Functional Role of p38 Mitogen Activated Protein Kinase in Platelet Activation induced by a Thromboxane A2 Analogue and by 8-iso-prostaglandin F2
          α

SummaryWe investigated similarities in the signaling pathways elicited by the F2 isoprostane 8-iso-PGF2α and by low doses of U46619 to induce platelet activation. Both 0.01-0.1 µmol/L U46619 and 0.01-1 µmol/L 8-isoPGF2α triggered shape change and filopodia extension, as well as adhesion to immobilized fibrinogen of washed platelets. At these doses the two platelet agonists failed to trigger secretion and aggregation, which were however induced by higher doses of U46619 (0.1-1 µmol/L). SB203580 (1-10 µmol/L), a specific inhibitor of the p38 mitogen activated protein (MAP) kinase blunted platelet shape change and adhesion induced by 0.05-1 µmol/L 8-iso-PGF2α and by 0.01 µmol/L U46619. These platelet responses were also inhibited by 20 µmol/L cytochalasin D, an inhibitor of actin polymerization, and 50 µmol/L piceatannol, an inhibitor of the Syk tyrosine kinases. Both 8-iso-PGF2α and U46619-induced p38 MAP kinase phosphorylation in suspended platelets and this was inhibited by piceatannol, indicating that Syk activation occurs upstream p38 MAP kinase phosphorylation. These findings suggest that the signaling pathway triggered by both 8-iso-PGF2α and low concentrations of U46619 to induce platelet adhesion and shape change implicates Syk, the p38 MAP kinase, and actin polymerization.

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Identification of the mitogen-activated protein kinase phosphorylation sites on human Sos1 that regulate interaction with Grb2.

Molecular and Cellular Biology ◽

10.1128/mcb.16.10.5674 ◽

1996 ◽

Vol 16 (10) ◽

pp. 5674-5682 ◽

Cited By ~ 100

Author(s):

S Corbalan-Garcia ◽

S S Yang ◽

K R Degenhardt ◽

D Bar-Sagi

Keyword(s):

Growth Factor ◽

Map Kinase ◽

Tyrosine Kinases ◽

Phosphorylation Site ◽

Mitogen Activated Protein Kinase ◽

Phosphorylation Sites ◽

Nucleotide Exchange ◽

Mitogen Activated Protein ◽

Son Of Sevenless ◽

Kinase Phosphorylation

The Son of sevenless proteins (Sos) are guanine nucleotide exchange factors involved in the activation of Ras by cytoplasmic and receptor tyrosine kinases. Growth factor stimulation rapidly induces the phosphorylation of Sos on multiple serine and threonine sites. Previous studies have demonstrated that growth factor-induced Sos phosphorylation occurs at the C-terminal region of the protein and is mediated, in part, by mitogen-activated protein (MAP) kinase. In this report, we describe the identification of five MAP kinase sites (S-1137, S-1167, S-1178, S-1193, and S-1197) on hSos1. We demonstrate that four of these sites, S-1132, S-1167, S-1178, and S-1193, become phosphorylated following growth factor stimulation. The MAP kinase phosphorylation sites are clustered within a region encompassing three proline-rich SH3-binding sites in the C-terminal domain of hSos1. Replacing the MAP kinase phosphorylation sites with alanine residues results in an increase in the binding affinity of Grb2 to hSos1. Interestingly, hSos2 contains only one MAP kinase phosphorylation site and, as demonstrated previously, has an increased affinity toward Grb2 compared with hSos1. These results suggest a role for MAP kinase in the regulation of Grb2-Sos interactions. Since the binding of Grb2 is important for Sos function, the phosphorylation-dependent modulation of Grb2-Sos association may provide a means of controlling Ras activation.

