substrate adhesion
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Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3485
Author(s):  
Shashi Prakash Singh ◽  
Peter A. Thomason ◽  
Robert H. Insall

The lamellipodia and pseudopodia of migrating cells are produced and maintained by the Scar/WAVE complex. Thus, actin-based cell migration is largely controlled through regulation of Scar/WAVE. Here, we report that the Abi subunit—but not Scar—is phosphorylated in response to extracellular signalling in Dictyostelium cells. Like Scar, Abi is phosphorylated after the complex has been activated, implying that Abi phosphorylation modulates pseudopodia, rather than causing new ones to be made. Consistent with this, Scar complex mutants that cannot bind Rac are also not phosphorylated. Several environmental cues also affect Abi phosphorylation—cell-substrate adhesion promotes it and increased extracellular osmolarity diminishes it. Both unphosphorylatable and phosphomimetic Abi efficiently rescue the chemotaxis of Abi KO cells and pseudopodia formation, confirming that Abi phosphorylation is not required for activation or inactivation of the Scar/WAVE complex. However, pseudopodia and Scar patches in the cells with unphosphorylatable Abi protrude for longer, altering pseudopod dynamics and cell speed. Dictyostelium, in which Scar and Abi are both unphosphorylatable, can still form pseudopods, but migrate substantially faster. We conclude that extracellular signals and environmental responses modulate cell migration by tuning the behaviour of the Scar/WAVE complex after it has been activated.


Author(s):  
Jing Zou ◽  
Kun Jin ◽  
Tongsheng Chen ◽  
Xinlei Li

Abstract When cells are cultured on the micro- or nano- structure substrate, filamentous pseudopods are formed at specific locations due to the effects of substrate morphology and local membrane curvature, which provides a powerful method to guide cell migration and neurite orientation. However, it is unclear the effects of substrate surface morphology and initial cell membrane on pseudopod formation and growth. Here, we present a quantitative thermodynamic model to investigate the difficulty of pseudopod formation. Based on the established model, we studied the effects of substrate morphology and the curvature of the initial cell membrane on filamentous pseudopods formation by analyzing the magnitude of an average driving force. We find that the pseudopod-substrate adhesion and the larger curvature radius of the initial cell membrane can facilitate filamentous pseudopods formation due to the smaller minimum resistance energy. Furthermore, our theoretical results seem to show a broad agreement with experimental observations, which implies that these studies would provide useful guidance to control the pseudopods formation on substrate for biomedical applications.


2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Konrad Beyer ◽  
Simon Kracht ◽  
Jessica Kehrer ◽  
Mirko Singer ◽  
Dennis Klug ◽  
...  

Abstract Background Plasmodium sporozoites are the highly motile forms of malaria-causing parasites that are transmitted by the mosquito to the vertebrate host. Sporozoites need to enter and cross several cellular and tissue barriers for which they employ a set of surface proteins. Three of these proteins are members of the thrombospondin related anonymous protein (TRAP) family. Here, potential additive, synergistic or antagonistic roles of these adhesion proteins were investigated. Methods Four transgenic Plasmodium berghei parasite lines that lacked two or all three of the TRAP family adhesins TRAP, TLP and TREP were generated using positive–negative selection. The parasite lines were investigated for their capacity to attach to and move on glass, their ability to egress from oocysts and their capacity to enter mosquito salivary glands. One strain was in addition interrogated for its capacity to infect mice. Results The major phenotype of the TRAP single gene deletion dominates additional gene deletion phenotypes. All parasite lines including the one lacking all three proteins were able to conduct some form of active, if unproductive movement. Conclusions The individual TRAP-family adhesins appear to play functionally distinct roles during motility and infection. Other proteins must contribute to substrate adhesion and gliding motility. Graphical Abstract


2021 ◽  
pp. 2106908
Author(s):  
Danfeng Yu ◽  
Jianjia Huang ◽  
Zhenqiang Zhang ◽  
Jiahao Weng ◽  
Xiubin Xu ◽  
...  

2021 ◽  
Author(s):  
Shashi Prakash Singh ◽  
Peter Thomason ◽  
Robert Insall

The lamellipodia and pseudopodia of migrating cells are produced and maintained by the Scar/WAVE complex. Thus, actin-based cell migration is largely controlled through regulation of Scar/WAVE. Here we report that the Abi subunit - not Scar/WAVE - is phosphorylated in response to extracellular signalling. Like Scar, Abi is phosphorylated after the complex has been activated, implying that Abi phosphorylation modulates pseudopodia, rather than causing new ones to be made. Consistent with this, Scar/WAVE complex mutants that cannot bind Rac are also not phosphorylated. Several environmental cues also affect Abi phosphorylation - cell-substrate adhesion promotes it and increased extracellular osmolarity diminishes it. Both unphosphorylatable and phosphomimetic Abi efficiently rescue the chemotaxis of Abi KO cells and pseudopodia formation, confirming that Abi phosphorylation is not required for activation or inactivation of the Scar/WAVE complex. However, pseudopodia and Scar/WAVE patches in the cells with unphosphorylatable Abi protrude for longer, altering pseudopod dynamics and cell speed. Cells in which Scar and Abi are both unphosphorylatable can still form pseudopods, but migrate substantially faster. We conclude that extracellular signals and environmental responses modulate cell migration by tuning the behaviour of the Scar/WAVE complex after it has been activated.


