Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.248
Filtrar
1.
Int J Mol Sci ; 22(15)2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-34360739

RESUMO

Changes in plasma membrane curvature and intracellular ionic strength are two key features of cell volume perturbations. In this hypothesis we present a model of the responsible molecular apparatus which is assembled of two molecular motors [non-muscle myosin II (NMMII) and protrusive actin polymerization], a spring [a complex between the plasma membrane (PM) and the submembrane actin-based cytoskeleton (smACSK) which behaves like a viscoelastic solid] and the associated signaling proteins. We hypothesize that this apparatus senses changes in both the plasma membrane curvature and the ionic strength and in turn activates signaling pathways responsible for regulatory volume increase (RVI) and regulatory volume decrease (RVD). During cell volume changes hydrostatic pressure (HP) changes drive alterations in the cell membrane curvature. HP difference has opposite directions in swelling versus shrinkage, thus allowing distinction between them. By analogy with actomyosin contractility that appears to sense stiffness of the extracellular matrix we propose that NMMII and actin polymerization can actively probe the transmembrane gradient in HP. Furthermore, NMMII and protein-protein interactions in the actin cortex are sensitive to ionic strength. Emerging data on direct binding to and regulating activities of transmembrane mechanosensors by NMMII and actin cortex provide routes for signal transduction from transmembrane mechanosensors to cell volume regulatory mechanisms.


Assuntos
Citoesqueleto de Actina/metabolismo , Membrana Celular/metabolismo , Tamanho Celular , Miosina Tipo II/metabolismo , Transdução de Sinais , Actomiosina/metabolismo , Animais , Humanos , Pressão Hidrostática
2.
Nat Commun ; 12(1): 4096, 2021 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-34215746

RESUMO

Non-centrosomal microtubule arrays serve crucial functions in cells, yet the mechanisms of their generation are poorly understood. During budding of the epithelial tubes of the salivary glands in the Drosophila embryo, we previously demonstrated that the activity of pulsatile apical-medial actomyosin depends on a longitudinal non-centrosomal microtubule array. Here we uncover that the exit from the last embryonic division cycle of the epidermal cells of the salivary gland placode leads to one centrosome in the cells losing all microtubule-nucleation capacity. This restriction of nucleation activity to the second, Centrobin-enriched, centrosome is key for proper morphogenesis. Furthermore, the microtubule-severing protein Katanin and the minus-end-binding protein Patronin accumulate in an apical-medial position only in placodal cells. Loss of either in the placode prevents formation of the longitudinal microtubule array and leads to loss of apical-medial actomyosin and impaired apical constriction. We thus propose a mechanism whereby Katanin-severing at the single active centrosome releases microtubule minus-ends that are then anchored by apical-medial Patronin to promote formation of the longitudinal microtubule array crucial for apical constriction and tube formation.


Assuntos
Divisão Celular/fisiologia , Centrossomo/metabolismo , Microtúbulos/metabolismo , Actinas , Actomiosina/metabolismo , Animais , Centrossomo/ultraestrutura , Proteínas do Citoesqueleto/metabolismo , Drosophila , Katanina , Masculino , Proteínas dos Microfilamentos/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Morfogênese , Glândulas Salivares , Tubulina (Proteína)/metabolismo
3.
Int J Mol Sci ; 22(13)2021 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-34210098

RESUMO

Muscle energetics reflects the ability of myosin motors to convert chemical energy into mechanical energy. How this process takes place remains one of the most elusive questions in the field. Here, we combined experimental measurements of in vitro sliding velocity based on DNA-origami built filaments carrying myosins with different lever arm length and Monte Carlo simulations based on a model which accounts for three basic components: (i) the geometrical hindrance, (ii) the mechano-sensing mechanism, and (iii) the biased kinetics for stretched or compressed motors. The model simulations showed that the geometrical hindrance due to acto-myosin spatial mismatching and the preferential detachment of compressed motors are synergic in generating the rapid increase in the ATP-ase rate from isometric to moderate velocities of contraction, thus acting as an energy-conservation strategy in muscle contraction. The velocity measurements on a DNA-origami filament that preserves the motors' distribution showed that geometrical hindrance and biased detachment generate a non-zero sliding velocity even without rotation of the myosin lever-arm, which is widely recognized as the basic event in muscle contraction. Because biased detachment is a mechanism for the rectification of thermal fluctuations, in the Brownian-ratchet framework, we predict that it requires a non-negligible amount of energy to preserve the second law of thermodynamics. Taken together, our theoretical and experimental results elucidate less considered components in the chemo-mechanical energy transduction in muscle.


Assuntos
Actomiosina/metabolismo , Adenosina Trifosfatases/metabolismo , Músculos/fisiologia , Animais , Humanos , Cinética , Modelos Biológicos , Método de Monte Carlo , Contração Muscular
4.
Nat Commun ; 12(1): 4595, 2021 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-34321459

RESUMO

Constriction of the cytokinetic ring, a circular structure of actin filaments, is an essential step during cell division. Mechanical forces driving the constriction are attributed to myosin motor proteins, which slide actin filaments along each other. However, in multiple organisms, ring constriction has been reported to be myosin independent. How actin rings constrict in the absence of motor activity remains unclear. Here, we demonstrate that anillin, a non-motor actin crosslinker, indispensable during cytokinesis, autonomously propels the contractility of actin bundles. Anillin generates contractile forces of tens of pico-Newtons to maximise the lengths of overlaps between bundled actin filaments. The contractility is enhanced by actin disassembly. When multiple actin filaments are arranged into a ring, this contractility leads to ring constriction. Our results indicate that passive actin crosslinkers can substitute for the activity of molecular motors to generate contractile forces in a variety of actin networks, including the cytokinetic ring.


Assuntos
Actinas/metabolismo , Proteínas Contráteis/metabolismo , Miosinas/metabolismo , Citoesqueleto de Actina/metabolismo , Actomiosina/metabolismo , Animais , Divisão Celular , Proteínas Contráteis/genética , Citocinese , Drosophila melanogaster/metabolismo , Humanos , Proteínas dos Microfilamentos
5.
Development ; 148(10)2021 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-33999996

RESUMO

Movement of epithelial cells in a tissue occurs through neighbor exchange and drives tissue shape changes. It requires intercellular junction remodeling, a process typically powered by the contractile actomyosin cytoskeleton. This has been investigated mainly in homogeneous epithelia, where intercalation takes minutes. However, in some tissues, intercalation involves different cell types and can take hours. Whether slow and fast intercalation share the same mechanisms remains to be examined. To address this issue, we used the fly eye, where the cone cells exchange neighbors over ∼10 h to shape the lens. We uncovered three pathways regulating this slow mode of cell intercalation. First, we found a limited requirement for MyosinII. In this case, mathematical modeling predicts an adhesion-dominant intercalation mechanism. Genetic experiments support this prediction, revealing a role for adhesion through the Nephrin proteins Roughest and Hibris. Second, we found that cone cell intercalation is regulated by the Notch pathway. Third, we show that endocytosis is required for membrane removal and Notch activation. Taken together, our work indicates that adhesion, endocytosis and Notch can direct slow cell intercalation during tissue morphogenesis.


Assuntos
Adesão Celular/fisiologia , Proteínas de Drosophila/metabolismo , Drosophila/embriologia , Endocitose/fisiologia , Receptores Notch/metabolismo , Retina/embriologia , Células Fotorreceptoras Retinianas Cones/metabolismo , Actomiosina/metabolismo , Junções Aderentes/fisiologia , Animais , Padronização Corporal/fisiologia , Moléculas de Adesão Celular Neuronais/metabolismo , Comunicação Celular , Proteínas de Drosophila/genética , Células Epiteliais/citologia , Proteínas do Olho/metabolismo , Adesões Focais/fisiologia , Proteínas de Membrana/metabolismo , Miosina Tipo II/metabolismo , Receptores Notch/genética , Transdução de Sinais/fisiologia
6.
Am J Physiol Cell Physiol ; 320(6): C1153-C1163, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-33881935

RESUMO

Cells adapt to applied cyclic stretch (CS) to circumvent chronic activation of proinflammatory signaling. Currently, the molecular mechanism of the selective disassembly of actin stress fibers (SFs) in the stretch direction, which occurs at the early stage of the cellular response to CS, remains controversial. Here, we suggest that the mechanosensitive behavior of myosin II, a major cross-linker of SFs, primarily contributes to the directional disassembly of the actomyosin complex SFs in bovine vascular smooth muscle cells and human U2OS osteosarcoma cells. First, we identified that CS with a shortening phase that exceeds in speed the inherent contractile rate of individual SFs leads to the disassembly. To understand the biological basis, we investigated the effect of expressing myosin regulatory light-chain mutants and found that SFs with less actomyosin activities disassemble more promptly upon CS. We consequently created a minimal mathematical model that recapitulates the salient features of the direction-selective and threshold-triggered disassembly of SFs to show that disassembly or, more specifically, unbundling of the actomyosin bundle SFs is enhanced with sufficiently fast cell shortening. We further demonstrated that similar disassembly of SFs is inducible in the presence of an active LIM-kinase-1 mutant that deactivates cofilin, suggesting that cofilin is dispensable as opposed to a previously proposed mechanism.


Assuntos
Citoesqueleto de Actina/metabolismo , Fatores de Despolimerização de Actina/metabolismo , Actinas/metabolismo , Miosina Tipo II/metabolismo , Fibras de Estresse/metabolismo , Actomiosina/metabolismo , Animais , Bovinos , Linhagem Celular Tumoral , Células Cultivadas , Proteínas do Citoesqueleto/metabolismo , Humanos , Contração Muscular/fisiologia , Músculo Liso Vascular/metabolismo , Miócitos de Músculo Liso/metabolismo , Osteossarcoma/metabolismo , Estresse Mecânico
7.
Elife ; 102021 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-33835025

RESUMO

Actomyosin contractility is regulated by Rho-GTP in cell migration, cytokinesis and morphogenesis in embryo development. Whereas Rho activation by Rho-GTP exchange factor (GEF), RhoGEF2, is well known in actomyosin contractility during cytokinesis at the base of invaginating membranes in Drosophila cellularization, Rho inhibition by RhoGTPase-activating proteins (GAPs) remains to be studied. We have found that the RhoGAP, GRAF, inhibits actomyosin contractility during cellularization. GRAF is enriched at the cleavage furrow tip during actomyosin assembly and initiation of ring constriction. Graf depletion shows increased Rho-GTP, increased Myosin II and ring hyper constriction dependent upon the loss of the RhoGTPase domain. GRAF and RhoGEF2 are present in a balance for appropriate activation of actomyosin ring constriction. RhoGEF2 depletion and abrogation of Myosin II activation in Rho kinase mutants suppress the Graf hyper constriction defect. Therefore, GRAF recruitment restricts Rho-GTP levels in a spatiotemporal manner for inhibiting actomyosin contractility during cellularization.


Assuntos
Actomiosina/metabolismo , Proteínas de Transporte/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/embriologia , Morfogênese , Animais , Proteínas de Transporte/metabolismo , Proteínas de Drosophila/metabolismo , Embrião não Mamífero/metabolismo , Desenvolvimento Embrionário
8.
Dev Biol ; 476: 128-136, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33811855

RESUMO

The basic structure of the eye, which is crucial for visual function, is established during the embryonic process of optic cup morphogenesis. Molecular pathways of specification and patterning are integrated with spatially distinct cell and tissue shape changes to generate the eye, with discrete domains and structural features: retina and retinal pigment epithelium enwrap the lens, and the optic fissure occupies the ventral surface of the eye and optic stalk. Interest in the underlying cell biology of eye morphogenesis has led to a growing body of work, combining molecular genetics and imaging to quantify cellular processes such as adhesion and actomyosin activity. These studies reveal that intrinsic machinery and spatiotemporally specific extrinsic inputs collaborate to control dynamics of cell movements and morphologies. Here we consider recent advances in our understanding of eye morphogenesis, with a focus on the mechanics of eye formation throughout vertebrate systems, including insights and potential opportunities using organoids, which may provide a tractable system to test hypotheses from embryonic models.


Assuntos
Olho/embriologia , Disco Óptico/embriologia , Actomiosina/metabolismo , Animais , Movimento Celular , Olho/metabolismo , Olho/patologia , Humanos , Cristalino/embriologia , Morfogênese/genética , Morfogênese/fisiologia , Disco Óptico/metabolismo , Organogênese/genética , Organogênese/fisiologia , Retina/embriologia , Epitélio Pigmentado da Retina/citologia , Transdução de Sinais , Vertebrados/fisiologia
9.
Dev Cell ; 56(8): 1083-1099.e5, 2021 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-33831351

RESUMO

Paracellular permeability is regulated to allow solute transport or cell migration across epithelial or endothelial barriers. However, how cell-cell junction dynamics controls paracellular permeability is poorly understood. Here, we describe patency, a developmentally regulated process in Drosophila oogenesis, during which cell vertices in the follicular epithelium open transiently to allow paracellular transport of yolk proteins for uptake by the oocyte. We show that the sequential removal of E-cadherin, N-cadherin, NCAM/Fasciclin 2, and Sidekick from vertices precedes their basal-to-apical opening, while the subsequent assembly of tricellular occluding junctions marks the termination of patency and seals the paracellular barrier. E-cadherin-based adhesion is required to limit paracellular channel size, whereas stabilized adherens junctions, prolonged NCAM/Fasciclin 2 expression, blocked endocytosis, or increased actomyosin contractility prevent patency. Our findings reveal a key role of cell vertices as gateways controlling paracellular transport and demonstrate that dynamic regulation of adhesion and actomyosin contractility at vertices governs epithelial barrier properties.


Assuntos
Drosophila melanogaster/metabolismo , Epitélio/metabolismo , Oogênese , Folículo Ovariano/metabolismo , Actomiosina/metabolismo , Junções Aderentes/metabolismo , Animais , Transporte Biológico , Adesão Celular , Moléculas de Adesão Celular/metabolismo , Permeabilidade da Membrana Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Endocitose , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Feminino , Junções Íntimas/metabolismo , Vitelogênese
10.
Nat Commun ; 12(1): 2254, 2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-33859190

RESUMO

One of the grand challenges of bottom-up synthetic biology is the development of minimal machineries for cell division. The mechanical transformation of large-scale compartments, such as Giant Unilamellar Vesicles (GUVs), requires the geometry-specific coordination of active elements, several orders of magnitude larger than the molecular scale. Of all cytoskeletal structures, large-scale actomyosin rings appear to be the most promising cellular elements to accomplish this task. Here, we have adopted advanced encapsulation methods to study bundled actin filaments in GUVs and compare our results with theoretical modeling. By changing few key parameters, actin polymerization can be differentiated to resemble various types of networks in living cells. Importantly, we find membrane binding to be crucial for the robust condensation into a single actin ring in spherical vesicles, as predicted by theoretical considerations. Upon force generation by ATP-driven myosin motors, these ring-like actin structures contract and locally constrict the vesicle, forming furrow-like deformations. On the other hand, cortex-like actin networks are shown to induce and stabilize deformations from spherical shapes.


