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Department of Medicine, University of Iowa College of Medicine and Veterans Administration Medical Center, Iowa City, IA 52242
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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and 
1, and the
Ca2+-independent isoforms 
, 
, 
, µ, 
, and 
.
Western analysis showed that RSV caused no change in the amounts of
these isoforms. However, kinase activity assays demonstrated activation
of isoform within 10 min of infection, followed by a sustained
activation of isoforms 1, , , and µ 24–48 h postinfection.
A cell-permeable peptide inhibitor specific for the isoform
decreased early ERK kinase activation by RSV. Down-regulation of the
other PKC isoforms with PMA blocked the late sustained activation of
ERK by RSV. These studies suggest that RSV activates multiple PKC
isoforms with subsequent downstream activation of ERK
kinase. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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RSV is a negative-stranded RNA virus in the genus
Pneumovirus, family Paramyxoviridae
(14). RSV infection targets the respiratory epithelium and
elicits a local inflammatory response. This is characterized by
inflammatory cellular infiltration and release of inflammatory
mediators from both epithelial and activated immune cells
(14, 15, 16, 17, 18). Release of IL-8 by respiratory epithelial cells
is an important consequence of RSV infection. Although significant work
has been done on RSV-induced transcription of the IL-8 gene, not much
is understood about the second messenger pathways that generate this
response. Previous work in this laboratory has described the role of
the transcription factors NF-
B and AP-1 in the production of IL-8 by
RSV-infected epithelial cells (16, 17). We have also
established a link between activation of extracellular signal-related
kinase (ERK), a mitogen-activated protein kinase (MAPK), and release of
IL-8 after RSV infection (15). In this study, we extend
these observations by showing that RSV produces a biphasic activation
of ERK. An early ERK activation after infection appears consistent with
viral binding and entry, the later activation consistent with active
viral replication. Activation of one or more protein kinase C (PKC)
isoforms is a likely candidate for upstream events leading to ERK
activation by RSV.
The MAPK family of signaling molecules is involved in multiple cell
functions, including differentiation, division, and death
(19). Five distinguishable MAPK subfamilies have been
identified in mammalian systems; the best described of these are the
ERK (p42/p44), p38, and c-Jun N-terminal kinase pathways
(20, 21, 22, 23, 24). Downstream events linked to ERK activation
include phosphorylation of cytoplasmic (p90RSK, cytosolic phospholipase
A2, and epidermal growth factor receptor) and nuclear
(Elk-1, c-fos, c-Myc, Sap-1, and c-Jun) substrates
(25, 26, 27). Additionally, we have established a link between
ERK kinase activation and RSV-induced IL-8 release (15).
Our present study focuses on the upstream events leading to activation
of ERK during RSV infection. ERK is activated by phosphorylation of
both threonine and tyrosine by the upstream kinase MAP/ERK kinase
(MEK). Potential candidates for the upstream activators of MEK and ERK
include PKC and Raf-1 (20, 21, 28).
The PKC family of proteins phosphorylates serine or threonine residues
on multiple protein substrates. These kinases modulate membrane
structure events, mediate immune responses, and regulate gene
transcription and cell growth (29). The PKC enzyme family
includes multiple isoforms that display different activities in the
presence or absence of cofactors, including calcium,
diacyl-glycerols (DAG), and phospholipids (29, 30). The
PKC isoforms can be categorized into three classes based on these
differences: the conventional isoforms (designated , 1, 2, and
) are dependent on both Ca2+ and DAG, the
novel isoforms (, , , µ, and ) are
Ca2+ independent but DAG dependent, and the
atypical isoforms (
and ) are neither Ca2+
nor DAG dependent (31, 32). As a part of this study, we
have determined the PKC isoforms present in A549 cells and evaluated
their activation by RSV.
