Identification of LpeA, a PsaA-like membrane protein that promotes cell entry by Listeria monocytogenes.
The intracellular life of Listeria monocytogenes starts by a complex process of entry involving several bacterial ligands and eukaryotic receptors. In this work, we identified in silico from the sequence of the genome of L. monocytogenes a previously unknown gene designated lpeA (for lipoprotein promoting entry) encoding a 35-kDa protein homologous to PsaA, a lipoprotein belonging to the LraI family and implicated in the cell adherence of Streptococcus pneumoniae and related species. By constructing a mutant of L. monocytogenes in which lpeA is deleted (lpeA mutant), we show that the PsaA-like protein LpeA is not involved in bacterial adherence but is required for entry of L. monocytogenes in eukaryotic cells. In contrast to wild-type bacteria, mutant bacteria failed to invade the epithelial Caco-2 and hepatocyte TIB73 cell lines, as confirmed by confocal microscopy. The mutant bacteria rapidly penetrated in mouse bone marrow-derived macrophages. Surprisingly, lpeA mutant bacteria survive better in macrophages than do wild-type bacteria. This was correlated with a weak exacerbation of virulence of the lpeA mutant in the mouse. LpeA is therefore a novel invasin favoring the entry of L. monocytogenes into nonprofessional phagocytes but not its invasion of macrophages. This is the first report of a lipoprotein promoting cell invasion of an intracellular pathogen.
Réglier-Poupet
Hélène
H
INSERM U570, Faculté de Médecine Necker-Enfants Malades, 75730 Paris cedex 15, France.
Pellegrini
Elisabeth
E
Charbit
Alain
A
Berche
Patrick
P
D018829:Adhesins, Bacterial; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008074:Lipoproteins / Q000235:genetics* / Q000378:metabolism*; D008089:Listeria monocytogenes / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D008088:Listeriosis / Q000382:microbiology / Q000401:mortality; D008264:Macrophages / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D008969:Molecular Sequence Data; D014774:Virulence
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008074:Lipoproteins; C470924:LpeA protein, Listeria monocytogenes; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C085000:PsaA protein, Streptococcus