Assuntos
Actomiosina/metabolismo , Divisão Celular/fisiologia , Modelos Biológicos , Biologia Sintética/métodos , Lipossomas Unilamelares/metabolismo , Actomiosina/genética , Actomiosina/isolamento & purificação , Animais , Linhagem Celular , Drosophila , Humanos , Microscopia Intravital , Microscopia Confocal , Modelos Moleculares , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo
11.
Nat Commun ; 12(1): 2359, 2021 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-33883558

RESUMO

How adhesive forces are transduced and integrated into biochemical signals at focal adhesions (FAs) is poorly understood. Using cells adhering to deformable micropillar arrays, we demonstrate that traction force and FAK localization as well as traction force and Y397-FAK phosphorylation are linearly coupled at individual FAs on stiff, but not soft, substrates. Similarly, FAK phosphorylation increases linearly with external forces applied to FAs using magnetic beads. This mechanosignaling coupling requires actomyosin contractility, talin-FAK binding, and full-length vinculin that binds talin and actin. Using an in vitro 3D biomimetic wound healing model, we show that force-FAK signaling coupling coordinates cell migration and tissue-scale forces to promote microtissue repair. A simple kinetic binding model of talin-FAK interactions under force can recapitulate the experimental observations. This study provides insights on how talin and vinculin convert forces into FAK signaling events regulating cell migration and tissue repair.


Assuntos
Quinase 1 de Adesão Focal/metabolismo , Adesões Focais/metabolismo , Modelos Biológicos , Actomiosina/metabolismo , Animais , Fenômenos Biomecânicos , Biomimética , Movimento Celular/fisiologia , Células Cultivadas , Fibroblastos/metabolismo , Quinase 1 de Adesão Focal/deficiência , Quinase 1 de Adesão Focal/genética , Mecanotransdução Celular , Camundongos , Camundongos Knockout , Fosforilação , RNA Interferente Pequeno/genética , Transdução de Sinais , Talina/antagonistas & inibidores , Talina/genética , Talina/metabolismo , Cicatrização/fisiologia
12.
Nat Commun ; 12(1): 2226, 2021 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-33850145

RESUMO

At the basis of cell shape and behavior, the organization of actomyosin and its ability to generate forces are widely studied. However, the precise regulation of this contractile network in space and time is unclear. Here, we study the role of the epithelial-specific protein EpCAM, a contractility modulator, in cell shape and motility. We show that EpCAM is required for stress fiber generation and front-rear polarity acquisition at the single cell level. In fact, EpCAM participates in the remodeling of a transient zone of active RhoA at the cortex of spreading epithelial cells. EpCAM and RhoA route together through the Rab35/EHD1 fast recycling pathway. This endosomal pathway spatially organizes GTP-RhoA to fine tune the activity of actomyosin resulting in polarized cell shape and development of intracellular stiffness and traction forces. Impairment of GTP-RhoA endosomal trafficking either by silencing EpCAM or by expressing Rab35/EHD1 mutants prevents proper myosin-II activity, stress fiber formation and ultimately cell polarization. Collectively, this work shows that the coupling between co-trafficking of EpCAM and RhoA, and actomyosin rearrangement is pivotal for cell spreading, and advances our understanding of how biochemical and mechanical properties promote cell plasticity.


Assuntos
Endossomos/metabolismo , Molécula de Adesão da Célula Epitelial/metabolismo , Células Epiteliais/metabolismo , Proteína rhoA de Ligação ao GTP/metabolismo , Actomiosina/metabolismo , Células CACO-2 , Movimento Celular/fisiologia , Polaridade Celular , Forma Celular , Células HeLa , Humanos , Miosina Tipo II/metabolismo , Fibras de Estresse/metabolismo
13.
Food Chem ; 356: 129655, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-33831832

RESUMO

Phosphorylation of myosin regulatory light chain (MRLC) can regulate muscle contraction and thus affect actomyosin dissociation and meat quality. The objective of this study was to explore the mechanism by how MRLC phosphorylation regulates actomyosin dissociation and thus develop strategies for improving meat quality. Here, the phosphorylation status of MRLC was modulated by myosin light chain kinase and myosin light chain kinase inhibitor. MRLC phosphorylation at Ser17 decreased the kinetic energy and total energy of actomyosin, thus stabilized the structure, facilitating the interaction between myosin and actin; this was one possible way that MRLC phosphorylation at Ser17 negatively affects actomyosin dissociation. Moreover, MRLC phosphorylation at Ser17 was beneficial to the formation of ionic bonds, hydrogen bonds, and hydrophobic interaction between myosin and actin, and was the second possible way that MRLC phosphorylation at Ser17 negatively affects actomyosin dissociation.


