<p>The
crossing of host barriers (intestinal, blood-brain, and placental) is a critical
step for systemic infections caused by entero-invasive pathogens. In the
intestine, the epithelial cells are the first line of defense against
enteric pathogens. <i>Listeria monocytogenes</i> is a
facultative-intracellular foodborne pathogen that first crosses the intestinal
barrier to cause a systemic infection. However, the underlying
mechanism is not well understood.</p><p><br></p>
<p>We
demonstrate that <i>Listeria</i> adhesion protein (LAP) promotes
the translocation of <i>L. monocytogenes </i>across the intestinal
barrier in mouse models (A/J and C57BL/6). Relative to the wild-type
(WT; serotype 4b) or the isogenic bacterial invasion protein
Internalin A mutant (Δ<i>inlA</i>) strain, the <i>lap<sup>─</sup></i>
strain showed significant defect in translocation across the intestinal
barrier and colonization of the mesenteric-lymph nodes, liver and
spleen in the early phase of infection (24 h and 48
h). LAP induces intestinal epithelial barrier dysfunction for
increased translocation as evidenced by increased permeability
to 4-kDa FITC-dextran (FD4), a marker of paracellular
permeability, in the serum and urine of WT and Δ<i>inlA</i>- infected
mice and across Caco-2 cell barrier, but not the <i>lap<sup>─</sup></i> mutant
strain. Microscopic examination confirmed localization of the WT
and Δ<i>inlA</i> strains in the tight junction, a crucial
barrier of intestinal paracellular permeability, in the mouse ileal tissue
but the <i>lap<sup>─</sup></i> strain remained confined in the
lumen. LAP also upregulates TNF-α and IL-6 in intestinal epithelia
of mice and in Caco-2 cells for increased permeability. </p><p><br></p>
<p>Investigation
of the underlying molecular mechanisms of LAP-mediated increase in intestinal
permeability by using <i>lap<sup>─</sup></i> mutant strain, purified
LAP and shRNA-mediated Hsp60 suppression, we demonstrate that LAP
interacts with its host receptor, Hsp60, and activates the canonical NF-κB
signaling, which in turn facilitates myosin light-chain
kinase (MLCK)-mediated opening of the epithelial barrier via the cellular
redistribution of major epithelial junctional proteins claudin-1, occludin, and
E-cadherin. Pharmacological inhibition of NF-κB or MLCK in cells or
genetic ablation of MLCK in mice (C57BL/6) prevents mislocalization of
epithelial junctional proteins, intestinal permeability and <i>L.
monocytogenes</i> translocation across the intestinal barrier.</p>
<p><br></p><p>Furthermore,
LAP also promotes <i>L. monocytogenes </i>translocation
across the intestinal barrier and systemic dissemination in a
Mongolian gerbil that are permissive to the bacterial invasion proteins;
InlA-and InlB-mediated pathways; similar to that in humans. We show
a direct LAP-dependent and InlA-independent pathway<i> </i>for <i>L.
monocytogenes</i> paracellular translocation across the intestinal
epithelial cells that do not express luminally accessible
E-cadherin. Additionally, we show a functional InlA/E-cadherin interaction
pathway that aids <i>L. monocytogenes</i> translocation by targeting
cells with luminally accessible E-cadherin such as cells at the site of
epithelial cell extrusion, epithelial folds and mucus-expelling goblet
cells. Thus, <i>L. monocytogenes</i> uses LAP to exploit
epithelial innate defense in the early phase of infection to cross the
intestinal epithelial barrier, independent of other invasion proteins.</p><p><br></p>
<p>This
work fills a critical gap in our understanding of <i>L.
monocytogenes </i>pathogenesis and sheds light to the complex interplay
between host-pathogen interactions for bacterial crossing of the crucial
intestinal barrier.</p>
<br>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7396934 |
| Date | 14 January 2021 |
| Creators | Rishi Drolia (5929649) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/CELLULAR_AND_MOLECULAR_MECHANISM_OF_LISTERIA_ADHESION_PROTEIN-MEDIATED_BACTERIAL_CROSSING_OF_THE_INTESTINAL_BARRIER/7396934 |
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