RESUMEN
Polarized cells rely on a polarized cytoskeleton to function. Yet, how cortical polarity cues induce cytoskeleton polarization remains elusive. Here, we capitalized on recently established designed 2D protein arrays to ectopically engineer cortical polarity of virtually any protein of interest during mitosis in various cell types. This enables direct manipulation of polarity signaling and the identification of the cortical cues sufficient for cytoskeleton polarization. Using this assay, we dissected the logic of the Par complex pathway, a key regulator of cytoskeleton polarity during asymmetric cell division. We show that cortical clustering of any Par complex subunit is sufficient to trigger complex assembly and that the primary kinetic barrier to complex assembly is the relief of Par6 autoinhibition. Further, we found that inducing cortical Par complex polarity induces two hallmarks of asymmetric cell division in unpolarized mammalian cells: spindle orientation, occurring via Par3, and central spindle asymmetry, depending on aPKC activity.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Polaridad Celular , Técnicas Citológicas , Mitosis , Animales , Citoesqueleto/metabolismo , Mamíferos/metabolismo , Microtúbulos/metabolismo , Proteína Quinasa C/metabolismo , Proteínas Adaptadoras Transductoras de Señales/metabolismoRESUMEN
Gravity controls directional growth of plants, and the classical starch-statolith hypothesis proposed more than a century ago postulates that amyloplast sedimentation in specialized cells initiates gravity sensing, but the molecular mechanism remains uncharacterized. The LAZY proteins are known as key regulators of gravitropism, and lazy mutants show striking gravitropic defects. Here, we report that gravistimulation by reorientation triggers mitogen-activated protein kinase (MAPK) signaling-mediated phosphorylation of Arabidopsis LAZY proteins basally polarized in root columella cells. Phosphorylation of LAZY increases its interaction with several translocons at the outer envelope membrane of chloroplasts (TOC) proteins on the surface of amyloplasts, facilitating enrichment of LAZY proteins on amyloplasts. Amyloplast sedimentation subsequently guides LAZY to relocate to the new lower side of the plasma membrane in columella cells, where LAZY induces asymmetrical auxin distribution and root differential growth. Together, this study provides a molecular interpretation for the starch-statolith hypothesis: the organelle-movement-triggered molecular polarity formation.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Plastidios , Arabidopsis/fisiología , Proteínas de Arabidopsis/metabolismo , Sensación de Gravedad , Raíces de Plantas/metabolismo , Plastidios/metabolismo , Almidón/metabolismo , Proteínas de la Membrana/metabolismoRESUMEN
Membrane tension is thought to be a long-range integrator of cell physiology. Membrane tension has been proposed to enable cell polarity during migration through front-back coordination and long-range protrusion competition. These roles necessitate effective tension transmission across the cell. However, conflicting observations have left the field divided as to whether cell membranes support or resist tension propagation. This discrepancy likely originates from the use of exogenous forces that may not accurately mimic endogenous forces. We overcome this complication by leveraging optogenetics to directly control localized actin-based protrusions or actomyosin contractions while simultaneously monitoring the propagation of membrane tension using dual-trap optical tweezers. Surprisingly, actin-driven protrusions and actomyosin contractions both elicit rapid global membrane tension propagation, whereas forces applied to cell membranes alone do not. We present a simple unifying mechanical model in which mechanical forces that engage the actin cortex drive rapid, robust membrane tension propagation through long-range membrane flows.
Asunto(s)
Actinas , Actomiosina , Actinas/metabolismo , Actomiosina/metabolismo , Citoesqueleto de Actina/metabolismo , Membrana Celular/metabolismo , Movimiento Celular/fisiologíaRESUMEN
Cell polarity is fundamental for tissue morphogenesis in multicellular organisms. Plants and animals evolved multicellularity independently, and it is unknown whether their polarity systems are derived from a single-celled ancestor. Planar polarity in animals is conferred by Wnt signaling, an ancient signaling pathway transduced by Dishevelled, which assembles signalosomes by dynamic head-to-tail DIX domain polymerization. In contrast, polarity-determining pathways in plants are elusive. We recently discovered Arabidopsis SOSEKI proteins, which exhibit polar localization throughout development. Here, we identify SOSEKI as ancient polar proteins across land plants. Concentration-dependent polymerization via a bona fide DIX domain allows these to recruit ANGUSTIFOLIA to polar sites, similar to the polymerization-dependent recruitment of signaling effectors by Dishevelled. Cross-kingdom domain swaps reveal functional equivalence of animal and plant DIX domains. We trace DIX domains to unicellular eukaryotes and thus show that DIX-dependent polymerization is an ancient mechanism conserved between kingdoms and central to polarity proteins.
Asunto(s)
Arabidopsis/química , Arabidopsis/citología , Polaridad Celular/fisiología , Células Vegetales/fisiología , Polimerizacion , Dominios Proteicos , Animales , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Proteína Axina/química , Proteína Axina/metabolismo , Bryopsida/química , Bryopsida/citología , Bryopsida/genética , Bryopsida/crecimiento & desarrollo , Células COS , Chlorocebus aethiops , Proteínas Dishevelled/metabolismo , Células HEK293 , Humanos , Marchantia/química , Marchantia/citología , Marchantia/genética , Marchantia/crecimiento & desarrollo , Proteínas de la Membrana/química , Proteínas de la Membrana/metabolismo , Plantas Modificadas Genéticamente , Proteínas Represoras/metabolismo , Vía de Señalización WntRESUMEN
Prion-like proteins can assume distinct conformational and physical states in the same cell. Sequence analysis suggests that prion-like proteins are prevalent in various species; however, it remains unclear what functional space they occupy in multicellular organisms. Here, we report the identification of a prion-like protein, Herzog (CG5830), through a multimodal screen in Drosophila melanogaster. Herzog functions as a membrane-associated phosphatase and controls embryonic patterning, likely being involved in TGF-ß/BMP and FGF/EGF signaling pathways. Remarkably, monomeric Herzog is enzymatically inactive and becomes active upon amyloid-like assembly. The prion-like domain of Herzog is necessary for both its assembly and membrane targeting. Removal of the prion-like domain impairs activity, while restoring assembly on the membrane using a heterologous prion-like domain and membrane-targeting motif can restore phosphatase activity. This study provides an example of a prion-like domain that allows an enzyme to gain essential functionality via amyloid-like assembly to control animal development.
Asunto(s)
Proteínas Amiloidogénicas/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriología , Desarrollo Embrionario , Fosfoproteínas Fosfatasas/metabolismo , Monoéster Fosfórico Hidrolasas/metabolismo , Proteínas Amiloidogénicas/química , Proteínas Amiloidogénicas/genética , Animales , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Fosfoproteínas Fosfatasas/química , Fosfoproteínas Fosfatasas/genética , Monoéster Fosfórico Hidrolasas/química , Monoéster Fosfórico Hidrolasas/genética , Priones/química , Dominios ProteicosRESUMEN
Polarization along an apico-basolateral axis is a hallmark of epithelial cells and is essential for their selective barrier and transporter functions, as well as for their ability to provide mechanical resiliency to organs. Loss of polarity along this axis perturbs development and is associated with a wide number of diseases. We describe three steps involved in polarization: symmetry breaking, polarity establishment, and polarity maintenance. While the proteins involved in these processes are highly conserved among epithelial tissues and species, the execution of these steps varies widely and is context dependent. We review both theoretical principles underlying these steps and recent work demonstrating how apico-basolateral polarity is established in vivo in different tissues, highlighting how developmental and physiological contexts play major roles in the execution of the epithelial polarity program.