Assuntos
Actomiosina/metabolismo , Cadeias Leves de Miosina/metabolismo , Actinas/metabolismo , Actomiosina/química , Animais , Calorimetria , Simulação de Dinâmica Molecular , Cadeias Leves de Miosina/química , Quinase de Cadeia Leve de Miosina/metabolismo , Fosforilação , Ligação Proteica , Estrutura Terciária de Proteína , Serina/metabolismo
14.
Food Chem ; 356: 129696, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-33838605

RESUMO

This study aimed to assess the effects of acetylation levels on actomyosin disassociation and phosphorylation of lamb during incubation at 4 °C. Samples of whole proteins from lamb longissimus thoracis muscles were prepared and assigned into three treatments (high, middle and low acetylation groups). The results showed that deacetylation of myosin heavy chain and actin was inhibited by lysine deacetylase inhibitor trichostatin A and nicotinamide in this study. Phosphorylation levels of myosin heavy chain and actin were inhibited by their acetylation during incubation in vitro. Actomyosin disassociation degree in high acetylation group was significantly lower than that in middle and low acetylation groups (P < 0.05). The ATPase activity in high acetylation group was significantly higher than that in middle and low acetylation groups (P < 0.05). In conclusion, acetylation of myosin heavy chain and actin inhibited actomyosin dissociation by inhibiting their phosphorylation at 4 °C in vitro.


Assuntos
Actomiosina/metabolismo , Músculos/metabolismo , Acetilação/efeitos dos fármacos , Actinas/antagonistas & inibidores , Actinas/metabolismo , Actomiosina/antagonistas & inibidores , Animais , Sítios de Ligação , Temperatura Baixa , Ácidos Hidroxâmicos/farmacologia , Simulação de Dinâmica Molecular , Cadeias Pesadas de Miosina/antagonistas & inibidores , Cadeias Pesadas de Miosina/metabolismo , Niacinamida/farmacologia , Fosforilação , Ovinos
15.
Nat Commun ; 12(1): 1892, 2021 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-33767187

RESUMO

Plasmodium falciparum, the causative agent of malaria, moves by an atypical process called gliding motility. Actomyosin interactions are central to gliding motility. However, the details of these interactions remained elusive until now. Here, we report an atomic structure of the divergent Plasmodium falciparum actomyosin system determined by electron cryomicroscopy at the end of the powerstroke (Rigor state). The structure provides insights into the detailed interactions that are required for the parasite to produce the force and motion required for infectivity. Remarkably, the footprint of the myosin motor on filamentous actin is conserved with respect to higher eukaryotes, despite important variability in the Plasmodium falciparum myosin and actin elements that make up the interface. Comparison with other actomyosin complexes reveals a conserved core interface common to all actomyosin complexes, with an ancillary interface involved in defining the spatial positioning of the motor on actin filaments.


Assuntos
Citoesqueleto de Actina/metabolismo , Actomiosina/metabolismo , Movimento Celular/fisiologia , Plasmodium falciparum/fisiologia , Plasmodium falciparum/ultraestrutura , Actinas/metabolismo , Microscopia Crioeletrônica , Malária Falciparum/parasitologia , Miosinas/metabolismo , Conformação Proteica , Proteínas de Protozoários/metabolismo
16.
Food Chem ; 352: 129398, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-33652197