We found that RSV infection activated ERK kinase in epithelial cells in
a biphasic pattern, both immediately following viral binding and later
during active viral replication. In evaluating the upstream events
responsible for ERK activation, we found that activation of the
atypical isoform, PKC , was involved in early ERK activation. We
also found that multiple Ca2+-dependent PKC
isoforms and Raf-1 were associated with the long-term activation of ERK
by RSV.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CL-4B beads were purchased from Sigma (St. Louis, MO). Myelin
basic protein (MBP) was purchased from Upstate Biotechnology (Lake
Placid, NY). GammaBind Sepharose beads were purchased from Pharmacia
Biotech (Piscataway, NJ). Abs (ERK 2, sc-4024, Raf-1, sc-133, PKC ,
sc-208, PKC 1, sc-209, PKC 2, sc-210, PKC , sc-937, PKC ,
sc-214, PKC , sc-215, PKC µ, sc-935, and PKC , sc-726) were
purchased from Santa Cruz Biotechnology (Beverly, MA).
Phosphorylation-specific Abs were purchased from Cell Signaling
(phosphoERK, threonine 202/tyrosine 204) and Upstate Biotechnology
(phosphoRaf-1, serine 338). Anti-rabbit, anti-mouse, anti-rat,
and anti-goat HRP-linked Abs and nitrocellulose paper were
purchased from Jackson ImmunoResearch (West Grove, PA) and Amersham
Life Science (Arlington Heights, IL), respectively. Goat anti-RSV
antiserum was purchased from Biodesign International (Kennebunk, ME;
B65860G). [-32P]ATP was purchased from
DuPont-NEN Life Science Products (BLU 502Z; Boston, MA).
Cell culture
A549 cells, a tumor cell line with properties of alveolar epithelial cells (33, 34), were obtained from American Type Culture Collection (ATCC, Manassas, VA). We have previously shown that the response of A549 cells to RSV is similar to that of normal airway epithelial cells (16). The cells were incubated at 37oC in 5% CO2. The tissue culture medium was Eagle’s MEM (Life Technologies, Grand Island, NY) supplemented with 10% FBS (HyClone, Logan, UT), and 40 mg/ml gentamicin. The A549 cells used in our studies had been subcultured by trypsinization no more than 25 times from stock originally designated at pass 70.
Virus
RSV, strain A2, lot 995594, was obtained from ATCC, where it was harvested at a concentration of 106 tissue culture-infective dose (TCID50)/ml, as measured in confluent HEP-2 cells. TCID50 refers to the quantity of virus that will produce obvious cytopathic effects in 50% of the tissue culture plates infected and was calculated using the method of Reed and Munch (16). Sterile vials were kept frozen at -135°C. For all experiments, the virus was rapidly thawed at 37°C and used immediately.
Western analysis
Western analysis was used to evaluate PKC isoform presence and viral replication. For these assays, whole cell proteins were obtained from A549 cell controls and cells infected with RSV at a final dilution of 2 x 104 TCID50/ml, a concentration previously shown to produce maximal IL-8 release by A549 cells (16). At sequential time points following exposure to RSV, cells were harvested in lysis buffer that contained 0.05 M Tris, pH 7.4, 0.15 M NaCl, 1% Nonidet P-40, 0.5 M PMSF, 50 µg/ml aprotinin, 10 µg/ml leupeptin, 50 µg/ml pepstatin, 0.4 mM sodium orthovanadate, 10 mM sodium fluoride, and 10 mM sodium pyrophosphate (all protease inhibitors were obtained from Boehringer Mannheim, Indianapolis, IN). The cells were then sonicated for 20 s to ensure complete lysis. The lysate solution was then centrifuged at 15,000 x g for 10 min, and the supernatant was saved. Protein concentration in the cell lysates was measured by Bradford assay, mixed 1:1 with 2x sample buffer (20% glycerol, 4% SDS, 10% 2-ME, 0.05% bromophenol blue, and 1.25 M Tris, pH 6.8, all chemicals were obtained from Sigma), and separated by SDS-PAGE. Cell proteins were transferred to a nitrocellulose membrane by electroblotting. The membrane was then blocked with 5% nonfat milk in TTBS (Tris-buffered saline with 0.1% Tween 20) for 1 h, then incubated in with the desired primary Ab diluted in 5% milk TTBS for an additional hour (in the case of the phosphorylation-specific Abs, the blots were incubated with the primary Ab overnight at 4°C). The blots were then washed four times with TTBS and incubated for 1 h with HRP-conjugated secondary Ab. Immunoreactive bands were developed using a chemiluminescent substrate (ECL Plus; Amersham) and visualized by autoradiography.
