Host membrane lipids are trafficked to membranes of intravacuolar bacteriumEhrlichia chaffeensis

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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Reduction of phospholipase D activity during coxsackievirus infection

Journal of General Virology ◽

10.1099/vir.0.83169-0 ◽

2007 ◽

Vol 88 (11) ◽

pp. 3027-3030 ◽

Cited By ~ 1

Author(s):

Daniël Duijsings ◽

Els Wessels ◽

Sjenet E. van Emst-de Vries ◽

Willem J. G. Melchers ◽

Peter H. G. M. Willems ◽

...

Keyword(s):

Host Cell ◽

Phospholipase D ◽

Cell Membranes ◽

Ectopic Expression ◽

Rna Replication ◽

Enterovirus Infection ◽

Defective Mutant ◽

Infected Cells ◽

Host Cell Membranes ◽

Adp Ribosylation Factor

During enterovirus infection, host cell membranes are rigorously rearranged and modified. One ubiquitously expressed lipid-modifying enzyme that might contribute to these alterations is phospholipase D (PLD). Here, we investigated PLD activity in coxsackievirus-infected cells. We show that PLD activity is not required for efficient coxsackievirus RNA replication. Instead, PLD activity rapidly decreased upon infection and upon ectopic expression of the viral 3A protein, which inhibits the PLD activator ADP-ribosylation factor 1. However, similar decreases were observed during infection with coxsackieviruses carrying defective mutant 3A proteins. Possible causes for the reduction of PLD activity and the biological consequences are discussed.

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

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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Human Cytomegalovirus Tegument Protein pUL71 Is Required for Efficient Virion Egress

mBio ◽

10.1128/mbio.00282-10 ◽

2010 ◽

Vol 1 (5) ◽

Cited By ~ 34

Author(s):

Andrew Womack ◽

Thomas Shenk

Keyword(s):

Host Cell ◽

Human Cytomegalovirus ◽

Cell Membranes ◽

Viral Assembly ◽

Mutant Virus ◽

Wild Type Virus ◽

Virus Particles ◽

Infected Cells ◽

Host Cell Membranes ◽

Assembly Compartment

ABSTRACT The human cytomegalovirus virion is composed of a DNA genome packaged in an icosahedral capsid, surrounded by a tegument of protein and RNA, all enclosed within a glycoprotein-studded envelope. Achieving this intricate virion architecture requires a coordinated process of assembly and egress. We show here that pUL71, a component of the virion tegument with a previously uncharacterized function, is required for the virus-induced reorganization of host cell membranes, which is necessary for efficient viral assembly and egress. A mutant that did not express pUL71 was able to efficiently accumulate viral genomes and proteins that were tested but was defective for the production and release of infectious virions. The protein localized to vesicular structures at the periphery of the viral assembly compartment, and during infection with a pUL71-deficient virus, these structures were grossly enlarged and aberrantly contained a cellular marker of late endosomes/lysosomes. Mutant virus preparations exhibited less infectivity per unit genome than wild-type virus preparations, due to aggregation of virus particles and their association with membrane fragments. Finally, mutant virus particles accumulated within the cytoplasm of infected cells and were localized to the periphery of large structures with properties of lysosomes, whose formation was kinetically favored in mutant-virus-infected cells. Together, these observations point to a role for pUL71 in the establishment and/or maintenance of a functional viral assembly compartment that is required for normal virion trafficking and egress from infected cells. IMPORTANCE In addition to causing disease in immunocompromised individuals, human cytomegalovirus is the leading known infectious cause of birth defects. To induce these pathologies, the virus must spread from its site of introduction to various organs and tissues in the body. The processes of viral assembly and egress, which underlie the spread of infection, are incompletely understood. We elucidate a role for a virus-coded protein, pUL71, in these processes and demonstrate the importance of maintaining an intricate, virus-induced reorganization of host cell membranes for efficient virus spread.

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