250% that of control values without a significant effect on corticosterone production. Similar dose-response curves were obtained when increasing concentrations of potassium, ammonium, rubidium and caesium ions were tested. Aldosterone production was maximal at concentrations of 7 mval/1 and was significantly lower at higher concentrations. When ammonium chloride and ACTH were simultaneously added to the incubation medium, the production of aldosterone and of corticosterone was lower than with ACTH alone. On the other hand, the stimulating activity on aldosterone and corticosterone production by »TPN« (NADP) and glucose-6-phosphate was enhanced by the simultaneous addition of ammonium chloride.

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