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1.
Science ; 368(6496): 1205-1210, 2020 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-32527825

RESUMO

Cell migration is driven by local membrane protrusion through directed polymerization of F-actin at the front. However, F-actin next to the plasma membrane also tethers the membrane and thus resists outgoing protrusions. Here, we developed a fluorescent reporter to monitor changes in the density of membrane-proximal F-actin (MPA) during membrane protrusion and cell migration. Unlike the total F-actin concentration, which was high in the front of migrating cells, MPA density was low in the front and high in the back. Back-to-front MPA density gradients were controlled by higher cofilin-mediated turnover of F-actin in the front. Furthermore, nascent membrane protrusions selectively extended outward from areas where MPA density was reduced. Thus, locally low MPA density directs local membrane protrusions and stabilizes cell polarization during cell migration.


Assuntos
Actinas/metabolismo , Movimento Celular , Extensões da Superfície Celular , Actinas/química , Actinas/genética , Membrana Celular , Polaridade Celular , Proteínas de Fluorescência Verde/química , Proteínas de Fluorescência Verde/genética , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos
2.
Commun Biol ; 2: 427, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31799429

RESUMO

Brain stem cells stop dividing in late Drosophila embryos and begin dividing again in early larvae after feeding induces reactivation. Quiescent neural stem cells (qNSCs) display an unusual cytoplasmic protrusion that is no longer present in reactivated NSCs. The protrusions join the qNSCs to the neuropil, brain regions that are thought to maintain NSCs in an undifferentiated state, but the function of the protrusions is not known. Here we show that qNSC protrusions contain clustered mitochondria that are likely maintained in position by slow forward-and-backward microtubule growth. Larvae treated with a microtubule-stabilizing drug show bundled microtubules and enhanced mitochondrial clustering in NSCs, together with reduced qNSC reactivation. We further show that intestinal stem cells contain mitochondria-enriched protrusions. The qNSC and intestinal stem-cell protrusions differ from previously reported cytoplasmic extensions by forming stem-cell-to-niche mitochondrial bridges that could potentially both silence genes and sense signals from the stem cell niche.


Assuntos
Células-Tronco Adultas/metabolismo , Encéfalo/citologia , Encéfalo/metabolismo , Extensões da Superfície Celular/metabolismo , Mucosa Intestinal/citologia , Mucosa Intestinal/metabolismo , Mitocôndrias/metabolismo , Células-Tronco Adultas/ultraestrutura , Animais , Extensões da Superfície Celular/ultraestrutura , Drosophila , Imunofluorescência , Microscopia de Fluorescência , Microtúbulos/metabolismo
3.
Int J Mol Sci ; 20(22)2019 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-31718063

RESUMO

Increasing evidence during the past two decades shows that cells interconnect and communicate through cytonemes. These cytoskeleton-driven extensions of specialized membrane territories are involved in cell-cell signaling in development, patterning, and differentiation, but also in the maintenance of adult tissue homeostasis, tissue regeneration, and cancer. Brain tumor cells in glioblastoma extend ultralong membrane protrusions (named tumor microtubes, TMs), which contribute to invasion, proliferation, radioresistance, and tumor progression. Here we review the mechanisms underlying cytoneme formation, regulation, and their roles in cell signaling and communication in epithelial cells and other cell types. Furthermore, we discuss the recent discovery of glial cytonemes in the Drosophila glial cells that alter Wingless (Wg)/Frizzled (Fz) signaling between glia and neurons. Research on cytoneme formation, maintenance, and cell signaling mechanisms will help to better understand not only physiological developmental processes and tissue homeostasis but also cancer progression.


