Jerrold Turner, M.D., Ph.D.

Tight Junctions and Epithelial Barrier Function

Research Summary

Transporting epithelia, such as those found in the intestines, kidneys, and lungs, must balance absorptive and secretory transport with the maintenance of an impermeant barrier. Transport across these epithelia occurs via transcellular and paracellular pathways. The transcellular pathway relies on specific transporters and is therefore highly selective and saturable. In contrast, the paracellular pathway is less specific but has a much greater overall capacity. Transit through the paracellular pathway is regulated by the tight junction, a rate-limiting determinant that restricts passage of hydrophilic solutes based on size and charge. Coordinated regulation of transcellular and paracellular pathways allows the epithelia to complement the selectivity of the transcellular pathway with the carrying capacity of the paracellular pathway. However, dysregulation of these pathways can lead to disease, with loss of barrier function, mixing of the tissue interstitium with luminal compartments, and inappropriate immune activation.

Dr. Turner’s laboratory has primarily used the intestine as a model system in which to study the coordinated regulation of transcellular and paracellular transport, with mechanisms of this regulation and its disruption in disease the major focus of the research efforts. To this end Dr. Turner’s laboratory uses a broad range of advanced techniques based on molecular genetic, proteomic, and morphologic, and functional analysis of cultured cells, transgenic animals, and human tissues.

There are three major areas of investigation in Dr. Turner’s laboratory. The first focuses on tight junction regulation secondary to physiological, pharmacological, and pathophysiological stimuli using the full array of technologies listed above. Recent work has pioneered live cell imaging using fluorescent fusion constructs of tight junction proteins expressed in cell lines and transgenic animals. This work also includes development of cell permeant peptides that inhibit regulatory pathways. These peptides are currently being evaluated as novel therapies for inflammatory bowel disease and graft versus host disease.

The second major area of interest focuses on cytoskeletal regulation of cellular function, with particular emphasis on actomyosin and myosin light chain kinase. These studies have led to the identification of novel patterns of gene regulation and alternative splicing that are closely related to cell differentiation and specialized function in health and disease.

The third major area of investigation is the intracellular signal transduction pathways that control coordinated activation of intestinal nutrient transporters. This has led to the observation that nutrient and ion transporters are rapidly recruited from intracellular pools to the plasma membrane. In addition to being important in activating the intestinal absorptive epithelium to rapidly respond to luminal nutrients, this observation may also shed light on similar regulatory events in other cell types.

Selected Papers

Tomson FL, Koutsouris A, Viswanathan VK, Turner JR, Savkovic SD, Hecht G. (2004). Differing roles of PKCz in disruption of tight junction barrier by enteropathogenic and enterohemorrhagic E. coli. Gastroenterology 2004. 127:859-69.

Savkovic SD, Villanueva J, Turner JR, Matkowskyj KA, Hecht G. (2005). Mouse model of enteropathogenic E. coli (EPEC) infection. Infect Immun. 73:1161-70.

Clayburgh DR, Rosen S, Witkowski ED, Wang F, Blair S, Dudek S, Garcia JGN, Alverdy JC, Turner JR. (2004). A differentiation-dependent splice variant of myosin light chain kinase, MLCK1, regulates epithelial tight junction permeability. J Biol Chem.  279:55506-55513.

Kohler JE, Zaborina O, Wu L, Wang Y, Shevchenko O, Bethel C, Chen Y, Shapiro J, Turner JR*, Alverdy JC*. (2005). Intestinal epithelial hypoxia triggers the sense and respond circuitry of Pseudomonas. Amer J Physiol- Gastrointest Liver Physiol. 288:1048-54. *co-senior authorship

Arvans DL, Vavricka SR, Ren H, Musch MW, Kang L, Rocha FG, Lucioni A, Turner JR, Alverdy J, Chang EB. (2005). Luminal bacterial flora determines physiological expression of intestinal epithelial cytoprotective heat shock proteins, Hsp 25 and Hsp 72. Amer J Physiol- Gastrointest Liver Physiol. 288:G696-G704.

Wang F, Graham WV, Wang Y, Witkowski ED, Schwarz BT, Turner JR. (2005). IFN-beta and TNF-alpha synergize to induce intestinal epithelial barrier dysfunction by upregulating MLC kinase expression. Amer J Pathol. 166:409-19.

Shiue H, Musch MW, Wang Y, Chang EB, Turner JR. (2005). Akt2 phosphorylates ezrin to trigger NHE3 translocation and activation. J Biol Chem. 280:1688-95.

Russo JM, Florian P, Shen L, Graham WV, Tretiakova MS, Gitter AH, Mrsny RJ, Turner JR. (2005). Distinct temporal-spatial roles for rho kinase and myosin light chain kinase in epithelial purse-string wound closure. Gastroenterology. 128:987-1001.

Gill RK, Saksena S, Tyagi S, Alrefai WA, Malakooti J, Sarwar Z, Turner JR, Ramaswamy K, Dudeja PK. (2005). Serotonin inhibits Na+/H+ exchange activity via 5-HT4 receptors and activation of PKC-alpha in human intestinal epithelial cells. Gastroenterology. 2005. 128:962-974.

Owens S, Graham WV, Siccardi D, Turner JR, Mrsny RJ. (2005). A strategy to identify stable membrane-permeant peptide inhibitors of myosin light chain kinase. Pharm Res. 2005. 22:703-9.

Schaefer KL, Wada K, Takahashi H, Matsuhashi N, Ohnishi S, Wolfe MM, Turner JR, Nakajima A, Borkan SC, Saubermann LJ. (2005). Peroxisome proliferator-activated receptor gamma inhibition prevents adhesion to the extracellular matrix and induces anoikis in hepatocellular carcinoma cells. Cancer Res. 2005. 65:2251-9.

Kles KA, Vavricka SR, Turner JR, Musch MW, Hanauer SB and Chang EB. (2005). Comparative analysis of the in vitro prosecretory effects of balsalazide, sulfasalazine, olsalazine, and mesalamine in rabbit distal ileum. Inflamm Bowel Dis. 11:253-257.

Shen L, Turner JR. (2005). Actin depolymerization disrupts tight junctions via caveolae-mediated endocytosis. Mol Biol Cell. 16:3919-36.

Wang J, Anders RA, Wang Y, Turner JR, Abraham C, Pfeffer K, Fu Y-X. (2005). The critical role of LIGHT in promoting intestinal inflammation and Crohn’s disease. J Immunol. 174:8173-82.

Wu L, Estrada O, Zaborina O, Bains M, Shen L, Kohler JE, Patel N, Musch MW, Chang EB, Fu Y-X, Olson MV, Jacobs MA, Nishimura MI, Hancock REW, Turner JR, Alverdy JC. (2005). Recognition of host immune activation by Pseudomonas aeruginosa: role of interferon-?. Science. 309:774-7.

Shifflett DE, Clayburgh DR, Koutsouris A, Turner JR*, Hecht GA*. (2005). Enteropathogenic E. coli disrupts tight junction barrier function and structure in vivo. Lab Invest. 2005. In press. *co-senior authorship

Yu LCH, Flynn AN, Turner JR, Buret AG. (2005). SGLT-1-mediated glucose uptake protects intestinal epithelial cells against LPS-induced apoptosis and barrier defects: a novel cellular rescue mechanism? FASEB J. 2005. In press.

Kimura Y, Turner JR, Brassch D, Buddington RK. (2005). Lumenal adenosine and adenosine 5'-monophosphate rapidly increase glucose transport by intact small intestine. Amer J Physiol- Gastrointest Liver Physiol. 2005. In press.

Utech M, Ivanov AI, Bruewer M, Turner JR, Mrsny RJ, Parkos CA, Nusrat A. (2005). Mechanism of IFN-× induced endocytosis of tight junction proteins: myosin II-dependent vacuolarization of the apical plasma membrane. Mol Biol Cell. 2005. In press.

Clayburgh DR, Barrett TA, Tang Y, Meddings JB, Van Eldik LJ, Watterson DM, Clarke LL, Mrsny RJ, Turner JR. (2005). Epithelial myosin light chain kinase-dependent barrier dysfunction mediates T cell activation-induced diarrhea in vivo. J Clin Invest. In press.

Marski M, Kandula S, Turner JR, Abraham C. (2005). CD18 is required for optimal development and function of CD4+ CD25+ T regulatory cells. J Immunol. In press.