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Interaction of Rac Exchange Factors Tiam1 and Ras-GRF1 with a Scaffold for the p38 Mitogen-Activated Protein Kinase Cascade

Molecular and Cellular Biology ◽

10.1128/mcb.22.12.4073-4085.2002 ◽

2002 ◽

Vol 22 (12) ◽

pp. 4073-4085 ◽

Cited By ~ 131

Author(s):

Rachel J. Buchsbaum ◽

Beth A. Connolly ◽

Larry A. Feig

Keyword(s):

Map Kinase ◽

P38 Map Kinase ◽

Mitogen Activated Protein Kinase ◽

Nucleotide Exchange ◽

Rac Gtpase ◽

Signaling Specificity ◽

Map Kinase Cascade ◽

Mitogen Activated Protein ◽

Kinase Cascade ◽

In Cells

ABSTRACT Tiam1 and Ras-GRF1 are guanine nucleotide exchange factors (GEFs) that activate the Rac GTPase. The two GEFs have similar N-terminal regions containing pleckstrin homology domains followed by coiled-coils and additional sequences that function together to allow regulated GEF activity. Here we show that this N-terminal region of both proteins binds to the scaffold protein IB2/JIP2. IB2/JIP2 is a scaffold for the p38 mitogen-activated protein (MAP) kinase cascade because it binds to the Rac target MLK3, the MAP kinase kinase MKK3, and the p38 MAP kinase. Expression of IB2/JIP2 in cells potentiates the ability of Tiam1 or Ras-GRF1 to activate the p38 MAP kinase cascade but not the Jnk MAP kinase cascade. In addition, Tiam1 or Ras-GRF1 binding to IB2/JIP2 increases the association of the components of the p38 MAP kinase signaling cassette with IB2/JIP2 in cells and activates scaffold-associated p38. These findings imply that Tiam1 and Ras-GRF1 can contribute to Rac signaling specificity by their ability to form a complex with a scaffold that binds components of one of the many known Rac effector pathways.

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Mitogen-activated protein kinase in human eggs

Zygote ◽

10.1017/s0967199499000556 ◽

1999 ◽

Vol 7 (2) ◽

pp. 181-185 ◽

Cited By ~ 18

Author(s):

Qing-Yuan Sun ◽

Zeev Blumenfeld ◽

Sara Rubinstein ◽

Shlomit Goldman ◽

Yael Gonen ◽

...

Keyword(s):

Map Kinase ◽

Mammalian Species ◽

Germinal Vesicle ◽

Mitogen Activated Protein Kinase ◽

Early Embryos ◽

Protein Map ◽

Mitogen Activated Protein ◽

Kinase Phosphorylation ◽

Cycle Regulation ◽

Kinase Expression

Mitogen-activated protein (MAP) kinase in human eggs has been investigated by using immunoblotting with both anti-Active MAPK and anti-ERK2 antibodies. The results showed that the main form of MAP kinase was p42ERK2. It was in a dephosphorylated form in oocytes at the germinal vesicle stage, but fully phosphorylated in unfertilised mature eggs. MAP kinase phosphorylation was significantly decreased when pronuclei were formed after intracytoplasmic sperm injection. Neither MAP kinase expression nor activity was detected in morphologically degenerated eggs. Although MAP kinase still existed in early embryos arrested at the 8-cell or morula stages, little, if any, activity could be detected. These data suggest that MAP kinase may play an important role in the cell cycle regulation of human eggs, as in other mammalian species.

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Legionella pneumophila Suppresses Macrophage Interleukin-12 Production by Activating the p42/44 Mitogen-Activated Protein Kinase Cascade

Infection and Immunity ◽

10.1128/iai.71.11.6672-6675.2003 ◽

2003 ◽

Vol 71 (11) ◽

pp. 6672-6675 ◽

Cited By ~ 9

Author(s):

Kazuto Matsunaga ◽

Hiroyuki Yamaguchi ◽

Thomas W. Klein ◽

Herman Friedman ◽

Yoshimasa Yamamoto

Keyword(s):

Map Kinase ◽

Legionella Pneumophila ◽

Kinase Inhibitors ◽

Selective Inhibition ◽

P38 Map Kinase ◽

Mitogen Activated Protein Kinase ◽

Interleukin 12 ◽

Map Kinase Cascade ◽

Mitogen Activated Protein ◽

Kinase Cascade

ABSTRACT A possible involvement of the mitogen-activated protein (MAP) kinase cascade in the inhibition of macrophage interleukin-12 (IL-12) production by Legionella pneumophila infection was examined. The results of MAP kinase inhibition by p42/44 and p38 MAP kinase inhibitors and of p42/44 MAP kinase activity assays indicate that L. pneumophila infection of macrophages causes a selective inhibition of lipopolysaccharide-induced IL-12 production by activating the p42/44 MAP kinase cascade. In addition, it was also revealed that the p38 MAP kinase may be important for the production of IL-12 but not for the inhibition caused by L. pneumophila infection.

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Mechanism of prostaglandin E2-stimulated heat shock protein 27 induction in osteoblast-like MC3T3-E1 cells

Journal of Endocrinology ◽

10.1677/joe.0.1720271 ◽

2002 ◽

Vol 172 (2) ◽

pp. 271-281 ◽

Cited By ~ 19

Author(s):

H Tokuda ◽

O Kozawa ◽

M Niwa ◽

H Matsuno ◽

K Kato ◽

...

Keyword(s):

Heat Shock ◽

Heat Shock Protein ◽

Prostaglandin E2 ◽

Map Kinase ◽

Specific Inhibitor ◽

Heat Shock Protein 27 ◽

P38 Map Kinase ◽

Calphostin C ◽

Mitogen Activated Protein ◽

Upstream Kinase

We investigated the effect of prostaglandin E2 (PGE2) on the induction of heat shock protein 27 (HSP27) and HSP70, and the mechanism behind the induction in osteoblast-like MC3T3-E1 cells. PGE2 time-dependently increased the level of HSP27 without affecting the level of HSP70. PGE2 stimulated the accumulation of HSP27 dose-dependently in the range between 10 nM and 10 microM. PGE2 stimulated the increase in the level of the mRNA for HSP27. Staurosporine and calphostin C, inhibitors of protein kinase C (PKC), suppressed the PGE2-induced HSP27 accumulation. The effect of PGE2 on HSP27 accumulation was reduced in the PKC down-regulated cells. BAPTA/AM, a chelator of intracellular Ca2+, or TMB-8, an inhibitor of intracellular Ca2+ mobilization, reduced the accumulation of HSP27 induced by PGE2. Dibutyryl cAMP had little effect on the basal level of HSP27. PGE2 induced the phosphorylation of both p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase. PD98059 and U-0126, inhibitors of the upstream kinase of p44/p42 MAP kinase, reduced the accumulation of HSP27 induced by PGE2. SB203580, a specific inhibitor of p38 MAP kinase, suppressed the HSP27 accumulation induced by PGE2. U-73122, an inhibitor of phospholipase C, and calphostin C reduced the PGE2-induced phosphorylation of both p44/p42 MAP kinase and p38 MAP kinase. These results indicate that PGE2 stimulates the induction of HSP27 through PKC-dependent activations of both p44/p42 MAP kinase and p38 MAP kinase in osteoblasts.

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Role of MLK3 in the Regulation of Mitogen-Activated Protein Kinase Signaling Cascades

Molecular and Cellular Biology ◽

10.1128/mcb.25.9.3670-3681.2005 ◽

2005 ◽

Vol 25 (9) ◽

pp. 3670-3681 ◽

Cited By ~ 87

Author(s):

Deborah Brancho ◽

Juan-Jose Ventura ◽

Anja Jaeschke ◽

Beth Doran ◽

Richard A. Flavell ◽

...

Keyword(s):

Protein Kinase ◽

Map Kinase ◽

Selective Reduction ◽

P38 Map Kinase ◽

Mitogen Activated Protein Kinase ◽

Signaling Cascades ◽

Extracellular Signal ◽

Mitogen Activated Protein ◽

Jnk Activation ◽

Protein Kinase Signaling

ABSTRACT Mixed-lineage protein kinase 3 (MLK3) is a member of the mitogen-activated protein (MAP) kinase kinase kinase group that has been implicated in multiple signaling cascades, including the NF-κB pathway and the extracellular signal-regulated kinase, c-Jun NH2-terminal kinase (JNK), and p38 MAP kinase pathways. Here, we examined the effect of targeted disruption of the murine Mlk3 gene. Mlk3 −/− mice were found to be viable and healthy. Primary embryonic fibroblasts prepared from these mice exhibited no major signaling defects. However, we did find that MLK3 deficiency caused a selective reduction in tumor necrosis factor (TNF)-stimulated JNK activation. Together, these data demonstrate that MLK3 contributes to the TNF signaling pathway that activates JNK.

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Role of Phosphoinositide 3-Kinase in Activation of Ras and Mitogen-Activated Protein Kinase by Epidermal Growth Factor

Molecular and Cellular Biology ◽

10.1128/mcb.19.6.4279 ◽

1999 ◽

Vol 19 (6) ◽

pp. 4279-4288 ◽

Cited By ~ 206

Author(s):

Stefan Wennström ◽

Julian Downward

Keyword(s):

Growth Factor ◽

Epidermal Growth Factor ◽

Map Kinase ◽

Tyrosine Kinases ◽

Kinase Inhibitors ◽

Egf Receptor ◽

Mitogen Activated Protein Kinase ◽

Ras Activation ◽

Mitogen Activated Protein ◽

Epidermal Growth

ABSTRACT The paradigm for activation of Ras and extracellular signal-regulated kinase (ERK)/mitogen-activated protein (MAP) kinase by extracellular stimuli via tyrosine kinases, Shc, Grb2, and Sos does not encompass an obvious role for phosphoinositide (PI) 3-kinase, and yet inhibitors of this lipid kinase family have been shown to block the ERK/MAP kinase signalling pathway under certain circumstances. Here we show that in COS cells activation of both endogenous ERK2 and Ras by low, but not high, concentrations of epidermal growth factor (EGF) is suppressed by PI 3-kinase inhibitors; since Ras activation is less susceptible than ERK2 activation, PI 3-kinase-sensitive events may occur both upstream of Ras and between Ras and ERK2. However, strong elevation of PI 3-kinase lipid product levels by expression of membrane-targeted p110α is by itself never sufficient to activate Ras or ERK2. PI 3-kinase inhibition does not affect EGF-induced receptor autophosphorylation or adapter protein phosphorylation or complex formation. The concentrations of EGF for which PI 3-kinase inhibitors block Ras activation induce formation of Shc-Grb2 complexes but not detectable EGF receptor phosphorylation and do not activate PI 3-kinase. The activation of Ras by low, but mitogenic, concentrations of EGF is therefore dependent on basal, rather than stimulated, PI 3-kinase activity; the inhibitory effects of LY294002 and wortmannin are due to their ability to reduce the activity of PI 3-kinase to below the level in a quiescent cell and reflect a permissive rather than an upstream regulatory role for PI 3-kinase in Ras activation in this system.

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p38 mitogen-activated protein (MAP) kinase but not p44/p42 MAP kinase is involved in prostaglandin E1-induced vascular endothelial growth factor synthesis in osteoblasts

Journal of Endocrinology ◽

10.1677/joe.0.1700629 ◽

2001 ◽

Vol 170 (3) ◽

pp. 629-638 ◽

Cited By ~ 16

Author(s):

H Tokuda ◽

O Kozawa ◽

M Miwa ◽

T Uematsu

Keyword(s):

Map Kinase ◽

Cholera Toxin ◽

Prostaglandin E1 ◽

Specific Inhibitor ◽

P38 Map Kinase ◽

Vascular Endothelial ◽

Kinase Activation ◽

Protein Map ◽

Mitogen Activated Protein ◽

Endothelial Growth Factor

We investigated the mechanism underlying vascular endothelial growth factor (VEGF) synthesis stimulated by prostaglandin E1 (PGE1) in osteoblast-like MC3T3-E1 cells. PGE1 induced the phosphorylation of both p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase. SB203580, a specific inhibitor of p38 MAP kinase, inhibited the PGE1-stimulated VEGF synthesis as well as PGE1-induced phosphorylation of p38 MAP kinase. PD98059, an inhibitor of the upstream kinase that activates p44/p42 MAP kinase, which reduced the PGE1-induced phosphorylation of p44/p42 MAP kinase, had little effect on the VEGF synthesis stimulated by PGE1. AH-6809, an antagonist of the subtypes of the PGE receptor, EP1 and EP2, or SC-19220, an antagonist of EP1 receptor, did not inhibit the PGE1-induced VEGF synthesis. H-89, an inhibitor of cAMP-dependent protein kinase, and SQ22536, an inhibitor of adenylate cyclase, reduced the VEGF synthesis induced by PGE1. Cholera toxin, an activator of G(s), and forskolin, an activator of adenylate cyclase, induced VEGF synthesis. SB203580 and PD169316, another specific inhibitor of p38 MAP kinase, reduced the cholera toxin-, forskolin- or 8bromo-cAMP-stimulated VEGF synthesis. However, PD98059 failed to affect the VEGF synthesis stimulated by cholera toxin, forskolin or 8-bromoadenosine-3',5'-cyclic monophosphate (8bromo-cAMP). SB203580 reduced the phosphorylation of p38 MAP kinase induced by forskolin or 8bromo-cAMP. These results strongly suggest that p44/p42 MAP kinase activation is not involved in the PGE1-stimulated VEGF synthesis in osteoblasts but that p38 MAP kinase activation is involved.

