| First Author | Qureshi N | Year | 2003 |
| Journal | J Immunol | Volume | 171 |
| Issue | 3 | Pages | 1515-25 |
| PubMed ID | 12874245 | Mgi Jnum | J:156236 |
| Mgi Id | MGI:4419084 | Doi | 10.4049/jimmunol.171.3.1515 |
| Citation | Qureshi N, et al. (2003) The proteasome as a lipopolysaccharide-binding protein in macrophages: differential effects of proteasome inhibition on lipopolysaccharide-induced signaling events. J Immunol 171(3):1515-25 |
| abstractText | We have developed a novel LPS probe using a highly purified and homogenous preparation of [(3)H] Escherichia coli LPS from the deep rough mutant, which contains a covalently linked, photoactivable 4-p-(azidosalicylamido)-butylamine group. This cross-linker was used to identify the LPS-binding proteins in membranes of the murine-macrophage-like cell line RAW 264.7. The alpha-subunit (PSMA1 C2, 29.5 kDa) and the beta-subunit (PSMB4 N3, 24.36 kDa) of the 20S proteasome complex were identified as LPS-binding proteins. This is the first report demonstrating LPS binding to enzymes such as the proteasome subunits. Functionally, LPS enhanced the chymotrypsin-like activity of the proteasome to degrade synthetic peptides in vitro and, conversely, the proteasome inhibitor lactacystin completely blocked the LPS-induced proteasome's chymotrypsin activity as well as macrophage TNF-alpha secretion and the expression of multiple inflammatory mediator genes. Lactacystin also completely blocked the LPS-induced expression of Toll-like receptor 2 mRNA. In addition, lactacystin dysregulated mitogen-activated protein kinase phosphorylation in LPS-stimulated macrophages, but failed to inhibit IL-1 receptor-associated kinase-1 activity. Importantly, lactacystin also prevented LPS-induced shock in mice. These data strongly suggest that the proteasome complex regulates the LPS-induced signal transduction and that it may be an important therapeutic target in Gram-negative sepsis. |
