K. Pattni et al., A PtdIns(3)P-specific probe cycles on and off host cell membranes during Salmonella invasion of mammalian cells, CURR BIOL, 11(20), 2001, pp. 1636-1642
Salmonella invade nonphagocytic cells by eliciting their own internalizatio
n; upon contact with the host cell, the bacteria induce membrane ruffles hi
ghly localized to the point of contact between the invading bacterium and t
he host cell [1, 2]. The bacterium is then internalized into an unusual cyt
osolic organelle, the Salmonella-containing vacuole (SCV). Early endosomal
markers (including EEA1) have recently been shown to be associated with the
SCV shortly after invasion [3]. EEA1, a protein involved in early endosome
fusion, is recruited to early endosomal membranes in part by the interacti
on between its FYVE finger and phosphatidylinositol 3-phosphate [PtdIns(3)P
] [4], a characteristic lipid of early endosomes. This suggests a possible
role for PtdIns(3)P during Salmonella infection. To investigate this, we ge
nerated a highly specific probe for PtdIns(3)P that was used to follow inva
sion of Salmonella in nonphagocytic cells. Here, we show that PtdIns(3)P is
present on the membranes of SCVs shortly after invasion and also that it i
s present on the membrane ruffles produced immediately prior to invasion. W
e also show that this specific probe cycles on and off the membranes of nas
cent SCVs even when PtdIns 3-kinase activity is inhibited, demonstrating th
at invading Salmonella influence the composition of the membranes that enve
lop them during invasion.