Spatiotemporal regulation of the Pak1 kinase

2005 ◽  
Vol 33 (4) ◽  
pp. 646-648 ◽  
Author(s):  
M.C. Parrini ◽  
M. Matsuda ◽  
J. de Gunzburg
Keyword(s):  
Extracellular Matrix ◽  
Actin Cytoskeleton ◽  
Cell Motility ◽  
Current Knowledge ◽  
Living Cells ◽  
Kinetic Control ◽  
Multiprotein Complexes ◽  
Spatiotemporal Regulation ◽  
P21 Activated Kinase

Pak1 (p21-activated kinase 1) is a key regulator of the actin cytoskeleton, adhesion and cell motility. Such biological roles require a tight spatial and kinetic control of its localization and activity. We summarize here the current knowledge on Pak1 dynamics in vivo. Inactive dimeric Pak1 is mainly cytosolic. Localized interaction with the activators Cdc42-GTP and Rac1-GTP stimulates the kinase at the sites of cellular protrusions. Moreover, Pak1 is dynamically engaged into multiprotein complexes forming adhesions to the extracellular matrix. Cutting edge microscopy technologies on living cells are finally shedding light on the intricate spatiotemporal mechanisms regulating Pak1.

Force-dependent vinculin binding to talin in live cells: a crucial step in anchoring the actin cytoskeleton to focal adhesions

2014 ◽  
Vol 306 (6) ◽  
pp. C607-C620 ◽  
Author(s):  
Hiroaki Hirata ◽  
Hitoshi Tatsumi ◽  
Chwee Teck Lim ◽  
Masahiro Sokabe
Keyword(s):  
Actin Cytoskeleton ◽  
Focal Adhesions ◽  
Living Cells ◽  
Live Cells ◽  
Mechanical Forces ◽  
Actin Network ◽  
Crucial Step

Mechanical forces play a pivotal role in the regulation of focal adhesions (FAs) where the actin cytoskeleton is anchored to the extracellular matrix through integrin and a variety of linker proteins including talin and vinculin. The localization of vinculin at FAs depends on mechanical forces. While in vitro studies have demonstrated the force-induced increase in vinculin binding to talin, it remains unclear whether such a mechanism exists at FAs in vivo. In this study, using fibroblasts cultured on elastic silicone substrata, we have examined the role of forces in modulating talin-vinculin binding at FAs. Stretching the substrata caused vinculin accumulation at talin-containing FAs, and this accumulation was abrogated by expressing the talin-binding domain of vinculin (domain D1, which inhibits endogenous vinculin from binding to talin). These results indicate that mechanical forces loaded to FAs facilitate vinculin binding to talin at FAs. In cell-protruding regions, the actin network moved backward over talin-containing FAs in domain D1-expressing cells while it was anchored to FAs in control cells, suggesting that the force-dependent vinculin binding to talin is crucial for anchoring the actin cytoskeleton to FAs in living cells.

scholarly journals A cytoskeletal clutch mediates cellular force transmission in a soft, three-dimensional extracellular matrix

2017 ◽  
Vol 28 (14) ◽  
pp. 1959-1974 ◽  
Author(s):  
Leanna M. Owen ◽  
Arjun S. Adhikari ◽  
Mohak Patel ◽  
Peter Grimmer ◽  
Natascha Leijnse ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Cell Migration ◽  
Actin Cytoskeleton ◽  
Dynamic Equilibrium ◽  
Three Dimensional ◽  
Time Lapse ◽  
Dermal Fibroblasts ◽  
Force Transmission ◽  
Ecm Remodeling

The ability of cells to impart forces and deformations on their surroundings underlies cell migration and extracellular matrix (ECM) remodeling and is thus an essential aspect of complex, metazoan life. Previous work has resulted in a refined understanding, commonly termed the molecular clutch model, of how cells adhering to flat surfaces such as a microscope coverslip transmit cytoskeletally generated forces to their surroundings. Comparatively less is known about how cells adhere to and exert forces in soft, three-dimensional (3D), and structurally heterogeneous ECM environments such as occur in vivo. We used time-lapse 3D imaging and quantitative image analysis to determine how the actin cytoskeleton is mechanically coupled to the surrounding matrix for primary dermal fibroblasts embedded in a 3D fibrin matrix. Under these circumstances, the cytoskeletal architecture is dominated by contractile actin bundles attached at their ends to large, stable, integrin-based adhesions. Time-lapse imaging reveals that α-actinin-1 puncta within actomyosin bundles move more quickly than the paxillin-rich adhesion plaques, which in turn move more quickly than the local matrix, an observation reminiscent of the molecular clutch model. However, closer examination did not reveal a continuous rearward flow of the actin cytoskeleton over slower moving adhesions. Instead, we found that a subset of stress fibers continuously elongated at their attachment points to integrin adhesions, providing stable, yet structurally dynamic coupling to the ECM. Analytical modeling and numerical simulation provide a plausible physical explanation for this result and support a picture in which cells respond to the effective stiffness of local matrix attachment points. The resulting dynamic equilibrium can explain how cells maintain stable, contractile connections to discrete points within ECM during cell migration, and provides a plausible means by which fibroblasts contract provisional matrices during wound healing.

