Date of Award

Spring 4-14-2025

Embargo Period

4-15-2030

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Regenerative Medicine and Cell Biology

College

College of Graduate Studies

First Advisor

Amy Engevik

Second Advisor

Garth Swanson

Third Advisor

Melinda Engevik

Fourth Advisor

Silvia Guglietta

Fifth Advisor

Robin Muise-Helmericks

Abstract

The intestinal epithelium functions as a dynamic barrier, relying on precise apical membrane organization to maintain homeostasis and respond to environmental challenges. While apical trafficking, glycoprotein localization, and microvillar organization are critical for barrier integrity, the molecular mechanisms regulating these processes and their roles in inflammation and mucosal defense remain incompletely understood.
This dissertation addresses these gaps in knowledge by investigating Myosin 5b (MYO5B), mucosal defense glycoproteins, and adhesion proteins involved in microvillar organization. I demonstrate that MYO5B plays a key role in colonic barrier function by regulating the mucus layer and limiting susceptibility to inflammation. In a heterozygous MYO5B mouse model, reduced MYO5B expression leads to a thinner mucus layer, increased bacterial permeability, and exacerbated injury in DSS-induced colitis. MYO5B-deficient cells and organoids exhibit heightened proinflammatory responses, suggesting that even partial MYO5B loss predisposes the intestine to inflammation, with implications for inflammatory bowel disease (IBD). Further, I show that MYO5B is critical for the apical trafficking of mucosal defense proteins, MUC13 and DMBT1. MYO5B deficiency in mouse models results in intracellular accumulation of these glycoproteins, which is maintained in vitro in epithelial-only organoid cultures. Additionally, MYO5B-inhibited cells have impaired wound healing in a scratch assay, suggesting that defective glycoprotein trafficking may disrupt epithelial regeneration. Beyond MYO5B, I investigate inflammation-induced changes in apical membrane composition. Clostridioides difficile infection (CDI) upregulates IL-22, promoting the expression of adherent mucins MUC1, MUC4, and MUC13 and altering N-glycosylation in patient samples and mouse models. These findings suggest that IL-22 enhances epithelial defense against CDI by modifying the mucosal surface to resist infection and promote repair. Finally, I investigate the structural adaptations of chemosensory intestinal tuft cells, revealing their enrichment with protocadherins, CDHR2 and CDHR5. Within tuft cells, these adhesion molecules localize to the apical membrane, suggesting a role in organizing microvilli to support sensory and defense functions.
Together, these findings illustrate how apical membrane dynamics shape intestinal homeostasis, mucosal defense, and epithelial repair. By elucidating these mechanisms, this dissertation provides new insights into intestinal epithelial regulation and identifies potential therapeutic targets for inflammatory and infectious diseases.

Rights

Copyright is held by the author. All rights reserved.

Download

Available for download on Monday, April 15, 2030

Share

COinS