Differential effects of tumor necrosis factor-alpha and CD40L on NF-kappa B inhibitory proteins I kappa B alpha, beta and epsilon and on the induction of the Jun amino-terminal kinase pathway in Ramos Burkitt lymphoma cells.
Interaction between the CD40 ligand and its cognate receptor is known to affect various aspects of B-cell biology. Less is known about the biological consequences of B-cell signaling through tumor necrosis factor alpha (TNF-alpha) and its two receptors. We have used Ramos germinal center (GC)-derived Burkitt's lymphoma (BL) cells as a model system to compare some of the early signaling events of TNF-alpha and CD40L on the NF-kappaB and c-Jun amino-terminal kinase (JNK) pathways. We have previously found that both TNF-alpha and CD40L induced enhanced cell aggregation, adherence and modified cell surface morphology of Ramos cells. In the present report, it was found that treatment with either TNF-alpha or CD40L resulted in a rapid degradation (within 15 min) of IkappaBalpha, followed by a recovery period lasting up to a few hours. The level of IkappaBbeta, another inhibitory molecule of the NF-kappaB pathway, also decreased following treatment with CD40L or TNF-alpha. However, whereas CD40L induced a rapid drop without significant recovery within 2 h, TNF-alpha caused a slow and gradual decline of IkappaBbeta. In addition, treatment with CD40L resulted in a gradual and modest decline of up to 60% of the level of IkappaBepsilon within 2 h, whereas a much smaller decline was seen with TNF-alpha (approx. 20%) Our results thus show that in Ramos cells, TNF-alpha and CD40L have common, as well as differential, signaling effects on the IkappaBalpha, IkappaBbeta and IkappaBepsilon, which form inhibitory complex(es) with the NF-kappaB cytosolic proteins. We also found that CD40L, but not TNF-alpha activates the JNK pathway through transient phosphorylation of its threonine183/tyrosine185 residues. As expected, c-Jun, which is known to be a substrate of JNK, was also phosphorylated at serine residue 73 by treatment with CD40L, but not by TNF-alpha.
Laskov
Reuven
R
Dept. of Experimental Medicine & Cancer Research Hebrew University-Hadassah Medical School, Ein Karem, Jerusalem 91120, Israel. laskov@md.huji.ac.il
Berger
Nir
N
Horwitz
Marshall S
MS
D000818:Animals; D002051:Burkitt Lymphoma / Q000201:enzymology / Q000378:metabolism*; D023201:CD40 Ligand / Q000502:physiology*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000502:physiology; D004790:Enzyme Induction / Q000502:physiology; D018922:HL-60 Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000096:biosynthesis* / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C105627:NFKBIE protein, human; C000606205:Nfkbia protein, mouse; D011518:Proto-Oncogene Proteins; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D023201:CD40 Ligand; D048031:JNK Mitogen-Activated Protein Kinases