Isolation of cytoplasmic and membrane PKC isoforms
Negative controls and A549 cells exposed to RSV at a dilution of 2 x 104 TCID50/ml were harvested by scraping in lysis buffer (see Western protocol) without Tween 20 (400 µl). The isolates were then sonicated for 10 s and fractionated by centrifuging at 100,000 x g for 10 min. The supernatant containing the cytoplasmic fraction was immediately frozen at -70°C for later analysis. The membrane pellet was resuspended in lysis buffer with 1% Tween 20 and sonicated for 5 s. Following a 20-min incubation on ice, cell debris was removed by centrifugation, and the supernatant containing membrane-associated proteins was frozen at -70°C. Western analysis was performed as described above.
PKC isoform depletion or inhibition
A549 cells were exposed to PMA (100 ng/ml) for 24 h,
followed by infection with RSV at 2 x 104
TCID50/ml for an additional 30 min or 24 h.
PKC protein depletion was evaluated by Western analysis for specific
PKC isoforms. To examine the effect of PKC isoform inhibition on ERK 2
kinase activity, specific inhibitory peptides (PKC ,
myr-SIYRRGARRWRKL-OH; PKC , myr-RFARKGALRQKNV-OH; nonsense,
myr-LRISRAGRYRANWYRKR-OH; the myristate on the N terminus of these
peptides allows for membrane permeability) were added to the culture
medium 1 h before RSV infection. Whole cell protein from treated
cells and appropriate controls was then harvested and assayed for ERK 2
kinase activity (see below).
Immunoprecipitation
Cells were harvested by rinsing with PBS, followed by scraping into lysis buffer (see Western blot protocol), and incubated on ice for 20 min. These lysates were then sonicated for 20 s and centrifuged at 15,000 x g for 10 min, and the supernatant was saved. Protein concentration was measured by Bradford assay. A quantity amounting to 200–600 µg of total protein from each sample was cleared by incubating for 2 h with nonspecific rabbit IgG (1 µg/sample), and unconjugated GammaBind Sepharose (10 µl/sample). After centrifuging, the supernatants were transferred to a tube containing 3 µg/sample of Ab bound to GammaBind Sepharose and rotated at 4°C overnight. The beads with the immunoprecipitated protein were subsequently washed three times with high salt buffer (0.5 M Tris, pH 7.4, 0.50 M NaCl, and 1% Nonidet P-40) and three times with lysis buffer. The immunoprecipitated complexes were either released with 2x sample buffer for Western analysis or used to determine kinase activity.
Kinase activity assay
The solution containing the immunoprecipitate was centrifuged to
pellet the Sepharose and attached Ab/kinase complex. The
protein-containing pellet was washed twice with kinase buffer (20 mM
MgCl2, 25 mM HEPES, 20 mM -glycerophosphate,
20 mM p-nitrophenylphosphate, 20 mM sodium orthovanadate,
and 2 mM DTT). The pellet was suspended in 20 µl kinase buffer, to
which 20 µM ATP and 5 µCi ATP (32) were added.
Substrates, 10 µg MBP (dephosphorylated MBP) or 5 µg MEK-1 or 5
µg ERK (polyhistidine-tagged fusion proteins from Santa Cruz
Biotechnology, Santa Cruz, CA), were added last to bring the total
assay volume to 25 µl. The reaction was continued at 25°C for 15
min to 1 h, depending on the kinase, and stopped by the
addition of 25 µl/sample of 2x sample buffer (see Western protocol).