RESUMO

We investigated the effects of ultrasonic treatment (400 W, 20 kHz, 45.52 W/L) and storage time (0 d, 3 d, 7 d and 10 d) on functional properties, structural changes and in vitro digestion of actomyosin complex isolated from vacuum-packed pork. As storage time increased, turbidity, surface hydrophobicity, active sulfhydryl and total sulfhydryl of actomyosin complex increased, while protein solubility decreased. Ultrasonic treatment increased surface hydrophobicity, protein solubility and active sulfhydryl content but decreased turbidity and total sulfhydryl content compared with the control. Ultrasonic treatment caused a reduction in α-helix content on 0 day and the fluorescence intensity of tryptophan and tyrosine residues. It increased pancreatin digestibility of actomyosin complex and the number of peptides of smaller than 1 kDa. However, it decreased the number of peptides. The findings provide a new insight into the application of appropriate ultrasonic treatment to promote meat digestibility.


Assuntos
Actomiosina/química , Digestão , Armazenamento de Alimentos , Carne/análise , Ondas Ultrassônicas , Actomiosina/metabolismo , Animais , Interações Hidrofóbicas e Hidrofílicas , Solubilidade , Compostos de Sulfidrila/química , Suínos
17.
PLoS Comput Biol ; 17(2): e1008780, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33617532

RESUMO

Biomineralization is the process by which organisms use minerals to harden their tissues and provide them with physical support. Biomineralizing cells concentrate the mineral in vesicles that they secret into a dedicated compartment where crystallization occurs. The dynamics of vesicle motion and the molecular mechanisms that control it, are not well understood. Sea urchin larval skeletogenesis provides an excellent platform for investigating the kinetics of mineral-bearing vesicles. Here we used lattice light-sheet microscopy to study the three-dimensional (3D) dynamics of calcium-bearing vesicles in the cells of normal sea urchin embryos and of embryos where skeletogenesis is blocked through the inhibition of Vascular Endothelial Growth Factor Receptor (VEGFR). We developed computational tools for displaying 3D-volumetric movies and for automatically quantifying vesicle dynamics. Our findings imply that calcium vesicles perform an active diffusion motion in both, calcifying (skeletogenic) and non-calcifying (ectodermal) cells of the embryo. The diffusion coefficient and vesicle speed are larger in the mesenchymal skeletogenic cells compared to the epithelial ectodermal cells. These differences are possibly due to the distinct mechanical properties of the two tissues, demonstrated by the enhanced f-actin accumulation and myosinII activity in the ectodermal cells compared to the skeletogenic cells. Vesicle motion is not directed toward the biomineralization compartment, but the vesicles slow down when they approach it, and probably bind for mineral deposition. VEGFR inhibition leads to an increase of vesicle volume but hardly changes vesicle kinetics and doesn't affect f-actin accumulation and myosinII activity. Thus, calcium vesicles perform an active diffusion motion in the cells of the sea urchin embryo, with diffusion length and speed that inversely correlate with the strength of the actomyosin network. Overall, our studies provide an unprecedented view of calcium vesicle 3D-dynamics and point toward cytoskeleton remodeling as an important effector of the motion of mineral-bearing vesicles.


Assuntos
Biomineralização , Cálcio/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Ouriços-do-Mar/fisiologia , Actomiosina/química , Actomiosina/metabolismo , Animais , Biologia Computacional/métodos , Citoesqueleto/metabolismo , Biologia do Desenvolvimento/métodos , Difusão , Ectoderma/metabolismo , Embrião não Mamífero/metabolismo , Endocitose , Fluoresceínas/química , Cinética , Movimento (Física) , Receptores de Fatores de Crescimento do Endotélio Vascular/metabolismo
18.
Dev Cell ; 56(4): 443-460.e11, 2021 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-33621492