Assuntos
Carcinogênese/metabolismo , Comunicação Celular , Extensões da Superfície Celular/metabolismo , Células Epiteliais/metabolismo , Citoesqueleto de Actina/metabolismo , Animais , Drosophila , Células Epiteliais/citologia , Transdução de Sinais
4.
Nat Commun ; 10(1): 4073, 2019 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-31501427

RESUMO

Several antitumor therapies work by increasing reactive oxygen species (ROS) within the tumor micromilieu. Here, we reveal that L-plastin (LPL), an established tumor marker, is reversibly regulated by ROS-induced thiol oxidation on Cys101, which forms a disulfide bridge with Cys42. LPL reduction is mediated by the Thioredoxin1 (TRX1) system, as shown by TRX1 trapping, TRX1 knockdown and blockade of Thioredoxin1 reductase (TRXR1) with auranofin. LPL oxidation diminishes its actin-bundling capacity. Ratiometric imaging using an LPL-roGFP-Orp1 fusion protein and a dimedone-based proximity ligation assay (PLA) reveal that LPL oxidation occurs primarily in actin-based cellular extrusions and strongly inhibits cell spreading and filopodial extension formation in tumor cells. This effect is accompanied by decreased tumor cell migration, invasion and extracellular matrix (ECM) degradation. Since LPL oxidation occurs following treatment of tumors with auranofin or γ-irradiation, it may be a molecular mechanism contributing to the effectiveness of tumor treatment with redox-altering therapies.


Assuntos
Actinas/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas dos Microfilamentos/metabolismo , Neoplasias/metabolismo , Alquilação , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Extensões da Superfície Celular/metabolismo , Cisteína/metabolismo , Matriz Extracelular/efeitos dos fármacos , Matriz Extracelular/metabolismo , Humanos , Peróxido de Hidrogênio/toxicidade , Modelos Biológicos , Mutação/genética , Oxirredução , Compostos de Sulfidrila/metabolismo , Tiorredoxina Redutase 1/metabolismo
5.
Int Wound J ; 16(6): 1457-1463, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31486290

RESUMO

In the present study, the age- and sex-related differences in platelet ultrastructure were investigated using transmission electron microscopy (TEM). A total of 15 healthy volunteers were grouped according to age, with 5 people in each of the following groups: young group (25-45 years), middle-aged group (46-65 years), and old-aged group (> 65 years). In the TEM micrographs, the internal components, specifically the α-granules, dense granules, and lysosomal granules, of 20 platelets were counted for each group. Two-way analysis of variance of age and sex variance was used to compare the results. The ultrastructure of the platelets in the old-aged group was observed to be quite different from those of the young and middle-aged groups. Specifically, with ageing, the platelet membrane becomes more irregular in shape and non-smooth, and multiple platelet membrane ruptures are observed. Furthermore, the pseudopodia and protuberances become more numerous and slender, and the number of α-granules is significantly reduced. These morphological changes indicate that ageing may affect the function of platelets, which in turn affects the efficacy of platelet concentrates. Thus, the effects of age should be considered when using platelet concentrates prepared from elderly autologous blood.


Assuntos
Envelhecimento , Plaquetas/ultraestrutura , Adulto , Idoso , Membrana Celular/ultraestrutura , Extensões da Superfície Celular/ultraestrutura , Grânulos Citoplasmáticos/ultraestrutura , Feminino , Voluntários Saudáveis , Humanos , Masculino , Microscopia Eletrônica de Transmissão , Pessoa de Meia-Idade
6.
J Microencapsul ; 36(5): 421-431, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31401914

RESUMO

This work describes viability and distribution of INS-1E beta cells in shell-crosslinked alginate capsules, focussing on cells located near the capsule surface. Capsules were formed by air-shearing alginate suspensions of INS-1E cells into a gelling bath, and coating with poly-l-lysine (PLL) and 50% hydrolysed poly(methylvinylether-alt-maleic anhydride) to form crosslinked networks reinforcing the capsule surfaces. The percentage of cells at the capsule surface were determined using 2D and 3D confocal colocalization mapping. Encapsulated INS-1E cells showed high cell viability and progressive cell clustering out to six weeks. About 30% of cells were initially colocated with the 20 micrometer thick alginate-PLL-PMM50 shell, with 7% of cells protruded at the capsule surfaces, both reflecting random cell distributions. Protruding cells may cause cell-based immune responses, weaken capsules, and potentially result in cell escape from the capsules. The data shown indicate that reinforcing capsules with crosslinked shells may assist in preventing cell exposure and escape.


Assuntos
Alginatos/química , Células Imobilizadas/citologia , Reagentes para Ligações Cruzadas/química , Células Secretoras de Insulina/citologia , Polilisina/análogos & derivados , Animais , Cápsulas/química , Linhagem Celular , Extensões da Superfície Celular/ultraestrutura , Sobrevivência Celular , Células Imobilizadas/ultraestrutura , Géis/química , Células Secretoras de Insulina/ultraestrutura , Anidridos Maleicos/química , Polilisina/química , Ratos
7.
Elife ; 82019 07 10.
Artigo em Inglês | MEDLINE | ID: mdl-31290739

RESUMO

Localization of RNAs to various subcellular destinations is a widely used mechanism that regulates a large proportion of transcripts in polarized cells. In many cases, such localized transcripts mediate spatial control of gene expression by being translationally silent while in transit and locally activated at their destination. Here, we investigate the translation of RNAs localized at dynamic cellular protrusions of human and mouse, migrating, mesenchymal cells. In contrast to the model described above, we find that protrusion-localized RNAs are not locally activated solely at protrusions, but can be translated with similar efficiency in both internal and peripheral locations. Interestingly, protrusion-localized RNAs are translated at extending protrusions, they become translationally silenced in retracting protrusions and this silencing is accompanied by coalescence of single RNAs into larger heterogeneous RNA clusters. This work describes a distinct mode of translational regulation of localized RNAs, which we propose is used to regulate protein activities during dynamic cellular responses.


Assuntos
Extensões da Superfície Celular/metabolismo , Regulação da Expressão Gênica , Biossíntese de Proteínas , RNA Mensageiro/metabolismo , Animais , Células Cultivadas , Humanos , Camundongos
8.
Essays Biochem ; 63(5): 595-606, 2019 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-31324705

RESUMO

Cell migration is a fundamental biological process involved in tissue formation and homeostasis. The correct polarization of motile cells is critical to ensure directed movement, and is orchestrated by many intrinsic and extrinsic factors. Of these, the subcellular distribution of mRNAs and the consequent spatial control of translation are key modulators of cell polarity. mRNA transport is dependent on cis-regulatory elements within transcripts, which are recognized by trans-acting proteins that ensure the efficient delivery of certain messages to the leading edge of migrating cells. At their destination, translation of localized mRNAs then participates in regional cellular responses underlying cell motility. In this review, we summarize the key findings that established mRNA targetting as a critical driver of cell migration and how the characterization of polarized mRNAs in motile cells has been expanded from just a few species to hundreds of transcripts. We also describe the molecular control of mRNA trafficking, subsequent mechanisms of local protein synthesis and how these ultimately regulate cell polarity during migration.


Assuntos
Movimento Celular/fisiologia , RNA Mensageiro/metabolismo , Actinas/metabolismo , Animais , Extensões da Superfície Celular/fisiologia , Humanos , Microtúbulos/metabolismo , Biossíntese de Proteínas/fisiologia , Transporte de RNA/fisiologia
9.
Sci Adv ; 5(7): eaaw7243, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31355337

RESUMO

How cells sense hydraulic pressure and make directional choices in confinement remains elusive. Using trifurcating Ψ-like microchannels of different hydraulic resistances and cross-sectional areas, we discovered that the TRPM7 ion channel is the critical mechanosensor, which directs decision-making of blebbing cells toward channels of lower hydraulic resistance irrespective of their cross-sectional areas. Hydraulic pressure-mediated TRPM7 activation triggers calcium influx and supports a thicker cortical actin meshwork containing an elevated density of myosin-IIA. Cortical actomyosin shields cells against external forces and preferentially directs cell entrance in low resistance channels. Inhibition of TRPM7 function or actomyosin contractility renders cells unable to sense different resistances and alters the decision-making pattern to cross-sectional area-based partition. Cell distribution in microchannels is captured by a mathematical model based on the maximum entropy principle using cortical actin as a key variable. This study demonstrates the unique role of TRPM7 in controlling decision-making and navigating migration in complex microenvironments.


Assuntos
Pressão Hidrostática , Mecanotransdução Celular , Proteínas Serina-Treonina Quinases/metabolismo , Canais de Cátion TRPM/metabolismo , Água/química , Actomiosina/metabolismo , Cálcio/metabolismo , Linhagem Celular Tumoral , Extensões da Superfície Celular/metabolismo , Entropia , Células HEK293 , Humanos , Ativação do Canal Iônico
10.
Life Sci Alliance ; 2(3)2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31160379

RESUMO

The F-BAR family of proteins play important roles in many cellular processes by regulating both membrane and actin dynamics. The CIP4 family of F-BAR proteins is widely recognized to function in endocytosis by elongating endocytosing vesicles. However, in primary cortical neurons, CIP4 concentrates at the tips of extending lamellipodia and filopodia and inhibits neurite outgrowth. Here, we report that the highly homologous CIP4 family member, FBP17, induces tubular structures in primary cortical neurons and results in precocious neurite formation. Through domain swapping and deletion experiments, we demonstrate that a novel polybasic region between the F-BAR and HR1 domains is required for membrane bending. Moreover, the presence of a poly-PxxP region in longer splice isoforms of CIP4 and FBP17 largely reverses the localization and function of these proteins. Thus, CIP4 and FBP17 function as an antagonistic pair to fine-tune membrane protrusion, endocytosis, and neurite formation during early neuronal development.


Assuntos
Extensões da Superfície Celular/metabolismo , Microtúbulos/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Crescimento Neuronal , Neurônios/fisiologia , Sequência de Aminoácidos , Animais , Biomarcadores , Linhagem Celular , Membrana Celular/metabolismo , Córtex Cerebral/citologia , Córtex Cerebral/metabolismo , Expressão Gênica , Humanos , Imuno-Histoquímica , Camundongos , Modelos Biológicos , Imagem Molecular , Família Multigênica , Mutação , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/genética , Ligação Proteica , Transporte Proteico
11.
Cells ; 8(6)2019 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-31234435

RESUMO

Tunneling nanotubes (TNTs) are thin membranous tubes that interconnect cells, representing a novel route of cell-to-cell communication and spreading of pathogens. TNTs form between many cell types, yet their inception mechanisms remain elusive. We review in this study general concepts related to the formation and stability of membranous tubular structures with a focus on a deviatoric elasticity model of membrane nanodomains. We review experimental evidence that tubular structures initiate from local membrane bending facilitated by laterally distributed proteins or anisotropic membrane nanodomains. We further discuss the numerical results of several theoretical and simulation models of nanodomain segregation suggesting the mechanisms of TNT inception and stability. We discuss the coupling of nanodomain segregation with the action of protruding cytoskeletal forces, which are mostly provided in eukaryotic cells by the polymerization of f-actin, and review recent inception mechanisms of TNTs in relation to motor proteins.


Assuntos
Nanotubos/química , Anisotropia , Extensões da Superfície Celular/metabolismo , Citoesqueleto/metabolismo , Nanotubos/ultraestrutura , Lipossomas Unilamelares/química
12.
PLoS Biol ; 17(6): e3000060, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31233488

RESUMO

Apicomplexan parasites invade host cells in an active process involving their ability to move by gliding motility. While the acto-myosin system of the parasite plays a crucial role in the formation and release of attachment sites during this process, there are still open questions regarding the involvement of other mechanisms in parasite motility. In many eukaryotes, a secretory-endocytic cycle leads to the recycling of receptors (integrins), necessary to form attachment sites, regulation of surface area during motility, and generation of retrograde membrane flow. Here, we demonstrate that endocytosis operates during gliding motility in Toxoplasma gondii and appears to be crucial for the establishment of retrograde membrane flow, because inhibition of endocytosis blocks retrograde flow and motility. We demonstrate that extracellular parasites can efficiently incorporate exogenous material, such as labelled phospholipids, nanogold particles (NGPs), antibodies, and Concanavalin A (ConA). Using labelled phospholipids, we observed that the endocytic and secretory pathways of the parasite converge, and endocytosed lipids are subsequently secreted, demonstrating the operation of an endocytic-secretory cycle. Together our data consolidate previous findings, and we propose an additional model, working in parallel to the acto-myosin motor, that reconciles parasite motility with observations in other eukaryotes: an apicomplexan fountain-flow-model for parasite motility.


Assuntos
Movimento Celular/fisiologia , Endocitose/fisiologia , Toxoplasma/metabolismo , Actinas/metabolismo , Animais , Adesão Celular/fisiologia , Extensões da Superfície Celular/fisiologia , Proteínas de Membrana/metabolismo , Miosinas/metabolismo , Parasitos , Proteínas de Protozoários/metabolismo , Via Secretória/fisiologia , Toxoplasma/fisiologia
13.
J Cell Biol ; 218(6): 1972-1993, 2019 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-31076452

RESUMO

Tunneling nanotubes (TNT) are thin, membranous, tunnel-like cell-to-cell connections, but the mechanisms underlying their biogenesis or functional role remains obscure. Here, we report, Rhes, a brain-enriched GTPase/SUMO E3-like protein, induces the biogenesis of TNT-like cellular protrusions, "Rhes tunnels," through which Rhes moves from cell to cell and transports Huntington disease (HD) protein, the poly-Q expanded mutant Huntingtin (mHTT). The formation of TNT-like Rhes tunnels requires the Rhes's serine 33, C-terminal CAAX, and a SUMO E3-like domain. Electron microscopy analysis revealed that TNT-like Rhes tunnels appear continuous, cell-cell connections, and <200 nm in diameter. Live-cell imaging shows that Rhes tunnels establish contact with the neighboring cell and deliver Rhes-positive cargoes, which travel across the plasma membrane of the neighboring cell before entering it. The Rhes tunnels carry Rab5a/Lyso 20-positive vesicles and transport mHTT, but not normal HTT, mTOR, or wtTau proteins. SUMOylation-defective mHTT, Rhes C263S (cannot SUMOylate mHTT), or CRISPR/Cas9-mediated depletion of three isoforms of SUMO diminishes Rhes-mediated mHTT transport. Thus, Rhes promotes the biogenesis of TNT-like cellular protrusions and facilitates the cell-cell transport of mHTT involving SUMO-mediated mechanisms.


Assuntos
Citoesqueleto de Actina/metabolismo , Comunicação Celular , Extensões da Superfície Celular/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Proteína Huntingtina/metabolismo , Nanotubos/química , Neurônios/metabolismo , Animais , Doença de Huntington , Camundongos , Camundongos Endogâmicos C57BL , Transporte Proteico
14.
Int J Parasitol ; 49(7): 523-530, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31077679

