P107 Comparing the Colonic Tissue Proteome of Active and Inactive Ulcerative Colitis

Abstract

Abstract Background Ulcerative colitis (UC) is an inflammatory bowel disease that begins at the rectum and can advance proximally and continuously throughout the colon. In this pilot study, we aim to differentiate the protein expression between active and inactive patients, comparing the same tissue region of the colon pairwise between active and inactive UC. Additionally, we are looking to build on previous work to determine which proteins are differentially proteolyzed in active UC and postulate whether this alternative post-translational processing significantly correlates to disease activity. Here, we aim to use a multi -omics approach to spatially profile the entire large intestine. Methods We used an N-terminomics proteomic approach to determine whether proteins are differentially expressed and proteolytically processed in all colon segments of patients with active and inactive UC. Colon tissues were retrieved from patients and classified according to disease activity. Five active and five inactive UC patients were compared from each of the colonic regions (rectum, sigmoid, transverse, ascending colon). Samples were quantified by liquid chromatography and tandem mass spectrometry (LC-MS/MS). Peptides were identified and matched at a 5% false discovery rate (FDR). Boxplot analysis was used to determine the upper and lower threshold for protein fold changes between conditions, and various bioinformatic software (MetaScape, StringDB, TopFINDer) were used to analyze the data. Results Primary analysis discovered a combined 36 statistically changing proteins in patients with active disease, including several that have previously been published and others that are direct interactors with known biomarkers for active UC, including calmodulin and S100A9. Interestingly, S100A9 was translated significantly more in the transverse colon of patients with active UC but was not in other colonic regions. Protease activity was noticeably different in active and inactive UC, in addition to having unique activity dependent on the region of the colon from which the samples were acquired. For example, delta-catenin was processed more in active UC in the rectum and transverse colon, whereas it’s processing was enriched in inactive UC in the sigmoid colon. Conclusion While this pilot study is incomplete, the promising initial results exhibit the power of a proteomics and N-terminomics approach to elucidate the mechanisms that contribute to UC pathogenesis. There appears to be a pattern in how proteins and their altered proteolysis leads to an increased likelihood of active UC.