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1.
Phys Rev Lett ; 124(11): 118002, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32242707

RESUMO

Motivated by the dynamics of particles embedded in active gels, both in vitro and inside the cytoskeleton of living cells, we study an active generalization of the classical trap model. We demonstrate that activity leads to dramatic modifications in the diffusion compared to the thermal case: the mean square displacement becomes subdiffusive, spreading as a power law in time, when the trap depth distribution is a Gaussian and is slower than any power law when it is drawn from an exponential distribution. The results are derived for a simple, exactly solvable, case of harmonic traps. We then argue that the results are robust for more realistic trap shapes when the activity is strong.


Assuntos
Biopolímeros/química , Modelos Químicos , Citoesqueleto de Actina/química , Trifosfato de Adenosina/química , Difusão , Géis/química , Miosina Tipo II/química
2.
Proc Natl Acad Sci U S A ; 117(5): 2506-2512, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31964823

RESUMO

Blebs and pseudopods can both power cell migration, with blebs often favored in tissues, where cells encounter increased mechanical resistance. To investigate how migrating cells detect and respond to mechanical forces, we used a "cell squasher" to apply uniaxial pressure to Dictyostelium cells chemotaxing under soft agarose. As little as 100 Pa causes a rapid (<10 s), sustained shift to movement with blebs rather than pseudopods. Cells are flattened under load and lose volume; the actin cytoskeleton is reorganized, with myosin II recruited to the cortex, which may pressurize the cytoplasm for blebbing. The transition to bleb-driven motility requires extracellular calcium and is accompanied by increased cytosolic calcium. It is largely abrogated in cells lacking the Piezo stretch-operated channel; under load, these cells persist in using pseudopods and chemotax poorly. We propose that migrating cells sense pressure through Piezo, which mediates calcium influx, directing movement with blebs instead of pseudopods.


Assuntos
Dictyostelium/citologia , Dictyostelium/metabolismo , Canais Iônicos/metabolismo , Proteínas de Protozoários/metabolismo , Pseudópodes/metabolismo , Fenômenos Biomecânicos , Movimento Celular , Citoplasma/química , Citoplasma/genética , Citoplasma/metabolismo , Dictyostelium/química , Dictyostelium/genética , Canais Iônicos/genética , Mecanotransdução Celular , Miosina Tipo II/genética , Miosina Tipo II/metabolismo , Pressão , Proteínas de Protozoários/genética , Pseudópodes/genética
3.
Arch Biochem Biophys ; 680: 108228, 2020 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-31843643

RESUMO

Myosin II molecules in the thick filaments of striated muscle form a structure in which the heads interact with each other and fold back onto the tail. This structure, the "interacting heads motif" (IHM), provides a mechanistic basis for the auto-inhibition of myosin in relaxed thick filaments. Similar IHM interactions occur in single myosin molecules of smooth and nonmuscle cells in the switched-off state. In addition to the interaction between the two heads, which inhibits their activity, the IHM also contains an interaction between the motor domain of one head and the initial part (subfragment 2, S2) of the tail. This is thought to be a crucial anchoring interaction that holds the IHM in place on the thick filament. S2 appears to cross the head at a specific location within a broader region of the motor domain known as the myosin mesa. Here, we show that the positive and negative charge distribution in this part of the mesa is complementary to the charge distribution on S2. We have designated this the "mesa trail" owing to its linear path across the mesa. We studied the structural sequence alignment, the location of charged residues on the surface of myosin head atomic models, and the distribution of surface charge potential along the mesa trail in different types of myosin II and in different species. The charge distribution in both the mesa trail and the adjacent S2 is relatively conserved. This suggests a common basis for IHM formation across different myosin IIs, dependent on attraction between complementary charged patches on S2 and the myosin head. Conservation from mammals to insects suggests that the mesa trail/S2 interaction plays a key role in the inhibitory function of the IHM.


Assuntos
Miosina Tipo II/metabolismo , Animais , Aracnídeos/química , Aracnídeos/metabolismo , Proteínas de Artrópodes/química , Proteínas de Artrópodes/metabolismo , Dictyostelium/química , Dictyostelium/metabolismo , Insetos , Mamíferos , Modelos Moleculares , Miosina Tipo II/química , Domínios e Motivos de Interação entre Proteínas , Proteínas de Protozoários/química , Proteínas de Protozoários/metabolismo , Especificidade da Espécie
4.
Proc Natl Acad Sci U S A ; 117(1): 432-438, 2020 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-31871203

RESUMO

Cadherin-mediated cell-cell adhesion is actin-dependent, but the precise role of actin in maintaining cell-cell adhesion is not fully understood. Actin polymerization-dependent protrusive activity is required to push distally separated cells close enough to initiate contact. Whether protrusive activity is required to maintain adhesion in confluent sheets of epithelial cells is not known. By electron microscopy as well as live cell imaging, we have identified a population of protruding actin microspikes that operate continuously near apical junctions of polarized Madin-Darby canine kidney (MDCK) cells. Live imaging shows that microspikes containing E-cadherin extend into gaps between E-cadherin clusters on neighboring cells, while reformation of cadherin clusters across the cell-cell boundary correlates with microspike withdrawal. We identify Arp2/3, EVL, and CRMP-1 as 3 actin assembly factors necessary for microspike formation. Depleting these factors from cells using RNA interference (RNAi) results in myosin II-dependent unzipping of cadherin adhesive bonds. Therefore, actin polymerization-dependent protrusive activity operates continuously at cadherin cell-cell junctions to keep them shut and to prevent myosin II-dependent contractility from tearing cadherin adhesive contacts apart.


Assuntos
Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Actinas/metabolismo , Junções Aderentes/metabolismo , Caderinas/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Fosfoproteínas/metabolismo , Junções Íntimas/metabolismo , Citoesqueleto de Actina/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Junções Aderentes/ultraestrutura , Animais , Adesão Celular , Cães , Microscopia Intravital , Células Madin Darby de Rim Canino , Microscopia Eletrônica , Miosina Tipo II/metabolismo , Proteínas do Tecido Nervoso/genética , Fosfoproteínas/genética , Interferência de RNA , Junções Íntimas/ultraestrutura
5.
Nat Commun ; 10(1): 5200, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31729365

RESUMO

The regulation of actin dynamics is essential for various cellular processes. Former evidence suggests a correlation between the function of non-conventional myosin motors and actin dynamics. Here we investigate the contribution of myosin 1b to actin dynamics using sliding motility assays. We observe that sliding on myosin 1b immobilized or bound to a fluid bilayer enhances actin depolymerization at the barbed end, while sliding on myosin II, although 5 times faster, has no effect. This work reveals a non-conventional myosin motor as another type of depolymerase and points to its singular interactions with the actin barbed end.


Assuntos
Actinas/química , Actinas/metabolismo , Miosina Tipo I/metabolismo , Citoesqueleto de Actina/enzimologia , Citoesqueleto de Actina/metabolismo , Actinas/genética , Animais , Humanos , Miosina Tipo I/genética , Miosina Tipo II/química , Miosina Tipo II/genética , Miosina Tipo II/metabolismo , Polimerização , Coelhos
6.
ACS Appl Mater Interfaces ; 11(49): 45520-45530, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31714734

RESUMO

Recent studies have found discordant mechanosensitive outcomes when comparing 2D and 3D, highlighting the need for tools to study mechanotransduction in 3D across a wide spectrum of stiffness. A gelatin methacryloyl (GelMA) hydrogel with a continuous stiffness gradient ranging from 5 to 38 kPa was developed to recapitulate physiological stiffness conditions. Adipose-derived stem cells (ASCs) were encapsulated in this hydrogel, and their morphological characteristics and expression of both mechanosensitive proteins (Lamin A, YAP, and MRTFa) and differentiation markers (PPARγ and RUNX2) were analyzed. Low-stiffness regions (∼8 kPa) permitted increased cellular and nuclear volume and enhanced mechanosensitive protein localization in the nucleus. This trend was reversed in high stiffness regions (∼30 kPa), where decreased cellular and nuclear volumes and reduced mechanosensitive protein nuclear localization were observed. Interestingly, cells in soft regions exhibited enhanced osteogenic RUNX2 expression, while those in stiff regions upregulated the adipogenic regulator PPARγ, suggesting that volume, not substrate stiffness, is sufficient to drive 3D stem cell differentiation. Inhibition of myosin II (Blebbistatin) and ROCK (Y-27632), both key drivers of actomyosin contractility, resulted in reduced cell volume, especially in low-stiffness regions, causing a decorrelation between volume expansion and mechanosensitive protein localization. Constitutively active and inactive forms of the canonical downstream mechanotransduction effector TAZ were stably transfected into ASCs. Activated TAZ resulted in higher cellular volume despite increasing stiffness and a consistent, stiffness-independent translocation of YAP and MRTFa into the nucleus. Thus, volume adaptation as a function of 3D matrix stiffness can control stem cell mechanotransduction and differentiation.


Assuntos
Adipogenia/genética , Diferenciação Celular/efeitos dos fármacos , Mecanotransdução Celular/genética , Osteogênese/genética , Citoesqueleto de Actina/genética , Actomiosina/genética , Adipogenia/efeitos dos fármacos , Amidas/farmacologia , Proteínas de Ciclo Celular/genética , Diferenciação Celular/genética , Encapsulamento de Células/métodos , Núcleo Celular/química , Tamanho Celular/efeitos dos fármacos , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Gelatina/química , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Humanos , Hidrogéis/química , Hidrogéis/farmacologia , Lamina Tipo A/genética , Células-Tronco Mesenquimais/citologia , Miosina Tipo II/genética , PPAR gama/genética , Piridinas/farmacologia , Transativadores/genética , Fatores de Transcrição/genética , Quinases Associadas a rho/genética
7.
EMBO Rep ; 20(12): e47755, 2019 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-31663248

RESUMO

The spatial and temporal dynamics of cell contractility plays a key role in tissue morphogenesis, wound healing, and cancer invasion. Here, we report a simple optochemical method to induce cell contractions in vivo during Drosophila morphogenesis at single-cell resolution. We employed the photolabile Ca2+ chelator o-nitrophenyl EGTA to induce bursts of intracellular free Ca2+ by laser photolysis in the epithelial tissue. Ca2+ bursts appear within seconds and are restricted to individual target cells. Cell contraction reliably followed within a minute, causing an approximately 50% drop in the cross-sectional area. Increased Ca2+ levels are reversible, and the target cells further participated in tissue morphogenesis. Depending on Rho kinase (ROCK) activity but not RhoGEF2, cell contractions are paralleled with non-muscle myosin II accumulation in the apico-medial cortex, indicating that Ca2+ bursts trigger non-muscle myosin II activation. Our approach can be, in principle, adapted to many experimental systems and species, as no specific genetic elements are required.


Assuntos
Drosophila melanogaster/citologia , Células Epiteliais/fisiologia , Animais , Animais Geneticamente Modificados , Fenômenos Biomecânicos , Quelantes de Cálcio/farmacologia , Sinalização do Cálcio/efeitos dos fármacos , Sinalização do Cálcio/fisiologia , Forma Celular/efeitos dos fármacos , Forma Celular/fisiologia , Proteínas de Drosophila/fisiologia , Drosophila melanogaster/genética , Drosophila melanogaster/fisiologia , Ácido Egtázico/análogos & derivados , Ácido Egtázico/farmacologia , Células Epiteliais/citologia , Células Epiteliais/efeitos dos fármacos , Feminino , Miosina Tipo II/fisiologia , Processos Fotoquímicos , Análise de Célula Única , Análise Espaço-Temporal
10.
Essays Biochem ; 63(5): 497-508, 2019 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-31551323

