Serpin 2a Is Induced in Activated Macrophages and Conjugates to a Ubiquitin Homolog

• Published in: The Journal of immunology (1950) 2002-03, Vol.168 (5), p.2415-2423
• Main Authors: Hamerman, Jessica A, Hayashi, Fumitaka, Schroeder, Lea A, Gygi, Steven P, Haas, Arthur L, Hampson, Lynne, Coughlin, Paul, Aebersold, Ruedi, Aderem, Alan
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Bacterial Infections - genetics; Bacterial Infections - immunology; Cell Line; Cytokines - metabolism; g-Interferon; Interferon-gamma - pharmacology; ISG15 gene; Listeria monocytogenes; Macromolecular Substances; Macrophage Activation; Macrophages - drug effects; Macrophages - immunology; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Molecular Sequence Data; Polysaccharides, Bacterial - pharmacology; RNA, Messenger - biosynthesis; Salmonella typhimurium; serpin 2a; Serpins - biosynthesis; Serpins - genetics; Serpins - metabolism; Transcriptional Activation; Ubiquitin - genetics; Ubiquitins; Up-Regulation
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.168.5.2415

After i.p. infection of mice with the intracellular bacterium Mycobacterium bovis bacillus Calmette-Guérin, macrophages recovered from the peritoneal cavity display classical signs of immune activation. We have identified a member of the serine protease inhibitor (serpin) family which is highly induced in macrophages during bacillus Calmette-Guérin infection. Serpin 2a (spi2a) expression is also induced in macrophages in vivo during infection with Salmonella typhimurium and Listeria monocytogenes, and in vitro by a variety of bacteria and bacterial products. The cytokine IFN-gamma also induces spi2a expression in macrophages, and this induction is synergistic with bacterial products. We also demonstrate here that a ubiquitin homolog, IFN-stimulated gene of 15-kDa (ISG15), is strongly induced during in vitro and in vivo activation of macrophages and that it conjugates to spi2a in activated macrophages. The ISG15-spi2a conjugates were identified by tandem mass spectrometry and contained spi2a conjugated to either one or two molecules of ISG15. Whereas spi2a was induced by either bacterial products or IFN-gamma, ISG15 was induced only by bacterial products. Although many protein targets have been described for ubiquitin conjugation, spi2a is the first ISG15-modified protein to be reported. Macrophage activation is accompanied by the activation of a variety of proteases. It is of interest that a member of the serine protease inhibitor family is concomitantly induced and modified by a ubiquitin-like protein.