The Cleavage of the Urokinase Receptor Regulates Its Multiple Functions

• Published in: The Journal of biological chemistry 2002-12, Vol.277 (49), p.46932-46939
• Main Authors: Montuori, Nunzia, Carriero, Maria Vincenza, Salzano, Salvatore, Rossi, Guido, Ragno, Pia
• Format: Article
• Language: English
• Subjects: Blotting, Western; Cell Adhesion; Cell Division; Cell Line; Cell Movement; DNA, Complementary - metabolism; Humans; Ligands; Microscopy, Fluorescence; Mutation; Plasmids - metabolism; Precipitin Tests; Protein Binding; Protein Structure, Tertiary; Receptors, Cell Surface - chemistry; Receptors, Cell Surface - physiology; Receptors, Formyl Peptide; Receptors, Immunologic - metabolism; Receptors, Peptide - metabolism; Receptors, Urokinase Plasminogen Activator; Reverse Transcriptase Polymerase Chain Reaction; Time Factors; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M207494200

The urokinase-type plasminogen activator (uPA) is able to cleave its cell surface receptor (uPAR) anchored to the cell membrane through a glycophosphatidylinositol tail. The cleavage leads to the formation of cell surface truncated forms, devoid of the N-terminal domain 1 (D1) and unmasks or disrupts, depending on the cleavage site, a sequence in the D1-D2 linker region (residues 88–92), which in the soluble form is a potent chemoattractant for monocyte-like cells. To investigate the possible role(s) of the cleaved forms of cell surface glycophosphatidylinositol-anchored uPAR, uPAR-negative human embrional kidney 293 cells were transfected with the cDNA of intact uPAR (uPAR-293) or with cDNAs corresponding to the truncated forms of uPAR exposing (D2D3-293) or lacking (D2D3wc-293) the peptide 88–92 (P88–92). Cell adhesion assays and co-immunoprecipitation experiments indicated that the removal of D1, independently of the presence of P88–92, abolished the lateral interaction of uPAR with integrins and its capability to regulate integrin adhesive functions. The expression of intact uPAR induced also a moderate increase in 293 cell proliferation, which was accompanied by the activation of ERK. Also this effect was abolished by D1 removal, independently of the presence of P88–92. The expression of intact and truncated uPARs regulated cell directional migration toward uPA, the specific uPAR ligand, and toward fMLP, a bacterial chemotactic peptide. In fact, the uPA-dependent cell migration required the expression of intact uPAR, including D1, whereas the fMLP-dependent cell migration required the expression of a P88–92 containing uPAR and was independent of the presence of D1. Together these observations indicate that uPA-mediated uPAR cleavage and D1 removal, occurring on the cell surface of several cell types, can play a fundamental role in the regulation of multiple uPAR functions.