Tpl2/cot signals activate ERK, JNK, and NF-kappaB in a cell-type and stimulus-specific manner.
Macrophages and B-cells from Tpl2 knock-out mice exhibit a restricted defect in lipopolysaccharide and death receptor signaling that is limited to the activation of ERK. Here we show that Tpl2-/- MEFs exhibit defects in ERK, JNK, and NF-kappaB activation, or ERK activation only when stimulated with tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta, respectively. In addition, we show that the activation of Tpl2 by TNF-alpha depends on signals transduced by both TRAF2 and RIP1. Activated Tpl2 phosphorylates MKK4/SEK1 upstream of JNK and stimulates NF-kappaB DNA binding and transcriptional activity by mechanisms that are independent of the nuclear translocation of p50 and p65. Tpl2-transduced TNF-alpha signals instead promote the phosphorylation of p65 at Ser276 and modulate the spectrum of proteins associated with p65. Phosphorylation stimulates the transcriptional activity of NF-kappaB but does not affect its ability to bind DNA, which may be affected by the composition of the nuclear NF-kappaB complexes. These data confirm that defects caused by a single mutation may be cell-type and signal-specific and delineate the role of Tpl2 in the transduction of TNF-alpha signals that activate JNK and NF-kappaB in MEFs.
Das
Santasabuj
S
Molecular Oncology Research Institute, Tufts-New England Medical Center, Boston, Massachusetts 02111, USA.
Cho
Jeonghee
J
Lambertz
Irina
I
Kelliher
Michelle A
MA
Eliopoulos
Aristides G
AG
Du
Keyong
K
Tsichlis
Philip N
PN
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D014409:Tumor Necrosis Factor-alpha; D012694:Serine; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C489843:Map3k8 protein, mouse