Myosin II activity dependent and independent vinculin recruitment to the sites of E-cadherin-mediated cell-cell adhesion

<p>Abstract</p> <p>Background</p> <p>Maintaining proper adhesion between neighboring cells depends on the ability of cells to mechanically respond to tension at cell-cell junctions through the actin cytoskeleton. Thus, identifying the molecules involved in responding to cell tension would provide insight into the maintenance, regulation, and breakdown of cell-cell junctions during various biological processes. Vinculin, an actin-binding protein that associates with the cadherin complex, is recruited to cell-cell contacts under increased tension in a myosin II-dependent manner. However, the precise role of vinculin at force-bearing cell-cell junctions and how myosin II activity alters the recruitment of vinculin at quiescent cell-cell contacts have not been demonstrated.</p> <p>Results</p> <p>We generated vinculin knockdown cells using shRNA specific to vinculin and MDCK epithelial cells. These vinculin-deficient MDCK cells form smaller cell clusters in a suspension than wild-type cells. In wound healing assays, GFP-vinculin accumulated at cell-cell junctions along the wound edge while vinculin-deficient cells displayed a slower wound closure rate compared to vinculin-expressing cells. In the presence of blebbistatin (myosin II inhibitor), vinculin localization at quiescent cell-cell contacts was unaffected while in the presence of jasplakinolide (F-actin stabilizer), vinculin recruitment increased in mature MDCK cell monolayers.</p> <p>Conclusion</p> <p>These results demonstrate that vinculin plays an active role at adherens junctions under increased tension at cell-cell contacts where vinculin recruitment occurs in a myosin II activity-dependent manner, whereas vinculin recruitment to the quiescent cell-cell junctions depends on F-actin stabilization.</p

A conceptual enquiry into communities of practice as praxis in international doctoral education

Undertaking a PhD entails diverse and multi-faceted challenges as doctoral researchers enter a distinct academic culture that requires transition to a new level and threshold of learning – with both knowledge acquisition and production at the core. While doctoral researchers are expected to secure different dimensions of knowledge, which necessitates meaningful ‘dialogue’ with experts, the colossal task is still ironically associated with isolated doctoral experience and somewhat limited postgraduate supervision provision. With the extra concerns typically confronting the international doctoral cohort, the pressure tends be intensified, and may lead to psychological well-being concerns. Nevertheless, there is evidence from the literature that highlights the often unacknowledged forms of learning opportunities and support mechanisms via community participation. By employing communities of practice as the main framework, this conceptual paper exemplifies the crucial role played by these communities – how these communities serve to scaffold doctoral researchers’ academic progress, support their psychological adjustments, and reinforce the crucial, but perhaps limited, formal doctoral support provision. By featuring effective examples of educational praxis via these communities, our paper offers a holistic understanding of formal and informal infrastructures as part of the wider doctoral ecology with a view to achieving a more holistic and meaningful doctoral experience

A conceptual enquiry into communities of practice as praxis in international doctoral education

Undertaking a PhD entails diverse and multi-faceted challenges as doctoral researchers enter a distinct academic culture that requires transition to a new level and threshold of learning – with both knowledge acquisition and production at the core. While doctoral researchers are expected to secure different dimensions of knowledge, which necessitates meaningful ‘dialogue’ with experts, the colossal task is still ironically associated with isolated doctoral experience and somewhat limited postgraduate supervision provision. With the extra concerns typically confronting the international doctoral cohort, the pressure tends be intensified, and may lead to psychological well-being concerns. Nevertheless, there is evidence from the literature that highlights the often unacknowledged forms of learning opportunities and support mechanisms via community participation. By employing communities of practice as the main framework, this conceptual paper exemplifies the crucial role played by these communities – how these communities serve to scaffold doctoral researchers’ academic progress, support their psychological adjustments, and reinforce the crucial, but perhaps limited, formal doctoral support provision. By featuring effective examples of educational praxis via these communities, our paper offers a holistic understanding of formal and informal infrastructures as part of the wider doctoral ecology with a view to achieving a more holistic and meaningful doctoral experience

Myosin IIA deficient cells migrate efficiently despite reduced traction forces at cell periphery

