title: Listeria monocytogenes uses Listeria adhesion protein (LAP) to promote bacterial transepithelial translocation and induces expression of LAP receptor Hsp60.
abstract: Listeria monocytogenes interaction with the intestinal epithelium is a key step in the infection process. We demonstrated that Listeria adhesion protein (LAP) promotes adhesion to intestinal epithelial cells and facilitates extraintestinal dissemination in vivo. The LAP receptor is a stress response protein, Hsp60, but the precise role for the LAP-Hsp60 interaction during Listeria infection is unknown. Here we investigated the influence of physiological stressors and Listeria infection on host Hsp60 expression and LAP-mediated bacterial adhesion, invasion, and transepithelial translocation in an enterocyte-like Caco-2 cell model. Stressors such as heat (41°C), tumor necrosis factor alpha (TNF-α) (100 U), and L. monocytogenes infection (10(4) to 10(6) CFU/ml) significantly (P < 0.05) increased plasma membrane and intracellular Hsp60 levels in Caco-2 cells and consequently enhanced LAP-mediated L. monocytogenes adhesion but not invasion of Caco-2 cells. In transepithelial translocation experiments, the wild type (WT) exhibited 2.7-fold more translocation through Caco-2 monolayers than a lap mutant, suggesting that LAP is involved in transepithelial translocation, potentially via a paracellular route. Short hairpin RNA (shRNA) suppression of Hsp60 in Caco-2 cells reduced WT adhesion and translocation 4.5- and 3-fold, respectively, while adhesion remained unchanged for the lap mutant. Conversely, overexpression of Hsp60 in Caco-2 cells enhanced WT adhesion and transepithelial translocation, but not those of the lap mutant. Furthermore, initial infection with a low dosage (10(6) CFU/ml) of L. monocytogenes increased plasma membrane and intracellular expression of Hsp60 significantly, which rendered Caco-2 cells more susceptible to subsequent LAP-mediated adhesion and translocation. These data provide insight into the role of LAP as a virulence factor during intestinal epithelial infection and pose new questions regarding the dynamics between the host stress response and pathogen infection.
authors.affiliation: Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, IN 47907-2009, USA.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Burkholder
authors.forename: Arun K
authors.initials: AK
authors.lastname: Bhunia
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism / Q000502:physiology*; D001422:Bacterial Adhesion / Q000502:physiology; D018988:Bacterial Translocation / Q000502:physiology*; D018938:Caco-2 Cells / Q000378:metabolism / Q000382:microbiology; D018834:Chaperonin 60 / Q000096:biosynthesis* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D054884:Host-Pathogen Interactions / Q000502:physiology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology; D008089:Listeria monocytogenes / Q000378:metabolism / Q000502:physiology*; D008088:Listeriosis / Q000378:metabolism / Q000382:microbiology*; D008856:Microscopy, Fluorescence; D011971:Receptors, Immunologic / Q000096:biosynthesis* / Q000502:physiology
chemical_list: D018829:Adhesins, Bacterial; D018834:Chaperonin 60; D011971:Receptors, Immunologic; C047105:bacterial adhesin receptor