Suppression of macrophage responses to bacterial lipopolysaccharide (LPS) by secretory leukocyte protease inhibitor (SLPI) is independent of its anti-protease function.
Secretory leukocyte protease inhibitor (SLPI), a potent serine protease inhibitor, has been shown to suppress macrophage responses to bacterial lipopolysaccharide (LPS). SLPI contains two topologically superimposable domains. Its C-terminal domain binds and inhibits target proteases. It is not clear whether SLPI's anti-protease function plays a role in the LPS-inhibitory action of SLPI. Four single amino acid substitution mutants of SLPI, M73G, M73F, M73E and M73K, were generated. Wild type SLPI is a potent inhibitor of chymotrypsin and elastase. Mutants M73G and M73F selectively lost inhibitory function towards chymotrypsin and elastase, respectively, whereas mutants M73K and M73E inhibited neither elastase nor chymotrypsin. Macrophage cell lines were established from RAW264.7 cells to stably express each SLPI mutant. Expression of the SLPI protease inhibition mutants suppressed NO and TNF production in response to LPS in a similar fashion as wild type SLPI. Expression of truncated forms of SLPI, containing only its N-terminus or its C-terminus, was similarly sufficient to confer inhibition of LPS responses. Thus, the LPS-inhibitory action of SLPI is independent of its anti-protease function.
Yang
Jingxuan
J
Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
Zhu
Jing
J
Sun
Dongxu
D
Ding
Aihao
A
D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D002918:Chymotrypsin / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D008070:Lipopolysaccharides / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009569:Nitric Oxide / Q000378:metabolism; D010196:Pancreatic Elastase / Q000378:metabolism; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D053481:Secretory Leukocyte Peptidase Inhibitor; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D008070:Lipopolysaccharides; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins; D053481:Secretory Leukocyte Peptidase Inhibitor; C506815:Slpi protein, mouse; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D002918:Chymotrypsin; D010196:Pancreatic Elastase