Mechanism by which U937 promonocytic cells inactivate human interferon-gamma.
Mononuclear phagocytes produce proteinases that are thought to play a role in regulating the activity of cytokines. Activated macrophages secrete urokinase-type plasminogen activator (uPA), which mediates the formation of the serine proteinase plasmin from the ubiquitous zymogen plasminogen. We previously observed a correlation between in vitro plasminogen activation by the promonocytic cell line U937 and the apparent ability of these cells to inactivate recombinant interferon-gamma (rIFN-gamma) by proteolysis. The present study was designed to test the hypothesis that plasmin, generated in U937 cell cultures, is both necessary and sufficient to inactivate rIFN-gamma by limited proteolysis. The following observations are consistent with this hypothesis: (1) inactivation of rIFN-gamma was prevented by inhibitors of serine proteinases or an antibody that specifically immunodepleted plasmin activity; (2) purified plasmin inactivated rIFN-gamma as efficiently as U937 culture supernatants and was similarly sensitive to serine proteinase inhibitors; and (3) plasmin removed an 11 amino acid carboxyl-terminal peptide from rIFN-gamma, which included a region known to be required for bioactivity. Overall, these data indicate that plasminogen activation by U937 promonocytic cells leads to the proteolytic inactivation of IFN-gamma by a process that only requires the production of plasmin.
Duval-Jobe
C
C
Department of Microbiology, University of Kansas Medical Center, Kansas City 66160-7420, USA.
Leeson
M
M
Rawitch
A
A
Parmely
M J
MJ
D000595:Amino Acid Sequence; D002460:Cell Line; D005341:Fibrinolysin / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000201:enzymology*; D006801:Humans; D006868:Hydrolysis; D007371:Interferon-gamma / Q000037:antagonists & inhibitors*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000201:enzymology*; D011994:Recombinant Proteins; D014568:Urokinase-Type Plasminogen Activator / Q000097:blood*
D011994:Recombinant Proteins; D007371:Interferon-gamma; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator