title: Human tryptase cleaves pro-nerve growth factor (pro-NGF): hints of local, mast cell-dependent regulation of NGF/pro-NGF action.
abstract: Several factors regulate nerve growth factor (NGF), which is formed from pro-NGF by intracellular and extracellular enzymatic cleavage. The close proximity between mast cells expressing the protease tryptase and NGF-producing smooth muscle-like peritubular cells in the testes of infertile patients led us to examine whether tryptase is among those factors. Human peritubular cells express functional tryptase receptors (PAR-2). Recombinant enzymatically active β-tryptase increased NGF levels in the culture medium of primary human peritubular cells, but the peptide agonist for PAR-2 (SLIGKV) did not. Neither tryptase nor the peptide increased NGF mRNA levels. To test whether the increase in NGF is due to enzymatic activity of tryptase acting on pro-NGF, supernatants of peritubular cells and synthetic pro-NGF were treated with tryptase. Results of Western blot studies indicate enzymatic cleavage of pro-NGF by active tryptase. Heat-inactivated tryptase or SLIGKV was not effective. Mass spectrometry analysis of in vitro cleavage products from recombinant tryptase and synthetic pro-NGF revealed multiple cleavage sites within the pro-NGF sequence. The results also indicate the generation of mature NGF and smaller NGF fragments as a result of tryptase action. Thus, tryptase-secreting mast cells in the vicinity of pro-NGF/NGF-secreting cells in any human tissue are likely able to alter the ratios of pro-NGF/NGF. As NGF and pro-NGF have different affinities for their receptors, this indicates a novel way by which mast cells, via tryptase, can modify the microenvironment in human tissues with regard to neurotrophin actions.
authors.affiliation: Institute for Cell Biology and Anatomy, Ludwig Maximilians University, Biedersteiner Strasse 29, D-80802 Munich, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Spinnler
authors.forename: Thomas
authors.initials: T
authors.lastname: Fröhlich
authors.forename: Georg J
authors.initials: GJ
authors.lastname: Arnold
authors.forename: Lars
authors.initials: L
authors.lastname: Kunz
authors.forename: Artur
authors.initials: A
authors.lastname: Mayerhofer
mesh_terms: D002478:Cells, Cultured; D006801:Humans; D008297:Male; D008407:Mast Cells / Q000502:physiology*; D009130:Muscle, Smooth / Q000166:cytology; D020932:Nerve Growth Factor / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D011498:Protein Precursors / Q000378:metabolism; D059748:Proteolysis; D013737:Testis / Q000166:cytology; D053802:Tryptases / Q000378:metabolism*
chemical_list: D009414:Nerve Growth Factors; D010446:Peptide Fragments; D011498:Protein Precursors; D020932:Nerve Growth Factor; D053802:Tryptases