Host membrane lipids are trafficked to membranes of intravacuolar bacterium Ehrlichia chaffeensis
| Autor: | Mingqun Lin, Sriram Subramaniam, Yasuko Rikihisa, Lisa M. Hartnell, Giovanna Grandinetti, Donald Bliss |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Intravital Microscopy
Endosome THP-1 Cells Membrane lipids Endocytic cycle Endosomes Microbiology Time-Lapse Imaging chemistry.chemical_compound intraluminal vesicles Dogs Ehrlichia chaffeensis Animals Humans Secretion Phosphatidylinositol glycerophospholipids Inclusion Bodies Multidisciplinary biology Chemistry Ehrlichia Cell Membrane Autophagosomes Ehrlichiosis cholesterol Biological Sciences biology.organism_classification Cell biology Membrane HEK293 Cells membranes Host-Pathogen Interactions Vacuoles Microscopy Electron Scanning Phosphatidylcholines lipids (amino acids peptides and proteins) |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | Significance Biological membranes are essential for life. Although bacteria and eukaryotic cells have evolved to produce membranes of different compositions, several bacterial pathogens can hijack and utilize host-synthesized membrane lipids. Here, we show that an obligatory intracellular pathogen, Ehrlichia chaffeensis, deficient in biosynthesis of cholesterol and some glycerophospholipids, actively acquires host-derived membrane components within membrane-bound inclusions (vacuoles). The trafficking of host membrane components to Ehrlichia and membrane-bound inclusions appears to occur via endocytosis and autophagy induced by a bacteria-secreted protein. Numerous intraluminal vesicles were found in Ehrlichia inclusions that may function as a membrane reserve for rapid proliferation of Ehrlichia. Our findings provide insights into host membrane assimilation by an intracellular pathogen, which can be exploited for antibacterial therapy. Ehrlichia chaffeensis, a cholesterol-rich and cholesterol-dependent obligate intracellular bacterium, partially lacks genes for glycerophospholipid biosynthesis. We found here that E. chaffeensis is 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. chaffeensis cannot 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 to Ehrlichia inclusion and bacterial membranes, but DiI-prelabeled Ehrlichia membranes were not trafficked to host-cell membranes. The trafficking of host-cell membranes to Ehrlichia inclusions 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 to Ehrlichia. In addition, DiI-labeled host-cell membranes were trafficked to autophagosomes induced by the E. chaffeensis type IV secretion system effector Etf-1, which traffic to and fuse with Ehrlichia inclusions. 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 that Ehrlichia inclusions 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. |
| Databáze: | OpenAIRE |
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