出版社：American Society for Biochemistry and Molecular Biology
摘要：Listeria monocytogenes causes listeriosis, a foodborne disease with high mortality rates in vulnerable populations. This Gram-positive intracellular pathogen
disseminates through mammalian tissues via actin-based motility and subsequent formation of host plasma membrane (PM) protrusions to cross cellular
junctions. Recently, we found that 25-hydroxycholesterol (25HC) potently suppressed L. monocytogenes infection by internalizing a specific pool of cholesterol,
termed “accessible cholesterol,” from the PM, preventing induction of membrane protrusions and cell-to-cell spread (1). Accessible cholesterol is a
mobile fraction of PM cholesterol that has been previously shown to regulate cholesterol homeostasis and Hedgehog signaling (2–4). The development of
ALOD4, a toxin-based biosensor of accessible cholesterol, has allowed for visualization of this signaling lipid on the surface of cultured cells (2).
This widefield microscopy image shows binding of ALOD4 (blue) to Caco-2 intestinal epithelial cells (dashed lines outline contact borders) that were
preinfected with L. monocytogenes expressing GFP (green). Bacteria that formed membrane protrusions were identified by their encapsulation by the PM
marker Membrane-RFP (red) (1). Image analysis revealed high concentrations of ALOD4 decorating the Membrane-RFP positive protrusions encapsulating
L. monocytogenes that are poised to cross over from one cell to another (Boxes A and B, closed arrows). In contrast, cytosolic bacteria did not colocalize
with either ALOD4 or Membrane-RFP (Box A, open arrows). When combined with a previous result showing that accessible cholesterol is enriched in
microvilli of CHO cells (3), this image suggests that accessible cholesterol may be important for generating highly curved membrane structures on the PM.