RESUMO

Genera Myxobolus Bütschli, 1882 and Henneguya Thélohan, 1892 (Myxobolidae) are specious myxozoan genera. They comprise nearly half of overall known myxozoan species diversity. A typical spore feature of Henneguya is the presence of two caudal appendages of the spore valves, which distinguishes them from species of the genus Myxobolus. Several Myxobolus spp., however, were reported to show aberrant spores with Henneguya-like caudal appendages. We found such aberrant spores in Myxobolus tsangwuensis and Myxobolus wulii. We studied the ultrastructure of M. wulii and Myxobolus oralis spores with caudal appendages by transmission electron microscopy (TEM). TEM of these aberrant spores revealed that their caudal appendages have the same ultrastructure as the appendages of Henneguya spp. Small caudal appendages of M. wulii spores observed only on TEM suggested that this character may be often overlooked and more Myxobolus species potentially have the ability to express the caudal appendages on the myxospore. In order to trace the evolution of this character, we performed broad phylogenetic analysis of all species of the family Myxobolidae which are available in GenBank including nearly 300 taxa. We found at least eight independent evolutionary origins of spores with two appendages, three origins of a single appendage and 12 apparent secondary losses of the spore projections. Therefore, genus Henneguya with typical two-tailed myxospores is polyphyletic, however a majority of its species has a common ancestor and groups in the second largest subclade of the Myxobolus clade. We also mapped the biological characteristics (host, site of infection and environment) of Myxobolidae species on the phylogenetic tree. We revealed an evident host-associated evolutionary pattern in all parts of the Myxobolus clade with a distinct and species-rich subclade containing almost exclusively species infecting species of the Order Cypriniformes.


Assuntos
Extensões da Superfície Celular/ultraestrutura , Myxozoa/classificação , Myxozoa/ultraestrutura , Filogenia , Esporos de Protozoários/classificação , Esporos de Protozoários/ultraestrutura , Animais , Microscopia Eletrônica de Transmissão , Myxozoa/genética , Esporos de Protozoários/genética
15.
Nat Commun ; 10(1): 1518, 2019 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-30944331

RESUMO

When migrating in vivo, cells are exposed to numerous conflicting signals: chemokines, repellents, extracellular matrix, growth factors. The roles of several of these molecules have been studied individually in vitro or in vivo, but we have yet to understand how cells integrate them. To start addressing this question, we used the cephalic neural crest as a model system and looked at the roles of its best examples of positive and negative signals: stromal-cell derived factor 1 (Sdf1/Cxcl12) and class3-Semaphorins. Here we show that Sdf1 and Sema3A antagonistically control cell-matrix adhesion via opposite effects on Rac1 activity at the single cell level. Directional migration at the population level emerges as a result of global Semaphorin-dependent confinement and broad activation of adhesion by Sdf1 in the context of a biased Fibronectin distribution. These results indicate that uneven in vivo topology renders the need for precise distribution of secreted signals mostly dispensable.


Assuntos
Movimento Celular/fisiologia , Junções Célula-Matriz/fisiologia , Crista Neural/citologia , Animais , Adesão Celular/efeitos dos fármacos , Adesão Celular/fisiologia , Comunicação Celular/fisiologia , Linhagem Celular , Forma Celular/efeitos dos fármacos , Extensões da Superfície Celular/efeitos dos fármacos , Junções Célula-Matriz/efeitos dos fármacos , Junções Célula-Matriz/metabolismo , Quimiocina CXCL12/metabolismo , Feminino , Fibronectinas/metabolismo , Masculino , Manganês/metabolismo , Camundongos , Proteínas do Tecido Nervoso/fisiologia , Crista Neural/efeitos dos fármacos , Crista Neural/metabolismo , Receptores CXCR4/metabolismo , Semaforinas/metabolismo , Xenopus laevis/embriologia , Proteínas rac1 de Ligação ao GTP/metabolismo
16.
PLoS Biol ; 17(4): e3000235, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-31002663

