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Infect. Immun., 11 1995, 4531-4534, Vol 63, No. 11
H Marquis, V Doshi and DA Portnoy
Intracellular growth of Listeria monocytogenes begins after lysis of the
primary vacuole formed upon bacterial entry into a host cell. Listeriolysin
O (LLO), a pore-forming hemolysin encoded by hly, is essential for vacuolar
lysis in most cell types. However, in human epithelial cells, LLO- mutants
are capable of growth, suggesting that gene products other than LLO are
capable of mediating escape from a vacuole. In this study, we investigated
the role of other bacterial gene products in lysis of the primary vacuole
in the human epithelial cell line Henle 407. Double internal in-frame
deletion mutants were constructed by introducing a mutated hly allele into
strains harboring deletions in either of the phospholipase C (PLC)-encoding
genes or a metalloprotease-encoding gene. Bacterial escape from the primary
vacuole, intracellular growth, and cell-to-cell spread were evaluated in
Henle 407 cells. The results indicated that, in the absence of LLO, the
broad-range PLC and the metalloprotease were both required for lysis of the
primary vacuole in Henle 407 cells. Although phosphatidylinositol-specific
PLC was not required, the efficiency of escape was reduced in an LLO
phosphatidylinositol-specific PLC double mutant. These observations suggest
that the relative importance of LLO, the phospholipases, and the
metalloprotease may vary in different cell types or in cells from different
species. In addition, these studies provide insight into the mechanisms of
action of virulence determinants involved in the lysis of vacuolar
membranes.
Copyright © 1995, American Society for Microbiology
The broad-range phospholipase C and a metalloprotease mediate listeriolysin O-independent escape of Listeria monocytogenes from a primary vacuole in human epithelial cells
Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
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