To infect or not to infect: molecular determinants of bacterial outer membrane vesicle internalization by host membranes

Mapping Intimacies ◽

10.1101/763334 ◽

2019 ◽

Author(s):

Damien Jefferies ◽

Syma Khalid

Keyword(s):

Host Cell ◽

Outer Membrane ◽

Cell Membranes ◽

Outer Membrane Vesicles ◽

Coarse Grained ◽

Shape Preservation ◽

Target Cells ◽

Bacterial Membranes ◽

Host Pathogen ◽

Host Cell Membranes

AbstractOuter membrane vesicles (OMVs) are spherical liposomes that are secreted by almost all forms of Gram-negative bacteria. The nanospheres contribute to bacterial pathogenesis by trafficking molecular cargo from bacterial membranes to target cells at the host-pathogen interface. We have simulated the interaction of OMVs with host cell membranes to understand why OMV uptake depends on the length of constituent lipopolysaccharide macromolecules. Using coarse-grained molecular dynamics simulations, we show that lipopolysaccharide lipid length affects OMV shape at the host-pathogen interface: OMVs with long (smooth-type) lipopolysaccharide lipids retain their spherical shape when they interact with host cell membranes, whereas OMVs with shorter (rough-type) lipopolysaccharide lipids distort and spread over the host membrane surface. In addition, we show that OMVs preferentially coordinate domain-favoring ganglioside lipids within host membranes to enhance curvature and affect the local lipid composition. We predict that these differences in shape preservation affect OMV internalization on long timescales: spherical nanoparticles tend to be completely enveloped by host membranes, whereas low sphericity nanoparticles tend to remain on the surface of cells.

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Large fluctuations of the fusion intermediate help SARS-CoV-2 capture host cell membranes

10.1101/2021.04.09.439051 ◽

2021 ◽

Author(s):

Rui Su ◽

Jin Zeng ◽

Ben O'Shaughnessy

Keyword(s):

Host Cell ◽

Drug Targets ◽

Cell Membranes ◽

Computational Models ◽

Coarse Grained ◽

Mechanical Assembly ◽

Large Fluctuations ◽

Target Membrane ◽

Coarse Grained Simulations ◽

Host Cell Membranes

Cell entry of SARS-CoV-2 is accomplished by the S2 subunit of the spike S protein on the virion surface by fusion of viral and host cell membranes. Fusion requires the prefusion S2 to transit to its potent, fusogenic form, the fusion intermediate (FI). However, the FI structure is unknown, detailed computational models of the FI are not available, and the mechanisms of fusion and entry remain unclear. Here, we constructed a full-length model of the CoV-2 FI by extrapolating from known CoV-2 pre- and postfusion structures. Atomistic and coarse-grained simulations showed the FI is a remarkably flexible mechanical assembly executing large orientational and extensional fluctuations due to three hinges in the C-terminal base. Fluctuations lead to a large fusion peptide exploration volume and may aid capture of the host cell target membrane and define the clock for fluctuation-triggered refolding and membrane fusion. This work suggests several novel potential drug targets.

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Host membrane lipids are trafficked to membranes of intravacuolar bacteriumEhrlichia chaffeensis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1921619117 ◽

2020 ◽

Vol 117 (14) ◽

pp. 8032-8043 ◽

Cited By ~ 4

Author(s):

Mingqun Lin ◽

Giovanna Grandinetti ◽

Lisa M. Hartnell ◽

Donald Bliss ◽

Sriram Subramaniam ◽

...

Keyword(s):

Host Cell ◽

Cell Membranes ◽

Membrane Lipids ◽

Ion Beam ◽

Multivesicular Bodies ◽

Bacterial Membranes ◽

Bacterial Proliferation ◽

Early Endosomes ◽

Infected Cells ◽

Host Cell Membranes

Ehrlichia chaffeensis, a cholesterol-rich and cholesterol-dependent obligate intracellular bacterium, partially lacks genes for glycerophospholipid biosynthesis. We found here thatE. chaffeensisis dependent on host glycerolipid biosynthesis, as an inhibitor of host long-chain acyl CoA synthetases, key enzymes for glycerolipid biosynthesis, significantly reduced bacterial proliferation.E. chaffeensiscannot synthesize phosphatidylcholine or cholesterol but encodes enzymes for phosphatidylethanolamine (PE) biosynthesis; however, exogenous NBD-phosphatidylcholine, Bodipy-PE, and TopFluor-cholesterol were rapidly trafficked to ehrlichiae in infected cells. DiI (3,3′-dioctadecylindocarbocyanine)-prelabeled host-cell membranes were unidirectionally trafficked toEhrlichiainclusion and bacterial membranes, but DiI-prelabeledEhrlichiamembranes were not trafficked to host-cell membranes. The trafficking of host-cell membranes toEhrlichiainclusions was dependent on both host endocytic and autophagic pathways, and bacterial protein synthesis, as the respective inhibitors blocked both infection and trafficking of DiI-labeled host membranes toEhrlichia. In addition, DiI-labeled host-cell membranes were trafficked to autophagosomes induced by theE. chaffeensistype IV secretion system effector Etf-1, which traffic to and fuse withEhrlichiainclusions. Cryosections of infected cells revealed numerous membranous vesicles inside inclusions, as well as multivesicular bodies docked on the inclusion surface, both of which were immunogold-labeled by a GFP-tagged 2×FYVE protein that binds to phosphatidylinositol 3-phosphate. Focused ion-beam scanning electron microscopy of infected cells validated numerous membranous structures inside bacteria-containing inclusions. Our results support the notion thatEhrlichiainclusions are amphisomes formed through fusion of early endosomes, multivesicular bodies, and early autophagosomes induced by Etf-1, and they provide host-cell glycerophospholipids and cholesterol that are necessary for bacterial proliferation.

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