Urokinase-type plasminogen activator-induced monocyte adhesion requires a carboxyl-terminal lysine and cAMP-dependent signal transduction.
Urokinase-type plasminogen activator (u-PA) or its amino-terminal fragment (ATF) containing the u-PA receptor (u-PAR) binding domain, is known to promote monocyte adhesion. In the present study, U937 monocyte adhesion to a plastic surface was used to investigate the mechanism of its promotion by u-PA and ATF. Adhesion was found to be inhibited by cycloheximide or actinomycin D, implicating protein synthesis and gene expression in u-PA-induced monocyte adhesion. Adhesion was prevented by 2'-deoxyadenosine 3'-monophosphate, indicating that a cAMP-dependent pathway of signal transduction was involved. This concept was supported by the complementary finding that u-PA-induced adhesion was greatly promoted by forskolin, cholera toxin, or 8-bromo-cAMP, which by themselves induced little adhesion. Furthermore, similar to many other cAMP-dependent activities, cGMP diminished u-PA-induced adhesion. When u-PA or ATF was treated with immobilized carboxypeptidase B, its proadhesive effect was abolished, implicating the involvement of carboxyl-terminal lysine residues (Lys158 on u-PA and Lys135 on ATF). Moreover, when a carboxyl-terminal lysine analog was added, the proadhesive effect of carboxypeptidase B-treated u-PA or ATF was restored. In conclusion, the present study indicates that u-PA- or ATF-induced monocyte adhesion involves cAMP-dependent signal transduction, which is triggered by u-PAR binding. It is also critically dependent on the presence of a carboxyl-terminal lysine.
Vascular Research Laboratory, Deaconess Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA.
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D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D001665:Binding Sites; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D006801:Humans; D007531:Isoflurophate / Q000494:pharmacology; D007700:Kinetics; D009000:Monocytes / Q000187:drug effects / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology*
C524898:PLAUR protein, human; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D007531:Isoflurophate; D003609:Dactinomycin; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D003513:Cycloheximide; D000242:Cyclic AMP; D014568:Urokinase-Type Plasminogen Activator; D006152:Cyclic GMP