title: Proteolytic regulation of the urokinase receptor/CD87 on monocytic cells by neutrophil elastase and cathepsin G.
abstract: The urokinase receptor (CD87) participates to the pericellular proteolytic potential of migrating cells and to the recruitment of leukocytes during inflammation. It consists of three structurally homologous domains, with the C-terminal domain D3 attached to cell membranes through a GPI anchor. CD87 is susceptible to an endoproteolytic processing removing the N-terminal domain D1 and generating truncated D2D3 membrane species, thus modulating CD87-associated functions. Full-length or truncated CD87 can be also released from cells via juxtamembrane cleavage by phospholipases and/or by yet unidentified proteinases. Using a recombinant CD87 and the CD87-positive monocytic U937 cell line and isolated blood monocytes, we show by protein immunoblotting and flow immunocytometry that the human neutrophil serine-proteinases elastase and cathepsin G cleave CD87 within the D1-D2 linker sequence, while in addition cathepsin G is highly efficient in cleaving the C terminus of D3. The combination of cathepsin G and elastase provided by degranulated neutrophils results in enzymatic cooperation leading to the release from monocytic cells of a truncated D2D3 species resembling that previously described in pathological body fluids. Using mass spectrometry analysis, the proteolytic fragmentation of synthetic peptides mapping the D1-D2 linker and D3 C-terminal domains identifies potential cleavage sites for each enzyme and suggests the existence of a mechanism regulating the CD87(D1-D2)-associated chemotactic activity. Finally, isolated or combined elastase and cathepsin G drastically reduce the capacity of cells to bind urokinase. Secretable leukocyte serine-proteinases are thus endowed with high potential for the regulation of CD87 expression and function on inflammatory cells.
authors.affiliation: Unité de Défense Innée et Inflammation, Institut National de la Santé et de la Recherche Médicale, Equipe 336, Institut Pasteur, 25 rue du Dr. Roux, F-75724 Paris cedex 15, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Beaufort
authors.forename: Dominique
authors.initials: D
authors.lastname: Leduc
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Rousselle
authors.forename: Viktor
authors.initials: V
authors.lastname: Magdolen
authors.forename: Thomas
authors.initials: T
authors.lastname: Luther
authors.forename: Abdelkader
authors.initials: A
authors.lastname: Namane
authors.forename: Michel
authors.initials: M
authors.lastname: Chignard
authors.forename: Dominique
authors.initials: D
authors.lastname: Pidard
mesh_terms: D000595:Amino Acid Sequence; D001667:Binding, Competitive; D056649:Cathepsin G; D002403:Cathepsins / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D004357:Drug Synergism; D006801:Humans; D006868:Hydrolysis; D015151:Immunoblotting; D019272:Leukocyte Elastase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009000:Monocytes / Q000201:enzymology* / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology* / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012697:Serine Endopeptidases; D012995:Solubility; D020298:U937 Cells; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; C524898:PLAUR protein, human; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D019272:Leukocyte Elastase; D014568:Urokinase-Type Plasminogen Activator