Asunto(s)
Membrana Basal/metabolismo , Polaridad Celular , Células Epiteliales/citología , Epitelio/metabolismo , Animales , Membrana Basal/citología , Comunicación Celular , Matriz Extracelular/metabolismo , Humanos , Proteínas de la Membrana/metabolismo , Transducción de SeñalRESUMEN
Microtubules are core components of the cytoskeleton and serve as tracks for motor protein-based intracellular transport. Microtubule networks are highly diverse across different cell types and are believed to adapt to cell type-specific transport demands. Here we review how the spatial organization of different subsets of microtubules into higher-order networks determines the traffic rules for motor-based transport in different animal cell types. We describe the interplay between microtubule network organization and motor-based transport within epithelial cells, oocytes, neurons, cilia, and the spindle apparatus.
Asunto(s)
Microtúbulos/metabolismo , Animales , Polaridad Celular , Citoesqueleto/química , Citoesqueleto/metabolismo , Humanos , Proteínas Asociadas a Microtúbulos/metabolismo , Microtúbulos/química , Proteínas Motoras Moleculares/metabolismo , Transporte de Proteínas , Huso Acromático/química , Huso Acromático/metabolismoRESUMEN
Cell polarity in plants operates across a broad range of spatial and temporal scales to control processes from acute cell growth to systemic hormone distribution. Similar to other eukaryotes, plants generate polarity at both the subcellular and tissue levels, often through polarization of membrane-associated protein complexes. However, likely due to the constraints imposed by the cell wall and their extremely plastic development, plants possess novel polarity molecules and mechanisms highly tuned to environmental inputs. Considerable progress has been made in identifying key plant polarity regulators, but detailed molecular understanding of polarity mechanisms remains incomplete in plants. Here, we emphasize the striking similarities in the conceptual frameworks that generate polarity in both animals and plants. To this end, we highlight how novel, plant-specific proteins engage in common themes of positive feedback, dynamic intracellular trafficking, and posttranslational regulation to establish polarity axes in development. We end with a discussion of how environmental signals control intrinsic polarity to impact postembryonic organogenesis and growth.
Asunto(s)
Polaridad Celular , Células Vegetales/fisiología , Animales , División Celular , Pared Celular/química , Células Eucariotas/citología , Células Vegetales/química , Células Vegetales/enzimología , Proteínas de Plantas/metabolismo , Proteínas de Unión al GTP rho/metabolismoRESUMEN
A conserved molecular machinery centered on the Cdc42 GTPase regulates cell polarity in diverse organisms. Here we review findings from budding and fission yeasts that reveal both a conserved core polarity circuit and several adaptations that each organism exploits to fulfill the needs of its lifestyle. The core circuit involves positive feedback by local activation of Cdc42 to generate a cluster of concentrated GTP-Cdc42 at the membrane. Species-specific pathways regulate the timing of polarization during the cell cycle, as well as the location and number of polarity sites.
Asunto(s)
Polaridad Celular , Saccharomyces cerevisiae/citología , Actinas/metabolismo , Ciclo Celular , Modelos BiológicosRESUMEN
Objects are commonly moved within the cell by either passive diffusion or active directed transport. A third possibility is advection, in which objects within the cytoplasm are moved with the flow of the cytoplasm. Bulk movement of the cytoplasm, or streaming, as required for advection, is more common in large cells than in small cells. For example, streaming is observed in elongated plant cells and the oocytes of several species. In the Drosophila oocyte, two stages of streaming are observed: relatively slow streaming during mid-oogenesis and streaming that is approximately ten times faster during late oogenesis. These flows are implicated in two processes: polarity establishment and mixing. In this review, I discuss the underlying mechanism of streaming, how slow and fast streaming are differentiated, and what we know about the physiological roles of the two types of streaming.
Asunto(s)
Corriente Citoplasmática , Drosophila/citología , Oocitos/citología , Animales , Polaridad Celular , OogénesisRESUMEN
Most single animal cells have an internal vector that determines where recycling membrane is added to the cell's surface. Because of the specific molecular composition of this added membrane, a dynamic asymmetry is formed on the surface of the cell. The consequences of this dynamic asymmetry are discussed, together with what they imply for how cells move. The polarity of a single-celled embryo, such as that of the nematode Caenorhabditis elegans, is explored in a similar framework.
