Intestinal barrier function is compromised in infectious and immune-mediated intestinal diseases. This program, now completing its third funding cycle, has focused on the mechanisms and impact of intestinal epithelial barrier dysfunction. In previous cycles we defined epithelial myosin light chain kinase (MLCK) as a critical regulator of tight junction barrier function in response to inflammatory stimuli. This work has been replicated widely and extended to other systems. We went on to show that MLCK-dependent increases in permeability promote progression of inflammatory bowel disease and graft-versus-host disease. We also defined signaling events downstream of MLCK activation and found that while the barrier is regulated by the immune system, MLCK-dependent increases in tight junction permeability are also able to regulate mucosal immunity that triggers increases in claudin-2 expression. This led to our co-discovery of the pore and leak pathways of trans-tight junction flux; a model that is now widely accepted. In the current cycle we focused on the pore and leak pathways and found that, in the context of infectious disease, increased tight junction permeability as a result of claudin-2 expression is beneficial and promotes pathogen clearance. In addition, we identified a specific MLCK splice variant, MLCK1, as a critical regulator of tight junction permeability. In addition to activating MLCK transcription and enzymatic activity, we found that inflammatory stimuli cause MLCK1 to be recruited to the perijunctional actomyosin ring. We identified a specific domain, immunoglobulin- cell adhesion molecule domain 3 (IgCAM3) as being required for MLCK1 recruitment and sufficient to act as a dominant negative to block recruitment. We went on to solve the IgCAM3 crystal structure, identify a potential drug-binding pocket that was conserved between human and mouse IgCAM3 but absent in other MLCK IgCAMs, and perform an in silico screen of a NCI library of ~140,000 drug-like molecules. We identified one, termed Divertin, that prevents MLCK1 recruitment without inhibiting epithelial or smooth muscle MLCK enzymatic function. By blocking MLCK1 recruitment to the perijunctional actomyosin ring, Divertin prevents MLCK1 from phosphorylating myosin II regulatory light chain at that site. This, in turn, blocks inflammation- induced barrier loss in vitro, in vivo (mice), and ex vivo (human intestinal biopsies). Divertin attenuated all features of experimental immune-mediated inflammatory bowel disease (mice), including barrier loss, immune activation, and mortality.
The aim of this proposal is to identify the intracellular protein interactions modified by Divertin and define the molecular mechanisms of MLCK1 recruitment. The studies described will characterize MLCK1 binding partners we have already discovered as well as new binding partners identified through cutting-edge proteomic approaches. At completion, these studies will have defined the MLCK1 interactome and mechanisms by which recruitment is regulated as well as the potential benefits and risks of inhibiting MLCK1 recruitment. These advances will enable future development of Divertin-like agents for human use.

Public Health Relevance

The intestinal lining (epithelium) must maintain a barrier that keeps the intestinal contents separate from the remainder of the body. This function is frequently compromised in intestinal disease and has been implicated as an early step in disease development. The proposed studies will advance mechanistic understanding of barrier regulation and dysregulation and will lay a foundation for development of novel therapeutic approaches to improve human health.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK068271-16
Application #
9935039
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Greenwel, Patricia
Project Start
2005-07-01
Project End
2023-06-30
Budget Start
2020-07-01
Budget End
2021-06-30
Support Year
16
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
030811269
City
Boston
State
MA
Country
United States
Zip Code
02115
Krug, S M; Bojarski, C; Fromm, A et al. (2018) Tricellulin is regulated via interleukin-13-receptor ?2, affects macromolecule uptake, and is decreased in ulcerative colitis. Mucosal Immunol 11:345-356
Odenwald, Matthew A; Choi, Wangsun; Kuo, Wei-Ting et al. (2018) The scaffolding protein ZO-1 coordinates actomyosin and epithelial apical specializations in vitro and in vivo. J Biol Chem 293:17317-17335
Buckley, Aaron; Turner, Jerrold R (2018) Cell Biology of Tight Junction Barrier Regulation and Mucosal Disease. Cold Spring Harb Perspect Biol 10:
Syed, Sana; Yeruva, Sunil; Herrmann, Jeremy et al. (2018) Environmental Enteropathy in Undernourished Pakistani Children: Clinical and Histomorphometric Analyses. Am J Trop Med Hyg 98:1577-1584
Drolia, Rishi; Tenguria, Shivendra; Durkes, Abigail C et al. (2018) Listeria Adhesion Protein Induces Intestinal Epithelial Barrier Dysfunction for Bacterial Translocation. Cell Host Microbe 23:470-484.e7
Sallis, Benjamin F; Erkert, Lena; Mo├▒ino-Romero, Sherezade et al. (2018) An algorithm for the classification of mRNA patterns in eosinophilic esophagitis: Integration of machine learning. J Allergy Clin Immunol 141:1354-1364.e9
Almansour, Khaled; Taverner, Alistair; Turner, Jerrold R et al. (2018) An intestinal paracellular pathway biased toward positively-charged macromolecules. J Control Release 288:111-125
Hu, Madeleine D; Ethridge, Alexander D; Lipstein, Rebecca et al. (2018) Epithelial IL-15 Is a Critical Regulator of ?? Intraepithelial Lymphocyte Motility within the Intestinal Mucosa. J Immunol 201:747-756
Hou, Qihang; Ye, Lulu; Liu, Haofei et al. (2018) Lactobacillus accelerates ISCs regeneration to protect the integrity of intestinal mucosa through activation of STAT3 signaling pathway induced by LPLs secretion of IL-22. Cell Death Differ 25:1657-1670
Edelblum, Karen L; Sharon, Gil; Singh, Gurminder et al. (2017) The Microbiome Activates CD4 T-cell-mediated Immunity to Compensate for Increased Intestinal Permeability. Cell Mol Gastroenterol Hepatol 4:285-297

Showing the most recent 10 out of 103 publications