RESUMO

Multiple types of microvilliated sensory cells exhibit an apical extension thought to be instrumental in the detection of sensory cues. The investigation of the mechanisms underlying morphogenesis of sensory apparatus is critical to understand the biology of sensation. Most of what we currently know comes from the study of the hair bundle of the inner ear sensory cells, but morphogenesis and function of other sensory microvilliated apical extensions remain poorly understood. We focused on spinal sensory neurons that contact the cerebrospinal fluid (CSF) through the projection of a microvilliated apical process in the central canal, referred to as cerebrospinal fluid-contacting neurons (CSF-cNs). CSF-cNs respond to pH and osmolarity changes as well as mechanical stimuli associated with changes of flow and tail bending. In vivo time-lapse imaging in zebrafish embryos revealed that CSF-cNs are atypical neurons that do not lose their apical attachment and form a ring of actin at the apical junctional complexes (AJCs) that they retain during differentiation. We show that the actin-based protrusions constituting the microvilliated apical extension arise and elongate from this ring of actin, and we identify candidate molecular factors underlying every step of CSF-cN morphogenesis. We demonstrate that Crumbs 1 (Crb1), Myosin 3b (Myo3b), and Espin orchestrate the morphogenesis of CSF-cN apical extension. Using calcium imaging in crb1 and espin mutants, we further show that the size of the apical extension modulates the amplitude of CSF-cN sensory response to bending of the spinal cord. Based on our results, we propose that the apical actin ring could be a common site of initiation of actin-based protrusions in microvilliated sensory cells. Furthermore, our work provides a set of actors underlying actin-based protrusion elongation shared by different sensory cell types and highlights the critical role of the apical extension shape in sensory detection.


Assuntos
Mecanotransdução Celular/fisiologia , Microvilosidades/fisiologia , Células Receptoras Sensoriais/fisiologia , Actinas/metabolismo , Animais , Diferenciação Celular , Extensões da Superfície Celular/fisiologia , Líquido Cefalorraquidiano/fisiologia , Morfogênese/fisiologia , Neurônios/fisiologia , Medula Espinal/metabolismo , Peixe-Zebra/metabolismo
17.
PLoS Comput Biol ; 15(4): e1006352, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-31022168

RESUMO

In many biological settings, two or more cells come into physical contact to form a cell-cell interface. In some cases, the cell-cell contact must be transient, forming on timescales of seconds. One example is offered by the T cell, an immune cell which must attach to the surface of other cells in order to decipher information about disease. The aspect ratio of these interfaces (tens of nanometers thick and tens of micrometers in diameter) puts them into the thin-layer limit, or "lubrication limit", of fluid dynamics. A key question is how the receptors and ligands on opposing cells come into contact. What are the relative roles of thermal undulations of the plasma membrane and deterministic forces from active filopodia? We use a computational fluid dynamics algorithm capable of simulating 10-nanometer-scale fluid-structure interactions with thermal fluctuations up to seconds- and microns-scales. We use this to simulate two opposing membranes, variously including thermal fluctuations, active forces, and membrane permeability. In some regimes dominated by thermal fluctuations, proximity is a rare event, which we capture by computing mean first-passage times using a Weighted Ensemble rare-event computational method. Our results demonstrate a parameter regime in which the time it takes for an active force to drive local contact actually increases if the cells are being held closer together (e.g., by nonspecific adhesion), a phenomenon we attribute to the thin-layer effect. This leads to an optimal initial cell-cell separation for fastest receptor-ligand binding, which could have relevance for the role of cellular protrusions like microvilli. We reproduce a previous experimental observation that fluctuation spatial scales are largely unaffected, but timescales are dramatically slowed, by the thin-layer effect. We also find that membrane permeability would need to be above physiological levels to abrogate the thin-layer effect.


