Plasmin and plasminogen activator inhibitor type 1 promote cellular motility by regulating the interaction between the urokinase receptor and vitronectin.
The urokinase receptor (uPAR) coordinates plasmin-mediated cell-surface proteolysis and promotes cellular adhesion via a binding site for vitronectin on uPAR. Because vitronectin also binds plasminogen activator inhibitor type 1 (PAI-1), and plasmin cleavage of vitronectin reduces PAI-1 binding, we explored the effects of plasmin and PAI-1 on the interaction between uPAR and vitronectin. PAI-1 blocked cellular binding of and adhesion to vitronectin by over 80% (IC50 approximately 5 nM), promoted detachment of uPAR-bearing cells from vitronectin, and increased cellular migration on vitronectin. Limited cleavage of vitronectin by plasmin also abolished cellular binding and adhesion and induced cellular detachment. A series of peptides surrounding a plasmin cleavage site (arginine 361) near the carboxy-terminal end of vitronectin were synthesized. Two peptides spanning res 364-380 blocked binding of uPAR to vitronectin (IC50 approximately 8-25 microM) identifying this region as an important site of uPAR-vitronectin interaction. These data illuminate a complex regulatory scheme for uPAR-dependent cellular adhesion to vitronectin: Active urokinase promotes adhesion and also subsequent detachment through activation of plasmin or complex formation with PAI-1. Excess PAI-1 may also promote migration by blocking cellular adhesion and/or promoting detachment, possibly accounting in part for the strong correlation between PAI-1 expression and tumor cell metastasis.
Waltz
D A
DA
Division of Respiratory Diseases, Children's Hospital, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02115, USA. waltz@a1.tch.harvard.edu
Natkin
L R
LR
Fujita
R M
RM
Wei
Y
Y
Chapman
H A
HA
D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D002846:Chromatography, Affinity; D005341:Fibrinolysin / Q000494:pharmacology*; D005353:Fibronectins; D006801:Humans; D007668:Kidney; D015479:Leukemia, Myelomonocytic, Acute; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000502:physiology*; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins / Q000096:biosynthesis; D014162:Transfection; D014407:Tumor Cells, Cultured; D019096:Vitronectin / Q000302:isolation & purification / Q000502:physiology*
D005353:Fibronectins; C524898:PLAUR protein, human; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; D019096:Vitronectin; D005341:Fibrinolysin