Epithelial barrier dysfunction contributes to progression of intestinal and systemic disease. However, there is a fundamental gap that separates clinicopathologic significance from molecular understanding of the mechanisms responsible for barrier regulation. The major components of the tight junction, which forms the paracellular barrier, have been identified over the past two decades and fall into three major groups;scaffold proteins, e.g. ZO-1;transmembrane structural proteins, e.g. occludin;and pore-forming proteins, e.g. claudins. How these proteins interact to regulate the barrier is incompletely understood. Thus, tight junction biology is at a crossroads that requires a transition from protein discovery to identification of essential regulatory mechanisms. These must be considered in the context of distinct components of paracellular permeability that define flux of either large solutes or small ions and water. We have recently shown that these aspects of barrier function are differentially regulated by the pathologically-relevant cytokines TNF and IL-13, respectively. The long term goal of these studies is to understand tight junction structure and regulation in molecular terms and to leverage this knowledge to develop approaches to modulate specific barrier components and improve health. The objective of this application is to define the interactions among tight junction components that regulate dynamic protein behavior and barrier function using newly-developed in vitro and in vivo approaches. Our central hypothesis is that the interactions responsible for tight junction protein anchoring and trafficking are the primary determinants of paracellular barrier function. This hypothesis has been formulated on the basis of strong preliminary data produced with support of the current funding cycle. The rationale for this project is that it will provide unprecedented insight into the molecular interactions that regulate barrier function and, in turn, will allow manipulation of these processes for therapeutic benefit. The hypothesis will be tested via specific aims: 1) To define the contributions of specific ZO-1 domains to trafficking, anchoring, and tight junction barrier regulation;2) To determine the structural elements and phosphorylation events that regulate occludin trafficking, interprotein interactions, and in vitro and in vivo barrier function;and 3) To identify the structural elements and functional interactions by which claudin domains regulate pore assembly and opening. While each aim focuses on a critical tight junction protein or protein family, interactions among these will allow integration and development of a unified model of tight junction structure and regulation. The proposal is innovative because it explores the novel idea that dynamic regulation of protein interactions controls barrier function, which signals a major shift in our understanding of tight junction biology. The proposed research is significant because it will enhance our understanding of barrier dysfunction and link specific mechanisms of barrier loss to disease. The concepts and tools developed will make it possible to develop agents that target distinct barrier components and, ultimately, to treat diseases of epithelial and endothelial barriers.

Public Health Relevance

The proposed research is relevant to public health because discovery of the mechanisms that regulate tissue barriers that separate sterile internal compartments from those colonized by microbiota, e.g. the intestinal lumen, will allow development of means to prevent or correct barrier defects in disease. This work will therefore directly support the overall NIH mission of developing fundamental knowledge that will help reduce the burden of human disease and promote the NIDDK goal of improving digestive health.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
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Grey, Michael J
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University of Chicago
Schools of Medicine
United States
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Yu, Linda Chia-Hui; Shih, Yi-An; Wu, Li-Ling et al. (2014) Enteric dysbiosis promotes antibiotic-resistant bacterial infection: systemic dissemination of resistant and commensal bacteria through epithelial transcytosis. Am J Physiol Gastrointest Liver Physiol 307:G824-35
Turner, Jerrold R; Buschmann, Mary M; Romero-Calvo, Isabel et al. (2014) The role of molecular remodeling in differential regulation of tight junction permeability. Semin Cell Dev Biol 36:204-12
Wu, Li-Ling; Peng, Wei-Hao; Kuo, Wei-Ting et al. (2014) Commensal bacterial endocytosis in epithelial cells is dependent on myosin light chain kinase-activated brush border fanning by interferon-?. Am J Pathol 184:2260-74
Nalle, Sam C; Kwak, H Aimee; Edelblum, Karen L et al. (2014) Recipient NK cell inactivation and intestinal barrier loss are required for MHC-matched graft-versus-host disease. Sci Transl Med 6:243ra87
Odenwald, Matthew A; Turner, Jerrold R (2013) Intestinal permeability defects: is it time to treat? Clin Gastroenterol Hepatol 11:1075-83
Bergmann, Kelly R; Liu, Shirley X L; Tian, Runlan et al. (2013) Bifidobacteria stabilize claudins at tight junctions and prevent intestinal barrier dysfunction in mouse necrotizing enterocolitis. Am J Pathol 182:1595-606
Su, Liping; Nalle, Sam C; Shen, Le et al. (2013) TNFR2 activates MLCK-dependent tight junction dysregulation to cause apoptosis-mediated barrier loss and experimental colitis. Gastroenterology 145:407-15
Buschmann, Mary M; Shen, Le; Rajapakse, Harsha et al. (2013) Occludin OCEL-domain interactions are required for maintenance and regulation of the tight junction barrier to macromolecular flux. Mol Biol Cell 24:3056-68
Rubin, David T; Huo, Dezheng; Kinnucan, Jami A et al. (2013) Inflammation is an independent risk factor for colonic neoplasia in patients with ulcerative colitis: a case-control study. Clin Gastroenterol Hepatol 11:1601-8.e1-4
Edelblum, Karen L; Shen, Le; Weber, Christopher R et al. (2012) Dynamic migration of ýýýý intraepithelial lymphocytes requires occludin. Proc Natl Acad Sci U S A 109:7097-102

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