Date of Completion
gp96/grp94, gp93, chaperone, TLR, integrin, CNPY, colitis, macrophage, inflammation-induced colon tumorigenesis, Drosophila
Dr. Zihai Li
Dr. Anthony Vella
Dr. Linda Cauley
Field of Study
Doctor of Philosophy
Gp96, a mammalian endoplasmic reticulum chaperone, is required for expression of multiple Toll-Like Receptors (TLRs) and integrins. This heat shock protein is upregulated in cancer and tumor associated macrophages, and it is known to cross-present tumor antigens. A better understanding of gp96 biology will aid the design of cancer drugs, as gp96 is a possible target. To study this molecule, we investigated an orthologous system in Drosophila. A BLAST search identified Drosophila gp93, an uncharacterized molecule, with 74% amino acid homology. Gp93 was found to rescue gp96 client expression in a gp96-deficient murine pre-B cell line. It was further demonstrated that CNPYb is a TLR-specific cochaperone of gp93. Therefore, we have not only identified gp93 as the Drosophila ortholog of gp96, but we have also established a simpler system by which to further study gp96 biochemistry.
Since gp96, TLRs, and macrophages have all been implicated in cancer, we decided to further explore their role in tumorigenesis. We therefore utilized a macrophage-specific gp96 knockout (KO) mouse to study the role of macrophage-derived gp96. Both wild type and KO mice were treated with either Dextran Sulfate Sodium (DSS) alone to induce colitis, or Azoxymethane plus DSS to induce inflammation-associated colon tumorigenesis. KO mice are protected from both diseases, suggesting that macrophage-intrinsic gp96 plays a promoting role. Mechanistically, gp96 induces IL-17, IL-23, TNFα, Wnt signaling, and β–catenin mutations while reducing CD4+IFNγ+ cells. Our data thus help to explain the manner in which gp96 promotes cancer, thus identifying possible targets for therapeutic development.
Morales, Crystal, "Investigating Gp96 Biology and its Macrophage-Intrinsic Role in Colitis-Associated Colon Tumorigenesis" (2013). Doctoral Dissertations. 23.