2021 ◽  
Author(s):  
Christian M Cammarota ◽  
Nicole S Dawney ◽  
Qingyuan Jia ◽  
Maren M Jung ◽  
Joseph A Glichowski ◽  
...  

Organ surfaces are lined by epithelial monolayers - sheets of cells that are one-cell thick. This architecture underlies tissue function, and its loss is associated with disease, including cancer. Studies of in-plane epithelial cell behaviors show that a developing epithelium behaves as a fluid in respect to the tissue plane, and can therefore readily adapt to varying mechanical influences during morphogenesis. We asked the question of how monolayer architecture is achieved, and whether it demonstrates the same fluid behavior. To address this problem, we cultured MDCK (Madin-Darby Canine Kidney) cell layers at different densities and timepoints and analyzed their architectures using a novel tool, Automated Layer Analysis (ALAn), which we introduce here. Our experimental and theoretical results lead us to propose that epithelial monolayer architecture is governed by a balance of counteracting forces due to cell-cell and cell-substrate adhesion, and that this balance is influenced by cell density. MDCK cells do not undergo obvious rearrangement along the apical-basal axis; instead, cells that do not contact the substrate aggregate on top of the monolayer. Our findings therefore imply that monolayered architecture is under more rigid control than planar tissue shape in epithelia.


Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 906
Author(s):  
Jinhong Zhang

An atomic force microscope (AFM) was applied to study of the adsorption of xanthate on bornite surfaces in situ in aqueous solutions. AFM images showed that xanthate, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbed strongly on bornite, and the adsorbate bound strongly with the mineral surface without being removed by flushing with ethanol alcohol. The AFM images also showed that the adsorption increased with the increased collector concentration and contact time. Xanthate adsorbed on bornite in a similar manner when the solution pH changed to pH 10. The AFM force measurement results showed that the probe–substrate adhesion increased due to the adsorption of xanthate on bornite. The sharp “jump-in” and “jump-off” points on force curve suggest that the adsorbate is not “soft” in nature, ruling out the existence of dixanthogen, an oily substance. Finally, the ATR-FTIR (attenuated total reflection-Fourier-transform infrared) result confirms that the adsorbate on bornite in xanthate solutions is mainly in the form of insoluble cuprous xanthate (CuX) instead of dixanthogen. This xanthate/bornite adsorption mechanism is very similar to what is obtained with the xanthate/chalcocite system, while it is different from the xanthate/chalcopyrite system, for which oily dixanthogen is the main adsorption product on the chalcopyrite surface. The present study helps clarify the flotation mechanism of bornite in industry practice using xanthate as a collector.


2021 ◽  
Author(s):  
Siavash Monfared ◽  
Guruswami Ravichandran ◽  
José E. Andrade ◽  
Amin Doostmohammadi

Cell layers eliminate unwanted cells through the extrusion process, which underlines healthy versus flawed tissue behaviors. Although several biochemical pathways have been identified, the underlying mechanical basis including the forces involved in cellular extrusion remain largely unexplored. Utilizing a phase-field model of a three-dimensional cell layer, we study the interplay of cell extrusion with cell-cell and cell-substrate interactions, in a monolayer. Independent tuning of cell-cell versus cell-substrate adhesion forces in the model reveals that a higher cell-substrate adhesion leads to a lower number of total extrusion events. We find extrusion events to be linked to both half-integer topological defects in the orientation field of the cells and to five-fold disclinations in cellular arrangements. We also show that increasing the relative cell-cell adhesion forces translates into a higher likelihood for an extrusion event to be associated with a five-fold disclination and a weaker correlation with +1/2 topological defects. We unify our findings by accessing mechanical stress fields: an extrusion event acts as a mechanism to relieve localized stress concentration.


Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2067
Author(s):  
Ying Tian ◽  
Tao Wang ◽  
Qingxia Zhu ◽  
Xingcai Zhang ◽  
Anita Sagadevan Ethiraj ◽  
...  

Improved OLED systems have great potential for next-generation display applications. Carbon nanotubes (CNTs) and the conductive polymers poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) have attracted great interest for advanced applications, such as optoelectronic products. In this paper, the simultaneous enhancement of the conductivity, roughness, and adhesion properties of transparent conductive films with PEDOT: PSS/CNTs is reported. These films prepared by a simple spin-coating process were successfully used to produce high-performance organic light-emitting diodes (OLEDs) with an improved lifetime. Addition of PEDOT: PSS lowered the film sheet resistance and CNTs helped to enhance the stability and maintain the lifetime of the OLEDs. In addition, treatment with methanol and nitric acid changed the morphology of the polymer film, which led to greatly reduced sheet resistance, enhanced substrate adhesion, and reduced film roughness. The best performance of the film (PEDOT: PSS: CNT = 110: 1, W/W) was 100.34 Ω/sq.@ 90.1 T%. High transmittance, low sheet resistance, excellent adhesion, and low roughness (3.11 nm) were achieved synchronously. The fabricated OLED demonstrated a low minimum operating voltage (3 V) and could endure high voltage (20 V), at which its luminance reached 2973 cd/m2. Thus, the incorporation of CNTs within PEDOT: PSS electrodes has great potential for the improvement of the performance of OLED devices.


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