Expression of urokinase plasminogen activator receptor in resting and activated bovine neutrophils.
Changes in urokinase-plasminogen activator (u-PA) and u-PA receptor (u-PAR) expression at the protein and mRNA level in resting neutrophils and in neutrophils activated by phorbol myristate acetate (PMA) were examined. Low amounts of u-PA were found intracellularly or membrane-bound in resting neutrophils. However, incubation of resting neutrophils with purified exogenous u-PA (10 IU/ml) revealed extensive binding of u-PA to cell membranes. Excess amino-terminal fragment of the u-PA molecule, a proteolytically inactive fragment of u-PA (amino acids 1-135) blocked binding of exogenous u-PA to the cell membrane. These results, collectively, indicate that the binding of u-PA is specific and that resting neutrophils have unoccupied u-PA receptors on their cell membrane. Addition of PMA led to an increase (P < 0.01) in total cell-associated, membrane-bound u-PA activity and u-PA mRNA expression by bovine neutrophils. In contrast. PMA increased u-PAR mRNA levels but this was accompanied by a decrease (2.5-fold; P < 0.01) in free, unoccupied u-PA binding sites. No significant effects on total cell-associated or membrane-bound u-PA were found when neutrophils were treated with 4-phorbol 12,13 didecanoate, a phorbol ester that does not activate protein kinase C (PKC). Furthermore, addition of 1-(5-isoquinolinesylphonyl)-2-methlylpiperazine dihydrochloride (H-7), a potent PKC inhibitor, blocked the effect of PMA on total cell-associated u-PA activity. Thus, PKC plays a role in the modulation of u-PA and u-PAR by PMA in bovine neutrophils.
Politis
Ioannis
I
Department of Animal Production, Agricultural University of Athens, Greece.
Zavizjon
Boris
B
Cheli
Federica
F
Baldi
Antonella
A
D000818:Animals; D001667:Binding, Competitive; D015152:Blotting, Northern / Q000662:veterinary; D002273:Carcinogens / Q000494:pharmacology; D002417:Cattle; D005260:Female; D005341:Fibrinolysin / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism*
D002273:Carcinogens; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011493:Protein Kinase C; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate