By
From the * Consiglio Nazionale delle Ricerche Center of Molecular and Cellular Pharmacology and the
Department of Biotechnology and Biological Sciences, Second University of Milano, 20126 Milano,
Italy; and the Department of Microbiology and Immunology, University of British Columbia,
Vancouver V6T 1Z3, British Columbia, Canada
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Abstract |
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Although dendritic cell (DC) activation is a critical event for the induction of immune responses,
the signaling pathways involved in this process have not been characterized. In this report, we
show that DC activation induced by lipopolysaccharide (LPS) can be separated into two distinct
processes: first, maturation, leading to upregulation of MHC and costimulatory molecules, and second, rescue from immediate apoptosis after withdrawal of growth factors (survival). Using a DC
culture system that allowed us to propagate immature growth factor-dependent DCs, we have investigated the signaling pathways activated by LPS. We found that LPS induced nuclear translocation of the nuclear factor (NF)-B transcription factor. Inhibition of NF-
B activation blocked
maturation of DCs in terms of upregulation of major histocompatibility complex and costimulatory molecules. In addition, we found that LPS activated the extracellular signal-regulated kinase
(ERK), and that specific inhibition of MEK1, the kinase which activates ERK, abrogated the ability
of LPS to prevent apoptosis but did not inhibit DC maturation or NF-
B nuclear translocation.
These results indicate that ERK and NF-
B regulate different aspects of LPS-induced DC activation: ERK regulates DC survival whereas NF-
B is responsible for DC maturation.
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Introduction |
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Dendritic cells (DCs) are now recognized as major players in the regulation of immune responses to a variety of antigens, including bacterial and viral agents (1). DCs direct both the quality and the extent of the immune response, but the ability of DCs to activate naive T cells depends on their maturation. Fully mature DCs have a high surface expression of MHC and costimulatory molecules and are located in lymphoid organs. In contrast, immature DCs are mainly distributed in tissues interfacing with the external environment where they capture and process antigens with high efficiency (1). After microbe internalization and inflammation, DC leave the tissue to reach the lymphoid organs. During this migration the DC undergo maturation and acquire the ability to prime T cells. This second functional stage is irreversible and is followed by apoptosis (2). Among the inflammatory signals that induce DC maturation, LPS, a Gram-negative bacterial cell wall component, has been shown to fully activate DC both in vitro and in vivo (2).
To oppose bacterial infections and inflammation, DCs
have to respond rapidly to changes in their microenvironment. Most types of signals induce cellular responses by
binding to specific cell-surface receptors that respond to
occupancy by triggering one or more signal transduction
pathways (5). One of the most common responses to receptor engagement is the activation of transcription factors and the synthesis of new proteins. Among the transcription
factors, the active heterodimer p50/p65 form of nuclear
factor (NF)-B plays a central role in immunological processes by inducing expression of a variety of genes involved
in inflammatory responses (6). In macrophages, NF-
B can
be activated by exposure to LPS as well as by inflammatory
cytokines (TNF-
and IL-1) and viral infections (7).
Mature DCs express high levels of the NF-
B family of transcription factors (10) and signaling by members of the
TNF-
receptor family, such as CD40 and RANK, results
in activation of NF-
B (1). Other transcription factors are
regulated by signal transduction pathways that involve enzymatic cascades of mitogen-activated protein (MAP) kinases. The latter are activated by many receptors, as well as
by environmental stresses, and have been shown to mediate
both mitogenic and apoptotic responses (11). LPS has
been shown to activate the extracellular signal-regulated kinase, c-Jun NH2-terminal kinase (JNK), and p38 MAP
kinases in murine macrophages (15) but, to date, the
signal transduction pathways activated during DC maturation have not been characterized.
In vitro studies of immature mouse DCs have been hampered because it has not been possible to arrest spontaneous
DC maturation and cell death (18). Recently, we have described a DC culture system (D1 cells) that allows us to
maintain the immature DC phenotype in vitro. DC proliferation is growth factor dependent, and maturation can be
induced by inflammatory signals and by bacteria (2, 19),
thus mimicking the in vivo response (3). Survival of the
immature D1 cells is maintained by a mixture of cytokines contained in the DC conditioned medium (CM). Deprivation of CM causes D1 cells to undergo apoptotic cell death
within 48 h. Using this unique system, we were able to investigate the kinetics of DC maturation and survival and to
identify some of the molecular events involved in these
processes. Here it is shown that, in addition to inducing
DC maturation, LPS arrests DC proliferation and promotes
DC survival after CM deprivation. We also found that LPS
activates both the ERK MAP kinase and the NF-B transcription factor. The two signal transduction pathways are
independent and regulate different aspects of LPS-induced
DC activation.
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Materials and Methods |
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Cells and Reagents.
The D1 cells were derived from murine splenic DCs and maintained in vitro as growth factor-dependent immature DCs (2, 19). D1 cells were grown in complete IMDM supplemented with 30% R1 CM containing 30 ng/ml GM-CSF as previously described (2). LPS (Escherichia coli serotype 026:B6) and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) were purchased from Sigma Chemical Co. (St. Louis, MO). MEK inhibitor PD98059 was from BIOMOL Research Labs., Inc. (Plymouth Meeting, PA).Cell Stimulation and Preparation of Cell Lysates.
5 × 106 D1 cells were resuspended in 1 ml of modified Hepes-buffered saline (20), warmed to 37°C, and stimulated with LPS (10 µg/ml) for the indicated times. Where indicated, the cells were pretreated at 37°C with 50 or 100 µM MEK inhibitor PD98059 for 30 min or with 15 µM TPCK for 1.5 h before being stimulated with LPS. Reactions were stopped by adding ice-cold PBS containing 1 mM Na3VO4 and then centrifuging the cells for 3 min in the cold. The cells were pelleted and then solubilized in buffers containing 1% Triton X-100 or NP-40 as well as protease and phosphatase inhibitors. Detergent-insoluble material was removed by centrifugation.In Vitro Kinase Assays.
In vitro kinase assays for ERK, JNK, and MAP kinase-activated protein (MAPKAP) kinase-2 have been described previously (21). For ERK assays, lysates from 5 × 106 D1 cells were immunoprecipitated with an agarose-conjugated antibody that recognizes ERK2, and to a lesser extent ERK1 (antibody C-14; Santa Cruz Biotechnology Inc., Santa Cruz, CA). For JNK and MAPKAP kinase-2 assays, lysates from 5 × 106 D1 cells were immunoprecipitated with an antibody to either JNK1 (antibody C-17; Santa Cruz Biotechnology) or MAPKAP kinase-2 (Upstate Biotechnology Inc., Lake Placid, NY) and immune complexes were collected on protein A-Sepharose (Sigma Chemical Co.). After washing, immune complexes were incubated with 32P-Assessment of Apoptosis by Flow Cytometry.
Cells were preincubated or not with 50 µM PD98059 for 30 min and then with 10 µg/ml LPS for 8, 24, or 48 h. Cells were detached, double stained with FITC-conjugated Annexin V (PharMingen, San Diego, CA) and 1.25 µg/ml propidium iodide (Sigma Chemical Co.), and analyzed by flow cytometry.Antibodies, Cytokine Assays, and Flow Cytometry Analysis.
At different time points after LPS activation, Dl cells were detached with PBS/2 mM EDTA and incubated with one of the following mAbs: anti-(I-Ad/I-Ed) or anti-CD86 (B7.2; PharMingen). Staining was carried out in the presence of 2-4G2 (anti-CD32) antibody supernatant to block Fc receptor binding. The cells were washed and analyzed using the FACScan® (Becton Dickinson, San Jose, CA). Culture supernatants were collected 24 h after treatment with LPS in the presence or absence of indicated concentrations of PD98059, and TNF-NF-B Nuclear Translocation.
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Results and Discussion |
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Murine Langerhans cells purified from the skin as well as bone marrow-derived DCs have a limited life-span in culture even in the presence of granulocyte-macrophage colony stimulating factor (1). Cultured DCs undergo spontaneous maturation and cell death (18). We have described a DC culture system (D1 cells) that allows us to maintain the immature DC phenotype in vitro. Growth of D1 cells is supported by a pool of cytokines present in CM. We have previously shown that incubation of D1 cells with LPS induced functional maturation of the cells (2), here we have shown that it also arrests the cell cycle, and promotes survival after CM deprivation (Fig. 1). More than 50% of the cells were still viable 5 d after growth-factor withdrawal, whereas in the absence of LPS, cells died within 48 h. This indicates that LPS promotes survival of DCs.
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To understand the molecular mechanisms involved in DC maturation, we investigated the signaling pathways activated by LPS in D1 cells. MAP kinases are activated by many receptors, as well as by environmental stresses, and have been shown to mediate both mitogenic and apoptotic responses (11). There are three main families of MAP kinases that are involved in signal transduction, the ERKs, the JNKs, and the p38 kinases. These kinases are activated by MAP kinase kinases (MKKs), which phosphorylate threonine and tyrosine residues in the Thr-X-Tyr activation motif (22, 23). Upon activation, MAP kinases can migrate to the nucleus where they phosphorylate and activate transcription factors. Each MAP kinase family targets a different set of transcription factors.
Since LPS has been shown to activate the ERK, JNK, and p38 MAP kinases in murine macrophages (15), we investigated whether LPS activated MAP kinases in the D1 cells. The D1 cells were incubated with LPS and in vitro kinase assays were performed to measure the activity of ERK1/2, JNK1, and MAPKAP kinase-2, a downstream target of the p38 MAP kinase. We chose to assay MAPKAP kinase-2 activity instead of directly assaying p38 MAP kinase activity since the MAPKAP kinase-2 assay is more sensitive. Activation of MAPKAP kinase-2 has been shown to be entirely dependent on p38 activation (reference 24; Sutherland, C.L., and M.R. Gold, unpublished results). We found that exposing D1 cells to LPS for 15 min resulted in a fivefold activation of the ERK MAP kinases (Fig. 2). In contrast, LPS caused very little activation (~1.5-fold stimulation) of the JNK MAP kinase and only modest activation (2-2.5-fold stimulation) of MAPKAP kinase-2. Thus, the ERK MAP kinases appear to be the major MAP kinase target of LPS signaling in D1 cells.
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To evaluate the role of ERK in both DC survival and DC maturation, we investigated the effect of a highly selective inhibitor of the ERK pathway on D1 cells. PD98059 (25) is a specific inhibitor of MEK1, the kinase that phosphorylates and activates the ERK kinases. DC maturation correlates with the upregulation of a panel of surface markers including MHC and costimulatory molecules. We found that pretreating D1 cells with the MEK inhibitor PD98059 had no effect on the ability of LPS to increase the surface expression of MHC and costimulatory molecules (Fig. 3 A). Thus ERK activation is not involved in DC maturation.
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In contrast, we found that MEK activity was essential for DC survival. We found that the ability of LPS to prevent apoptosis of D1 cells was dramatically reduced when the cells were pre-treated with the MEK inhibitor PD98059 (Fig. 3 B). Apoptosis of D1 cells due to growth factor withdrawal was analyzed using annexin V-FITC, which detects the appearance of the early apoptotic marker phosphatidylserine on the cell surface. D1 cells cultured in medium alone, in the absence of CM, underwent rapid apoptosis with 20% of the cells binding annexin V-FITC after 8 h (data not shown). In the presence of LPS, the number of apoptotic D1 cells was reduced to <5% after 24 h and ~18% after 48 h (Fig. 3 B). However, when the D1 cells were pretreated with the MEK inhibitor, the ability of LPS to prevent apoptosis was greatly reduced with 25% of the cell becoming apoptotic after 24 h and nearly 50% being apoptotic after 48 h (Fig. 3 B). The same feature was observed when viability of the cells was analyzed at different time points (Fig. 3 B, inset). Although PD98059 blocked the ability of LPS to prevent apoptosis of D1 cells, it did not block the ability of CM to prevent apoptosis. This shows that PD98059 is not toxic to the D1 cells, that its ability to block LPS-induced survival of D1 cells is a specific effect, and that the ability of CM to prevent D1 cell apoptosis does not depend on the MEK/ERK pathway. Thus, activation of the MEK/ERK pathway is required for LPS, but not CM, to prevent apoptosis of D1 cells due to growth factor withdrawal. The role of ERK in promoting the survival of D1 cells is consistent with the finding that ERK activation is also essential for preventing apoptosis of PC-12 cells after growth factor withdrawal (14).
ERK Activation Is Necessary to Promote TNF-Since TNF- has been shown to maintain the viability of
Langerhans cells in culture (26), we investigated whether
the MEK inhibitor blocked the ability of LPS to stimulate
TNF-
production by D1 cells. Fig. 3 C shows that LPS
causes a large increase in TNF-
release by D1 cells but
that this response is substantially reduced in the presence of
the MEK inhibitor PD98059. Thus, TNF-
production
correlates with DC viability and the ability of LPS to prevent apoptosis of D1 cells.
Experiments
using the MEK inhibitor PD98059 showed that the MEK/
ERK pathway is essential for LPS to promote DC survival but not for LPS-induced DC maturation. To elucidate the
signaling requirements for LPS-induced DC maturation,
we investigated whether NF-B is involved in this maturation program. The NF-
B transcription factor (p50-p65) is
the prototype of a family of homodimeric and heterodimeric protein complexes comprised of subunits related to
the c-rel protooncogene. Five mammalian proteins of the
Rel/NF-
B family, NF-
B1 (p50, p105), NF-
B2 (p52,
p100), Rel A (p65), Rel B, and Rel have been described so
far (for review see references 27, 28). These proteins are
widely expressed and regulate transcription by binding to
decameric sequences (
B motifs) that control transcription,
particularly of proteins involved in immune and inflammatory responses (6, 29). Before stimulation, Rel/NF-
B is
retained in the cytoplasm in an inactive form due to its
binding to the inhibitor (I
B) proteins (27). In response to
a number of different stimuli, I
B is first phosphorylated
and then ubiquitinated and targeted to the proteasome for
degradation. This allows Rel/NF-
B to translocate to the
nucleus and activate transcription of target genes.
Mature DCs express high levels of the NF-B family of
transcription factors (10) and signaling by members of the
TNF-
receptor family, such as CD40 and RANK, results
in activation of NF-
B (1). We found that a small proportion of activated Rel A protein was present in the nucleus
of immature D1 cells, but that a 30-min treatment with
LPS induced massive translocation of the p65 molecule to
the nucleus (Fig. 4, A and B). LPS-induced nuclear translocation of p65 was not blocked by the MEK inhibitor, indicating that NF-
B activation does not depend on the
MEK/ERK pathway (Fig. 4 C). This is consistent with recent findings that activation of NF-
B by TNF-
or IL-1
involves the NF-kB inducing kinase (NIK)/IKK kinase
complex (27, 30), which is independent of the ERK pathway. This pathway is of particular interest because the
number of catalytic steps is minimized in order to reduce
the chances that low molecular weight metabolites such as
those produced by microorganisms can suppress the immune response (27). Nevertheless, a recent report has
shown that bacteria of the Yersinia enterocolitica strain can
modulate the immune response of the host by interfering
with activation of NF-
B transcription factor in J774 macrophage cell line (31). This strategy is used by the bacteria
to suppress TNF-
production and this contributes to trigger macrophage cell death by apoptosis.
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To test
whether activation of NF-B is involved in LPS-induced
DC maturation, we used the serine protease inhibitor
TPCK, which blocks nuclear translocation of Rel/NF-
B by
preventing I
B-
degradation. Chloromethyl ketones such
as TPCK have been shown to block NF-
B-dependent
nitric oxide synthase in murine macrophages (32) and to
induce apoptosis in murine B cells (33) by preventing Rel/
NF-
B translocation to the nucleus. We found that TPCK
effectively blocked LPS-induced nuclear translocation of
p65 (data not shown). Functionally, this correlated with inhibition of LPS-induced D1 cell maturation in that the
ability of LPS to increase the cell surface expression of
MHC and costimulatory molecules was blocked by TPCK
treatment (Fig. 4 D). Inhibition of LPS-induced DC maturation by TPCK was dose dependent, with maximal inhibition at 20 µM TPCK. However, this dose of TPCK decreased the viability of immature D1 cells, suggesting a role
for other members of the Rel/NF-kB family in the growth
factor-dependent survival of these cells. Consistent with
this idea, a role for Rel B in the constitutive expression of
B-containing housekeeping genes in DCs has been proposed based on studies done on rel B knockout mice (34,
35). Furthermore, a recent report has shown that in B lymphocytes NF-
B1 and c-Rel are used differently to regulate apoptosis and cell cycle progression in resting and activated cells (36).
DCs have the unique ability to sense the external world
by capturing antigens. In the presence of inflammatory signals, maturing DCs abandon the inflamed site and reach the
draining lymph node. During this process, DCs have to initiate two differentiation responses, one being maturation
(upregulation of surface MHC and costimulatory molecules)
and the other being survival in a growth-arrested state in the
absence of growth factors. We have shown that LPS can
promote both of these differentiation responses but that the two processes are mediated by different, independent signaling pathways. The ability of LPS to promote DC survival in the
absence of growth factors is dependent on the MEK/ERK
pathway, whereas the ability of LPS to induce DC maturation,
in terms of upregulation of MHC II and B7.2, is dependent
on nuclear translocation of the NF-B transcription factor.
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Footnotes |
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Address correspondence to Paola Ricciardi-Castagnoli, CNR Center of Molecular and Cellular Pharmacology, University of Milano, Via Vanvitelli 32, 20129 Milano, Italy. Phone: 39-2-7014-6283; Fax: 39-2-7014-6373; E-mail: paola{at}farma8.csfic.mi.cnr.it
Received for publication 23 July 1998 and in revised form 28 September 1998.
We thank our colleagues for discussions.
This work was supported by EC grants (TMR and Biotechnology) to P. Ricciardi-Castagnoli and grants from the Arthritis Society of Canada and the Medical Research Council of Canada to M.R. Gold.
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References |
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![]() ![]() ![]() ![]() ![]() ![]() |
---|
1. | Banchereau, J., and R.M. Steinman. 1998. Dendritic cells and the control of immunity. Nature. 392: 245-251 [Medline]. |
2. |
Winzler, C.,
P. Rovere,
M. Rescigno,
F. Granucci,
G. Penna,
L. Adorini,
V.S. Zimmermann,
J. Davoust, and
P. Ricciardi-Castagnoli.
1997.
Maturation stages of mouse dendritic cells in growth factor-dependent long-term cultures.
J.
Exp. Med.
185:
317-328
|
3. | De Smedt, T., B. Pajak, E. Muraille, L. Lespagnard, E. Heinen, P. De Baetselier, J. Urbain, O. Leo, and M. Moser. 1996. Regulation of dendritic cell numbers and maturation by lipopolysaccharide in vivo. J. Exp. Med. 184: 1413-1424 [Abstract]. |
4. | Cella, M., A. Hengering, V. Pinet, J. Pieters, and A. Lanzavecchia. 1997. Inflammatory stimuli induces accumulation of MHC class II complexes on dendritic cells. Nature 388: 782-787 [Medline]. |
5. | May, M.J., and S. Ghosh. 1998. Signal transduction through NF-kappa B. Immunol. Today. 19: 80-88 [Medline]. |
6. |
Baldwin, A.S..
