Mitogen activated protein (MAP) kinase signal transduction pathways and novel anti-inflammatory targets

Butyrate induces cytodifferentiation in many tumor cells of different origin, suggesting that an as yet unidentified common mechanism inherent to malignant cells is the target of butyrate action. This study determined the role of different mitogen-activated protein (MAP) kinase signal transduction pathways in butyrate-induced erythroid differentiation of K562 human leukemia cells. Using a panel of anti-ERK, JNK, and p38 phosphospecific antibodies, the study showed that phosphorylation of ERK and JNK is decreased following treatment of cells with butyrate, whereas phosphorylation of p38 is increased. In contrast, a K562 subline defective in butyrate-mediated induction of erythroid differentiation did not reveal these changes in phosphorylation patterns. Inhibition of ERK activity by UO126 induces erythroid differentiation and acts synergistically with butyrate on hemoglobin synthesis and inhibition of cell proliferation, whereas inhibition of p38 activity by SB203580 completely abolished induction of hemoglobin expression by butyrate. Taken together, our data suggest a model in which butyrate induces erythroid differentiation of K562 cells by inhibition of ERK and activation of p38 signal transduction pathways.

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A role for autophosphorylation revealed by activated alleles of FUS3, the yeast MAP kinase homolog.

Molecular Biology of the Cell ◽

10.1091/mbc.5.3.297 ◽

1994 ◽

Vol 5 (3) ◽

pp. 297-312 ◽

Cited By ~ 45

Author(s):

J A Brill ◽

E A Elion ◽

G R Fink

Keyword(s):

Escherichia Coli ◽

Signal Transduction ◽

Map Kinase ◽

Signal Transduction Pathway ◽

Transduction Pathway ◽

Phosphorylated Form ◽

Protein Map ◽

Mitogen Activated Protein ◽

Mating Signal

We have isolated dominant gain-of-function (gf) mutations in FUS3, a Saccharomyces cerevisiae mitogen-activated protein (MAP) kinase homolog, that constitutively activate the yeast mating signal transduction pathway and confer hypersensitivity to mating pheromone. Surprisingly, the phenotypes of dominant FUS3gf mutations require the two protein kinases, STE7 and STE11. FUS3gf kinases are hyperphosphorylated in yeast independently of STE7. Consistent with this, FUS3gf kinases expressed in Escherichia coli exhibit an increased ability to autophosphorylate on tyrosine in vivo. FUS3gf mutations suppress the signal transduction defect of a severely catalytically impaired allele of STE7. This finding suggests that the tyrosine-phosphorylated form of FUS3 is a better substrate for activation by STE7. Furthermore, these results imply that the degree of autophosphorylation of a MAP kinase determines its threshold of sensitivity to upstream signals.

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Signal transduction pathways involved in the regulation of protein synthesis by insulin in L6 myoblasts

AJP Cell Physiology ◽

10.1152/ajpcell.1998.274.1.c221 ◽

1998 ◽

Vol 274 (1) ◽

pp. C221-C228 ◽

Cited By ~ 105

Author(s):

Scot R. Kimball ◽

Rick L. Horetsky ◽

Leonard S. Jefferson

Keyword(s):

Signal Transduction ◽

Protein Synthesis ◽

Map Kinase ◽

Mitogen Activated Protein Kinase ◽

Initiation Factor ◽

Signal Transduction Pathways ◽

Ribosomal Protein S6 ◽

Mitogen Activated Protein ◽

Induced Changes ◽

Stimulation Of

The phosphorylation states of three proteins implicated in the action of insulin on translation were investigated, i.e., 70-kDa ribosomal protein S6 kinase (p70 S6k ), eukaryotic initiation factor (eIF) 4E, and the eIF-4E binding protein 4E-BP1. Addition of insulin caused a stimulation of protein synthesis in L6 myoblasts in culture, an effect that was blocked by inhibitors of phosphatidylinositide-3-OH kinase (wortmannin), p70 S6k (rapamycin), and mitogen-activated protein kinase (MAP kinase) kinase (PD-98059). The stimulation of protein synthesis was accompanied by increased phosphorylation of p70 S6k , an effect that was blocked by rapamycin and wortmannin but not PD-98059. Insulin caused dephosphorylation of eIF-4E, an effect that appeared to be mediated by the p70 S6k pathway. Insulin also stimulated phosphorylation of 4E-BP1 as well as dissociation of the 4E-BP1 ⋅ eIF-4E complex. Both rapamycin and wortmannin completely blocked the insulin-induced changes in 4E-BP1 phosphorylation and association of 4E-BP1 and eIF-4E; PD-98059 had no effect on either parameter. Finally, insulin stimulated formation of the active eIF-4G ⋅ eIF-4E complex, an effect that was not prevented by any of the inhibitors. Overall, the results suggest that insulin stimulates protein synthesis in L6 myoblasts in part through utilization of both the p70 S6k and MAP kinase signal transduction pathways.

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Butyrate-induced erythroid differentiation of human K562 leukemia cells involves inhibition of ERK and activation of p38 MAP kinase pathways

Blood ◽

10.1182/blood.v95.7.2391 ◽

2000 ◽

Vol 95 (7) ◽

pp. 2391-2396 ◽

Cited By ~ 151

Author(s):

Olaf Witt ◽

Katrin Sand ◽

Arnulf Pekrun

Keyword(s):

Signal Transduction ◽

Map Kinase ◽

K562 Cells ◽

Erythroid Differentiation ◽

P38 Map Kinase ◽

Leukemia Cells ◽

Common Mechanism ◽

Signal Transduction Pathways ◽

Human Leukemia ◽

Mitogen Activated Protein

Abstract Butyrate induces cytodifferentiation in many tumor cells of different origin, suggesting that an as yet unidentified common mechanism inherent to malignant cells is the target of butyrate action. This study determined the role of different mitogen-activated protein (MAP) kinase signal transduction pathways in butyrate-induced erythroid differentiation of K562 human leukemia cells. Using a panel of anti-ERK, JNK, and p38 phosphospecific antibodies, the study showed that phosphorylation of ERK and JNK is decreased following treatment of cells with butyrate, whereas phosphorylation of p38 is increased. In contrast, a K562 subline defective in butyrate-mediated induction of erythroid differentiation did not reveal these changes in phosphorylation patterns. Inhibition of ERK activity by UO126 induces erythroid differentiation and acts synergistically with butyrate on hemoglobin synthesis and inhibition of cell proliferation, whereas inhibition of p38 activity by SB203580 completely abolished induction of hemoglobin expression by butyrate. Taken together, our data suggest a model in which butyrate induces erythroid differentiation of K562 cells by inhibition of ERK and activation of p38 signal transduction pathways.

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