Contribution of phosphatidylserine to membrane surface charge and protein targeting during phagosome maturation.
During phagocytosis, the phosphoinositide content of the activated membrane decreases sharply, as does the associated surface charge, which attracts polycationic proteins. The cytosolic leaflet of the plasma membrane is enriched in phosphatidylserine (PS); however, a lack of suitable probes has precluded investigation of the fate of this phospholipid during phagocytosis. We used a recently developed fluorescent biosensor to monitor the distribution and dynamics of PS during phagosome formation and maturation. Unlike the polyphosphoinositides, PS persists on phagosomes after sealing even when other plasmalemmal components have been depleted. High PS levels are maintained through fusion with endosomes and lysosomes and suffice to attract cationic proteins like c-Src to maturing phagosomes. Phagocytic vacuoles containing the pathogens Legionella pneumophila and Chlamydia trachomatis, which divert maturation away from the endolysosomal pathway, are devoid of PS, have little surface charge, and fail to recruit c-Src. These findings highlight a function for PS in phagosome maturation and microbial killing.
Yeung
Tony
T
Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G1X8, Canada.
Heit
Bryan
B
Dubuisson
Jean-Francois
JF
Fairn
Gregory D
GD
Chiu
Basil
B
Inman
Robert
R
Kapus
Andras
A
Swanson
Michele
M
Grinstein
Sergio
S
D000818:Animals; D015374:Biosensing Techniques; D002478:Cells, Cultured; D002692:Chlamydia trachomatis; D016952:Legionella pneumophila; D008164:Luminescent Proteins / Q000032:analysis; D051379:Mice; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000737:chemistry / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000235:genetics / Q000502:physiology; D010718:Phosphatidylserines / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D021382:Protein Sorting Signals; D021381:Protein Transport; D015398:Signal Transduction; D013499:Surface Properties
D008164:Luminescent Proteins; D018129:Phosphatidylinositol Phosphates; D010718:Phosphatidylserines; D021382:Protein Sorting Signals; C055525:phosphatidylinositol 3-phosphate