The samples were incubated for 5 min at 95°C and run on a 12%
SDS-PAGE gel. The gel was dried, and autoradiography was performed to
visualize the 32P-labeled MBP, MEK-1, or ERK.
Densitometry measurements of individual bands were obtained, and fold
increase was calculated.
Statistical analysis
Statistical analysis of the densitometric data was performed by determining the fold increase of all the samples as they relate to the control. Statistical comparisons were performed using a paired t test, with a probability value of p < 0.05 considered to be significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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We initially determined whether RSV infection of A549 cells
activated the MAPK, ERK 2. To do this, we seeded A549 cells at a
subconfluent density, allowed them to grow for 1 day, then added RSV.
At sequential time points, whole cell protein was harvested and in
vitro kinase activity assays were performed (Fig. 1
). In all experiments, we found both an
early and a later, more pronounced activation of ERK by RSV. In some
experiments, we also found a peak of activity that occurred at 6
h; however, this was not a consistent finding. For this reason, all
additional experiments were done at the early (10–30 min) and late
(24–48 h) time points. The early activation (10–30 min) coincides
with viral binding; the late activation accompanies viral replication.
It is of interest that we have previously shown that there also is a
biphasic response of IL-8 mRNA to RSV (16, 17). These data
were confirmed using Western analysis for activated ERK (phosphorylated
on threonine 202 and tyrosine 204) (Fig. 2). The Western for activated ERK showed
a significant increase in the amounts of activated ERK at both early
and late time points after RSV infection.
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We next evaluated the activation of Raf-1 by RSV. Raf-1 is a
well-described activator of MEK, the kinase directly upstream of ERK
(35, 36, 37). Raf-1 was immunoprecipitated from RSV-treated
whole cell lysates and in vitro kinase activity assays performed. Fig. 2
demonstrates that RSV activates Raf-1 and consequently MEK at 24 and
48 h, but not at earlier time points. Because MEK is the kinase
directly upstream of ERK, the data suggest that the early activation of
ERK seen in Fig. 1 cannot be a consequence of Raf-1 activity. This is
confirmed in a Western for activated Raf-1 (serine 338 phosphorylation)
(Fig. 3) (38).
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To demonstrate a temporal association of RSV replication with the
late activation of ERK, we evaluated the time course of viral protein
synthesis in A549 cells by Western analysis. Whole cell proteins from
RSV-infected A549 cells were separated by SDS-PAGE, transferred to
membranes, and immunoblotted for viral proteins. In Fig. 4, we show that detectable viral protein
first appears at 24 h postinfection. Ongoing viral replication
continues through the 48-h time point. Beyond 48 h, infected A549
cells rapidly progress toward cell death (data not shown). These
studies show that significant RSV replication is temporally associated
with the late sustained activation of ERK by RSV.
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Multiple studies in other systems have demonstrated that PKC or
specific PKC isoforms are involved in Raf-1 and subsequent ERK
activation (39, 40, 41, 42). To investigate this possibility in
RSV-induced ERK activation, we initially determined the profile of PKC
isoforms present in A549 cells. Western analysis for each of the11
described PKC isoforms showed that only six (, 1, , , µ,
and ) are present in A549 cells (Fig. 5). The total amounts of each specific
isoform did not appear to change over the time course of RSV infection,
as shown by analysis of both control cells and of cells 48 h
postinfection (Fig. 5).
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The effect of RSV on PKC activation was determined by performing
in vitro kinase activity assays at sequential time points following
infection. The activity was determined for the individual PKC isoforms
by using specific Abs to separately immunoprecipitate each isoform from
whole cell lysates before the activity assay. Fig. 6 shows that RSV activates the isoforms
PKC and at early time points (<3 h), and 1, , , and
µ at later time points (>24 h). PKC activation has been associated
with translocation of the enzyme to the cell membrane (29, 32). To confirm PKC isoform activation by RSV infection, we also
evaluated the translocation of these enzymes from the cytoplasm to the
membrane. We harvested cytosol and membrane protein fractions from
cells infected with RSV for 48 h and noninfected controls. Western
analysis for individual PKC isoforms was then performed on the separate
fractions. Fig. 7 shows an increase in
the membrane-associated quantities of PKC isoforms 1, , , and
µ at 48 h postinfection. These are the same isoforms with
increased activity at later time points by in vitro kinase assay.
Combined, these results provide substantial evidence that RSV activates
the PKC isoforms and shortly after binding, and isoforms 1,
, , and µ after initiation of viral protein synthesis.
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is necessary for RSV-induced ERK activation
at early time points
We have previously shown in alveolar macrophages that LPS
activates ERK in a PKC -dependent manner (28). Based on
this information and the increase in PKC activity within minutes of
RSV infection, we next evaluated the role of PKC in RSV activation
of ERK. To do this, we made use of pseudosubstrate-specific peptides.
PKC isoforms are maintained in an inactive form by the binding of a
pseudosubstrate region on their N-terminal to the substrate-binding
domain in the catalytic region (32, 43).
Pseudosubstrate-specific peptides inhibit the catalytic activity of PKC
isoforms by binding to the substrate-binding domain (Fig. 8C). Myristolation on the N
terminus of the peptides makes them membrane permeable. In these
experiments, A549 cells were treated with myristolated inhibitory
peptides (PKC pseudosubstrate specific, PKC pseudosubstrate
specific, or nonsense) for 1 h before addition of RSV. Whole cell
proteins were obtained and an ERK kinase activity assay was performed.
Fig. 8A shows that blocking PKC prevents RSV-induced ERK
2 activation. Control experiments with a nonsense peptide or an
isoform-specific inhibitory peptide showed no effect on ERK 2 activity.
These data were confirmed using Western analysis and Abs to activated
ERK (pThr202 and pTyr204)
(Fig. 8B).
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To examine the role of other PKC enzymes in ERK activation,
RSV-stimulated ERK 2 activity was studied in cells depleted of the
conventional and novel PKC isoforms. PMA has been shown to result in
activation and eventual depletion of all PKC isoforms except the
atypical () isoform (44, 45, 46). Following 24-h
pretreatment with PMA, A549 cells were infected with RSV and
subsequently harvested at 30 min and 48 h. Western blotting for
individual isoforms and ERK 2 in vitro kinase assays was subsequently
performed on the isolated whole cell protein. Fig. 9A shows a striking decrease
in the levels of all PKC isoforms except in the PMA-treated cells.
Fig. 9, B and C, shows that PMA pretreatment
abolished the late ERK 2 activation, but had no substantial effect on
the early activation of ERK 2 by RSV. These studies suggest that
multiple Ca2+-dependent PKC isoforms are involved
in RSV replication-dependent ERK activation.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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).
The early time point, consistent with viral binding, was matched by
activation of PKC . Furthermore, inhibiting PKC blocked the
early activation of ERK by RSV. Other studies (insulin signaling) have
demonstrated that PKC can activate MEK, the dual kinase that
phosphorylates the threonine and tyrosine responsible for ERK
activation (47). The late activation of ERK was temporally
related to viral protein synthesis and replication. This late
activation did not correlate with the activity of PKC , but rather
with the activities of Raf-1 and the PKC isoforms 1, , , and
µ. Depleting these isoforms by PMA pretreatment did not inhibit early
activation, but did block the late, sustained ERK activation.
Therefore, late activation of ERK may result from PKC-induced
activation of Raf-1, leading to activation of MEK and subsequently ERK.
Taken together, these studies suggest that RSV-induced ERK activation
and subsequent inflammation depend on the differential activation of
multiple PKC isoforms in a time-dependent manner.
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We have previously shown that RSV-induced IL-8 mRNA increases occur in
a biphasic manner, an early activation that accompanies viral binding
and a later peak that requires viral replication (15, 17).
We have also demonstrated that IL-8 production is linked to ERK
activation (15). Fiedler et al. (54) have
demonstrated that blocking viral replication with ribavirin also blocks
RSV-induced IL-8 release and NF-B activation. These studies confirm
the importance of replication in the inflammatory response of
epithelial cells to RSV. They suggest that viral protein synthesis or
the accumulation of viral proteins is coincident with activation of
signaling pathways upstream of cytokine production. These patterns of
intracellular signaling appear to be distinct from cellular responses
to viral binding and internalization at the earlier time points.
A number of studies have suggested the possibility that activation of the ERK MAPK is linked not only to cytokine production, but also to the effectiveness of viral replication or infection. Yang et al. (55) reported that that ERK was involved in activation of HIV-1 gene expression in latently infected cells. The induction of HIV-1 protein synthesis by cytokines and phorbol esters was inhibited by PD98059, a specific inhibitor of ERK. In a second study, they found that the HIV-1 proteins, Rev, Tat, p17 (Gag), and Nef, could all be directly phosphorylated in vitro by activated ERK (56). In another HIV-1 study, Jacque et al. (57) identified ERK as a virion-associated protein that increased HIV-1 infectivity. In this system also, PD98059 had a major effect, decreasing viral infectivity (57).
The data presented in this study suggest that activation of the ERK
MAPK by RSV is regulated in part by activation of a number of PKC
isoforms. There is an early and a late sustained activation of ERK. Our
data suggest that the upstream activators involved in the two time
points are different. As with insulin and LPS, PKC appears to be
the upstream activator of ERK at the early time point with RSV
infection (28, 47). Later, the sustained activation of ERK
(24–48 h) is linked to activation of Raf-1, and this in turn is linked
to a number of conventional and novel PKC isoforms. The biological
relevance of these findings relates in part to our prior observations,
which have shown that ERK activation is linked to the production of
inflammatory mediators by RSV.
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Footnotes |
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2 Address correspondence and reprint requests to Martha M. Monick, Division of Pulmonary, Critical Care, and Occupational Medicine, Room 100, Ekstein Medical Research Building, University of Iowa Hospitals and Clinic, Iowa City, IA 52242.
3 Abbreviations used in this paper: RSV, respiratory syncytial virus; DAG, diacylglycerol(s); ERK, extracellular signal-related kinase; MAPK, mitogen-activated protein kinase; MBP, myelin basic protein; MEK, MAP/ERK kinase; PKC, protein kinase C; TCID50, tissue culture-infective dose.
Received for publication June 26, 2000. Accepted for publication November 22, 2000.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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B, and sequestration of protein phosphatase 2A by the viral phosphoprotein. J. Virol. 72:5610.B and NF-IL-6. J. Infect. Dis. 174:262.[Medline]
B in respiratory syncytial virus-induced interleukin-8 gene expression in airway epithelium. J. Infect. Dis. 177:1275.[Medline]
in respiratory syncytial virus-infected pulmonary epithelial cells in vitro. Immunology 95:501.[Medline]
production by human monocytes involves the raf-1/MEK1-MEK2/ERK1-ERK2 pathway. Infect. Immun. 67:3824.1-induced activation of the Raf-MEK-MAPK signaling pathway in rat lung fibroblasts via a PKC-dependent mechanism. Biochem. Biophys. Acta 249:456.
-cells: evidence using Go 6976 and Ro 31-8220 as PKC inhibitors. Biochem. Biophys. Acta 227:672.
-protein kinase C by cyclic AMP in PC12 cells occurs through phosphorylation by protein kinase A. J. Neurochem. 67:1023.[Medline]
and phosphoinositide-dependent protein kinase-1 are required for insulin-induced activation of ERK in rat adipocytes. J. Biol. Chem. 274:30495.B activation and interleukin-8 gene expression in A549 cells. J. Virol. 70:9079.[Abstract]
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