This R03 proposal stems directly from studies and career development activities outlined in my current K01 award and represents a new research direction that will enhance my advancement towards independence. This award will allow me to obtain additional skills in combining genetic mouse models of disease with systems biology approaches in order to define novel mechanisms of autophagy regulation in the intestine and colon with direct relevance to Inflammatory Bowel Disease and colorectal cancer. This will be achieved with the guidance of my research mentor, Dr. Rustgi, my K01 interdisciplinary advisory committee of Drs. Wu (Chair), Kaestner, Lengner, and Lynch, as well as new collaborator Dr. Premal Shah. Autophagy is a mechanism by which cells adapt and survive in response to stress under certain conditions. During homeostasis, autophagy can be protective in the intestinal epithelium following acute injury, which is underscored by recent studies describing defective autophagy in Crohn's disease patients. Post-transcriptional regulation of intestinal epithelial homeostasis via RNA-binding proteins (RBPs), including IMP1 (IGF2 mRNA- binding protein 1=IMP1), represents a critical, acute layer of gene expression control through modulation of target transcript splicing, stability, localization and translation. Our preliminary data demonstrate phenotypic and functional alterations in the autophagy pathway in mice with intestinal epithelial cell (IEC)-specific deletion of Imp1 (Imp1?IEC), where autophagic flux is enhanced during homeostasis. Imp1?IEC mice exhibit enhanced regeneration following injury, which can be reversed with autophagy inhibition. RNP-immunoprecipitation (RIP) assays have unraveled specific autophagy transcripts bound by IMP1, previously unknown. These data support the scientific premise that IMP1 may normally suppress intestinal epithelial autophagy via direct biochemical binding. Despite these functional links between IMP1 and autophagy, it remains unknown whether high IMP1 expression directly downregulates autophagy and whether this could contribute to disease phenotypes in Crohn's patients. We will therefore test the hypothesis that intestinal epithelial IMP1 functions to suppress autophagy directly and promote susceptibility to inflammation-induced injury. Specifically, we will utilize our newly generated mouse model in which Imp1 is conditionally overexpressed in the intestine and colon epithelium (Imp1OE, OE=overexpression) combined with targeted and unbiased approaches (RNA-sequencing and ribosome profiling) to dissect the direct mechanism of autophagy regulation by IMP1. The long-term objective of these studies (to be achieved through future NIH R01 funding) is to understand fundamental intestinal epithelial biology via regulation of RNA-binding proteins and evaluate IMP1 as a new therapeutic target for enhancing autophagy in patients with defective autophagy (including Crohn's disease).
This proposal will provide a foundation for understanding regulation of intestinal epithelial homeostasis and disease through new mechanisms, namely the RNA binding protein, IMP1. These studies will dissect the molecular mechanisms governing IMP1 regulation of autophagy, which is defective in some human diseases including Crohn's disease. Advances made with these studies will allow for the development of new therapeutic strategies that may augment the autophagy pathway in order to restore intestinal epithelial homeostasis.
| Hamilton, Kathryn E (2018) Microfabricated Crypt Scaffolds: A New Foundation for Evaluating Human Colon Stem Cells. Cell Mol Gastroenterol Hepatol 5:161-162 |
| Kasagi, Yuta; Chandramouleeswaran, Prasanna M; Whelan, Kelly A et al. (2018) The Esophageal Organoid System Reveals Functional Interplay Between Notch and Cytokines in Reactive Epithelial Changes. Cell Mol Gastroenterol Hepatol 5:333-352 |
| Chatterji, Priya; Hamilton, Kathryn E; Liang, Shun et al. (2018) The LIN28B-IMP1 post-transcriptional regulon has opposing effects on oncogenic signaling in the intestine. Genes Dev 32:1020-1034 |
| Hall, Timothy M; Tétreault, Marie-Pier; Hamilton, Kathryn E et al. (2018) Autophagy as a cytoprotective mechanism in esophageal squamous cell carcinoma. Curr Opin Pharmacol 41:12-19 |
| Mizuno, Rei; Chatterji, Priya; Andres, Sarah et al. (2018) Differential Regulation of LET-7 by LIN28B Isoform-Specific Functions. Mol Cancer Res 16:403-416 |
