title: Unexpected transcriptional induction of monocyte chemoattractant protein 1 by proteasome inhibition: involvement of the c-Jun N-terminal kinase-activator protein 1 pathway.
abstract: Proteasome inhibitors, the well-known inhibitors of NF-kappaB, are recently considered therapeutic agents for inflammation. However, the anti-inflammatory properties of these agents have not been fully evaluated. In this report we describe a novel effect of proteasome inhibitors on the expression of monocyte chemoattractant protein 1 (MCP-1) in mesangial cells. We found that proteasome inhibitor MG132 dose-dependently induced expression of MCP-1 at the transcriptional level. The stimulatory effect was similarly observed with other proteasome inhibitors (proteasome inhibitor 1 and lactacystin) and in other cell types (NRK fibroblasts). The 5'-flanking region of the MCP-1 gene contains multiple AP-1 sites. To explore the mechanisms involved, we examined the effects of proteasome inhibition on the AP-1 pathway. Northern blot analysis showed that MG132 rapidly induced the expression of c-jun, but not c-fos. Immunoblot analysis showed that MG132 prevented degradation of c-Jun protein. Kinase assay revealed that c-Jun N-terminal kinase (JNK) was rapidly activated by MG132. Consistent with these results, a reporter assay showed that AP-1 activity was up-regulated after treatment with MG132. Curcumin, a pharmacological inhibitor of the JNK-AP-1 pathway, abrogated the induction of MCP-1 by MG132. Similarly, stable transfection with a dominant-negative mutant of c-Jun attenuated both MG132-induced activation of AP-1 and expression of MCP-1. The transcriptional activation by proteasome inhibitors was observed not only in MCP-1, but also in other AP-1-dependent genes, including stromelysin and mitogen-activated protein kinase phosphatase 1. These data revealed that proteasome inhibition triggered the expression of MCP-1 and other genes via the multistep induction of the JNK-c-Jun/AP-1 pathway.
authors.affiliation: Department of Medicine, Royal Free and University College Medical School, University College London, Jules Thorn Institute, Middlesex Hospital, Mortimer Street, London W1T 3AA, UK.
authors.forename: K
authors.initials: K
authors.lastname: Nakayama
authors.forename: A
authors.initials: A
authors.lastname: Furusu
authors.forename: Q
authors.initials: Q
authors.lastname: Xu
authors.forename: T
authors.initials: T
authors.lastname: Konta
authors.forename: M
authors.initials: M
authors.lastname: Kitamura
mesh_terms: D000818:Animals; D002460:Cell Line; D018932:Chemokine CCL2 / Q000096:biosynthesis* / Q000235:genetics*; D003546:Cysteine Endopeptidases / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D048031:JNK Mitogen-Activated Protein Kinases; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000502:physiology; D046988:Proteasome Endopeptidase Complex; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D018808:Transcription Factor AP-1 / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000276:immunology*; D014162:Transfection
chemical_list: D018932:Chemokine CCL2; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde