Carboxypeptidase cathepsin X mediates beta2-integrin-dependent adhesion of differentiated U-937 cells.
Cathepsin X is a lysosomal carboxypeptidase with a potential role in processes of inflammation and immune response. The integrin-binding motifs RGD and ECD, present in the pro- and in mature forms of cathepsin X, respectively, suggest that this enzyme might have a function in cell signaling and adhesion. In this study, we report that cysteine protease inhibitors E-64 and CA-074 and 2F12 monoclonal antibody, all of which inhibit cathepsin X activity, significantly reduced adhesion of differentiated U-937 cells to polystyrene- and fibrinogen-coated surfaces via Mac-1 integrin receptor, whereas their binding to vitronectin, fibronectin or Matrigel was not affected. On the other hand, cathepsin X, added to differentiating U-937 cells, stimulated their adhesion. Using confocal microscopy, we demonstrated that the pro-form of cathepsin X was co-localized with beta(2) and beta(3) integrin subunits and its mature form solely with the beta(2) integrin subunit with the most intense signal in cell-cell junctions in differentiated U-937 cells and in co-cultures with endothelial cells. Our results indicate that active cathepsin X mediates the function of beta(2) integrin receptors during cell adhesion and that it could also be involved in other processes associated with beta(2) integrin receptors such as phagocytosis and T cell activation.
Obermajer
Natasa
N
Faculty of Pharmacy, University of Ljubljana, Askerceva 7, SI-1000 Ljubljana, Slovenia.
Premzl
Ales
A
Zavasnik Bergant
Tina
T
Turk
Boris
B
Kos
Janko
J
D000911:Antibodies, Monoclonal / Q000276:immunology; D001665:Binding Sites; D018821:CD18 Antigens / Q000378:metabolism*; D002268:Carboxypeptidases / Q000737:chemistry / Q000378:metabolism*; D056657:Cathepsin K; D002403:Cathepsins / Q000737:chemistry / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003911:Dextrans / Q000737:chemistry; D042783:Endothelial Cells / Q000166:cytology; D006801:Humans; D019344:Lactic Acid / Q000276:immunology; D049329:Nanostructures / Q000737:chemistry; D010587:Phagocytosis / Q000276:immunology; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D020298:U937 Cells; D019096:Vitronectin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D015853:Cysteine Proteinase Inhibitors; D003911:Dextrans; D011108:Polymers; D021122:Protein Subunits; D019096:Vitronectin; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D002268:Carboxypeptidases; D002403:Cathepsins; C534130:CTSK protein, human; D056657:Cathepsin K