scholarly journals Structural control for the coordinated assembly into functional pathogenic type-3 secretion systems

2019 ◽  
Author(s):  
Nikolaus Goessweiner-Mohr ◽  
Vadim Kotov ◽  
Matthias J. Brunner ◽  
Julia Mayr ◽  
Jiri Wald ◽  
...  
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Helical Structure ◽  
Structural Basis ◽  
Protein Chain ◽  
Assembly Process ◽  
Secretion Systems ◽  
Ring Assembly ◽  
Serovar Typhimurium ◽  
Type 3

AbstractFunctional injectisomes of the type-3 secretion system assemble into highly defined and stoichiometric bacterial molecular machines essential for infecting human and other eukaryotic cells. However, the mechanism that governs the regulated step-wise assembly process from the nucleation-phase, to ring-assembly, and the filamentous phase into a membrane embedded needle complex is unclear. We here report that the formation of a megadalton-sized needle complexes from Salmonella enterica serovar Typhimurium (SPI-1, Salmonella pathogenicity island-1) with proper stoichiometries is highly structurally controlled competing against the self-assembly propensity of injectisome components, leading to a highly unusual structurally-pleiotropic phenotype. The structure of the entire needle complex from pathogenic injectisomes was solved by cryo electron microscopy, focused refinements (2.5-4 Å) and co-variation analysis revealing an overall asymmetric arrangement containing cyclic, helical, and asymmetric sub-structures. The centrally located export apparatus assembles into a conical, pseudo-helical structure and provides a structural template that guides the formation of a 24-mer cyclic, surrounding ring, which then serves as a docking interface comprising three different conformations for sixteen N-terminal InvG subunits of the outer secretin ring. Unexpectedly, the secretin ring excludes the 16th protein chain at the C-terminal outer ring, resulting in a pleiotropic 16/15-mer ring and consequently to an overall 24:16/15 basal body structure. Finally, we report how the transition from the pseudo-helical export apparatus into the helical filament is structurally resolved to generate the protein secretion channel, which provides the structural basis to restrict access of unfolded effector substrates. These results highlight the diverse molecular signatures required for a highly coordinated assembly process and provide the molecular basis for understanding triggering and transport of unfolded proteins through injectisomes.

scholarly journals Salmonella enterica Serovar Typhimurium SPI-1 and SPI-2 Shape the Global Transcriptional Landscape in a Human Intestinal Organoid Model System

mBio ◽  
2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Anna-Lisa E. Lawrence ◽  
Basel H. Abuaita ◽  
Ryan P. Berger ◽  
David R. Hill ◽  
Sha Huang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Intestinal Epithelium ◽  
Salmonella Enterica ◽  
Secretion System ◽  
Host Responses ◽  
Secretion Systems ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Type 3

ABSTRACT The intestinal epithelium is a primary interface for engagement of the host response by foodborne pathogens, like Salmonella enterica Typhimurium. While the interaction of S. Typhimurium with the mammalian host has been well studied in transformed epithelial cell lines or in the complex intestinal environment in vivo, few tractable models recapitulate key features of the intestine. Human intestinal organoids (HIOs) contain a polarized epithelium with functionally differentiated cell subtypes, including enterocytes and goblet cells and a supporting mesenchymal cell layer. HIOs contain luminal space that supports bacterial replication, are more amenable to experimental manipulation than animals and are more reflective of physiological host responses. Here, we use the HIO model to define host transcriptional responses to S. Typhimurium infection, also determining host pathways dependent on Salmonella pathogenicity island-1 (SPI-1)- and -2 (SPI-2)-encoded type 3 secretion systems (T3SS). Consistent with prior findings, we find that S. Typhimurium strongly stimulates proinflammatory gene expression. Infection-induced cytokine gene expression was rapid, transient, and largely independent of SPI-1 T3SS-mediated invasion, likely due to continued luminal stimulation. Notably, S. Typhimurium infection led to significant downregulation of host genes associated with cell cycle and DNA repair, leading to a reduction in cellular proliferation, dependent on SPI-1 and SPI-2 T3SS. The transcriptional profile of cell cycle-associated target genes implicates multiple miRNAs as mediators of S. Typhimurium-dependent cell cycle suppression. These findings from Salmonella-infected HIOs delineate common and distinct contributions of SPI-1 and SPI-2 T3SSs in inducing early host responses during enteric infection and reinforce host cell proliferation as a process targeted by Salmonella. IMPORTANCE Salmonella enterica serovar Typhimurium (S. Typhimurium) causes a significant health burden worldwide, yet host responses to initial stages of intestinal infection remain poorly understood. Due to differences in infection outcome between mice and humans, physiological human host responses driven by major virulence determinants of Salmonella have been more challenging to evaluate. Here, we use the three-dimensional human intestinal organoid model to define early responses to infection with wild-type S. Typhimurium and mutants defective in the SPI-1 or SPI-2 type-3 secretion systems. While both secretion system mutants show defects in mouse models of oral Salmonella infection, the specific contributions of each secretion system are less well understood. We show that S. Typhimurium upregulates proinflammatory pathways independently of either secretion system, while the downregulation of the host cell cycle pathways relies on both SPI-1 and SPI-2. These findings lay the groundwork for future studies investigating how SPI-1- and SPI-2-driven host responses affect infection outcome and show the potential of this model to study host-pathogen interactions with other serovars to understand how initial interactions with the intestinal epithelium may affect pathogenesis.

scholarly journals Salmonella enterica serovar Typhimurium SPI-1 and SPI-2 shape the transcriptional landscape of epithelial cells in a human intestinal organoid model system

2020 ◽  
Author(s):  
Anna-Lisa E. Lawrence ◽  
Basel H. Abuaita ◽  
Ryan P. Berger ◽  
David R. Hill ◽  
Sha Huang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Host Cell ◽  
Intestinal Epithelium ◽  
Salmonella Enterica ◽  
Secretion System ◽  
Host Responses ◽  
Secretion Systems ◽  
Serovar Typhimurium ◽  
Type 3

AbstractThe intestinal epithelium is a primary interface for engagement of the host response by foodborne pathogens, like Salmonella enterica serovar Typhimurium (STm). While interaction of STm with the mammalian host has been well studied in vitro in transformed epithelial cell lines or in the complex intestinal environment in vivo, few tractable models recapitulate key features of the intestinal epithelium. Human intestinal organoids (HIOs) contain a polarized epithelium with functionally differentiated cell subtypes, including enterocytes and goblet cells. HIOs contain luminal space that supports bacterial replication and are more amenable to experimental manipulation than animals while more reflective of physiological epithelial responses. Here we use the HIO model to define transcriptional responses of the host epithelium to STm infection, also determining host pathways dependent on Salmonella Pathogenicity Island-1 (SPI-1) and -2 (SPI-2) encoded Type 3 secretion systems (T3SS). Consistent with prior findings, we find that STm strongly stimulates pro-inflammatory gene expression. Infection-induced cytokine gene expression was rapid, transient and largely independent of SPI-1 T3SS-mediated invasion, likely due to continued luminal stimulation. Notably, STm infection led to significant down-regulation of host genes associated with cell cycle and DNA repair, an effect that required SPI-1 and SPI-2 T3SS. The transcriptional profile of cell cycle-associated target genes implicates multiple miRNAs as likely mediators of STm-dependent cell cycle suppression. These findings from Salmonella-infected HIOs delineate common and distinct contributions of SPI-1 and SPI-2 T3SSs in inducing early host responses during enteric infection and reveal host cell cycle as a potential target during STm intracellular infection.ImportanceSalmonella enterica serovar Typhimurium (STm) causes a significant health burden worldwide, yet host responses to initial stages of intestinal infection remain poorly understood. Due to differences in infection outcome between mice and humans, evaluating physiological host responses driven by major virulence determinants of Salmonella have been difficult to date. Here we use the 3D human intestinal organoid model to define early responses to infection with wildtype STm and mutants defective in the SPI-1 or SPI-2 Type 3 secretion systems. Both secretion system mutants show defects in a mouse model of oral Salmonella infection but the specific contributions of each secretion system are less well understood. We show that STm upregulates pro-inflammatory pathways independently of either secretion system while downregulation of host cell cycle pathways is dependent on both SPI-1 and SPI-2. These findings lay the groundwork for future studies investigating how SPI-1- and SPI-2-driven host responses affect infection outcome and show the potential of this model to study host-pathogen interactions with other serovars to understand how initial interactions with the intestinal epithelium may affect pathogenesis.

Biomimetic materials: An introduction

1992 ◽  
Vol 50 (2) ◽  
pp. 1020-1021 ◽  
Author(s):  
M. Sarikaya ◽  
J. T. Staley ◽  
I. A. Aksay
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Hierarchical Structures ◽  
Ceramic Composites ◽  
Advanced Materials ◽  
Length Scale ◽  
Spider Webs ◽  
Biomimetic Materials ◽  
Synthetic Materials ◽  
All Ceramic

Biomimetics is an area of research in which the analysis of structures and functions of natural materials provide a source of inspiration for design and processing concepts for novel synthetic materials. Through biomimetics, it may be possible to establish structural control on a continuous length scale, resulting in superior structures able to withstand the requirements placed upon advanced materials. It is well recognized that biological systems efficiently produce complex and hierarchical structures on the molecular, micrometer, and macro scales with unique properties, and with greater structural control than is possible with synthetic materials. The dynamism of these systems allows the collection and transport of constituents; the nucleation, configuration, and growth of new structures by self-assembly; and the repair and replacement of old and damaged components. These materials include all-organic components such as spider webs and insect cuticles (Fig. 1); inorganic-organic composites, such as seashells (Fig. 2) and bones; all-ceramic composites, such as sea urchin teeth, spines, and other skeletal units (Fig. 3); and inorganic ultrafine magnetic and semiconducting particles produced by bacteria and algae, respectively (Fig. 4).

Folding-Controlled Assembly of Ortho-Phenylene-Based Macrocycles

2020 ◽  
Author(s):  
Viraj kirinda ◽  
Scott Hartley
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Structural Changes ◽  
Condensation Product ◽  
Gel Permeation Chromatography ◽  
Emergent Behavior ◽  
Order Structure ◽  
High Level ◽  
Alkoxy Groups ◽  
Energy Surfaces

The self-assembly of foldamers into macrocycles is a simple approach to non-biological higher-order structure. Previous work on the co-assembly of ortho-phenylene foldamers with rod-shaped linkers has shown that folding and self-assembly affect each other; that is, the combination leads to new emergent behavior, such as access to otherwise unfavorable folding states. To this point this relationship has been passive. Here, we demonstrate control of self-assembly by manipulating the foldamers’ conformational energy surfaces. A series of o-phenylene decamers and octamers have been assembled into macrocycles using imine condensation. Product distributions were analyzed by gel-permeation chromatography and molecular geometries extracted from a combination of NMR spectroscopy and computational chemistry. The assembly of o-phenylene decamers functionalized with alkoxy groups or hydrogens gives both [2+2] and [3+3] macrocycles. The mixture results from a subtle balance of entropic and enthalpic effects in these systems: the smaller [2+2] macrocycles are entropically favored but require the oligomer to misfold, whereas a perfectly folded decamer fits well within the larger [3+3] macrocycle that is entropically disfavored. Changing the substituents to fluoro groups, however, shifts assembly quantitatively to the [3+3] macrocycle products, even though the structural changes are well-removed from the functional groups directly participating in bond formation. The electron-withdrawing groups favor folding in these systems by strengthening arene–arene stacking interactions, increasing the enthalpic penalty to misfolding. The architectural changes are substantial even though the chemical perturbation is small: analogous o-phenylene octamers do not fit within macrocycles when perfectly folded, and quantitatively misfold to give small macrocycles regardless of substitution. Taken together, these results represent both a high level of structural control in structurally complex foldamer systems and the demonstration of large-amplitude structural changes as a consequence of a small structural effects.

Preparation of BSA Nanoparticles by Desolvation Technique Using Acetone as Desolvating Agent

2012 ◽  
Vol 5 (1) ◽  
pp. 1643-1647
Author(s):  
Krishna Sailaja A ◽  
Amareshwar P
Keyword(s):  
Aqueous Solution ◽  
Standard Deviation ◽  
Process Parameters ◽  
Self Assembly ◽  
Size Control ◽  
Polymeric Materials ◽  
Preparation Condition ◽  
Assembly Process ◽  
Average Size

In order to see the functionality and toxicity of nanoparticles in various food and drug applications, it is important to establish procedures to prepare nanoparticles of a controlled size. Desolvation is a thermodynamically driven self-assembly process for polymeric materials. In this study, we prepared BSA nanoparticles using the desolvation technique using acetone as desolvating agent. Acetone was added intermittently into 1% BSA solution at different pH under stirring at 700 rpm. Amount of acetone added, intermittent timeline of acetone addition, and pH of solution were considered as process parameters to be optimized. The effect of the process parameters on size of the nanoparticles was studied. The results indicated that the size control of BSA nanoparticles was achieved by adding acetone intermittently. The standard deviation of average size of BSA nanoparticles at each preparation condition was minimized by adding acetone intermittently. The intermittent addition in polymeric aqueous solution can be useful for size control for food or drug applications.  