RESUMO

All is flux, nothing stays still. Heraclitus of Ephesus' characterization of the universe holds true for cells within animals and for proteins within cells. In this review, we examine the dynamics of actin and non-muscle myosin II within cells, and how their dynamics power the movement of cells within tissues. The 3D environment that migrating cells encounter along their path also changes over time, and cells can adopt various mechanisms of motility, depending on the topography, mechanics and chemical composition of their surroundings. We describe the differential spatio-temporal regulation of actin and myosin II-mediated contractility in mesenchymal, lobopodial, amoeboid, and swimming modes of cell migration. After briefly reviewing the biochemistry of myosin II, we discuss the role actomyosin contractility plays in the switch between modes of 3D migration that cells use to adapt to changing environments.


Assuntos
Movimento Celular/fisiologia , Miosina Tipo II/metabolismo , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Animais , Humanos , Pseudópodes/metabolismo
11.
Cell Biochem Biophys ; 77(4): 357-366, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31562588

RESUMO

This study aimed to investigate for the first time, the profile of Physarum microplasmodial phosphatase (PPH) activity toward the phosphorylated light chain of Physarum myosin II (PLCM) at pH 7.6, the velocity of cytoplasmic streaming, and PPH expression in spherule formation during dark starvation (DS). In this study, we cloned the full-length cDNA of PPH using polymerase chain reaction, based on the N-terminal amino acid sequence of the purified enzyme. The cDNA contained an open reading frame (ORF) of 1245 bp, corresponding to 415 amino acids. We confirmed that a rapid increase in PPH activity toward PLCM and a rapid decrease in cytoplasmic streaming velocity precede spherule formation by Physarum microplasmodia. The profiles of increase in PPH activity toward PLCM, PPH expression, and PPH accumulation during DS were correlated with spherule formation in the Physarum microplasmodia. Moreover, application of the wheat germ cell-free expression system resulted in the successful production of recombinant PPH and in the expression of phosphatase activity toward PLCM. These results suggest that PPH is involved in the cessation of cytoplasmic streaming in Physarum microplasmodia during DS.


Assuntos
Corrente Citoplasmática/fisiologia , Monoéster Fosfórico Hidrolases/metabolismo , Physarum/enzimologia , Proteínas de Protozoários/metabolismo , Sequência de Aminoácidos , Clonagem Molecular , Miosina Tipo II/metabolismo , Monoéster Fosfórico Hidrolases/química , Monoéster Fosfórico Hidrolases/genética , Fosforilação , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação
12.
F1000Res ; 82019.
Artigo em Inglês | MEDLINE | ID: mdl-31497286

RESUMO

Myosin 2 plays a central role in numerous, fundamental, actin-based biological processes, including cell migration, cell division, and the adhesion of cells to substrates and other cells. Here, we highlight recent studies in which the forces created by actomyosin 2 have been shown to also impact tension-sensitive ion channels and cell metabolism.


Assuntos
Actomiosina/fisiologia , Canais Iônicos/fisiologia , Miosina Tipo II/fisiologia , Adesão Celular , Divisão Celular , Movimento Celular , Humanos
13.
Nature ; 572(7770): 467-473, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31413363

RESUMO

Tissue morphogenesis arises from coordinated changes in cell shape driven by actomyosin contractions. Patterns of gene expression regionalize cell behaviours by controlling actomyosin contractility. Here we report two modes of control over Rho1 and myosin II (MyoII) activation in the Drosophila endoderm. First, Rho1-MyoII are induced in a spatially restricted primordium via localized transcription of the G-protein-coupled receptor ligand Fog. Second, a tissue-scale wave of Rho1-MyoII activation and cell invagination progresses anteriorly away from the primordium. The wave does not require sustained gene transcription, and is not governed by regulated Fog delivery. Instead, MyoII inhibition blocks Rho1 activation and propagation, revealing a mechanical feedback driven by MyoII. We find that MyoII activation and invagination in each row of cells drives adhesion to the vitelline membrane mediated by integrins, apical spreading, MyoII activation and invagination in the next row. Endoderm morphogenesis thus emerges from local transcriptional initiation and a mechanically driven cycle of cell deformation.


Assuntos
Drosophila melanogaster/embriologia , Drosophila melanogaster/genética , Morfogênese/genética , Ativação Transcricional , Animais , Adesão Celular , Forma Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Endoderma/citologia , Endoderma/embriologia , Endoderma/metabolismo , Integrinas/metabolismo , Miosina Tipo II/metabolismo , Membrana Vitelina/metabolismo , Proteínas rho de Ligação ao GTP/metabolismo
14.
Integr Biol (Camb) ; 11(6): 280-292, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-31365063

RESUMO

We used particle-based computer simulations to study the emergent properties of the actomyosin cytoskeleton. Our model accounted for biophysical interactions between filamentous actin and non-muscle myosin II and was motivated by recent experiments demonstrating that spatial regulation of myosin activity is required for fibroblasts responding to spatial gradients of platelet derived growth factor (PDGF) to undergo chemotaxis. Our simulations revealed the spontaneous formation of actin asters, consistent with the punctate actin structures observed in chemotacting fibroblasts. We performed a systematic analysis of model parameters to identify biochemical steps in myosin activity that significantly affect aster formation and performed simulations in which model parameter values vary spatially to investigate how the model responds to chemical gradients. Interestingly, spatial variations in motor stiffness generated time-dependent behavior of the actomyosin network, in which actin asters continued to spontaneously form and dissociate in different regions of the gradient. Our results should serve as a guide for future experimental investigations.


Assuntos
Citoesqueleto de Actina/metabolismo , Actomiosina/fisiologia , Quimiotaxia , Simulação por Computador , Fibroblastos/citologia , Animais , Movimento Celular , Humanos , Modelos Biológicos , Miosina Tipo II/metabolismo , Reconhecimento Automatizado de Padrão , Fator de Crescimento Derivado de Plaquetas/metabolismo , Transdução de Sinais
15.
Mol Biol Cell ; 30(19): 2490-2502, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31390285

RESUMO

Collective cell migration is emerging as a major driver of embryonic development, organogenesis, tissue homeostasis, and tumor dissemination. In contrast to individually migrating cells, collectively migrating cells maintain cell-cell adhesions and coordinate direction-sensing as they move. While nonmuscle myosin II has been studied extensively in the context of cells migrating individually in vitro, its roles in cells migrating collectively in three-dimensional, native environments are not fully understood. Here we use genetics, Airyscan microscopy, live imaging, optogenetics, and Förster resonance energy transfer to probe the localization, dynamics, and functions of myosin II in migrating border cells of the Drosophila ovary. We find that myosin accumulates transiently at the base of protrusions, where it functions to retract them. E-cadherin and myosin colocalize at border cell-border cell contacts and cooperate to transmit directional information. A phosphomimetic form of myosin is sufficient to convert border cells to a round morphology and blebbing migration mode. Together these studies demonstrate that distinct and dynamic pools of myosin II regulate protrusion dynamics within and between collectively migrating cells and suggest a new model for the role of protrusions in collective direction sensing in vivo.