1995.
The NF-![]() ![]() |
7. |
Beg, A.A., and
D. Baltimore.
1996.
An essential role for NF-![]() ![]() |
8. |
Wang, C.-Y.,
M.W. Mayo, and
A.S.J. Baldwin.
1996.
TNF
and cancer therapy-induced apoptosis: potentiation by inhibition of NF-![]() |
9. |
Van Antwerp, D.J.,
S.J. Martin,
T. Kafri,
D.R. Green, and
I.M. Vermat.
1996.
Suppression of TNF-![]() ![]() |
10. | Granelli-Piperno, A., M. Pope, K. Inaba, and R.M. Steinman. 1995. Coexpression of NF-kappa B/Rel and Sp1 transcription factors in human immunodeficiency virus 1-induced, dendritic cell-T-cell syncytia. Proc. Natl. Acad. Sci. USA. 92: 10944-10948 [Abstract]. |
11. | Cobb, M.H., T.G. Boulton, and D.J. Robbins. 1991. Extracellular signal-regulated kinases: ERKs in progress. Cell Regul. 2: 965-978 [Medline]. |
12. | Welham, M.J., V. Duronio, J.S. Sanghera, S.L. Pelech, and W. Schrader. 1992. Multiple hemopoietic growth factors stimulate activation of mitogen-activated protein kinase family members. J. Biol. Chem. 267: 1683-1693 . |
13. |
Raingeaud, J.,
S. Gupta,
J.S. Rogers,
M. Dickens,
J. Han,
R.J. Ulevitch, and
R.J. Davis.
1995.
Pro-inflammatory cytokines and environmental stress cause p38 mitogen-activated
protein kinase activation by dual phosphorylation on tyrosine
and threonine.
J. Biol. Chem.
270:
7420-7426
|
14. | Xia, Z., M. Dickens, J. Raingeaud, R.J. Davis, and M.E. Greenberg. 1995. Opposing effects of ERK and JNK-p38 MAP kinases on apoptosis. Science. 270: 1326-1331 [Abstract]. |
15. |
Weinstein, S.L.,
J.S. Sangher,
K. Lemke,
A.L. DeFranco, and
S.L. Pelech.
1992.
Bacterial lipopolysaccharide induces tyrosine
phosphorylation and activation of mitogen-activated protein
kinases in macrophages.
J. Biol. Chem.
267:
14955-14962
|
16. |
Hambleton, J.,
L.L. Lem, and
A.L. DeFranco.
1996.
Activation of c-Jun N-terminal kinase in bacterial lipopolysaccharide-stimulated macrophages.
Proc. Natl. Acad. Sci. USA.
93:
2774-2778
|
17. | Han, J., J.D. Lee, L. Bibbs, and R.J. Ulevitch. 1994. A MAP kinase targeted by endotoxin and hyperosmolarity in mammalian cells. Science. 265: 808-811 [Medline]. |
18. | Pierre, P., S.J. Turley, E. Gatti, M. Hull, J. Meltzer, A. Mirza, K. Inaba, R.M. Steinman, and I. Mellman. 1997. Developmental regulation of MHC class II transport in mouse dendritic cells. Nature. 388: 787-792 [Medline]. |
19. |
Rescigno, M.,
S. Citterio,
C. Théry,
M. Rittig,
D. Medaglini,
G. Pozzi,
S. Amigorena, and
P. Ricciardi-Castagnoli.
1998.
Bacteria-induced neo-biosynthesis, stabilization, and
surface expression of functional class I molecules in mouse
dendritic cells.
Proc. Natl. Acad. Sci. USA
95:
5229-5234
|
20. |
Saxton, T.M.,
I. van Oostveen,
D. Bowtell,
R. Aebersold, and
M.R. Gold.
1994.
B cell antigen receptor cross-linking
induces phosphorylation of the Ras activators SHC and
mSOS1 as well as assembly of complexes containing SHC,
GRB-2, mSOS1, and a 145-kDa tyrosine-phosphorylated
protein.
J. Immunol.
153:
623-636
|
21. | Sutherland, C.L., A.W. Heath, S.L. Pelech, P.R. Young, and M.R. Gold. 1996. Differential activation of the ERK, JNK, and p38 mitogen-activated protein kinases by CD40 and the B cell antigen receptor. J. Immunol. 157: 3381-3390 [Abstract]. |
22. |
Cobb, M.H., and
E.J. Goldsmith.
1995.
How MAP kinases
are regulated.
J. Biol. Chem.
270:
14843-14846
|
23. | Cano, E., and L.C. Mahadevan. 1995. Parallel signal processing among mammalian MAPKs. Trends Biochem. 20: 117-122 [Medline]. |
24. | Cuenda, A, J. Rouse, Y.N. Doza, R. Meier, P. Cohen, T.F. Gallagher, P.R. Young, and J.C. Lee. 1995. SB203580 is a specific inhibitor of a MAP kinase homologue which is stimulated by cellular stresses and interleukin-1. FEBS Lett 364: 229-233 [Medline]. |
25. | Dudley, D.T., L. Pang, S.J. Decker, A.J. Bridges, and A.R. Saltiel. 1995. A synthetic inhibitor of the mitogen-activated protein kinase cascade. Proc. Natl. Acad. Sci. USA 92: 7686-7689 [Abstract]. |
26. |
Koch, F.,
C. Heufler,
E. Kämpgen,
D. Schneeweiss,
G. Böck, and
G. Schuler.
1990.
Tumor necrosis factor ![]() |
27. |
Baeuerle, P.A..
1998.
Pro-inflammatory signaling: last pieces
in the NF-![]() |
28. |
Grilli, M.,
J.S. Chiu, and
M.J. Lenardo.
1993.
NF-![]() |
29. |
Baeuerle, P.A., and
T. Henkel.
1994.
Functional and activation of NF-![]() |
30. |
Maniatis, T..
1997.
Catalysis by a multiprotein I![]() |
31. |
Ruckdeschel, K.,
S. Harb,
A. Roggenkamp,
M. Hornef,
R. Zumbhil,
S. Kohler,
J. Heesemann, and
B. Rouot.
1998.
Yersinia enterocolitica impairs activation of transcription factor
NF-![]() ![]() |
32. |
Kim, H.,
H.S. Lee,
K.T. Chang,
T.H. Ko,
K.J. Baek, and
N.S. Kwon.
1995.
Chloromethyl ketones block induction of
nitric oxide synthase in murine macrophages by preventing
activation of nuclear factor-![]() |
33. |
Wu, M.,
H. Lee,
R.E. Bellas,
S.L. Schauer,
M. Arsura,
D. Katz,
M.J. FitzGerald,
T.L. Rothstein,
D.H. Sherr, and
G.E. Sonenshein.
1996.
Inhibition of NF-![]() |
34. |
Weih, F.,
D. Carrasco,
S.K. Durham,
D.S. Barton,
C.A. Rizzo,
R.P. Ryseck,
S.A. Lira, and
R. Bravo.
1995.
Multiorgan inflammation and hematopoietic abnormalities in mice
with a targeted disruption of RelB, a member of the NK-![]() |
35. | Burkly, L., C. Hession, L. Ogata, C. Reilly, L.A. Marconi, D. Olson, R. Tizard, R. Cate, and D. Lo. 1995. Expression of relB is required for the development of thymic medulla and dendritic cells. Nature. 373: 531-536 [Medline]. |
36. |
Grumont, R.J.,
I.J. Rourke,
L.O. O'Reilly,
A. Strasser,
K. Miyake,
W. Sha, and
S. Gerondakis.
1998.
B lymphocytes
differentially use the Rel and nuclear factor ![]() ![]() |