scholarly journals Centering based on active diffusion in mouse oocytes is non-specific

2019 ◽  
Author(s):  
Alexandra Colin ◽  
Nitzan Razin ◽  
Maria Almonacid ◽  
Wylie Ahmed ◽  
Timo Betz ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
High Temporal Resolution ◽  
Effective Pressure ◽  
Oil Droplets ◽  
Size Dependent ◽  
Mouse Oocytes ◽  
Fluorescent Beads ◽  
Tracer Particles ◽  
Biased Diffusion ◽  
Dependent Mechanism

AbstractThe mechanism for nucleus centering in mouse oocytes results from a gradient of actin-positive vesicles. By microinjecting oil droplets and fluorescent beads, we analyze the consequences of the gradient of activity on transport of exogenous tracer particles of different sizes. We also use optical tweezers to probe rheological properties of the cytoplasm. We find that the gradient activity induces a general centering force, akin to an effective pressure gradient, leading to centering of oil droplets with velocities comparable to nuclear ones. High temporal resolution measurements reveal that passive particles, larger than 1µm, experience the activity gradient by a biased diffusion towards the cell center. Unexpectedly, this general and size dependent mechanism is maintained in Meiosis I but contrasted by a further process that specifically off-centers the spindle. These antagonizing processes depend on myosin activity, thus we reconcile how the same molecular actors can have two opposite functions (centering versus off-centering).

scholarly journals Size-dependent mechanism of cargo sorting during lysosome-phagosome fusion is controlled by Rab34

2012 ◽  
Vol 109 (50) ◽  
pp. 20485-20490 ◽  
Author(s):  
B. Kasmapour ◽  
A. Gronow ◽  
C. K. E. Bleck ◽  
W. Hong ◽  
M. G. Gutierrez
Keyword(s):  
Size Dependent ◽  
Phagosome Fusion ◽  
Dependent Mechanism ◽  
Cargo Sorting

scholarly journals Active diffusion in oocytes nonspecifically centers large objects during prophase I and meiosis I

2020 ◽  
Vol 219 (3) ◽  
Author(s):  
Alexandra Colin ◽  
Gaëlle Letort ◽  
Nitzan Razin ◽  
Maria Almonacid ◽  
Wylie Ahmed ◽  
...  
Keyword(s):  
3D Model ◽  
Experimental Measurements ◽  
Test Model ◽  
Effective Pressure ◽  
Chromosome Movement ◽  
Model Simulations ◽  
Model Predictions ◽  
Biased Diffusion ◽  
Passive Tracers ◽  
Meiosis I

Nucleus centering in mouse oocytes results from a gradient of actin-positive vesicle activity and is essential for developmental success. Here, we analyze 3D model simulations to demonstrate how a gradient in the persistence of actin-positive vesicles can center objects of different sizes. We test model predictions by tracking the transport of exogenous passive tracers. The gradient of activity induces a centering force, akin to an effective pressure gradient, leading to the centering of oil droplets with velocities comparable to nuclear ones. Simulations and experimental measurements show that passive particles subjected to the gradient exhibit biased diffusion toward the center. Strikingly, we observe that the centering mechanism is maintained in meiosis I despite chromosome movement in the opposite direction; thus, it can counteract a process that specifically off-centers the spindle. In conclusion, our findings reconcile how common molecular players can participate in the two opposing functions of chromosome centering versus off-centering.

scholarly journals Transduction of Low-Copy Number Plasmids by Bacteriophage P22

Genetics ◽  
1997 ◽  
Vol 146 (2) ◽  
pp. 447-456 ◽  
Author(s):  
Brandon A Mann ◽  
James M Slauch
Keyword(s):  
Copy Number ◽  
Rolling Circle Replication ◽  
Bacteriophage P22 ◽  
Genome Packaging ◽  
Rolling Circle ◽  
Size Dependent ◽  
Recombination Proteins ◽  
Low Copy Number ◽  
Dependent Mechanism