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Role of the JIP4 Scaffold Protein in the Regulation of Mitogen-Activated Protein Kinase Signaling Pathways

Molecular and Cellular Biology ◽

10.1128/mcb.25.7.2733-2743.2005 ◽

2005 ◽

Vol 25 (7) ◽

pp. 2733-2743 ◽

Cited By ~ 113

Author(s):

Nyaya Kelkar ◽

Claire L. Standen ◽

Roger J. Davis

Keyword(s):

Map Kinase ◽

Signaling Pathway ◽

Scaffold Protein ◽

P38 Map Kinase ◽

Scaffold Proteins ◽

Mitogen Activated Protein Kinase ◽

Kinase Signaling ◽

Interacting Protein ◽

Jnk Signaling ◽

Mitogen Activated Protein

ABSTRACT The c-Jun NH2-terminal kinase (JNK)-interacting protein (JIP) group of scaffold proteins (JIP1, JIP2, and JIP3) can interact with components of the JNK signaling pathway and potently activate JNK. Here we describe the identification of a fourth member of the JIP family. The primary sequence of JIP4 is most closely related to that of JIP3. Like other members of the JIP family of scaffold proteins, JIP4 binds JNK and also the light chain of the microtubule motor protein kinesin-1. However, the function of JIP4 appears to be markedly different from other JIP proteins. Specifically, JIP4 does not activate JNK signaling. In contrast, JIP4 serves as an activator of the p38 mitogen-activated protein (MAP) kinase pathway by a mechanism that requires the MAP kinase kinases MKK3 and MKK6. The JIP4 scaffold protein therefore appears to be a new component of the p38 MAP kinase signaling pathway.

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Inhibition by adenylyl cyclase-cAMP system of ET-1-induced HSP27 in osteoblasts

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2001.281.6.e1260 ◽

2001 ◽

Vol 281 (6) ◽

pp. E1260-E1266 ◽

Cited By ~ 4

Author(s):

Daijiro Hatakeyama ◽

Osamu Kozawa ◽

Masayuki Niwa ◽

Hiroyuki Matsuno ◽

Kanefusa Kato ◽

...

Keyword(s):

Map Kinase ◽

Adenylyl Cyclase ◽

Mrna Level ◽

P38 Map Kinase ◽

Hsp 27 ◽

Kinase C ◽

Protein Map ◽

Mitogen Activated Protein ◽

Camp System ◽

Kinase Phosphorylation

We have previously reported that endothelin-1 (ET-1) stimulates heat shock protein (HSP) 27 induction in osteoblast-like MC3T3-E1 cells and that p38 mitogen-activated protein (MAP) kinase acts at a point downstream from protein kinase C (PKC) in HSP27 induction. In the present study, we investigated the effect of the adenylyl cyclase-cAMP system on ET-1-stimulated induction of HSP27 in MC3T3-E1 cells. Dibutyryl-cAMP (DBcAMP) dose dependently inhibited the HSP27 accumulation stimulated by ET-1. Forskolin and cholera toxin significantly suppressed the ET-1-stimulated accumulation of HSP27. However, dideoxyforskolin, a forskolin derivative that does not activate cAMP, failed to suppress the ET-1-induced HSP27 accumulation. Forskolin reduced the p38 MAP kinase phosphorylation induced by ET-1 or 12- O-tetradecanoylphorbol-13-acetate (TPA). PGE1, an extracellular agonist that activates cAMP production, reduced the ET-1-induced HSP27 accumulation. In addition, the phosphorylation of p38 MAP kinase induced by ET-1 or TPA was suppressed by PGE1. Forskolin, DBcAMP, and PGE1suppressed the ET-1-stimulated increase in the mRNA level for HSP27. These results indicate that the adenylyl cyclase-cAMP system has an inhibitory role in ET-1-stimulated HSP27 induction in osteoblasts and that the effect is exerted at the point between PKC and p38 MAP kinase in osteoblasts.

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