Premium
Thimet Oligopeptidase (EP24.15), a Neuropeptide Processing Enzyme Regulating Xenin Signaling
Author(s) -
Glucksman Marc,
Philibert Keith,
Mizuno Tooru,
Lew Piesan
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.943.1
Subject(s) - neurotensin , biochemistry , in silico , biology , chemistry , neuropeptide , microbiology and biotechnology , receptor , gene
Xenin is a 25 amino acid neuropeptide with sequence homology and actions similar to hypothalamic and ileal neurotensin (a satiety factor) as well as binding to the neurotensin receptor. Xenin is produced by a subgroup of chromogranin A+ cells in the duodenum and this neurohormone is involved in glucose homeostasis and increases the response to glucose‐dependent insulinotropic peptide (GIP). Upon its release after ingestion Xenin inhibits secretion of pancreatic exocrine peptides in the gastrointestinal tract. The mode of regulating the peptide hormone Xenin remains elusive. The metalloendopeptidase EC 3.4.24.15 (thimet oligopeptidase, EP24.15) has been demonstrated to play a key role in the cleavage and subsequent regulation of several neuropeptides that also exist in the gut such as neurotensin and somatostatin. A systems biology approach to regulating signaling beginning from high throughput structural analyses, in silico molecular modeling and potential substrate screening implicated Xenin as a substrate of EP24.15 and thus, this enzyme as a possible regulator of Xenin signaling. To substantiate a potential regulatory mechanism for the functioning of Xenin, we first identified potential active site binding and cleavage sites, measured enzymatic parameters, performed structural studies, and determined if EP24.15 and Xenin are co‐expressed in gut regions relevant to glucose homeostasis. After proprietary in silico modeling paradigms identifying a potential favorable interaction, EP24.15 and Xenin were co‐incubated and subjected to matrix‐assisted laser desorption ionization time‐of‐flight (MADLI‐TOF) mass spectrometry to confirm that EP24.15 can cleave Xenin in vitro. Enzyme kinetics were performed with standards via high performance liquid chromatography yielding results consistent with known substrates. Notably, Xenin is cleaved in a homologous manner as neurotensin. Double‐label immunohistochemistry demonstrated Xenin and EP24.15 immunoreactivity within the mouse small intestine and specifically co‐expression within the intestinal mucosa and submucosa. Furthermore, there is co‐expression of EP24.15 and Xenin in cells of both human and mouse stomach in the gastric mucosa. Taken together this data suggests that EP24.15 may act to cleave Xenin in vivo and represents an additional facet of the control mechanism of glucose homeostasis. As a potential pharmacological therapeutic target, understanding regulation of Xenin by the neuropeptide processing enzyme, EP24.15, may provide insight into an alternative strategy for glucose regulation and diseases such as diabetes and obesity. Support or Funding Information Supported by NIH OD010662 (MJG) and CIHR MOP123208 (TMM)