Inactivation of human gamma interferon by Pseudomonas aeruginosa proteases: elastase augments the effects of alkaline protease despite the presence of alpha 2-macroglobulin.
Pseudomonas aeruginosa alkaline protease (AP) has recently been shown to produce limited proteolysis of human gamma interferon (IFN-gamma) and thereby destroy the antiviral and macrophage-activating activities of the lymphokine. In the present study we describe some of the characteristics of Pseudomonas elastase (E) with regard to inactivation of human IFN-gamma. The inhibitory effect of E on IFN-gamma bioactivity differed from that of AP in that the direct effects of E were reduced in the presence of human serum. That this property of human serum was in large part attributable to the protease inhibitor alpha 2-macroglobulin (alpha 2-M) was suggested by the following observations: (i) methylamine treatment of serum reduced its effect on E, (ii) E interacted directly with alpha 2-M to induce a characteristic conformational change in the protease inhibitor, and (iii) preformed E-alpha 2-M complexes lacked IFN-gamma-degrading activity. Despite these findings, anti-E antiserum partially neutralized the effect that a Pseudomonas filtrate showed on IFN-gamma, suggesting that E contributes to the activity of bacterial filtrates. Treatment of IFN-gamma with E in the presence of a suboptimal concentration of AP resulted in an E dose-dependent inactivation of the lymphokine. Preformed E-alpha 2-M complexes, although ineffective by themselves at cleaving IFN-gamma, degraded the lymphokine, providing AP was also present in the reaction mixture. These data demonstrate that the destruction of small, biologically significant peptides by Pseudomonas proteases can involve protease-protease synergy that acts even in the presence of the serum protease inhibitor alpha 2-M.
Horvat
R T
RT
Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, 66103.
Clabaugh
M
M
Duval-Jobe
C
C
Parmely
M J
MJ
D010450:Endopeptidases / Q000097:blood / Q000502:physiology*; D006801:Humans; D006868:Hydrolysis; D007371:Interferon-gamma / Q000037:antagonists & inhibitors* / Q000097:blood; D046911:Macromolecular Substances; D008744:Methylamines / Q000494:pharmacology; D009500:Neutralization Tests; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors / Q000097:blood / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D000511:alpha-Macroglobulins / Q000037:antagonists & inhibitors / Q000502:physiology*
D046911:Macromolecular Substances; D008744:Methylamines; D011994:Recombinant Proteins; D000511:alpha-Macroglobulins; D007371:Interferon-gamma; C027451:methylamine; D010450:Endopeptidases; D012697:Serine Endopeptidases; D010196:Pancreatic Elastase; C032923:microbial serine proteinases