The ubiquitin-like protein MNSFbeta regulates ERK-MAPK cascade.
MNSFbeta is a ubiquitously expressed member of the ubiquitin-like family that has been implicated in various biological functions. Previous studies have demonstrated that MNSFbeta covalently binds to intracellular proapoptotic protein Bcl-G in mitogen-activated murine T cells. In this study, we further investigated the intracellular mechanism of action of MNSFbeta in macrophage cell line, Raw 264.7 cells. We present evidence that MNSFbeta.Bcl-G complex associates with ERKs in non-stimulated Raw 264.7. We found that MNSFbeta.Bcl-G directly bound to ERKs and inhibited ERK activation by MEK1. In Raw 264.7 cells treated with MNSFbeta small interfering RNA (siRNA) lipopolysaccharide (LPS)-induced ERK1/2 activation was enhanced and LPS-induced JNK and p38 activation was unaffected. SiRNA-mediated knockdown of MNSFbeta increased tumor necrosis factor alpha (TNFalpha) expression at mRNA and protein levels in LPS-stimulated Raw 264.7 cells. Finally, we found that transfection with MNSFbeta expression construct resulted in a significant inhibition of LPS-induced ERK activation and TNFalpha production. Co-transfection experiments with MNSFbeta and Bcl-G greatly enhanced this inhibition. Collectively, these findings indicate that MNSFbeta might be implicated in the macrophage response to LPS.
Nakamura
Morihiko
M
Department of Cooperative Medical Research, Collaboration Center, Shimane University, Izumo 693-8501, Japan. Electronic address: nkmr0515@med.shimane-u.ac.jp.
Yamaguchi
Seiji
S
Department of Cooperative Medical Research, Collaboration Center, Shimane University, Izumo 693-8501, Japan; Department of Pediatrics, Faculty of Medicine, Shimane University, Izumo 693-8501, Japan.
D000818:Animals; D002460:Cell Line; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D011817:Rabbits; D012697:Serine Endopeptidases / Q000378:metabolism; D015398:Signal Transduction; D013491:Suppressor Factors, Immunologic / Q000378:metabolism / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D008070:Lipopolysaccharides; D013491:Suppressor Factors, Immunologic; D025801:Ubiquitin; C072169:monoclonal nonspecific suppressor factor; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase