Bacterial colonization of host cells in the absence of cholesterol.
Reports implicating important roles for cholesterol and cholesterol-rich lipid rafts in host-pathogen interactions have largely employed sterol sequestering agents and biosynthesis inhibitors. Because the pleiotropic effects of these compounds can complicate experimental interpretation, we developed a new model system to investigate cholesterol requirements in pathogen infection utilizing DHCR24(-/-) mouse embryonic fibroblasts (MEFs). DHCR24(-/-) MEFs lack the Δ24 sterol reductase required for the final enzymatic step in cholesterol biosynthesis, and consequently accumulate desmosterol into cellular membranes. Defective lipid raft function by DHCR24(-/-) MEFs adapted to growth in cholesterol-free medium was confirmed by showing deficient uptake of cholera-toxin B and impaired signaling by epidermal growth factor. Infection in the absence of cholesterol was then investigated for three intracellular bacterial pathogens: Coxiella burnetii, Salmonella enterica serovar Typhimurium, and Chlamydia trachomatis. Invasion by S. Typhimurium and C. trachomatis was unaltered in DHCR24(-/-) MEFs. In contrast, C. burnetii entry was significantly decreased in -cholesterol MEFs, and also in +cholesterol MEFs when lipid raft-associated α(V)β(3) integrin was blocked, suggesting a role for lipid rafts in C. burnetii uptake. Once internalized, all three pathogens established their respective vacuolar niches and replicated normally. However, the C. burnetii-occupied vacuole within DHCR24(-/-) MEFs lacked the CD63-positive material and multilamellar membranes typical of vacuoles formed in wild type cells, indicating cholesterol functions in trafficking of multivesicular bodies to the pathogen vacuole. These data demonstrate that cholesterol is not essential for invasion and intracellular replication by S. Typhimurium and C. trachomatis, but plays a role in C. burnetii-host cell interactions.
Coxiella Pathogenesis Section, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America.
Stacey D
SD
Gilk
Diane C
DC
Cockrell
Courtney
C
Luterbach
Bryan
B
Hansen
Leigh A
LA
Knodler
J Antonio
JA
Ibarra
Olivia
O
Steele-Mortimer
Robert A
RA
Heinzen
D000818:Animals; D001419:Bacteria / Q000254:growth & development / Q000472:pathogenicity*; D001424:Bacterial Infections / Q000378:metabolism*; D018407:Bacterial Physiological Phenomena; D002478:Cells, Cultured; D002784:Cholesterol / Q000172:deficiency* / Q000378:metabolism; D015169:Colony Count, Microbial; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D054884:Host-Pathogen Interactions; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013045:Species Specificity
D002784:Cholesterol