Summary Cell motility is a cornerstone of embryogenesis, tissue remodeling and repair, and cancer cell invasion. It is generally thought that migrating cells grab and exert traction force onto the extracellular matrix in order to pull the cell body forward. While previous studies have shown that myosin II deficient cells migrate efficiently, whether these cells exert traction forces during cell migration in the absence of the major contractile machinery is currently unknown. Using an array of micron-sized pillars as a force sensor and shRNA specific to each myosin II isoform (A and B), we analyzed how myosin IIA and IIB individually regulate cell migration and traction force generation. Myosin IIA and IIB localized preferentially to the leading edge where traction force was greatest, and the trailing edge, respectively. When individual myosin II isoforms were depleted by shRNA, myosin IIA deficient cells lost actin stress fibers and focal adhesions, whereas myosin IIB deficient cells maintained similar actin organization and focal adhesions as wild-type cells. Interestingly, myosin IIA deficient cells migrated faster than wild-type or myosin IIB deficient cells on both a rigid surface and a pillar array, yet myosin IIA deficient cells exerted significantly less traction force at the leading edge than wild-type or myosin IIB deficient cells. These results suggest that, in the absence of myosin IIA mediated force-generating machinery, cells move with minimal traction forces at the cell periphery, thus demonstrating the remarkable ability of cells to adapt and migrate

Myosin IIA Dependent Retrograde Flow Drives 3D Cell Migration

Epithelial cell migration is an essential part of embryogenesis and tissue regeneration, yet their migration is least understood. Using our three-dimensional (3D) motility analysis, migrating epithelial cells formed an atypical polarized cell shape with the nucleus leading the cell front and a contractile cell rear. Migrating epithelial cells exerted traction forces to deform both the anterior and posterior extracellular matrix toward the cell body. The cell leading edge exhibited a myosin II-dependent retrograde flow with the magnitude and direction consistent with surrounding network deformation. Interestingly, on a two-dimensional substrate, myosin IIA-deficient cells migrated faster than wild-type cells, but in a 3D gel, these myosin IIA-deficient cells were unpolarized and immobile. In contrast, the migration rates of myosin IIB-deficient cells were similar to wild-type cells. Therefore, myosin IIA, not myosin IIB, is required for 3D epithelial cell migration

Synergistic Effect and Characterization of Graphene/Carbon Nanotubes/Polyvinyl Alcohol/Sodium Alginate Nanofibrous Membranes Formed Using Continuous Needleless Dynamic Linear Electrospinning

In this study, a self-made continuous needleless dynamic linear electrospinning technique is employed to fabricate large-scale graphene (Gr)/carbon nanotubes (CNT)/polyvinyl alcohol (PVA)/sodium alginate (SA) nanofibrous membranes. The synergistic effect of Gr and CNT fillers in the PVA/SA membrane is explored in depth by changing the volume ratio (v/v) of Gr and CNT as 10:0, 8:2, 6:4, 4:6, 2:8, and 0:10. Microstructure, functional group, conductivity, and hydrophilicity of PVA/SA/Gr/CNT membranes was characterized. Results show that the linear electrode needleless electrospinning technique can be spun into 200-nm diameter fibers. The PVA/SA/Gr/CNT fibrous membrane has good hydrophilicity and thermal stability. A Gr/CN ratio of 6:4 possessed the optimal synergistic effect, which showed the lowest surface resistivity of 2.53 &#215; 103 &#937;/m2. This study will provide a reference for the large-scale preparation of nanofibrous membrane used as a artificial nerve conduit in the future

Sub-femtosecond precision timing synchronization systems

We present a timing synchronization system that can synchronize optical and microwave signals with attosecond-level precision across kilometer distances. With this technique, the next-generation photon science facilities like X-ray free-electron lasers and intense laser beamlines can be enabled to observe ultrafast dynamics in atoms, molecules and condensed matter taking place on an attosecond time scale. We discuss some key technologies including master-laser jitter characterization, local one-color laser synchronization, remote two-color laser synchronization, and analyze technical noise contributions in the system. A 4.7-km laser-microwave network with 950-attosecond timing jitter is realized over tens of hours of continuous operation. Finally, an integrated balanced optical cross correlator is introduced. With the same input power level, the required operational power for each timing link is significantly reduced