Asunto(s)
Membrana Celular/química , Endocitosis , Animales , Biología/métodos , Caenorhabditis elegans , Movimiento Celular , Citoesqueleto/metabolismo , Dictyostelium , Fibroblastos/metabolismo , Células HeLa , Hemaglutininas/química , Humanos , Proteínas de la Membrana/química , Proteínas/químicaRESUMEN
Microvilli are actin-based structures found on the apical aspect of many epithelial cells. In this review, we discuss different types of microvilli, as well as comparisons with actin-based sensory stereocilia and filopodia. Much is known about the actin-bundling proteins of these structures; we summarize recent studies that focus on the components of the microvillar membrane. We pay special attention to mechanisms of membrane microfilament attachment by the ezrin/radixin/moesin family and regulation of this protein family. We also discuss the NHERF family of scaffolding proteins that are found in microvilli and their role in microvilli regulation. Microvilli on cultured cells are not static structures, and their dynamics and those of their components are discussed. Finally, we mention diseases related to microvilli and outline questions that our current knowledge will allow the field to address in the near future.
Asunto(s)
Células Epiteliales/fisiología , Microvellosidades/fisiología , Citoesqueleto de Actina/metabolismo , Citoesqueleto de Actina/fisiología , Actinas/metabolismo , Animales , Humanos , Membranas/metabolismo , Membranas/fisiologíaRESUMEN
Cell polarity networks are defined by quantitative features of their constituent feedback circuits, which must be tuned to enable robust and stable polarization, while also ensuring that networks remain responsive to dynamically changing cellular states and/or spatial cues during development. Using the PAR polarity network as a model, we demonstrate that these features are enabled by the dimerization of the polarity protein PAR-2 via its N-terminal RING domain. Combining theory and experiment, we show that dimer affinity is optimized to achieve dynamic, selective, and cooperative binding of PAR-2 to the plasma membrane during polarization. Reducing dimerization compromises positive feedback and robustness of polarization. Conversely, enhanced dimerization renders the network less responsive due to kinetic trapping of PAR-2 on internal membranes and reduced sensitivity of PAR-2 to the anterior polarity kinase, aPKC/PKC-3. Thus, our data reveal a key role for a dynamically oligomeric RING domain in optimizing interaction affinities to support a robust and responsive cell polarity network, and highlight how optimization of oligomerization kinetics can serve as a strategy for dynamic and cooperative intracellular targeting.
Asunto(s)
Membrana Celular , Polaridad Celular , Proteína Quinasa C , Multimerización de Proteína , Membrana Celular/metabolismo , Proteína Quinasa C/metabolismo , Animales , Unión ProteicaRESUMEN
Localized ion fluxes at the plasma membrane provide electrochemical gradients at the cell surface that contribute to cell polarization, migration, and division. Ion transporters, local pH gradients, membrane potential, and organization are emerging as important factors in cell polarization mechanisms. The power of electrochemical effects is illustrated by the ability of exogenous electric fields to redirect polarization in cells ranging from bacteria, fungi, and amoebas to keratocytes and neurons. Electric fields normally surround cells and tissues and thus have been proposed to guide cell polarity in development, cancer, and wound healing. Recent studies on electric field responses in model systems and development of new biosensors provide new avenues to dissect molecular mechanisms. Here, we review recent advances that bring molecular understanding of how electrochemistry contributes to cell polarity in various contexts.
Asunto(s)
Polaridad Celular/fisiología , Animales , Aniones/metabolismo , Cationes/metabolismo , División Celular , Movimiento Celular , Forma de la Célula , Dictyostelium/citología , Electroquímica , Campos Electromagnéticos , Peces , Hongos/citología , Concentración de Iones de Hidrógeno , Líquido Intracelular/química , Transporte Iónico/fisiología , Potenciales de la Membrana/fisiología , Regeneración , Electricidad Estática , Cicatrización de HeridasRESUMEN
Neural stem and progenitor cells have a central role in the development and evolution of the mammalian neocortex. In this review, we first provide a set of criteria to classify the various types of cortical stem and progenitor cells. We then discuss the issue of cell polarity, as well as specific subcellular features of these cells that are relevant for their modes of division and daughter cell fate. In addition, cortical stem and progenitor cell behavior is placed into a tissue context, with consideration of extracellular signals and cell-cell interactions. Finally, the differences across species regarding cortical stem and progenitor cells are dissected to gain insight into key developmental and evolutionary mechanisms underlying neocortex expansion.
