Mast cells and neutrophils proteolytically activate chemokine precursor CTAP-III and are subject to counterregulation by PF-4 through inhibition of chymase and cathepsin G

Blood. 2006 Mar 15;107(6):2234-42. doi: 10.1182/blood-2005-06-2424. Epub 2005 Nov 29.

Abstract

The CXC chemokines platelet factor 4 (PF-4/CXCL4) and connective tissue-activating peptide III (CTAP-III) are released by activated human platelets in micromolar concentrations. So far, neutrophils have been recognized to cleave the precursor CTAP-III to form the active chemokine neutrophil-activating peptide 2 (NAP-2/CXCL7) through limited proteolysis by membrane-associated cathepsin G. Here we show for the first time that activated human skin mast cells (MCs) convert CTAP-III into biologically active NAP-2 through proteolytic cleavage by released chymase. A direct comparison on a cell number basis revealed that unstimulated MCs exceed the CTAP-III-processing potency of neutrophils about 30-fold, whereas MCs activated by IgE cross-linking exhibit even 1000-fold higher CTAP-III-processing capacity than fMLP-stimulated neutrophils. Intriguingly, PF-4 counteracted MC- as well as neutrophil-mediated NAP-2 generation at physiologically relevant concentrations. Addressing the underlying mechanism, we obtained evidence that PF-4 acts as an inhibitor of the CTAP-III-processing enzymes cathepsin G and chymase without becoming cleaved itself as a competitive substrate. Because cleavage of the CTAP-III-unrelated substrate substance P was also affected by PF-4, our results suggest a regulatory role for PF-4 not only in NAP-2 generation but also in neutrophil- and MC-mediated processing of other physiologically relevant inflammatory mediators.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cathepsin G
  • Cathepsins / antagonists & inhibitors
  • Cathepsins / metabolism
  • Chymases
  • Humans
  • Immunoglobulin E / metabolism
  • Mast Cells / metabolism*
  • N-Formylmethionine Leucyl-Phenylalanine / pharmacology
  • Neutrophils / metabolism*
  • Nuclear Proteins / metabolism
  • Peptides / metabolism*
  • Platelet Factor 4 / physiology*
  • Serine Endopeptidases / metabolism*
  • Serine Proteinase Inhibitors*
  • Substance P / metabolism

Substances

  • NAP1L4 protein, human
  • Nuclear Proteins
  • Peptides
  • Serine Proteinase Inhibitors
  • Substance P
  • Platelet Factor 4
  • Immunoglobulin E
  • N-Formylmethionine Leucyl-Phenylalanine
  • connective tissue-activating peptide
  • Cathepsins
  • Serine Endopeptidases
  • CTSG protein, human
  • Cathepsin G
  • Chymases