Once thought to be little more than blobs of fat inside eukaryotic cells, lipid droplets may in fact provide a first line of defence against invading pathogens, according to evidence published today (October 15) in
Science. When a bacterium enters a cell's cytoplasm, intracellular lipid droplets close in, bringing with them an arsenal of antimicrobial proteins, the research shows.
"
This is the first evidence that there's a direct [immune] mechanism between lipid droplets and intracellular pathogens, and I thought that was just fascinating," says Stacey Gilk of the University of Nebraska Medical Center who studies microbial pathology and was not involved in the research.
"We've known about lipid droplets for over 100 years, but still don't know much about them," adds virologist Sue Crawford at Baylor College of Medicine who also did not participate in the study. "This is a fantastic paper," she says. It "really pinpointed some of the mechanisms by which lipid droplets have an antibacterial function."
Lipid droplets are a type of organelle that exists in all eukaryotic cells. They are jam-packed full of fats, as the name would suggest, and surrounded by a phospholipid monolayer (as opposed to the classic bilayer membrane surrounding most other organelles). Historically lipid droplets have been thought of as sites for storing excess fats and supplying them when and where needed — for instance, to the mitochondria for energy production. More recently, research has shown that certain cell-invading viruses, bacteria, and parasites exploit these fuel-rich droplets for survival and growth, says Crawford.
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