scholarly journals Osmotic regulation of insulin-induced mitogen-activated protein kinase phosphatase (MKP-1) expression in H4IIE rat hepatoma cells

2003 ◽  
Vol 371 (2) ◽  
pp. 609-619 ◽  
Author(s):  
Mohammad Reza LORNEJAD-SCHÄFER ◽  
Christine SCHÄFER ◽  
Dirk GRAF ◽  
Dieter HÄUSSINGER ◽  
Freimut SCHLIESS
Keyword(s):  
Insulin Resistance ◽  
Protein Kinase ◽  
Map Kinase ◽  
Hepatoma Cells ◽  
Kinase Activation ◽  
P70s6 Kinase ◽  
Mitogen Activated Protein ◽  
Pkc Ζ ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

A contribution of intracellular dehydration to insulin resistance has been established in human subjects and in different experimental systems. Here the effect of hyperosmolarity (405mosmol/l) on insulin-induced mitogen-activated protein (MAP) kinase phosphatase (MKP)-1 expression was studied in H4IIE rat hepatoma cells. Insulin induces robust MKP-1 expression which correlates with a vanadate-sensitive decay of extracellular-signal-regulated kinase (Erk-1/Erk-2) activity. Hyperosmolarity delays MKP-1 accumulation by insulin and this corresponds to impaired MKP-1 synthesis, whereas MKP-1 degradation remains unaffected by hyperosmolarity. Rapamycin, which inhibits signalling downstream from the mammalian target of rapamycin (mTOR) and a peptide inhibiting protein kinase C (PKC) ζ/λ abolish insulin-induced MKP-1 protein but not mRNA expression, suggesting the involvement of the p70 ribosomal S6 protein kinase (p70S6-kinase) and/or the eukaryotic initiation factor 4E-binding proteins (4E-BPs) as well as atypical PKCs in MKP-1 translation. Hyperosmolarity induces sustained suppression of p70S6-kinase and 4E-BP1 hyperphosphorylation by insulin, whereas insulin-induced tyrosine phosphorylation of the insulin receptor (IR) β subunit and the IR substrates IRS1 and IRS2, recruitment of the phosphoinositide 3-kinase (PI 3-kinase) regulatory subunit p85 to the receptor substrates as well as PI 3-kinase activation, and Ser-473 phosphorylation of protein kinase B and Thr-410/403 phosphorylation of PKC ζ/λ are largely unaffected under hyperosmotic conditions. The hyperosmotic impairment of both, MKP-1 expression and p70S6-kinase hyperphosphorylation by insulin is insensitive to K2CrO4, calyculin A and vanadate, and inhibition of the Erk-1/Erk-2 and p38 pathways. The suppression of MKP-1 may further contribute to insulin resistance under dehydrating conditions by allowing unbalanced MAP kinase activation.

scholarly journals Novel members of the mitogen-activated protein kinase activator family in Xenopus laevis

1993 ◽  
Vol 13 (9) ◽  
pp. 5738-5748
Author(s):  
B M Yashar ◽  
C Kelley ◽  
K Yee ◽  
B Errede ◽  
L I Zon
Keyword(s):  
Protein Kinase ◽  
Xenopus Laevis ◽  
Map Kinase ◽  
Protein Kinases ◽  
Map Kinases ◽  
Yeast Cells ◽  
Amino Acid Sequence Similarity ◽  
Kinase Activation ◽  
Mitogen Activated Protein ◽  
Activation Pathways

Mitogen-activated protein (MAP) kinases comprise an evolutionarily conserved family of proteins that includes at least three vertebrate protein kinases (p42, p44, and p55 MAPK) and five yeast protein kinases (SPK1, MPK1, HOG1, FUS3, and KSS1). Members of this family are activated by a variety of extracellular agents that influence cellular proliferation and differentiation. In Saccharomyces cerevisiae, there are multiple physiologically distinct MAP kinase activation pathways composed of structurally related kinases. The recently cloned vertebrate MAP kinase activators are structurally related to MAP kinase activators in these yeast pathways. These similarities suggest that homologous kinase cascades are utilized for signal transduction in many, if not all, eukaryotes. We have identified additional members of the MAP kinase activator family in Xenopus laevis by a polymerase chain reaction-based analysis of embryonic cDNAs. One of the clones identified (XMEK2) encodes a unique predicted protein kinase that is similar to the previously reported activator (MAPKK) in X. laevis. XMEK2, a highly expressed maternal mRNA, is developmentally regulated during embryogenesis and expressed in brain and muscle. Expression of XMEK2 in yeast cells suppressed the growth defect associated with loss of the yeast MAP kinase activator homologs, MKK1 and MKK2. Partial sequence of a second cDNA clone (XMEK3) identified yet another potential MAP kinase activator. The pattern of expression of XMEK3 is distinct from that of p42 MAPK and XMEK2. The high degree of amino acid sequence similarity of XMEK2, XMEK3, and MAPKK suggests that these three are related members of an amphibian family of protein kinases involved in the activation of MAP kinase. Discovery of this family suggests that multiple MAP kinase activation pathways similar to those in yeast cells exist in vertebrates.

B-Raf-dependent regulation of the MEK-1/mitogen-activated protein kinase pathway in PC12 cells and regulation by cyclic AMP

1994 ◽  
Vol 14 (10) ◽  
pp. 6522-6530
Author(s):  
R R Vaillancourt ◽  
A M Gardner ◽  
G L Johnson
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Map Kinase ◽  
Protein Kinase A ◽  
Pc12 Cells ◽  
Kinase Activation ◽  
Mitogen Activated Protein ◽  
Epidermal Growth ◽  
Camp Levels ◽  
Kinase A

Growth factor receptor tyrosine kinase regulation of the sequential phosphorylation reactions leading to mitogen-activated protein (MAP) kinase activation in PC12 cells has been investigated. In response to epidermal growth factor, nerve growth factor, and platelet-derived growth factor, B-Raf and Raf-1 are activated, phosphorylate recombinant kinase-inactive MEK-1, and activate wild-type MEK-1. MEK-1 is the dual-specificity protein kinase that selectively phosphorylates MAP kinase on tyrosine and threonine, resulting in MAP kinase activation. B-Raf and Raf-1 are growth factor-regulated Raf family members which regulate MEK-1 and MAP kinase activity in PC12 cells. Protein kinase A activation in response to elevated cyclic AMP (cAMP) levels inhibited B-Raf and Raf-1 stimulation in response to growth factors. Ras.GTP loading in response to epidermal growth factor, nerve growth factor, or platelet-derived growth factor was unaffected by protein kinase A activation. Even though elevated cAMP levels inhibited Raf activation, the growth factor activation of MEK-1 and MAP kinase was unaffected in PC12 cells. The results demonstrate that tyrosine kinase receptor activation of MEK-1 and MAP kinase in PC12 cells is regulated by B-Raf and Raf-1, whose activation is inhibited by protein kinase A, and MEK activators, whose activation is independent of cAMP regulation.

scholarly journals Novel members of the mitogen-activated protein kinase activator family in Xenopus laevis.

1993 ◽  
Vol 13 (9) ◽  
pp. 5738-5748 ◽  
Author(s):  
B M Yashar ◽  
C Kelley ◽  
K Yee ◽  
B Errede ◽  
L I Zon
Keyword(s):  
Protein Kinase ◽  
Xenopus Laevis ◽  
Map Kinase ◽  
Protein Kinases ◽  
Map Kinases ◽  
Yeast Cells ◽  
Amino Acid Sequence Similarity ◽  
Kinase Activation ◽  
Mitogen Activated Protein ◽  
Activation Pathways

Mitogen-activated protein (MAP) kinases comprise an evolutionarily conserved family of proteins that includes at least three vertebrate protein kinases (p42, p44, and p55 MAPK) and five yeast protein kinases (SPK1, MPK1, HOG1, FUS3, and KSS1). Members of this family are activated by a variety of extracellular agents that influence cellular proliferation and differentiation. In Saccharomyces cerevisiae, there are multiple physiologically distinct MAP kinase activation pathways composed of structurally related kinases. The recently cloned vertebrate MAP kinase activators are structurally related to MAP kinase activators in these yeast pathways. These similarities suggest that homologous kinase cascades are utilized for signal transduction in many, if not all, eukaryotes. We have identified additional members of the MAP kinase activator family in Xenopus laevis by a polymerase chain reaction-based analysis of embryonic cDNAs. One of the clones identified (XMEK2) encodes a unique predicted protein kinase that is similar to the previously reported activator (MAPKK) in X. laevis. XMEK2, a highly expressed maternal mRNA, is developmentally regulated during embryogenesis and expressed in brain and muscle. Expression of XMEK2 in yeast cells suppressed the growth defect associated with loss of the yeast MAP kinase activator homologs, MKK1 and MKK2. Partial sequence of a second cDNA clone (XMEK3) identified yet another potential MAP kinase activator. The pattern of expression of XMEK3 is distinct from that of p42 MAPK and XMEK2. The high degree of amino acid sequence similarity of XMEK2, XMEK3, and MAPKK suggests that these three are related members of an amphibian family of protein kinases involved in the activation of MAP kinase. Discovery of this family suggests that multiple MAP kinase activation pathways similar to those in yeast cells exist in vertebrates.

scholarly journals Identification of a Novel Mitogen-Activated Protein Kinase Kinase Activation Domain Recognized by the Inhibitor PD 184352

2002 ◽  
Vol 22 (21) ◽  
pp. 7593-7602 ◽  
Author(s):  
Amy M. Delaney ◽  
John A. Printen ◽  
Huifen Chen ◽  
Eric B. Fauman ◽  
David T. Dudley
Keyword(s):  
Protein Kinase ◽  
Map Kinase ◽  
Genetic Screen ◽  
Mitogen Activated Protein Kinase ◽  
Erk Signaling ◽  
Signaling Cascade ◽  
Kinase Activation ◽  
Basal Activity ◽  
Mitogen Activated Protein