Assuntos
Movimento Celular/fisiologia , Miosina Tipo II/metabolismo , Ovário/metabolismo , Actomiosina/metabolismo , Animais , Adesão Celular , Polaridade Celular/fisiologia , Proteínas do Citoesqueleto , Drosophila/metabolismo , Proteínas de Drosophila/metabolismo , Células Epiteliais/metabolismo , Feminino , Miosina Tipo II/fisiologia , Miosinas/metabolismo , Miosinas/fisiologia , Oogênese/fisiologia
16.
Commun Biol ; 2: 298, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31396578

RESUMO

Piezo channels transduce mechanical stimuli into electrical and chemical signals to powerfully influence development, tissue homeostasis, and regeneration. Studies on Piezo1 have largely focused on transduction of "outside-in" mechanical forces, and its response to internal, cell-generated forces remains poorly understood. Here, using measurements of endogenous Piezo1 activity and traction forces in native cellular conditions, we show that cellular traction forces generate spatially-restricted Piezo1-mediated Ca2+ flickers in the absence of externally-applied mechanical forces. Although Piezo1 channels diffuse readily in the plasma membrane and are widely distributed across the cell, their flicker activity is enriched near force-producing adhesions. The mechanical force that activates Piezo1 arises from Myosin II phosphorylation by Myosin Light Chain Kinase. We propose that Piezo1 Ca2+ flickers allow spatial segregation of mechanotransduction events, and that mobility allows Piezo1 channels to explore a large number of mechanical microdomains and thus respond to a greater diversity of mechanical cues.


Assuntos
Sinalização do Cálcio , Cálcio/metabolismo , Fibroblastos/metabolismo , Canais Iônicos/metabolismo , Mecanotransdução Celular , Miosina Tipo II/metabolismo , Células-Tronco Neurais/metabolismo , Animais , Células Cultivadas , Humanos , Canais Iônicos/deficiência , Canais Iônicos/genética , Masculino , Camundongos Knockout , Fatores de Tempo
17.
EMBO Rep ; 20(8): e47047, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31379129

RESUMO

We identify a novel endothelial membrane behaviour in transgenic zebrafish. Cerebral blood vessels extrude large transient spherical structures that persist for an average of 23 min before regressing into the parent vessel. We term these structures "kugeln", after the German for sphere. Kugeln are only observed arising from the cerebral vessels and are present as late as 28 days post fertilization. Kugeln do not communicate with the vessel lumen and can form in the absence of blood flow. They contain little or no cytoplasm, but the majority are highly positive for nitric oxide reactivity. Kugeln do not interact with brain lymphatic endothelial cells (BLECs) and can form in their absence, nor do they perform a scavenging role or interact with macrophages. Inhibition of actin polymerization, Myosin II, or Notch signalling reduces kugel formation, while inhibition of VEGF or Wnt dysregulation (either inhibition or activation) increases kugel formation. Kugeln represent a novel Notch-dependent NO-containing endothelial organelle restricted to the cerebral vessels, of currently unknown function.


Assuntos
Vasos Sanguíneos/citologia , Encéfalo/citologia , Células Endoteliais/ultraestrutura , Regulação da Expressão Gênica no Desenvolvimento , Neovascularização Fisiológica/genética , Peixe-Zebra/embriologia , Actinas/antagonistas & inibidores , Actinas/genética , Actinas/metabolismo , Animais , Animais Geneticamente Modificados , Vasos Sanguíneos/embriologia , Vasos Sanguíneos/metabolismo , Vasos Sanguíneos/ultraestrutura , Encéfalo/irrigação sanguínea , Encéfalo/embriologia , Encéfalo/metabolismo , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Circulação Cerebrovascular/genética , Embrião não Mamífero , Células Endoteliais/metabolismo , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Miosina Tipo II/antagonistas & inibidores , Miosina Tipo II/genética , Miosina Tipo II/metabolismo , Óxido Nítrico/metabolismo , Organelas/metabolismo , Organelas/ultraestrutura , Polimerização/efeitos dos fármacos , Receptores Notch/genética , Receptores Notch/metabolismo , Transdução de Sinais , Tiazolidinas/farmacologia , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismo , Proteínas Wnt/genética , Proteínas Wnt/metabolismo , Peixe-Zebra/genética , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
18.
Cells ; 8(8)2019 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-31382444

