The cleavage of the urokinase receptor regulates its multiple functions.
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.
Montuori
Nunzia
N
Istituto di Endocrinologia ed Oncologia Sperimentale, Consiglio Nazionale delle Ricerche, via Pansini 5, I-80131, Naples, Italy.
Carriero
Maria Vincenza
MV
Salzano
Salvatore
S
Rossi
Guido
G
Ragno
Pia
P
D015153:Blotting, Western; D002448:Cell Adhesion; D002455:Cell Division; D002460:Cell Line; D002465:Cell Movement; D018076:DNA, Complementary / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008856:Microscopy, Fluorescence; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000502:physiology*; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D008024:Ligands; C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D055293:Receptors, Urokinase Plasminogen Activator