scholarly journals Interfacial Crystallization and Supramolecular Self-Assembly of Spider Silk Inspired Protein at the Water-Air Interface

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4239
Author(s):  
Pezhman Mohammadi ◽  
Fabian Zemke ◽  
Wolfgang Wagermaier ◽  
Markus B. Linder
Keyword(s):  
Self Assembly ◽  
Spider Silk ◽  
Assembly Process ◽  
Protein Solution ◽  
Time Resolved ◽  
Macromolecular Assembly ◽  
X Ray Scattering ◽  
Air Interface ◽  
Fundamental Research ◽  
Β Sheet

Macromolecular assembly into complex morphologies and architectural shapes is an area of fundamental research and technological innovation. In this work, we investigate the self-assembly process of recombinantly produced protein inspired by spider silk (spidroin). To elucidate the first steps of the assembly process, we examined highly concentrated and viscous pendant droplets of this protein in air. We show how the protein self-assembles and crystallizes at the water–air interface into a relatively thick and highly elastic skin. Using time-resolved in situ synchrotron X-ray scattering measurements during the drying process, we showed that the skin evolved to contain a high β-sheet amount over time. We also found that β-sheet formation strongly depended on protein concentration and relative humidity. These had a strong influence not only on the amount, but also on the ordering of these structures during the β-sheet formation process. We also showed how the skin around pendant droplets can serve as a reservoir for attaining liquid–liquid phase separation and coacervation from the dilute protein solution. Essentially, this study shows a new assembly route which could be optimized for the synthesis of new materials from a dilute protein solution and determine the properties of the final products.

scholarly journals Self-Assembled Nanomaterials Based on Complementary Sn(IV) and Zn(II)-Porphyrins, and Their Photocatalytic Degradation for Rhodamine B Dye

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3598
Author(s):  
Nirmal K. Shee ◽  
Hee-Joon Kim
Keyword(s):  
Aqueous Solution ◽  
Visible Light Irradiation ◽  
Rhodamine B ◽  
Self Assembly ◽  
The Self ◽  
Assembly Process ◽  
Absorption Bands ◽  
Ligand Coordination ◽  
Rhodamine B Dye ◽  
Metal Ligand

A series of porphyrin triads (1–6), based on the reaction of trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP) with six different phenoxy Zn(II)-porphyrins (ZnLn), was synthesized. The cooperative metal–ligand coordination of 3-pyridyl nitrogens in the SnP with the phenoxy Zn(II)-porphyrins, followed by the self-assembly process, leads to the formation of nanostructures. The red-shifts and remarkable broadening of the absorption bands in the UV–vis spectra for the triads in CHCl3 indicate that nanoaggregates may be produced in the self-assembly process of these triads. The emission intensities of the triads were also significantly reduced due to the aggregation. Microscopic analyses of the nanostructures of the triads reveal differences due to the different substituents on the axial Zn(II)-porphyrin moieties. All these nanomaterials exhibited efficient photocatalytic performances in the degradation of rhodamine B (RhB) dye under visible light irradiation, and the degradation efficiencies of RhB in aqueous solution were observed to be 72~95% within 4 h. In addition, the efficiency of the catalyst was not impaired, showing excellent recyclability even after being applied for the degradation of RhB in up to five cycles.

scholarly journals Metal Oxide-Related Dendritic Structures: Self-Assembly and Applications for Sensor, Catalysis, Energy Conversion and Beyond

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1686
Author(s):  
Ruohong Sui ◽  
Paul A. Charpentier ◽  
Robert A. Marriott
Keyword(s):  
Metal Oxide ◽  
Energy Conversion ◽  
Self Assembly ◽  
Hierarchical Structures ◽  
The Self ◽  
Assembly Process ◽  
Electronic Noses ◽  
Dendritic Nanostructures ◽  
Energy Conversion And Storage ◽  
The Aesthetic

In the past two decades, we have learned a great deal about self-assembly of dendritic metal oxide structures, partially inspired by the nanostructures mimicking the aesthetic hierarchical structures of ferns and corals. The self-assembly process involves either anisotropic polycondensation or molecular recognition mechanisms. The major driving force for research in this field is due to the wide variety of applications in addition to the unique structures and properties of these dendritic nanostructures. Our purpose of this minireview is twofold: (1) to showcase what we have learned so far about how the self-assembly process occurs; and (2) to encourage people to use this type of material for drug delivery, renewable energy conversion and storage, biomaterials, and electronic noses.

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