scholarly journals PolyQ-dependent RNA–protein assemblies control symmetry breaking

2015 ◽  
Vol 208 (5) ◽  
pp. 533-544 ◽  
Author(s):  
ChangHwan Lee ◽  
Patricia Occhipinti ◽  
Amy S. Gladfelter
Keyword(s):  
Symmetry Breaking ◽  
Cell Polarity ◽  
Protein Interaction ◽  
Dendritic Growth ◽  
Physiological Function ◽  
Low Complexity ◽  
Asymmetric Distribution ◽  
Ashbya Gossypii ◽  
Polarized Growth ◽  
Protein Assemblies

Dendritic growth in fungi and neurons requires that multiple axes of polarity are established and maintained within the same cytoplasm. We have discovered that transcripts encoding key polarity factors including a formin, Bni1, and a polarisome scaffold, Spa2, are nonrandomly clustered in the cytosol to initiate and maintain sites of polarized growth in the fungus Ashbya gossypii. This asymmetric distribution requires the mRNAs to interact with a polyQ-containing protein, Whi3, and a Pumilio protein with a low-complexity sequence, Puf2. Cells lacking Whi3 or Puf2 had severe defects in establishing new sites of polarity and failed to localize Bni1 protein. Interaction of mRNAs with Whi3 and Puf2 promotes enrichment of transcripts at established sites of polarized growth and clustering of polarity transcripts throughout the cell body. Thus, aggregation-prone proteins make functional assemblies to position polarity transcripts, and nonrandom positioning of transcripts is required for symmetry-breaking events. This reveals a physiological function for polyQ-driven assemblies in regulating cell polarity.

scholarly journals Weakly nonlinear analysis of symmetry breaking in cell polarity models

2012 ◽  
Vol 9 (4) ◽  
pp. 045006 ◽  
Author(s):  
Boris Rubinstein ◽  
Brian D Slaughter ◽  
Rong Li
Keyword(s):  
Symmetry Breaking ◽  
Nonlinear Analysis ◽  
Cell Polarity ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Analysis

scholarly journals Diversity of left-right symmetry breaking strategy in animals

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 123 ◽  
Author(s):  
Hiroshi Hamada ◽  
Patrick Tam
Keyword(s):  
Fluid Flow ◽  
Embryonic Development ◽  
Symmetry Breaking ◽  
Cell Polarity ◽  
Molecular Interaction ◽  
Planar Cell Polarity ◽  
Entry Point ◽  
Visceral Organs ◽  
Distinct Mechanism ◽  
Actomyosin Interaction

Left-right (L-R) asymmetry of visceral organs in animals is established during embryonic development via a stepwise process. While some steps are conserved, different strategies are employed among animals for initiating the breaking of body symmetry. In zebrafish (teleost), Xenopus (amphibian), and mice (mammal), symmetry breaking is elicited by directional fluid flow at the L-R organizer, which is generated by motile cilia and sensed by mechanoresponsive cells. In contrast, birds and reptiles do not rely on the cilia-driven fluid flow. Invertebrates such as Drosophila and snails employ another distinct mechanism, where the symmetry breaking process is underpinned by cellular chirality acquired downstream of the molecular interaction of myosin and actin. Here, we highlight the convergent entry point of actomyosin interaction and planar cell polarity to the diverse L-R symmetry breaking mechanisms among animals.

scholarly journals Phosphoregulation provides specificity to biomolecular condensates in the cell cycle and cell polarity

2020 ◽  
Vol 219 (7) ◽  
Author(s):  
Therese M. Gerbich ◽  
Grace A. McLaughlin ◽  
Katelyn Cassidy ◽  
Scott Gerber ◽  
David Adalsteinsson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Nucleic Acids ◽  
Cell Polarity ◽  
Filamentous Fungus ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Ashbya Gossypii ◽  
Mrna Targets ◽  
Functional Identities

Biomolecular condensation is a way of organizing cytosol in which proteins and nucleic acids coassemble into compartments. In the multinucleate filamentous fungus Ashbya gossypii, the RNA-binding protein Whi3 regulates the cell cycle and cell polarity through forming macromolecular structures that behave like condensates. Whi3 has distinct spatial localizations and mRNA targets, making it a powerful model for how, when, and where specific identities are established for condensates. We identified residues on Whi3 that are differentially phosphorylated under specific conditions and generated mutants that ablate this regulation. This yielded separation of function alleles that were functional for either cell polarity or nuclear cycling but not both. This study shows that phosphorylation of individual residues on molecules in biomolecular condensates can provide specificity that gives rise to distinct functional identities in the same cell.

scholarly journals Complex+: Aided Decision-Making for the Study of Protein Complexes

2019 ◽  
Author(s):  
Mehrnoosh Oghbaie ◽  
Petr Šulc ◽  
David Fenyö ◽  
Michael Pennock ◽  
John LaCava
Keyword(s):  
Protein Interaction ◽  
Protein Interactions ◽  
Cell Biology ◽  
Protein Complexes ◽  
Conclusive Evidence ◽  
Computational Techniques ◽  
Protein Assemblies ◽  
Data Types ◽  
Research Strategies ◽  
Protein Interactome

AbstractProteins are the chief effectors of cell biology and their functions are typically carried out in the context of multi-protein assemblies; large collections of such interacting protein assemblies are often referred to as interactomes. Knowing the constituents of protein complexes is therefore important for investigating their molecular biology. Many experimental methods are capable of producing data of use for detecting and inferring the existence of physiological protein complexes. Each method has associated pros and cons, affecting the potential quality and utility of the data. Numerous informatic resources exist for the curation, integration, retrieval, and processing of protein interactions data. While each resource may possess different merits, none are definitive and few are wieldy, potentially limiting their effective use by non-experts. In addition, contemporary analyses suggest that we may still be decades away from a comprehensive map of a human protein interactome. Taken together, we are currently unable to maximally impact and improve biomedicine from a protein interactome perspective – motivating the development of experimental and computational techniques that help investigators to address these limitations. Here, we present a resource intended to assist investigators in (i) navigating the cumulative knowledge concerning protein complexes and (ii) forming hypotheses concerning protein interactions that may yet lack conclusive evidence, thus (iii) directing future experiments to address knowledge gaps. To achieve this, we integrated multiple data-types/different properties of protein interactions from multiple sources and after applying various methods of regularization, compared the protein interaction networks computed to those available in the EMBL-EBI Complex Portal, a manually curated, gold-standard catalog of macromolecular complexes. As a result, our resource provides investigators with reliable curation of bona fide and candidate physical interactors of their protein or complex of interest, prompting due scrutiny and further validation when needed. We believe this information will empower a wider range of experimentalists to conduct focused protein interaction studies and to better select research strategies that explicitly target missing information.

scholarly journals Yeast Rgd3 is a phospho-regulated F-BAR-containing RhoGAP involved in the regulation of Rho3 distribution and cell morphology

2020 ◽  
Author(s):  
Robert M. Gingras ◽  
Kyaw Myo Lwin ◽  
Abigail M. Miller ◽  
Anthony Bretscher
Keyword(s):  
Cell Polarity ◽  
Binding Motif ◽  
Restrictive Temperature ◽  
Secretory Vesicles ◽  
Polarized Growth ◽  
Related Protein ◽  
Myosin V ◽  
Over Expression ◽  
Dependent Transport

AbstractPolarized growth requires the integration of polarity pathways with the delivery of exocytic vesicles for cell expansion and counterbalancing endocytic uptake. In budding yeast, the myosin-V Myo2 is aided by the kinesin-related protein Smy1 in carrying out the essential Sec4-dependent transport of secretory vesicles to sites of polarized growth. Over-expression suppressors of a conditional myo2 smy1 mutant identified a novel F-BAR-containing RhoGAP, Rgd3, that has activity primarily on Rho3, but also Cdc42. Internally tagged Rho3 is restricted to the plasma membrane in a gradient corresponding to cell polarity that is altered upon Rgd3 over-expression. Rgd3 itself is localized to dynamic polarized vesicles that, while distinct from constitutive secretory vesicles, are dependent on actin and Myo2 function. In vitro Rgd3 associates with liposomes in a PIP2-enhanced manner. Further, the Rgd3 C-terminal region contains several phosphorylatable residues within a reported SH3-binding motif. An unphosphorylated mimetic construct is active and highly polarized, while the phospho-mimetic form is not. Rgd3 is capable of activating Myo2, dependent on its phospho-state and Rgd3 overexpression rescues aberrant Rho3 localization and cell morphologies seen at the restrictive temperature in the myo2 smy1 mutant. We propose a model where Rgd3 functions to modulate and maintain Rho3 polarity during growth.

scholarly journals Anisotropy of plasmalemmal sterols and cell mating require StARkin domain proteins Ysp2 and Lam4

2021 ◽  
Author(s):  
Neha Chauhan ◽  
Gregory D. Fairn
Keyword(s):  
Plasma Membrane ◽  
Map Kinase ◽  
Cell Polarity ◽  
Positive Feedback ◽  
Feedback Loop ◽  
Budding Yeast ◽  
Mapk Signaling ◽  
Polarized Growth ◽  
Positive Feedback Loop ◽  
Mating Efficiency

AbstractIn the budding yeast S. cerevisiae Cdc42 is required for polarized growth and the formation of mating projections (shmoos). Negatively charged lipids including phosphatidylserine and phosphatidylinositol 4,5-bisphosphate support a positive feedback loop that recruits Cdc42 effectors and MAP kinase scaffolds, many of which contain polybasic patches that directly interact with the membrane. Here, using genetically encoded sterol sensor ALOD4 we find that ergosterol is accumulated in the cytosolic leaflet of buds and shmoos. The accumulation of ergosterol in the plasma membrane requires both Osh and Lam proteins however cells lacking Ysp2/Lam2 and Lam4 displayed a reversal in the polarity of ergosterol. The redistribution of ergosterol impairs the polarization of phosphatidylserine and phosphatidylinositol 4,5-bisphophate which further impacts shmoo formation, MAPK signaling and mating efficiency. Our observations demonstrate that the ability of Lam proteins to deliver ergosterol from the plasma membrane to the ER helps maintain a gradient of ergosterol which in turn supports robust cell polarity.SummaryThe sterol sensor ALOD4 is enriched at sites of polarized growth. Elimination of the Osh proteins solubilized the ALOD4 whereas elimination of Ysp2 and Lam4 reversed ALOD4 polarization. Cells lacking Ysp2 and Lam4 have defects in mating and MAP kinase signaling.

scholarly journals Mechanochemical Control of Symmetry Breaking in the Caenorhabditis elegans Zygote

2021 ◽  
Vol 8 ◽  
Author(s):  
Wan Jun Gan ◽  
Fumio Motegi
Keyword(s):  
Caenorhabditis Elegans ◽  
Symmetry Breaking ◽  
Actin Cytoskeleton ◽  
Cell Polarity ◽  
Break Symmetry ◽  
Cell Cortex ◽  
Aurora A Kinase ◽  
Advective Flow ◽  
Polar State ◽  
Cellular Components

Cell polarity is the asymmetric organization of cellular components along defined axes. A key requirement for polarization is the ability of the cell to break symmetry and achieve a spatially biased organization. Despite different triggering cues in various systems, symmetry breaking (SB) usually relies on mechanochemical modulation of the actin cytoskeleton, which allows for advected movement and reorganization of cellular components. Here, the mechanisms underlying SB in Caenorhabditis elegans zygote, one of the most popular models to study cell polarity, are reviewed. A zygote initiates SB through the centrosome, which modulates mechanics of the cell cortex to establish advective flow of cortical proteins including the actin cytoskeleton and partitioning defective (PAR) proteins. The chemical signaling underlying centrosomal control of the Aurora A kinase–mediated cascade to convert the organization of the contractile actomyosin network from an apolar to polar state is also discussed.

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