The generalized transducing bacteriophage of Salmonella typhimurium, P22, can transduce plasmids in addition to chromosomal markers. Previous studies have concentrated on transduction of pBR322 by P22 and P22HT, the high transducing mutant of P22. This study investigates the mechanism of P22HT transduction of low-copy number plasmids, namely pSC101 derivatives. We show that P22HT transduces pSC101 derivatives that share homology with the chromosome by two distinct mechanisms. In the first mechanism, the plasmid integrates into the chromosome of the donor by homologous recombination. This chromosomal fragment is then packaged in the transducing particle. The second mechanism is a size-dependent mechanism involving a putative plasmid multimer. We propose that this multimer is formed by interplasmidic recombination. In contrast, P22HT can efficiently transduce pBR322 by a third mechanism, which is independent of plasmid homology with the chromosome. It has been proposed that the phage packages a linear concatemer created during rolling circle replication of pBR322, similar in fashion to phage genome packaging. This study investigates the role of RecA, RecD, and RecF recombination proteins in plasmid/plasmid and plasmid/chromosome interactions that form packageable substrates in the donor. We also examine the resolution of various transduced plasmid species in the recipient and the roles of RecA and RecD in these processes.

scholarly journals Size-dependent protein segregation creates a spatial switch for Notch and APP signaling

2020 ◽  
Author(s):  
Minsuk Kwak ◽  
Kaden M. Southard ◽  
Nam Hyeong Kim ◽  
Ramu Gopalappa ◽  
Woon Ryoung Kim ◽  
...  
Keyword(s):  
Cell Surface ◽  
Amyloid Precursor Proteins ◽  
High Cell ◽  
Downstream Signaling ◽  
Size Dependent ◽  
Enzyme Substrate ◽  
Secretase Activity ◽  
Precursor Proteins ◽  
Dependent Protein ◽  
Dependent Mechanism

Aberrant cleavage of Notch and amyloid precursor proteins (APPs) by γ-secretase is implicated in numerous diseases, but how cleavage is regulated in space and time is unclear. Here, we report that cadherin-based adherens junctions (cadAJs) are sites of high cell-surface γ-secretase activity, while simultaneously excluding these γ-secretase substrates by a size-dependent mechanism, prohibiting enzyme-substrate interactions. Upon activation, Notch and APP undergo drastic spatial rearrangements to cadAJs, concentrating them with γ-secretase, wherein they are further processed for downstream signaling. Spatial mutation by decreasing (or increasing) the size of Notch extracellular domain promotes (or inhibits) signaling, respectively. Dysregulation of this spatial switch also promotes formation of more amyloidogenic Aβ. Therefore, cadAJs creates distinct biochemical compartments regulating signaling events involving γ-secretase and prevent pathogenic activation of its substrates.

scholarly journals Mycobacterium tuberculosis cording in the cytosol of live lymphatic endothelial cells

2019 ◽  
Author(s):  
Thomas R. Lerner ◽  
Christophe J. Queval ◽  
Rachel P. Lai ◽  
Matthew Russell ◽  
Antony Fearns ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Mycobacterium Tuberculosis ◽  
Secretion System ◽  
Lymphatic Endothelial Cells ◽  
Rna Seq ◽  
Size Dependent ◽  
Type Vii Secretion ◽  
Type Vii Secretion System ◽  
Dependent Mechanism

AbstractThe ability of Mycobacterium tuberculosis to form serpentine cords is intrinsically related to its virulence, but specifically how M. tuberculosis cording contributes to pathogenesis remains obscure. We show that several M. tuberculosis clinical isolates form intracellular cords in primary human lymphatic endothelial cells (hLEC) in vitro and also in the lymph nodes of patients with tuberculosis. We identified via RNA-seq a transcriptional programme in hLEC that activates cellular pro-survival and cytosolic surveillance of intracellular pathogens pathways. Consistent with this, cytosolic access of hLEC is required for intracellular M. tuberculosis cording; and cord formation is dependent on the M. tuberculosis ESX-1 type VII secretion system and the mycobacterial lipid PDIM. Finally, we show that M. tuberculosis cording is a novel size-dependent mechanism used by the pathogen to evade xenophagy in the cytosol of endothelial cells. These results provide a mechanism that explains the long-standing association between M. tuberculosis cording and virulence.

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