ABSTRACT Utilizing a genetic screen in the yeast Saccharomyces cerevisiae, we identified a novel autoactivation region in mammalian MEK1 that is involved in binding the specific MEK inhibitor, PD 184352. The genetic screen is possible due to the homology between components of the yeast pheromone response pathway and the eukaryotic Raf-MEK-ERK signaling cascade. Using the FUS1::HIS3 reporter as a functional readout for activation of a reconstituted Raf-MEK-ERK signaling cascade, randomly mutagenized MEK variants that were insensitive to PD 184352 were obtained. Seven single-base-change mutations were identified, five of which mapped to kinase subdomains III and IV of MEK. Of the seven variants, only one, a leucine-to-proline substitution at amino acid 115 (Leu115Pro), was completely insensitive to PD 184352 in vitro (50% inhibitory concentration >10 μM). However, all seven mutants displayed strikingly high basal activity compared to wild-type MEK. Overexpression of the MEK variants in HEK293T cells resulted in an increase in mitogen-activated protein (MAP) kinase phosphorylation, a finding consistent with the elevated basal activity of these constructs. Further, treatment with PD 184352 failed to inhibit Leu115Pro-stimulated MAP kinase activation in HEK293T cells, whereas all other variants had some reduction in phospho-MAP kinase levels. By using cyclic AMP-dependent protein kinase (1CDK) as a template, an MEK homology model was generated, with five of the seven identified residues clustered together, forming a potential hydrophobic binding pocket for PD 184352. Additionally, the model allowed identification of other potential residues that would interact with the inhibitor. Directed mutation of these residues supported this region's involvement with inhibitor binding.

Osmotic Regulation of MAP-Kinase Activities and Gene Expression in H4IIE Rat Hepatoma Cells

1998 ◽  
Vol 379 (6) ◽  
pp. 667-672 ◽  
Author(s):  
Sabine Wiese ◽  
Freimut Schliess ◽  
Dieter Häussinger
Keyword(s):  
Gene Expression ◽  
Map Kinase ◽  
Hepatoma Cells ◽  
Osmotic Regulation ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

scholarly journals B-Raf-dependent regulation of the MEK-1/mitogen-activated protein kinase pathway in PC12 cells and regulation by cyclic AMP.

1994 ◽  
Vol 14 (10) ◽  
pp. 6522-6530 ◽  
Author(s):  
R R Vaillancourt ◽  
A M Gardner ◽  
G L Johnson
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Map Kinase ◽  
Protein Kinase A ◽  
Pc12 Cells ◽  
Kinase Activation ◽  
Mitogen Activated Protein ◽  
Epidermal Growth ◽  
Camp Levels ◽  
Kinase A

Growth factor receptor tyrosine kinase regulation of the sequential phosphorylation reactions leading to mitogen-activated protein (MAP) kinase activation in PC12 cells has been investigated. In response to epidermal growth factor, nerve growth factor, and platelet-derived growth factor, B-Raf and Raf-1 are activated, phosphorylate recombinant kinase-inactive MEK-1, and activate wild-type MEK-1. MEK-1 is the dual-specificity protein kinase that selectively phosphorylates MAP kinase on tyrosine and threonine, resulting in MAP kinase activation. B-Raf and Raf-1 are growth factor-regulated Raf family members which regulate MEK-1 and MAP kinase activity in PC12 cells. Protein kinase A activation in response to elevated cyclic AMP (cAMP) levels inhibited B-Raf and Raf-1 stimulation in response to growth factors. Ras.GTP loading in response to epidermal growth factor, nerve growth factor, or platelet-derived growth factor was unaffected by protein kinase A activation. Even though elevated cAMP levels inhibited Raf activation, the growth factor activation of MEK-1 and MAP kinase was unaffected in PC12 cells. The results demonstrate that tyrosine kinase receptor activation of MEK-1 and MAP kinase in PC12 cells is regulated by B-Raf and Raf-1, whose activation is inhibited by protein kinase A, and MEK activators, whose activation is independent of cAMP regulation.

scholarly journals Osmotic Regulation of MG-132-induced MAP-kinase Phosphatase MKP-1 Expression in H4IIE Rat Hepatoma Cells

2005 ◽  
Vol 16 (4-6) ◽  
pp. 193-206 ◽  
Author(s):  
Mohammad Lornejad-Schäfer ◽  
Christine Schäfer ◽  
Lisa Richter ◽  
Tilman Grune ◽  
Dieter Häussinger ◽  
...  
Keyword(s):  
Map Kinase ◽  
Hepatoma Cells ◽  
Osmotic Regulation ◽  
Map Kinase Phosphatase ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells
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