Intestinal Epithelial CD98 Directly Modulates the Innate Host Response to Enteric Bacterial Pathogens

Abstract

e CD98 is a type II transmembrane glycoprotein whose expression increases in intestinal epithelial cells (IECs) during intestinal inflammation. Enteropathogenic Escherichia coli (EPEC) is a food-borne human pathogen that attaches to IECs and injects effector proteins directly into the host cells, thus provoking an inflammatory response. In the present study, we investigated CD98 and EPEC interactions in vitro and ex vivo and examined FVB wild-type (WT) and villin-CD98 transgenic mice overexpressing human CD98 in IECs (hCD98 Tg mice) and infected with Citrobacter rodentium as an in vivo model. In vivo studies indicated that CD98 overexpression, localized to the apical domain of colonic cells, increased the attachment of C. rodentium in mouse colons and resulted in increased expression of proinflammatory markers and decreased expression of anti-inflammatory markers. The proliferative markers Ki-67 and cyclin D1 were significantly increased in the colonic tissue of C. rodentium-infected hCD98 Tg mice compared to that of WT mice. Ex vivo studies correlate with the in vivo data. Small interfering RNA (siRNA) studies with Caco2-BBE cells showed a decrease in adherence of EPEC to Caco2 cells in which CD98 expression was knocked down. In vitro surface plasmon resonance (SPR) experiments showed direct binding between recombinant hCD98 and EPEC/C. rodentium proteins. We also demonstrated that the partial extracellular loop of hCD98 was sufficient for direct binding to EPEC/C. rodentium. These findings demonstrate the importance of the extracellular loop of CD98 in the innate host defense response to intestinal infection by attaching and effacing (A/E) pathogens.

Membrane Protein 4F2/CD98 Is a Cell Surface Receptor Involved in the Internalization and Trafficking of Human β-Defensin 3 in Epithelial Cells

“…The exposure of CD98 to the cellular lumen enables the enteropathogenic bacteria to directly access CD98, resulting in attachment and bacterially induced inflammation. In addition, CD98 is highly expressed in several tumors, including lung and breast, and its overexpression is associated with a poor prognosis (Feng et al, 2006;Shames et al, 2010;Charania et al, 2013). It has been suggested that promotion of tumorigenesis is mediated by the interaction of CD98 with b 1 -integrins (Cantor and Ginsberg, 2012;Furuya et al, 2012;Kaira et al, 2011).…”

“…We unambiguously mapped the hBD3-interacting region to CD98 residues V304-H414, i.e. to the region of the protein that interacts with the proteins of EPEC and C. rodentium (Shames et al, 2010;Charania et al, 2013). This region, which corresponds to almost half the b barrel, is built of four b strands belonging to the barrel and three amphipathic a helices surrounding the barrel.…”

“…This region, which is part of the extracellular domain (see Figure 7A), is highly conserved; in fact, no variants have been described so far within this segment. Notably, the same region was shown by SPR to interact with proteins from enteropathogenic E. coli (EPEC) and Citrobacter rodentium (Shames et al, 2010;Charania et al, 2013).…”

PepT1 expressed in immune cells has an important role in promoting the immune response during experimentally induced colitis

“…Sections were blocked with 10% goat serum with 1% BSA in 1X TBS (Tris-buffered saline), and then incubated with Ly6G antibody (neutrophil marker) (1:1000 dilution) overnight at 4 1C. 42 After washing in TBS, sections were incubated with 0.3% H 2 O 2 and biotinylated goat anti-rat IgG from Vector Labs (Vector Laboratories, Burlingame, CA): Vectastain ABC reaction and DAB reaction (Dako, Carpinteria, CA) were performed subsequently. Slides were counter stained with hematoxylin.…”

Nanotherapeutics for the treatment of inflammatory bowel disease

“…CD98 glycoprotein is a type II membrane glycoprotein heterodimer that comprises a nonglycosylated light chain and a glycosylated heavy chain. Previous studies showed that CD98 is aberrantly overexpressed in intestinal macrophages and the apical plasma membrane of epithelial cells [22]. Moreover, CD98 expression is highly upregulated in colonic epithelial cells from mice with active colitis [23].…”