Asunto(s)
Neocórtex/crecimiento & desarrollo , Neurogénesis/fisiología , Animales , División Celular Asimétrica , Compartimento Celular , Linaje de la Célula , Membrana Celular/fisiología , Núcleo Celular/fisiología , Polaridad Celular , Líquido Cefalorraquídeo/fisiología , Humanos , Uniones Intercelulares/fisiología , Ventrículos Laterales/embriología , Lípidos de la Membrana/metabolismo , Microglía/fisiología , Mitosis , Neocórtex/citología , Neocórtex/embriología , Células-Madre Neurales/clasificación , Células-Madre Neurales/fisiología , Células Neuroepiteliales/citología , Células Neuroepiteliales/fisiología , Neuronas/fisiología , Orgánulos/fisiología , Especificidad de la EspecieRESUMEN
The opportunistic pathogen Pseudomonas aeruginosa adapts to solid surfaces to enhance virulence and infect its host. Type IV pili (T4P), long and thin filaments that power surface-specific twitching motility, allow single cells to sense surfaces and control their direction of movement. T4P distribution is polarized to the sensing pole by the chemotaxis-like Chp system via a local positive feedback loop. However, how the initial spatially resolved mechanical signal is translated into T4P polarity is incompletely understood. Here, we demonstrate that the two Chp response regulators PilG and PilH enable dynamic cell polarization by antagonistically regulating T4P extension. By precisely quantifying the localization of fluorescent protein fusions, we show that phosphorylation of PilG by the histidine kinase ChpA controls PilG polarization. Although PilH is not strictly required for twitching reversals, it becomes activated upon phosphorylation and breaks the local positive feedback mechanism established by PilG, allowing forward-twitching cells to reverse. Chp thus uses a main output response regulator, PilG, to resolve mechanical signals in space and employs a second regulator, PilH, to break and respond when the signal changes. By identifying the molecular functions of two response regulators that dynamically control cell polarization, our work provides a rationale for the diversity of architectures often found in non-canonical chemotaxis systems.
Asunto(s)
Proteínas Bacterianas , Proteínas Fimbrias , Proteínas Fimbrias/genética , Proteínas Fimbrias/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Pseudomonas aeruginosa/metabolismo , Fimbrias Bacterianas/fisiología , Movimiento CelularRESUMEN
Motile cells encounter microenvironments with locally heterogeneous mechanochemical composition. Individual compositional parameters, such as chemokines and extracellular matrix pore sizes, are well known to provide guidance cues for pathfinding. However, motile cells face diverse cues at the same time, raising the question of how they respond to multiple and potentially competing signals on their paths. Here, we reveal that amoeboid cells require nuclear repositioning, termed nucleokinesis, for adaptive pathfinding in heterogeneous mechanochemical micro-environments. Using mammalian immune cells and the amoeba Dictyostelium discoideum, we discover that frequent, rapid and long-distance nucleokinesis is a basic component of amoeboid pathfinding, enabling cells to reorientate quickly between locally competing cues. Amoeboid nucleokinesis comprises a two-step polarity switch and is driven by myosin-II forces that readjust the nuclear to the cellular path. Impaired nucleokinesis distorts path adaptions and causes cellular arrest in the microenvironment. Our findings establish that nucleokinesis is required for amoeboid cell navigation. Given that many immune cells, amoebae, and some cancer cells utilize an amoeboid migration strategy, these results suggest that nucleokinesis underlies cellular navigation during unicellular biology, immunity, and disease.
