N‑Terminomics/TAILS Profiling of Proteases and Their Substrates in Ulcerative Colitis

Dysregulated
protease activity is often implicated in the initiation
of inflammation and immune cell recruitment in gastrointestinal inflammatory
diseases. Using N-terminomics/TAILS (terminal amine isotopic labeling
of substrates), we compared proteases, along with their substrates
and inhibitors, between colonic mucosal biopsies of healthy patients
and those with ulcerative colitis (UC). Among the 1642 N-termini enriched
using TAILS, increased endogenous processing of proteins was identified
in UC compared to healthy patients. Changes in the reactome pathways
for proteins associated with metabolism, adherens junction proteins
(E-cadherin, liver-intestinal cadherin, catenin alpha-1, and catenin
delta-1), and neutrophil degranulation were identified between the
two groups. Increased neutrophil infiltration and distinct proteases
observed in ulcerative colitis may result in extensive break down,
altered processing, or increased remodeling of adherens junctions
and other cellular functions. Analysis of the preferred proteolytic
cleavage sites indicated that the majority of proteolytic activity
and processing comes from host proteases, but that key microbial proteases
may also play a role in maintaining homeostasis. Thus, the identification
of distinct proteases and processing of their substrates improves
the understanding of dysregulated proteolysis in normal intestinal
physiology and ulcerative colitis.