RESUMO

Intracellular pathogens alter their host cells' mechanics to promote dissemination through tissues. Conversely, host cells may respond to the presence of pathogens by altering their mechanics to limit infection. Here, we monitored epithelial cell monolayers infected with intracellular bacterial pathogens, Listeria monocytogenes or Rickettsia parkeri, over days. Under conditions in which these pathogens trigger innate immune signaling through NF-κB and use actin-based motility to spread non-lytically intercellularly, we found that infected cell domains formed three-dimensional mounds. These mounds resulted from uninfected cells moving toward the infection site, collectively squeezing the softer and less contractile infected cells upward and ejecting them from the monolayer. Bacteria in mounds were less able to spread laterally in the monolayer, limiting the growth of the infection focus, while extruded infected cells underwent cell death. Thus, the coordinated forceful action of uninfected cells actively eliminates large domains of infected cells, consistent with this collective cell response representing an innate immunity-driven process.


Assuntos
Competição entre as Células , Células Epiteliais/imunologia , Células Epiteliais/microbiologia , Imunidade Inata , Listeria monocytogenes/fisiologia , Listeriose/imunologia , Listeriose/microbiologia , Transdução de Sinais , Actomiosina/metabolismo , Animais , Apoptose , Fenômenos Biomecânicos , Adesão Celular , Linhagem Celular , Simulação por Computador , Cães , Interações Hospedeiro-Patógeno , Humanos , Junções Intercelulares/metabolismo , Terapia a Laser , Listeriose/genética , Células Madin Darby de Rim Canino , NF-kappa B/metabolismo , Imagem com Lapso de Tempo , Transcrição Genética
19.
Nat Mater ; 20(8): 1156-1166, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33603188

RESUMO

Actomyosin machinery endows cells with contractility at a single-cell level. However, within a monolayer, cells can be contractile or extensile based on the direction of pushing or pulling forces exerted by their neighbours or on the substrate. It has been shown that a monolayer of fibroblasts behaves as a contractile system while epithelial or neural progentior monolayers behave as an extensile system. Through a combination of cell culture experiments and in silico modelling, we reveal the mechanism behind this switch in extensile to contractile as the weakening of intercellular contacts. This switch promotes the build-up of tension at the cell-substrate interface through an increase in actin stress fibres and traction forces. This is accompanied by mechanotransductive changes in vinculin and YAP activation. We further show that contractile and extensile differences in cell activity sort cells in mixtures, uncovering a generic mechanism for pattern formation during cell competition, and morphogenesis.


Assuntos
Actomiosina/metabolismo , Fenômenos Mecânicos , Fenômenos Biomecânicos , Movimento Celular , Simulação por Computador , Modelos Biológicos
20.
Nat Commun ; 12(1): 791, 2021 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-33542237

RESUMO

Cells migrate collectively to form tissues and organs during morphogenesis. Contact inhibition of locomotion (CIL) drives collective migration by inhibiting lamellipodial protrusions at cell-cell contacts and promoting polarization at the leading edge. Here, we report a CIL-related collective cell behavior of myotubes that lack lamellipodial protrusions, but instead use filopodia to move as a cohesive cluster in a formin-dependent manner. We perform genetic, pharmacological and mechanical perturbation analyses to reveal the essential roles of Rac2, Cdc42 and Rho1 in myotube migration. These factors differentially control protrusion dynamics and cell-matrix adhesion formation. We also show that active Rho1 GTPase localizes at retracting free edge filopodia and that Rok-dependent actomyosin contractility does not mediate a contraction of protrusions at cell-cell contacts, but likely plays an important role in the constriction of supracellular actin cables. Based on these findings, we propose that contact-dependent asymmetry of cell-matrix adhesion drives directional movement, whereas contractile actin cables contribute to the integrity of the migrating cell cluster.


Assuntos
Movimento Celular/fisiologia , Morfogênese/fisiologia , Fibras Musculares Esqueléticas/fisiologia , Pseudópodes/metabolismo , Citoesqueleto de Actina/metabolismo , Actomiosina/metabolismo , Animais , Caderinas/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Proteínas de Ligação ao GTP/metabolismo , Microscopia Intravital , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas rho de Ligação ao GTP/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...