title: Post-translational modifications of pancreatic fluid proteins collected via the endoscopic pancreatic function test (ePFT).
abstract: BACKGROUND
  Early diagnosis of chronic pancreatitis by mass spectrometry-based proteomics may result in therapies to retard or modify disease progression. We aimed to identify differences in posttranslational modifications (PTMs) in pancreatic fluid proteins from individuals with chronic pancreatitis (n=9) and non-pancreatitis controls (n=9).
  
  
  METHODS
  We collected proteomic data from pancreatic fluid using mass spectrometry techniques. We performed database searches with emphasis on PTMs using ProteinPilot. We compared the frequency of specific PTMs in pancreatic fluid between cohorts and also to those identified in bile, gastroduodenal fluid, urine, and pancreatic duct and stellate cell lysates.
  
  
  RESULTS
  We identified 97 PTMs in endoscopically-collected pancreatic fluid, of which 11 were identified exclusively in one cohort and 9 others were significantly different in frequency between cohorts. Comparing pancreatic fluid with other specimens revealed differences in specific PTM frequencies, indicating that the identified PTMs were not merely artifacts of sample processing.
  
  
  CONCLUSIONS
  We determined PTMs of proteins extracted from pancreatic fluid which differed in frequency in chronic pancreatitis patients verses controls. Such PTMs may serve as biomarker candidates of chronic pancreatitis upon validation with larger cohorts. The analysis of the PTM profile of pancreatic fluid proteins offers an alternative method to standard protein-based biomarker discovery.
  
  
  CONCLUSIONS
  The early diagnosis of chronic pancreatitis is paramount in developing strategies to modify, retard, or halt disease progression. In the present study, we compared post-transitional modifications (PTMs) of proteins extracted from pancreatic fluid of chronic pancreatitis patients verses a control cohort. With many mass spectrometry-based proteomics workflows aimed to identify and quantify proteins, data for PTMs typically comes gratis, in that such data are collected during protein sequencing and, as such, require only downstream bioinformatics processing. We identified a total of 20 PTMs which were exclusive to or significantly different between cohorts. Upon validation with larger cohorts and enrichment of these PTMs may serve as biomarker candidates of chronic pancreatitis. PTM profiling of pancreatic fluid proteins is complementary to standard protein-based biomarker discovery, and may be readily applied to studies of pancreatic disease. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.
authors.affiliation: Department of Pathology, Children's Hospital Boston, Boston, MA, United States; Proteomics Center at Children's Hospital Boston, Boston, MA, United States; Center for Pancreatic Disease, Division of Gastroenterology, Hepatology and Endoscopy, Brigham and Women's Hospital and Department of Medicine, Harvard Medical School, Boston, MA, United States. Electronic address: joao_paulo@post.harvard.edu.
authors.forename: Joao A
authors.initials: JA
authors.lastname: Paulo
authors.forename: Vivek
authors.initials: V
authors.lastname: Kadiyala
authors.forename: Scott
authors.initials: S
authors.lastname: Brizard
authors.forename: Peter A
authors.initials: PA
authors.lastname: Banks
authors.forename: Hanno
authors.initials: H
authors.lastname: Steen
authors.forename: Darwin L
authors.initials: DL
authors.lastname: Conwell
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D015331:Cohort Studies; D016145:Endoscopy, Digestive System; D045604:Extracellular Fluid / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000378:metabolism* / Q000473:pathology; D050500:Pancreatitis, Chronic / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D011499:Protein Processing, Post-Translational; D040901:Proteomics / Q000379:methods*
chemical_list: D015415:Biomarkers
keywords: Biomarkers; Chronic pancreatitis; GeLC-MS/MS; LTQ-FTICR; Pancreas; Pancreas juice; Pancreatic function test; SDS-PAGE-based protein fractionation; TCA; ePFT; endoscopic pancreatic function test; linear trap quadrupole- Fourier transform ion cyclotron resonance mass spectrometry; trichloroacetic acid