Eugene Chang

Studies of epithelial cell biology and function under normal and disease states

The gut microbiome is pivotal to normal health and to the development of diseases such as inflammatory bowel diseases. Most microorganisms in the gut are not cultivatable and require molecular approaches for their identification and study. Our laboratory is exploring 16S rDNA and functional metagenomic approaches to interrogate intestinal microbes, particularly in the context of host mucosal gene expression. Using bioinformatics, novel interactions between host and microbes can be elucidated. An example of such a host-microbial interaction involves an epithelial organic cation transporter, OCTN2, that is used by host epithelial cells to monitor the status of the enteric flora by “tasting or sampling" small signaling peptides made by predominantly gram positive microorganisms¹. Among these molecules are small peptides are quorum sensing peptides that are used by microbes to control population growth and behavior. This form of host-microbial interaction is distinct from innate immune mechanisms such as NODs and TLRs and is important in mediating host-microbial symbiosis or mutualism. OCTN2 is within the IBD5 risk allele and polymorphisms of the gene have been implicated as potentially disease causing or modifying.

Heat shock proteins (HSPs) are a highly conserved family of molecules which are essential for numerous essential cellular functions. Although many types are constitutively expressed, some, such as HSP 70, are rapidly induced and preferentially synthesized under conditions of cellular stress and injury. In epithelial cells, their induction protects against toxic, oxidant, and thermal injury. Our laboratory, therefore, is investigating cellular and molecular mechanisms that mediate their cytoprotective effects in the context of mucosal inflammation. These studies involve correlations of molecular and biochemical techniques with physiological findings and imaging analysis. Our investigations reveal several novel roles for intestinal Hsp70, including immunomodulation of intestinal lymphoid cells and host defense against invasive pathogens.

3. Characterization of expression and function of Na-H exchange isoforms (NHE)

Although NHE isoforms are structurally similar and have similar transport characteristics, they markedly differ in tissue expression, regulation, and functional activation in a physiological setting. To study the structure-function properties of NHE isoforms, we are employing a combined approach of site-directed mutagenesis, cassette swapping, and chimeric constructions with physiological measurements in epithelial and mesenchymal cell expression systems. We are also characterizing the physiological determinants of tissue-specific NHE isoform expression. Specific transcriptional and post-translational mechanisms mediating alterations in expression are being studied. Finally, using chimeric constructs, mutational analysis, and natural mRNA splicing variants of NHE, we are trying to identify the determinants of NHE protein sorting and/or membrane stabilization in stable transfectants of epithelial cell lines. Membrane trafficking is followed biochemically and by laser scanning confocal microscopy. More recently, our lab has identified the adaptor protein, synaptotagmin I, in intestinal epithelial cells. Synaptotagmin I plays a pivotal role in Ca- and cyclic nucleotide-induced membrane endocytosis of NHE3 through recruitment of AP2 and clathrin. This protein also directs NHE3 to the recycling endosomal compartment, a process that results in inhibited Na transport. Using a murine model where an intestinal epithelial gene-targeted deletion of synaptotagmin I was constructed, we are studying the pivotal role of this adaptor in regulated Na transport of the gut.

Selected Publications

Urayama, S., Musch, M.W., Retsky, J., Madonna, M.B., Straus, D. and Chang, E.B. Dexamethasone protection of rat intestinal epithelial cells against oxidant injury is mediated by induction of heat shock protein 72. J. Clinical Investigation, 102:1860-1865, 1998.

Rocha, F., Musch, M.W., Lishanskiy, L., Bookstein, C., Sugi, K., Xie, X. and Chang, E.B. IFN-downregulates expression of Na+/H+ exchangers NHE2 and NHE3 in rat intestine and human Caco-2/bbe (C2) cells. American Journal of Physiology, 280:C1224-C1232, 2001.

Sugi, K., Musch, M.W., Field, M. and Chang, E.B. Inhibition of Na-K-ATPase by interferon-downregulated intestinal epithelial transport and barrier function. Gastroenterology, 120:1393-1403, 2001.

Kojima, K., Musch, M.W., Ren, H., Boone, D.L., Hendrickson, B.A., Ma, A. and Chang, E.B. Eneric flora and lymphocyte derived cytokines determine expression of Hsp in mouse colonic epithelial cells. Gastroenterology, 124: 1395-1407, 2003.

Tao, Y., Drabik, K.A., Waypa, T.S., Musch, M.W., Alverdy, J., Scheewind, O., Chang, E.B. and Petrof, E.O. Soluble factors from the probiotic Lactobacillus GG activate MAP kinase and induce cytoprotective heat shock proteins in intestinal epithelial cells. Am. J. Physiol., 290:C1018-1030, 2006.

Musch, M.W., Arvans, D., Walsh-Reitz, M., Uchiyama, K., Fukuda, M. and Chang, E.B. Synaptotagmin I binds intestinal epithelial NHE3 and mediates cAMP-and Ca2+-induced endocytosis by recruitment of AP2 and clathrin. Am. J. Physiol., 92(6):G1549-G1558, 2007.

Carlson, R.M., Vavricka, S.R., Eloranta, J.J., Musch, M.W., Arvans, D.L., Kles, K.A., Walsh-Reitz, M.M., Kullak-Ublick, G. and Chang, E.B. fMLP induces Hsp27 expression, attenuates NFkB activation and confers intestinal epithelial cell protein. Am. J. Physiol., 292(4):G1070-G1078, 2007.

Fujiya, M., Musch, M.W., Nakagawa, Y., Hu, S., Alverdy, J., Kohgo, Y., Schneewind, O., Jabri, B. and Chang, E.B. The Bacillus subtilis quorum-sensing molecule CSF contributes to intestinal homeostasis via OCTN2, a host cell membrane transporter. Cell (Host and Microbe), 1(4): 299-308, 2007.

Eugene Chang, M.D.

Research Summary

Selected Publications