Toll-like receptor-2 ligand peptidoglycan upregulates expression and ubiquitin ligase activity of CHIP through JNK pathway.
BACKGROUND
Peptidoglycan (PGN) is a component of cell wall in Gram-positive bacteria that stimulates inflammatory responses through Toll-like receptor 2 (TLR2). The carboxyl terminus of constitutive heat shock cognate 70 (HSC70)-interacting protein (CHIP, also known as Stub1) is a U-box-type E3 ubiquitin ligase, which plays an important role in protein quality control and inflammation through ubquitin-mediated proteasomal degradation. However, it is unclear whether TLR2 agonist PGN regulates the expression and activation of CHIP.


RESULTS
In this study, we showed that PGN significantly up-regulated the expression of CHIP in both mRNA and protein levels in RAW264.7 cells in a time-dependant manner, and the expression of CHIP induced by PGN was abolished in TLR2 knockout macrophages. No significant change in CHIP was observed after lipopolysaccharide (LPS, TLR4 agonist) and cytosine-phosphorous-guanine oligonucleotide (CpG ODN, TLR9 agonist) treatment. Moreover, PGN markedly induced the expression and activity of CHIP in macrophages, whereas this effect was attenuated by SP600125, a selective inhibitor of JNK.


CONCLUSIONS
Our study for the first time demonstrates that TLR2 activation enhances the expression and activity of CHIP through JNK signaling pathway.
Department of Pathology, Physiology and Pathophysiology, AnZhen Hospital the Key Laboratory of Remodeling-Related Cardiovascular Diseases, School of Basic Medical Sciences, Capital Medical University, Beijing, China.
Yan
Y
Meng
Chen
C
Chen
Lei
L
Wang
Xia
X
Wang
Cui
C
Tian
Jie
J
Du
Hui-Hua
HH
Li
D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D047468:Immunoprecipitation; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D010457:Peptidoglycan / Q000494:pharmacology*; D060888:Real-Time Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D008070:Lipopolysaccharides; D009838:Oligodeoxyribonucleotides; D010457:Peptidoglycan; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases