Proteolysis controls endogenous substance P levels

PLoS One. 2013 Jul 19;8(7):e68638. doi: 10.1371/journal.pone.0068638. Print 2013.


Substance P (SP) is a prototypical neuropeptide with roles in pain and inflammation. Numerous mechanisms regulate endogenous SP levels, including the differential expression of SP mRNA and the controlled secretion of SP from neurons. Proteolysis has long been suspected to regulate extracellular SP concentrations but data in support of this hypothesis is scarce. Here, we provide evidence that proteolysis controls SP levels in the spinal cord. Using peptidomics to detect and quantify endogenous SP fragments, we identify the primary SP cleavage site as the C-terminal side of the ninth residue of SP. If blocking this pathway increases SP levels, then proteolysis controls SP concentration. We performed a targeted chemical screen using spinal cord lysates as a proxy for the endogenous metabolic environment and identified GM6001 (galardin, ilomastat) as a potent inhibitor of the SP(1-9)-producing activity present in the tissue. Administration of GM6001 to mice results in a greater-than-three-fold increase in the spinal cord levels of SP, which validates the hypothesis that proteolysis controls physiological SP levels.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Enzyme Inhibitors / pharmacology
  • Female
  • Mass Spectrometry
  • Metalloproteases / antagonists & inhibitors
  • Metalloproteases / metabolism
  • Mice
  • Mice, Knockout
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism
  • Proteolysis / drug effects
  • Spinal Cord / metabolism
  • Substance P / chemistry
  • Substance P / metabolism*


  • Enzyme Inhibitors
  • Peptide Fragments
  • Substance P
  • Metalloproteases