(868.5) ErbB3 Promotes Intestinal Barrier Function and Expression of the Tight Junctional Protein Pmp22

Poster Board Number: E213

Jonathan Hsieh (Childrens Hospital Los Angeles, University of Southern California), Dana Almohazey (Imam Abdulrahman Bin Faisal University), Mark Frey (Childrens Hospital Los Angeles, University of Southern California)

Background: ErbB3 is a member of the ErbB/EGFR family of receptor tyrosine kinases, and is the constitutively-expressed neuregulin (NRG) receptor in the intestinal epithelium. Pathways downstream of ErbB3 have been implicated in regulating tight junctions in other systems, but a role for ErbB3 in barrier function in the gut has not been described. Here we tested the hypothesis that ErbB3 is required for maintenance of normal barrier function in the intestine.

Methods: We generated Villin-Cre;ErbB3flox/flox mice (ErbB3-IEKO) with ErbB3 deletion in the intestinal epithelium. All comparisons are to ErbB3flox/flox littermate controls. Mice were given a FITC-dextran 4 kDa gavage to assess intestinal permeability. Ileal samples were collected for RT-qPCR, immunohistochemistry, and bulk RNA-seq analysis. Enteroids were generated and treated with the ErbB3 ligand NRG-1β. Caco-2BBe cells were grown on Transwells, treated with NRG-1β, and assessed for TEER and FITC-dextran (4kDa) flux.

Results: ErbB3-IEKO mice displayed increased intestinal barrier permeability to 4kDa FITC-dextran compared to controls (p lt; 0.01). RNA-seq analysis showed a decrease in the expression of the putative tight junction protein Pmp22 in ErbB3-IEKO mice, while other tight junctional components were unchanged. RT-qPCR analysis of Ileal samples showed an 80% Pmp22 downregulation with ErbB3 loss (p lt; 0.01) compared to controls, with similar results in ErbB3-deficient enteroids. Immunohistochemical analysis confirmed near complete loss of PMP22 in ErbB3-IEKO mice. In vitro, treatment with NRG-1β induced Pmp22 expression in control enteroids (p lt; 0.001) but not in ErbB3-deficient enteroids. Furthermore, treatment of Caco-2BBe monolayers with NRG-1β increased TEER and reduced FITC-dextran flux, demonstrating active regulation of permeability. 

Conclusions: We demonstrate that loss of ErbB3 in the intestinal epithelium leads to reduced expression of the tight junction protein PMP22 and impaired barrier function in mice. This may represent a mechanism for regulation of the intestinal barrier through ErbB3 and PMP22. Furthermore, increased TEER in Caco-2BBe monolayers following NRG-1β treatment suggests induction of PMP22 may represent a means to enhance barrier function. Since disrupted intestinal barrier function contributes to the pathophysiology of chronic inflammatory conditions such as inflammatory bowel disease, these results may point to potential future therapeutic interventions targeting the barrier.

Supported by NIH awards R01DK095004 (MRF) and F31DK131856 (JJH)