scholarly journals Zebrafish in Inflammasome Research

Cells ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 901 ◽  
Author(s):  
Gabriel Forn-Cuní ◽  
Annemarie H. Meijer ◽  
Monica Varela
Keyword(s):  
Inflammatory Responses ◽  
Current Knowledge ◽  
Evolutionary Conservation ◽  
Intravital Imaging ◽  
Evolutionary Origin ◽  
Inflammasome Activation ◽  
Multiprotein Complexes ◽  
Zebrafish Larvae ◽  
Caspase 1

Inflammasomes are cytosolic multiprotein complexes that regulate inflammatory responses to danger stimuli and infection, and their dysregulation is associated with an increasing number of autoinflammatory diseases. In recent years, zebrafish models of human pathologies to study inflammasome function in vivo have started to emerge. Here, we discuss inflammasome research in zebrafish in light of current knowledge about mammalian inflammasomes. We summarize the evolutionary conservation of inflammasome components between zebrafish and mammals, highlighting the similarities and possible divergence in functions of these components. We present new insights into the evolution of the caspase-1 family in the teleost lineage, and how its evolutionary origin may help contextualize its functions. We also review existing infectious and non-infectious models in zebrafish in which inflammasomes have been directly implicated. Finally, we discuss the advantages of zebrafish larvae for intravital imaging of inflammasome activation and summarize available tools that will help to advance inflammasome research.

scholarly journals Tensile stress stimulates microtubule outgrowth in living cells

2002 ◽  
Vol 115 (11) ◽  
pp. 2283-2291 ◽  
Author(s):  
Irina Kaverina ◽  
Olga Krylyshkina ◽  
Karen Beningo ◽  
Kurt Anderson ◽  
Yu-Li Wang ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Actin Cytoskeleton ◽  
Cell Motility ◽  
Actin Filaments ◽  
Flexible Substrate ◽  
Living Cells ◽  
The Body ◽  
Traction Forces ◽  
Sensing Mechanism ◽  
Adhesion Sites

Cell motility is driven by the sum of asymmetric traction forces exerted on the substrate through adhesion foci that interface with the actin cytoskeleton. Establishment of this asymmetry involves microtubules, which exert a destabilising effect on adhesion foci via targeting events. Here, we demonstrate the existence of a mechano-sensing mechanism that signals microtubule polymerisation and guidance of the microtubules towards adhesion sites under increased stress. Stress was applied either by manipulating the body of cells moving on glass with a microneedle or by stretching a flexible substrate that cells were migrating on. We propose a model for this mechano-sensing phenomenon whereby microtubule polymerisation is stimulated and guided through the interaction of a microtubule tip complex with actin filaments under tension.

Kallikrein-related peptidases: bridges between immune functions and extracellular matrix degradation

2010 ◽  
Vol 391 (4) ◽  
Author(s):  
Georgia Sotiropoulou ◽  
Georgios Pampalakis
Keyword(s):  
Extracellular Matrix ◽  
Serine Proteases ◽  
Current Knowledge ◽  
Immune Functions ◽  
Proteolytic Activation ◽  
Specific Manner ◽  
Encoding Genes ◽  
Skin Wounding

Abstract Kallikrein-related peptidases (KLKs) constitute a family of 15 highly conserved serine proteases encoded by the largest uninterrupted cluster of protease-encoding genes within the human genome. Recent studies, mostly relying on in vitro proteolysis of recombinant proteins, have suggested that KLK activities are regulated by proteolytic activation cascades that can operate in a tissue-specific manner, such as the semen liquefaction and skin desquamation cascades. The validity of KLK activation cascades in vivo largely remains to be demonstrated. Here, we focus on recent investigations showing that KLKs represent interesting players in the broader field of immunology based on their ability to bridge their inherent ability to degrade the extracellular matrix with major functions of the immune system. More specifically, KLKs assist in the infiltration of immune cells through the skin and the blood brain barrier, whereas they catalyze the generation of antimicrobial peptides by proteolytic activation and further processing of protein precursors. In an attempt to integrate current knowledge, we propose KLK-mediated pathways that are putatively involved in inflammation associated with skin wounding and central nervous system disorders, including multiple sclerosis. Finally, we present evidence of KLK participation in autoimmune diseases and allergies.

Dynamics of Stretch-Induced Stress Fiber Remodeling in 3D Cell Culture

2011 ◽  
Author(s):  
Sheng-Lin Lee ◽  
Ali Nekouzadeh ◽  
Kenneth M. Pryse ◽  
Elliot L. Elson ◽  
Guy M. Genin
Keyword(s):  
Cell Culture ◽  
Extracellular Matrix ◽  
Actin Cytoskeleton ◽  
3D Cell Culture ◽  
Living Cells ◽  
Stress Fiber ◽  
Cell Physiology ◽  
Mechanical Stimuli ◽  
Tissue Development ◽  
Induced Stress

The responses of living cells to mechanical stimuli are believed to underlie diseases such as fibrotic cardiomyopathy [1] and asthma [2]. Emerging evidence suggests that mechanical signals transduced through the actin cytoskeleton and its connections to the extracellular matrix (ECM) have important effects on cell physiology and tissue development [13]. Understanding the responses of cells in realistic mechanical environments to mechanical stimuli is therefore of great importance to understanding development and disease.

Desmopressin (DDAVP) Enhances Platelet Adhesion to the Extracellular Matrix of Cultured Human Endothelial Cells through Increased Expression of Tissue Factor

1997 ◽  
Vol 77 (05) ◽  
pp. 0975-0980 ◽  
Author(s):  
Angel Gálvez ◽  
Goretti Gómez-Ortiz ◽  
Maribel Díaz-Ricart ◽  
Ginés Escolar ◽  
Rogelio González-Sarmiento ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Tissue Factor ◽  
Platelet Adhesion ◽  
Umbilical Vein ◽  
Procoagulant Activity ◽  
Experimental Conditions ◽  
Chromogenic Assay

SummaryThe effect of desmopressin (DDAVP) on thrombogenicity, expression of tissue factor and procoagulant activity (PCA) of extracellular matrix (ECM) generated by human umbilical vein endothelial cells cultures (HUVEC), was studied under different experimental conditions. HUVEC were incubated with DDAVP (1, 5 and 30 ng/ml) and then detached from their ECM. The reactivity towards platelets of this ECM was tested in a perfusion system. Coverslips covered with DD A VP-treated ECMs were inserted in a parallel-plate chamber and exposed to normal blood anticoagulated with low molecular weight heparin (Fragmin®, 20 U/ml). Perfusions were run for 5 min at a shear rate of 800 s1. Deposition of platelets on ECMs was significantly increased with respect to control ECMs when DDAVP was used at 5 and 30 ng/ml (p <0.05 and p <0.01 respectively). The increase in platelet deposition was prevented by incubation of ECMs with an antibody against human tissue factor prior to perfusion. Immunofluorescence studies positively detected tissue factor antigen on DDAVP derived ECMs. A chromogenic assay performed under standardized conditions revealed a statistically significant increase in the procoagulant activity of the ECMs produced by ECs incubated with 30 ng/ml DDAVP (p <0.01 vs. control samples). Northern blot analysis revealed increased levels of tissue factor mRNA in extracts from ECs exposed to DDAVP. Our data indicate that DDAVP in vitro enhances platelet adhesion to the ECMs through increased expression of tissue factor. A similar increase in the expression of tissue factor might contribute to the in vivo hemostatic effect of DDAVP.

Closure of Fetoscopic Access Sites with Amniotic Extracellular Matrix Scaffolds in an In Vivo Model

2006 ◽  
Vol 66 (S 01) ◽  
Author(s):  
N Ochsenbein-Kölble ◽  
J Jani ◽  
G Verbist ◽  
L Lewi ◽  
K Marquardt ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
In Vivo Model ◽  
Extracellular Matrix Scaffolds
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