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Étienne Fodor, Vishwajeet Mehandia, Jordi Comelles, Raghavan Thiagarajan, Nir S Gov, Paolo Visco, Frédéric van Wijland, Daniel Riveline
In living matter, shape fluctuations induced by acto-myosin are usually studied in vitro via reconstituted gels, whose properties are controlled by changing the concentrations of actin, myosin, and cross-linkers. Such an approach deliberately avoids consideration of the complexity of biochemical signaling inherent to living systems. Acto-myosin activity inside living cells is mainly regulated by the Rho signaling pathway, which is composed of multiple layers of coupled activators and inhibitors. Here, we investigate how such a pathway controls the dynamics of confluent epithelial tissues by tracking the displacements of the junction points between cells...
February 27, 2018: Biophysical Journal
Julio César López-Valdés
Mary Wollstonecraft Godwin (1797-1851), mejor conocida como Mary Shelley, con su visión romántica del mundo dio vida a una progenie interminable de historias en la literatura, y su escrito originó el mito del creador mortal que da vida a partir de la ciencia. Aunque parezca sorprendente, la historia ha llegado a considerarse un mito debido a los actos fundamentados en hechos de cierta forma «verídicos» que ayudaron a su origen, como fueron el galvanismo y el estudio del potencial eléctrico en los seres vivos llevados a cabo por dos italianos: Luigi Galvani y Giovanni Aldini...
2018: Gaceta Médica de México
Khaled Khairy, William Lemon, Fernando Amat, Philipp J Keller
Mechanics plays a key role in the development of higher organisms. However, understanding this relationship is complicated by the difficulty of modeling the link between local forces generated at the subcellular level and deformations observed at the tissue and whole-embryo levels. Here we propose an approach first developed for lipid bilayers and cell membranes, in which force-generation by cytoskeletal elements enters a continuum mechanics formulation for the full system in the form of local changes in preferred curvature...
January 23, 2018: Biophysical Journal
Ohad Cohen, Samuel A Safran
We theoretically predict and compare with experiments, transitions from spontaneous beating to dynamical entrainment of cardiomyocytes induced by an oscillating, external mechanical probe. In accord with recent experiments, we predict the dynamical behavior as a function of the probe amplitude and frequency. The theory is based on a phenomenological model for a non-linear oscillator, motivated by acto-myosin contractility. The generic behavior is independent of the detailed, molecular origins of the dynamics and, consistent with experiment, we find three regimes: spontaneous beating with the natural frequency of the cell, entrained beating with the frequency of the probe, and a "bursting" regime where the two frequencies alternate in time...
February 2, 2018: Scientific Reports
Julie Milanini, Racha Fayad, Mariagrazia Partisani, Patrick Lecine, Jean-Paul Borg, Michel Franco, Frédéric Luton
A key step of epithelial morphogenesis is the creation of the lumen. Luminogenesis by hollowing proceeds through the fusion of apical vesicles at cell-cell contact. The small nascent lumens grow through extension, coalescence and enlargement coordinated with cell division to give rise to a single central lumen. Here, using MDCK cells grown in 3D-culture, we show that EFA6A participates in luminogenesis. EFA6A recruits α-actinin 1 (ACTN1) through direct binding. In polarized cells, ACTN1 was found to be enriched at the tight junction where it acts as a primary effector of EFA6A for normal luminogenesis...
December 15, 2017: Journal of Cell Science
Umut Akalp, Carsten Schnatwinkel, Mark P Stoykovich, Stephanie J Bryant, Franck J Vernerey
The contraction and spreading of nonmuscle cells are important phenomena in a number of cellular processes such as differentiation, morphogenesis, and tissue growth. Recent experimental work has shown that the topology and the mechanical properties of the underlying substrate play a significant role in directing the cell's response. In this work, we introduce a multiscale model to understand the sensing, activation, and contraction of the actin cytoskeleton of nonmuscle cells based on the idea that acto-myosin cross-bridges display a catch-bond response...
2017: ACS Biomaterials Science & Engineering
Anne Karine Lagendijk, Guillermo A Gomez, Sungmin Baek, Daniel Hesselson, William E Hughes, Scott Paterson, Daniel E Conway, Heinz-Georg Belting, Markus Affolter, Kelly A Smith, Martin A Schwartz, Alpha S Yap, Benjamin M Hogan
Forces play diverse roles in vascular development, homeostasis and disease. VE-cadherin at endothelial cell-cell junctions links the contractile acto-myosin cytoskeletons of adjacent cells, serving as a tension-transducer. To explore tensile changes across VE-cadherin in live zebrafish, we tailored an optical biosensor approach, originally established in vitro. We validate localization and function of a VE-cadherin tension sensor (TS) in vivo. Changes in tension across VE-cadherin observed using ratio-metric or lifetime FRET measurements reflect acto-myosin contractility within endothelial cells...
November 10, 2017: Nature Communications
Ioannis Kasioulis, Raman M Das, Kate G Storey
Detachment of newborn neurons from the neuroepithelium is required for correct neuronal architecture and functional circuitry. This process, also known as delamination, involves adherens-junction disassembly and acto-myosin-mediated abscission, during which the centrosome is retained while apical/ciliary membranes are shed. Cell-biological mechanisms mediating delamination are, however, poorly understood. Using live-tissue and super-resolution imaging, we uncover a centrosome-nucleated wheel-like microtubule configuration, aligned with the apical actin cable and adherens-junctions within chick and mouse neuroepithelial cells...
October 23, 2017: ELife
Anne Combedazou, Stéphanie Gayral, Nathalie Colombié, Anne Fougerat, Muriel Laffargue, Damien Ramel
Collective cell migration is a critical mechanism involved in cell movement during various physiological and pathological processes such as angiogenesis and metastasis formation. During collective movement, cells remain functionally connected and can coordinate individual cell behaviors to ensure efficient migration. A cell-cell communication process ensures this complex coordination. Although the mechanisms regulating cell-cell communication remain unclear, recent findings indicate that it is based on acto-myosin cytoskeleton tension transmission from cell to cell through adherens junctions...
October 5, 2017: Small GTPases
Karin Fredriksson-Lidman, Christina M Van Itallie, Amber J Tietgens, James M Anderson
SORBS2 is a scaffolding protein associated with Abl/Arg non-receptor tyrosine kinase pathways and is known to interact with actin and several other cytoskeletal proteins in various cell types. Previous BioID proximity labeling of tight and adherens junction proteins suggested that SORBS2 is a component of the apical junction complex of epithelial cells. We asked whether SORBS2 plays a previously unappreciated role in controlling perijunctional actin and tight junction barrier function. Using super resolution imaging we confirmed that SORBS2 is localized at the apical junction complex but farther from the membrane than ZO-1 and located partially overlapping both the tight- and adherens junctions with a periodic concentration that alternates with myosin IIB in polarized epithelial cells...
2017: PloS One
Sieglind Wallner-Hahn, Maricela de la Torre-Castro
This study analyzes fishers', managers' and scientists' opinions on management measures to facilitate the initiation of management processes towards more sustainable small-scale seagrass fisheries in Zanzibar, Tanzania. The results show that most fishers and managers agreed on the need to include seagrasses specifically in future management. There was further agreement on dragnets being the most destructive gears, and the use of dragnets being a major threat to local seagrass ecosystems. Gear restrictions excluding illegal dragnets were the favored management measure among fishers...
September 15, 2017: Marine Pollution Bulletin
Gopal L Khatik, Ashok Kumar Datusalia, Waquar Ahsan, Paranjeet Kaur, Manish Vyas, Amit Mittal, Surendra Kumar Nayak
BACKGROUND: Heterocycles containing thiazole, a moiety with sulfur and nitrogen is a core structure which found in a number of biologically active compounds. The thiazole ring is notable as a component of the certain natural products, such as vitamin B1 (thiamine) and penicillins. Thiazole is also known as wonder nucleus and has versatile in different biological fields. A number of new compounds contain heterocycle thiazole moieties, thus it is one of the important areas of research. METHODS: We searched the scientific database using relevant keywords...
September 15, 2017: Current Drug Discovery Technologies
Sukanya Gayan, Abhishek Teli, Tuli Dey
Cellular migration, a process relevant to metastasis, is mostly studied in the conventional 2D condition. However, cells cultured in the 3D condition assumed to mimic the in vivo conditions better. The current study is designed to compare an invasive and non-invasive adenocarcinoma cell with an invasive fibrosarcoma cell to understand the migration pattern of the multicellular spheroid. It is observed that conventional haplotaxis, chemotactic and pseudo-3D migration assay cannot distinguish between the invasive and non-invasive cells conclusively under 2D condition...
September 14, 2017: Scientific Reports
Rika Hirakawa, Yusuke Nishikawa, Taro Q P Uyeda, Kiyotaka Tokuraku
Heavy meromyosin (HMM) forms clusters along actin filaments under low ATP concentrations. Here, we observed the growth of HMM clusters under low concentrations of ATP in real time using fluorescence microscopy. When actin filaments were loosely immobilized on positively charged lipid bilayers, clusters of HMM-GFP were readily formed. Time-lapse observation revealed that the clusters grew unidirectionally. When we used a mixture of actin filaments and copolymers of actin and acto-S1dC, a chimeric protein of actin and the myosin motor domain, HMM-GFP preferentially formed clusters along the copolymers...
December 2017: Cytoskeleton
Sujaan Das, Leandro Lemgruber, Chwen L Tay, Jake Baum, Markus Meissner
BACKGROUND: The phylum Apicomplexa includes intracellular parasites causing immense global disease burden, the deadliest of them being the human malaria parasite Plasmodium falciparum, which invades and replicates within erythrocytes. The cytoskeletal protein actin is well conserved within apicomplexans but divergent from mammalian actins, and was primarily reported to function during host cell invasion. However, novel invasion mechanisms have been described for several apicomplexans, and specific functions of the acto-myosin system are being reinvestigated...
August 15, 2017: BMC Biology
Lucas Smith, Sangkyun Cho, Dennis E Discher
Stem cells are particularly 'plastic' cell types that are induced by various cues to become specialized, tissue-functional lineages by switching on the expression of specific gene programs. Matrix stiffness is among the cues that multiple stem cell types can sense and respond to. This seminar-style review focuses on mechanosensing of matrix elasticity in the differentiation or early maturation of a few illustrative stem cell types, with an intended audience of biologists and physical scientists. Contractile forces applied by a cell's acto-myosin cytoskeleton are often resisted by the extracellular matrix and transduced through adhesions and the cytoskeleton ultimately into the nucleus to modulate gene expression...
November 2017: Seminars in Cell & Developmental Biology
R S Gormal, N Valmas, T Fath, F A Meunier
Bulk endocytosis allows stimulated neurons to take up a large portion of the presynaptic plasma membrane in order to regenerate synaptic vesicle pools. Actin, one of the most abundant proteins in eukaryotic cells, plays an important role in this process, but a detailed mechanistic understanding of the involvement of the cortical actin network is still lacking, in part due to the relatively small size of nerve terminals and the limitation of optical microscopy. We recently discovered that neurosecretory cells display a similar, albeit much larger, form of bulk endocytosis in response to secretagogue stimulation...
May 22, 2017: Molecular and Cellular Neurosciences
Péter Nánási, Marta Gaburjakova, Jana Gaburjakova, János Almássy
Due to the limited results achieved in the clinical treatment of heart failure, a new inotropic strategy of myosin motor activation has been developed. The lead molecule of myosin activator agents is omecamtiv mecarbil, which binds directly to the heavy chain of the cardiac β-myosin and enhances cardiac contractility by lengthening the lifetime of the acto-myosin complex and increasing the number of the active force-generating cross-bridges. In the absence of relevant data, the effect of omecamtiv mecarbil on canine cardiac ryanodine receptors (RyR 2) has been investigated in the present study by measuring the electrical activity of single RyR 2 channels incorporated into planar lipid bilayer...
May 13, 2017: European Journal of Pharmacology
Ravi Bharadwaj, Ranjana Arya, M Shahid Mansuri, Sudha Bhattacharya, Alok Bhattacharya
The protozoan parasite Entamoeba histolytica causes amoebiasis, a major public health problem in developing countries. Motility of E. histolytica is important for its pathogenesis. Blebbing is an essential process contributing to cellular motility in many systems. In mammalian cells, formation of plasma membrane blebs is regulated by Rho-GTPases through its effectors, such as Rho kinase, mDia1, and acto-myosin proteins. In this study, we have illuminated the role of EhRho1 in bleb formation and motility of E...
May 6, 2017: Cellular Microbiology
Li Wang, Katarzyna Kazmierczak, Chen-Ching Yuan, Sunil Yadav, Masataka Kawai, Danuta Szczesna-Cordary
We have investigated the physiology and mechanical profiles of skinned papillary muscle fibers from transgenic mice expressing the N47K mutation in the myosin regulatory light chain (RLC), shown to cause hypertrophic cardiomyopathy in humans. The results were compared with wild-type (WT) mice, both expressing the human ventricular RLC. Rate constants of a cross-bridge (XB) cycle were deduced from tension transients induced by sinusoidal length changes during maximal Ca(2+) activation, and were studied as a function of MgATP, MgADP, and Pi concentrations...
June 2017: FEBS Journal
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