Previous Article | Next Article ![]()
Mol. Cell. Biol., 11 1997, 6274-6282, Vol 17, No. 11
JL Swantek, MH Cobb and TD Geppert
The adverse effects of lipopolysaccharide (LPS) are mediated primarily by
tumor necrosis factor alpha (TNF-alpha). TNF-alpha production by LPS-
stimulated macrophages is regulated at the levels of both transcription and
translation. It has previously been shown that several mitogen- activated
protein kinases (MAPKs) are activated in response to LPS. We set out to
determine which MAPK signaling pathways are activated in our system and
which MAPK pathways are required for TNF-alpha gene transcription or
TNF-alpha mRNA translation. We confirm activation of the MAPK family
members extracellular-signal-regulated kinases 1 and 2 (ERK1 and ERK2),
p38, and Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK),
as well as activation of the immediate upstream MAPK activators MAPK/ERK
kinases 1 and 4 (MEK1 and MEK4). We demonstrate that LPS also activates
MEK2, MEK3, and MEK6. Furthermore, we demonstrate that dexamethasone, which
inhibits the production of cytokines, including TNF-alpha, significantly
inhibits LPS induction of JNK/SAPK activity but not that of p38, ERK1 and
ERK2, or MEK3, MEK4, or MEK6. Dexamethasone also blocks the sorbitol but
not anisomycin stimulation of JNK/SAPK activity. A kinase-defective mutant
of SAPKbeta, SAPKbeta K-A, blocked translation of TNF-alpha, as determined
by using a TNF-alpha translational reporting system. Finally,
overexpression of wild-type SAPKbeta was able to overcome the
dexamethasone-induced block of TNF-alpha translation. These data confirm
that three MAPK family members and their upstream activators are stimulated
by LPS and demonstrate that JNK/SAPK is required for LPS- induced
translation of TNF-alpha mRNA. A novel mechanism by which dexamethasone
inhibits translation of TNF-alpha is also revealed.
Copyright © 1997, American Society for Microbiology
Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) is required for lipopolysaccharide stimulation of tumor necrosis factor alpha (TNF-alpha) translation: glucocorticoids inhibit TNF-alpha translation by blocking JNK/SAPK
Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas 75235-9041, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»