The establishment and maintenance of epithelial tight junction integrity is essential to the normal function of epithelial organs;above all, the ability of the intestinal epithelium to serve as a selective barrier to antigens and pathogens while absorbing nutrients is fundamental to intestinal function. Also, tight junctions together with associated polarity complexes are critical for the maintenance of epithelial polarity. Our investigations of epithelial development and polarity have focused on the endosomal protein, endotubin. Endotubin is an integral membrane protein that is resident in apical endosomes of polarized epithelial cells. It is expressed at high levels in developing intestine, particularly when the enterocytes are establishing polarity. Moreover, endotubin regulates junctional integrity and epithelial polarity, possibly through interaction with aPKC and Rab14. In this proposal, we will elucidate the mechanism of action of endotubin and Rab14 in the establishment and maintenance of epithelial tight junctions and polarity. Experiments outlined in this proposal will define the role of endotubin and Rab14 in targeting of junctional and apical proteins and elucidate the motifs of endotubin critical for the establishment and maintenance of epithelial junctions. Our hypothesis is that endotubin serves as a scaffolding protein to organize and target junctional and polarity proteins from the apical endosomes. Loss of endotubin function could result in loss of barrier function and/or apical-basolateral polarity, leading to compromised immunity in the newborn, increased susceptibility to inflammatory bowel disease, and/or cancer.

Public Health Relevance

Maintenance of epithelial cell tight junctions is essential for intestinal epithelial barrier function. Understanding the role of membrane trafficking in the generation and maintenance of tight junctions is fundamental to our understanding of intestinal development, normal function, and pathology.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK084047-02
Application #
8212059
Study Section
Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
Program Officer
Carrington, Jill L
Project Start
2011-07-01
Project End
2016-06-30
Budget Start
2012-07-01
Budget End
2013-06-30
Support Year
2
Fiscal Year
2012
Total Cost
$329,513
Indirect Cost
$112,013
Name
University of Arizona
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
806345617
City
Tucson
State
AZ
Country
United States
Zip Code
85721
Lu, Ruifeng; Wilson, Jean M (2016) Rab14 specifies the apical membrane through Arf6-mediated regulation of lipid domains and Cdc42. Sci Rep 6:38249
Cox, Christopher M; Mandell, Edward K; Stewart, Lorraine et al. (2015) Endosomal regulation of contact inhibition through the AMOT:YAP pathway. Mol Biol Cell 26:2673-84
Lu, Ruifeng; Dalgalan, Dogukan; Mandell, Edward K et al. (2015) PKCι interacts with Rab14 and modulates epithelial barrier function through regulation of claudin-2 levels. Mol Biol Cell 26:1523-31
Lu, Ruifeng; Stewart, Lorraine; Wilson, Jean M (2015) Scaffolding protein GOPC regulates tight junction structure. Cell Tissue Res 360:321-32
Lu, Ruifeng; Johnson, Debra L; Stewart, Lorraine et al. (2014) Rab14 regulation of claudin-2 trafficking modulates epithelial permeability and lumen morphogenesis. Mol Biol Cell 25:1744-54
Parker, Sara S; Mandell, Edward K; Hapak, Sophie M et al. (2013) Competing molecular interactions of aPKC isoforms regulate neuronal polarity. Proc Natl Acad Sci U S A 110:14450-5