title: Listeria monocytogenes exploits normal host cell processes to spread from cell to cell.
abstract: The bacterial pathogen, Listeria monocytogenes, grows in the cytoplasm of host cells and spreads intercellularly using a form of actin-based motility mediated by the bacterial protein ActA. Tightly adherent monolayers of MDCK cells that constitutively express GFP-actin were infected with L. monocytogenes, and intercellular spread of bacteria was observed by video microscopy. The probability of formation of membrane-bound protrusions containing bacteria decreased with host cell monolayer age and the establishment of extensive cell-cell contacts. After their extension into a recipient cell, intercellular membrane-bound protrusions underwent a period of bacterium-dependent fitful movement, followed by their collapse into a vacuole and rapid vacuolar lysis. Actin filaments in protrusions exhibited decreased turnover rates compared with bacterially associated cytoplasmic actin comet tails. Recovery of motility in the recipient cell required 1-2 bacterial generations. This delay may be explained by acid-dependent cleavage of ActA by the bacterial metalloprotease, Mpl. Importantly, we have observed that low levels of endocytosis of neighboring MDCK cell surface fragments occurs in the absence of bacteria, implying that intercellular spread of bacteria may exploit an endogenous process of paracytophagy.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, California 94305-5307, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Robbins
authors.forename: A I
authors.initials: AI
authors.lastname: Barth
authors.forename: H
authors.initials: H
authors.lastname: Marquis
authors.forename: E L
authors.initials: EL
authors.lastname: de Hostos
authors.forename: W J
authors.initials: WJ
authors.lastname: Nelson
authors.forename: J A
authors.initials: JA
authors.lastname: Theriot
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism* / Q000382:microbiology; D048429:Cell Size; D003593:Cytoplasm / Q000378:metabolism / Q000382:microbiology*; D004285:Dogs; D004705:Endocytosis; D006863:Hydrogen-Ion Concentration; D007365:Intercellular Junctions / Q000378:metabolism / Q000382:microbiology; D007700:Kinetics; D008089:Listeria monocytogenes / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism; D018715:Microscopy, Video; D008954:Models, Biological; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000382:microbiology
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D015820:Cadherins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C072980:actA protein, Listeria monocytogenes; D008666:Metalloendopeptidases; C080367:mpl protein, Listeria monocytogenes