Lipopolysaccharide causes Sp1 protein degradation by inducing a unique trypsin-like serine protease in rat lungs.
We have previously demonstrated that challenge of rat or mice with lipopolysaccharide (LPS) in vivo promotes Sp1 protein degradation. The protease responsible for the LPS-induced Sp1 degradation has not been identified. In this study, we have identified, characterized and partially purified an LPS-inducible Sp1-degrading enzyme (LISPDE) activity from rat lungs. LISPDE activity selectively degraded Sp1, but not nuclear protein, C-fos, p65, I-kappaBalpha and protein actin. Nuclear extract contains approximately 14-fold of the LISPDE activity as that detected in cytoplasmic extract, suggesting that LISPDE is predominantly a nuclear protease. Using biochemical reagents, protease inhibitors and peptide substrates, we have characterized the LISPDE activity. Based on biochemical characteristics, inhibitor profile, and substrate specificity, we have shown that LISPDE activity is not 26S proteasome, caspase or cathepsin-like activity, but is a trypsin-like serine protease activity. Using soybean trypsin inhibitor (SBTI)-sepharose affinity column, we have partially purified the LISPDE protein, which has an estimated molecular mass of 33 kDa and selectively degrades native Sp1 protein. We mapped the initial site for proteolytic cleavage of Sp1 by LISPDE to be located within the region between amino acids 181-328. We conclude that LPS causes Sp1 degradation by inducing a unique trypsin-like serine protease, LISPDE.
Ye
Xiaobing
X
Department of Medicine, Division of Pulmonary and Critical Care Medicine, Long Island Jewish Medical Center, The Long Island Campus for the Albert Einstein College of Medicine, Research Building, RM B371, 270-05 76th Avenue, New Hyde Park, NY 11040, USA.
Liu
Shu Fang
SF
D000818:Animals; D020169:Caspases / Q000378:metabolism; D002403:Cathepsins / Q000378:metabolism; D002457:Cell Extracts; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects* / Q000201:enzymology*; D010449:Peptide Mapping; D010455:Peptides / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000032:analysis / Q000096:biosynthesis* / Q000302:isolation & purification; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013379:Substrate Specificity / Q000187:drug effects; D013997:Time Factors; D014357:Trypsin / Q000378:metabolism
D002457:Cell Extracts; D008070:Lipopolysaccharides; D010455:Peptides; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D016329:Sp1 Transcription Factor; C114880:trypsin-like serine protease; D002403:Cathepsins; C517968:LISPDE protein, human; D012697:Serine Endopeptidases; D014357:Trypsin; D020169:Caspases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease