TAILS N-Terminomics and Proteomics Show Protein Degradation Dominates over Proteolytic Processing by Cathepsins in Pancreatic Tumors

Anna Prudova, Vasilena Gocheva, Ulrich auf dem Keller, Ulrich Eckhard, Oakley C. Olson, Leila Akkari, Georgina S. Butler, Nikolaus Fortelny, Philipp F. Lange, Jennifer C. Mark, Johanna A. Joyce*, Christopher M. Overall

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Deregulated cathepsin proteolysis occurs across numerous cancers, but in vivo substrates mediating tumorigenesis remain ill-defined. Applying 8-plex iTRAQ terminal amine isotopic labeling of substrates (TAILS), a systems-level N-terminome degradomics approach, we identified cathepsin B, H, L, S, and Z in vivo substrates and cleavage sites with the use of six different cathepsin knockout genotypes in the Rip1-Tag2 mouse model of pancreatic neuroendocrine tumorigenesis. Among 1,935 proteins and 1,114 N termini identified by TAILS, stable proteolytic products were identified in wild-type tumors compared with one or more different cathepsin knockouts (17%–44% of 139 cleavages). This suggests a lack of compensation at the substrate level by other cathepsins. The majority of neo-N termini (56%–83%) for all cathepsins was consistent with protein degradation. We validated substrates, including the glycolytic enzyme pyruvate kinase M2 associated with the Warburg effect, the ER chaperone GRP78, and the oncoprotein prothymosin-alpha. Thus, the identification of cathepsin substrates in tumorigenesis improves the understanding of cathepsin functions in normal physiology and cancer.

Original languageEnglish
JournalCell Reports
Volume16
Issue number6
Pages (from-to)1762-1773
ISSN2211-1247
DOIs
Publication statusPublished - 2016
Externally publishedYes

Keywords

  • Cysteine cathepsins
  • Degradation
  • ECM
  • Lysosomal hydrolases
  • Pancreatic neuroendocrine cancer
  • Proteases
  • Proteolytic processing
  • Proteomics
  • Substrate discovery
  • TAILS degradomics

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