Asunto(s)
Amoeba , Dictyostelium , Animales , Movimiento Celular , Matriz Extracelular , MamíferosRESUMEN
Apical-basal polarity is maintained by distinct protein complexes that reside in membrane junctions, and polarity loss in monolayered epithelial cells can lead to formation of multilayers, cell extrusion, and/or malignant overgrowth. Yet, how polarity loss cooperates with intrinsic signals to control directional invasion toward neighboring epithelial cells remains elusive. Using the Drosophila ovarian follicular epithelium as a model, we found that posterior follicle cells with loss of lethal giant larvae (lgl) or Discs large (Dlg) accumulate apically toward germline cells, whereas cells with loss of Bazooka (Baz) or atypical protein kinase C (aPKC) expand toward the basal side of wildtype neighbors. Further studies revealed that these distinct multilayering patterns in the follicular epithelium were determined by epidermal growth factor receptor (EGFR) signaling and its downstream target Pointed, a zinc-finger transcription factor. Additionally, we identified Rho kinase as a Pointed target that regulates formation of distinct multilayering patterns. These findings provide insight into how cell polarity genes and receptor tyrosine kinase signaling interact to govern epithelial cell organization and directional growth that contribute to epithelial tumor formation.
Asunto(s)
Polaridad Celular , Proteínas de Drosophila , Receptores ErbB , Animales , Polaridad Celular/fisiología , Drosophila melanogaster , Proteínas de Drosophila/metabolismo , Células Epiteliales/metabolismo , Epitelio/metabolismo , Receptores ErbB/genética , Receptores ErbB/metabolismoRESUMEN
The multicellular haploid stage of land plants develops from a single haploid cell produced by meiosis - the spore. Starting from a non-polar state, these spores develop polarity, divide asymmetrically and establish the first axis of symmetry. Here, we show that the nucleus migrates from the cell centroid to the basal pole during polarisation of the Marchantia polymorpha spore cell. A microtubule organising centre on the leading edge of the nucleus initiates a microtubule array between the nuclear surface and the cortex at the basal pole. Simultaneously, cortical microtubules disappear from the apical hemisphere but persist in the basal hemisphere. This is accompanied by the formation a dense network of fine actin filaments between the nucleus and the basal pole cortex. Experimental depolymerisation of either microtubules or actin filaments disrupts cellular asymmetry. These data demonstrate that the cytoskeleton reorganises during spore polarisation and controls the directed migration of the nucleus to the basal pole. The presence of the nucleus at the basal pole provides the cellular asymmetry for the asymmetric cell division that establishes the apical-basal axis of the plant.
Asunto(s)
Citoesqueleto de Actina , Núcleo Celular , Polaridad Celular , Marchantia , Microtúbulos , Esporas , Microtúbulos/metabolismo , Núcleo Celular/metabolismo , Citoesqueleto de Actina/metabolismo , Marchantia/metabolismo , Marchantia/genética , Marchantia/citología , Polaridad Celular/fisiologíaRESUMEN
Mitochondrial morphology dynamics regulate signaling pathways during epithelial cell formation and differentiation. The mitochondrial fission protein Drp1 affects the appropriate activation of EGFR and Notch signaling-driven differentiation of posterior follicle cells in Drosophila oogenesis. The mechanisms by which Drp1 regulates epithelial polarity during differentiation are not known. In this study, we show that Drp1-depleted follicle cells are constricted in early stages and present in multiple layers at later stages with decreased levels of apical polarity protein aPKC. These defects are suppressed by additional depletion of mitochondrial fusion protein Opa1. Opa1 depletion leads to mitochondrial fragmentation and increased reactive oxygen species (ROS) in follicle cells. We find that increasing ROS by depleting the ROS scavengers, mitochondrial SOD2 and catalase also leads to mitochondrial fragmentation. Further, the loss of Opa1, SOD2 and catalase partially restores the defects in epithelial polarity and aPKC, along with EGFR and Notch signaling in Drp1-depleted follicle cells. Our results show a crucial interaction between mitochondrial morphology, ROS generation and epithelial cell polarity formation during the differentiation of follicle epithelial cells in Drosophila oogenesis.