The E. coli IbeA receptor Vimentin (Vim), in conjunction with its co-receptor PSF, plays an important role in the pathogenesis of neonatal sepsis and meningitis (NSM), which remains a major cause of death in newborns, especially in low-birth weight infants. The ibeA locus is able to modulate expression of several virulence factors (e.g., fim, ibeB, ompA and biofilm-associated genes) and predominantly contribute to E. coli K1-caused early-onset human NSM by inducing both pathogen penetration and polymorphonuclear neutrophil (PMN) transmigration (PMNT) across the blood-brain barrier (BBB), which consists mainly of brain microvascular endothelial cells (BMEC). Vim has emerged as an organizer of a number of critical proteins involved in cell adhesion/migration and cell signaling. Vim- and PSF-mediated signaling is required for IbeA-induced NF-kB activation, pathogen penetration and PMNT across the BBB, which are the three hallmark features of bacterial meningitis. Lipid rafts (LRs) serve as a signaling platform for Vim, PSF, ?7 nAChR (regulator of inflammation), and other signaling molecules (e.g., caveolin-1, ERK and CaM kinase II). Our recent studies have demonstrated for the first time that Vim and PSF cooperatively regulate IbeA+ E. coli K1-induced NF-kB signaling. Vim forms a complex with IkB, NF-kB and tubulins in the resting cells through its head domain (HD). Vim- mediated modulation of the ubiquitin proteasome system (UPS) is essential for NF-kB activation. IbeA is able to induce the IkB kinase (IKK) activation, dissociation of the Vim/IkB-NF-kB complex, and expression of Vim, ?7 nAChR and proinflammatory factors (PIFs). Nuclear translocation of NF-kB is correlated with increased PSF in the nucleus. Circulating BMECs (cBMEC) and endothelial progenitor cells (EPC) in the blood could be used as cell-based biomarkers for indexing of the CNS injury and for monitoring genome-wide expression signatures (GES) during NSM. Most importantly, we have shown that IbeA+ E. coli-induced NF-kB activation, bacterial invasion, PMNT and BBB permeability are significantly reduced in Vim KO (-/-) mice, which are consistent with the in vitro findings. Based on these results, we hypothesize that Vim- and PSF-induced signaling is a new paradigm in which microbial factors (e.g., IbeA) induce cytoplasmic activation and nuclear translocation of NF-kB through the formation of the initial signaling complexes with other signaling molecules (e.g., caveolin-1, PI3K, ERK, CaM kinase II and Rac1) in lipid rafts. Subsequent activation of the IKK/NF-kB pathway and eventual upregulation of Vim, ?7 nAChR and PIFs lead to CNS inflammation/BBB disorders, which can be detected by cBMEC/EPC-based approaches. Our hypothesis will be examined with the following specific aims: 1). Examine how Vim and PSF act in concert to modulate IbeA-induced NF-kB activation/translocation and how NF-kB subsequently up-regulates gene expression by defining Vim- and PSF-mediated signaling. 2). Determine how Vim and PSF contribute to IbeA-induced pathogen penetration and PMN transmigration across the BBB by SCP analysis of cBMEC and genetic blockage of Vim.

Public Health Relevance

The E. coli IbeA receptor vimentin, in conjunction with its co-receptor PSF, plays an important role in the pathogenesis of neonatal sepsis and meningitis (NSM), which remains a major cause of death in newborns, especially in low-birth weight infants. The novelty and uniqueness of this proposal are the comprehensive studies on the disease-causing mechanisms responsible for the three interrelated hallmark features of bacterial meningitis: NFkB activation, bacterial invasion and white blood cell transmigration across the blood-brain barrier.

Agency
National Institute of Health (NIH)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21NS083967-02
Application #
8660724
Study Section
Clinical Neuroimmunology and Brain Tumors Study Section (CNBT)
Program Officer
Wong, May
Project Start
Project End
Budget Start
Budget End
Support Year
2
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Children's Hospital of Los Angeles
Department
Type
DUNS #
City
Los Angeles
State
CA
Country
United States
Zip Code
90027