Assuntos
Permeabilidade da Membrana Celular/fisiologia , Membrana Celular/fisiologia , Extensões da Superfície Celular/fisiologia , Hidrodinâmica , Modelos Biológicos , Algoritmos , Adesão Celular/fisiologia , Biologia Computacional/métodos
18.
Dev Cell ; 49(2): 189-205.e6, 2019 04 22.
Artigo em Inglês | MEDLINE | ID: mdl-31014479

RESUMO

Efficient chemotaxis requires rapid coordination between different parts of the cell in response to changing directional cues. Here, we investigate the mechanism of front-rear coordination in chemotactic neutrophils. We find that changes in the protrusion rate at the cell front are instantaneously coupled to changes in retraction at the cell rear, while myosin II accumulation at the rear exhibits a reproducible 9-15-s lag. In turning cells, myosin II exhibits dynamic side-to-side relocalization at the cell rear in response to turning of the leading edge and facilitates efficient turning by rapidly re-orienting the rear. These manifestations of front-rear coupling can be explained by a simple quantitative model incorporating reversible actin-myosin interactions with a rearward-flowing actin network. Finally, the system can be tuned by the degree of myosin regulatory light chain (MRLC) phosphorylation, which appears to be set in an optimal range to balance persistence of movement and turning ability.


Assuntos
Quimiotaxia/fisiologia , Miosina Tipo II/fisiologia , Neutrófilos/fisiologia , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Animais , Animais Geneticamente Modificados , Linhagem Celular , Movimento Celular/fisiologia , Polaridade Celular/fisiologia , Extensões da Superfície Celular/fisiologia , Proteínas do Citoesqueleto/metabolismo , Citoesqueleto/metabolismo , Feminino , Humanos , Miosina Tipo II/metabolismo , Miosinas/metabolismo , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/metabolismo
19.
Int J Mol Sci ; 20(5)2019 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-30866487

RESUMO

Cell⁻cell communication is vital to multicellular organisms, and distinct types of cellular protrusions play critical roles during development, cell signaling, and the spreading of pathogens and cancer. The differences in the structure and protein composition of these different types of protrusions and their specific functions have not been elucidated due to the lack of a method for their specific isolation and analysis. In this paper, we described, for the first time, a method to specifically isolate distinct protrusion subtypes, based on their morphological structures or fluorescent markers, using laser capture microdissection (LCM). Combined with a unique fixation and protein extraction protocol, we pushed the limits of microproteomics and demonstrate that proteins from LCM-isolated protrusions can successfully and reproducibly be identified by mass spectrometry using ultra-high field Orbitrap technologies. Our method confirmed that different types of protrusions have distinct proteomes and it promises to advance the characterization and the understanding of these unique structures to shed light on their possible role in health and disease.


Assuntos
Extensões da Superfície Celular/metabolismo , Proteômica/métodos , Comunicação Celular , Células Cultivadas , Humanos , Microdissecção e Captura a Laser , Espectrometria de Massas , Microscopia , Anotação de Sequência Molecular
20.
Mol Syst Biol ; 15(3): e8585, 2019 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-30858181

RESUMO

Cellular protrusions are typically considered as distinct structures associated with specific regulators. However, we found that these regulators coordinately localize as propagating cortical waves, suggesting a common underlying mechanism. These molecular events fell into two excitable networks, the signal transduction network STEN and the cytoskeletal network CEN with different wave substructures. Computational studies using a coupled-network model reproduced these features and showed that the morphology and kinetics of the waves depended on strengths of feedback loops. Chemically induced dimerization at multiple nodes produced distinct, coordinated alterations in patterns of other network components. Taken together, these studies indicate: STEN positive feedback is mediated by mutual inhibition between Ras/Rap and PIP2, while negative feedback depends on delayed PKB activation; PKBs link STEN to CEN; CEN includes positive feedback between Rac and F-actin, and exerts fast positive and slow negative feedbacks to STEN The alterations produced protrusions resembling filopodia, ruffles, pseudopodia, or lamellipodia, suggesting that these structures arise from a common regulatory mechanism and that the overall state of the STEN-CEN system determines cellular morphology.


Assuntos
Extensões da Superfície Celular , Citoesqueleto/metabolismo , Modelos Teóricos , Transdução de Sinais , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Simulação por Computador , Microscopia Confocal , Pseudópodes , Imagem com Lapso de Tempo
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