RESUMO

It has been demonstrated that geometry can affect cell behaviors. Though curvature-sensitive proteins at the nanoscale are studied, it is unclear how cells sense curvature at the cellular and multicellular levels. To characterize and determine the mechanisms of curvature-dependent cell behaviors, we grow cells on open channels of the 60-µm radius. We found that cortical F-actin is 1.2-fold more enriched in epithelial cells grown on the curved surface compared to the flat control. We observed that myosin activity is required to promote cortical F-actin formation. Furthermore, cell-cell contact was shown to be indispensable for curvature-dependent cortical actin assembly. Our results indicate that the actomyosin network coupled with adherens junctions is involved in curvature-sensing at the multi-cellular level.


Assuntos
Actinas/metabolismo , Caderinas/metabolismo , Adesão Celular/fisiologia , Células Epiteliais , Glândulas Mamárias Animais/citologia , Miosina Tipo II/metabolismo , Citoesqueleto de Actina/ultraestrutura , Junções Aderentes , Animais , Linhagem Celular , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Epitélio/ultraestrutura , Feminino , Humanos
19.
J Biol Chem ; 294(39): 14267-14278, 2019 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-31387944

RESUMO

Striated muscle myosins are encoded by a large gene family in all mammals, including humans. These isoforms define several of the key characteristics of the different striated muscle fiber types, including maximum shortening velocity. We have previously used recombinant isoforms of the motor domains of seven different human myosin isoforms to define the actin·myosin cross-bridge cycle in solution. Here, we present data on an eighth isoform, the perinatal, which has not previously been characterized. The perinatal is distinct from the embryonic isoform, appearing to have features in common with the adult fast-muscle isoforms, including weak affinity of ADP for actin·myosin and fast ADP release. We go on to use a recently developed modeling approach, MUSICO, to explore how well the experimentally defined cross-bridge cycles for each isoform in solution can predict the characteristics of muscle fiber contraction, including duty ratio, shortening velocity, ATP economy, and load dependence of these parameters. The work shows that the parameters of the cross-bridge cycle predict many of the major characteristics of each muscle fiber type and raises the question of what sequence changes are responsible for these characteristics.


Assuntos
Adaptação Fisiológica , Contração Muscular , Miosina Tipo II/metabolismo , Difosfato de Adenosina/metabolismo , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Linhagem Celular , Humanos , Camundongos , Músculos/metabolismo , Músculos/fisiologia , Miosina Tipo II/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo
20.
Nat Commun ; 10(1): 2951, 2019 07 04.
Artigo em Inglês | MEDLINE | ID: mdl-31273212

RESUMO

Epithelial-mesenchymal transition (EMT) is an essential process both in physiological and pathological contexts. Intriguingly, EMT is often associated with tissue invagination during development; however, the impact of EMT on tissue remodeling remain unexplored. Here, we show that at the initiation of the EMT process, cells produce an apico-basal force, orthogonal to the surface of the epithelium, that constitutes an important driving force for tissue invagination in Drosophila. When EMT is ectopically induced, cells starting their delamination generate an orthogonal force and induce ectopic folding. Similarly, during mesoderm invagination, cells undergoing EMT generate an apico-basal force through the formation of apico-basal structures of myosin II. Using both laser microdissection and in silico physical modelling, we show that mesoderm invagination does not proceed if apico-basal forces are impaired, indicating that they constitute driving forces in the folding process. Altogether, these data reveal the mechanical impact of EMT on morphogenesis.


Assuntos
Drosophila melanogaster/embriologia , Transição Epitelial-Mesenquimal , Epitélio/embriologia , Morfogênese , Animais , Polaridade Celular , Simulação por Computador , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Embrião não Mamífero/citologia , Embrião não Mamífero/metabolismo , Epitélio/metabolismo , Mesoderma/citologia , Mesoderma/embriologia , Mesoderma/metabolismo , Modelos Moleculares , Miosina Tipo II/metabolismo
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