Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The adaptor protein Gab-2 coordinates the assembly of the IL-3 signalsome comprising Gab-2, Grb2, Shc, SHP-2 and PI3K. To investigate the role of the pleckstrin homology domain of Gab-2 in this process, epitope-tagged wild type Gab-2 (WTGab-2), Gab-2 lacking its PH domain (DeltaPHGab-2) and the Gab-2 PH domain alone (PHGab-2) were inducibly expressed in IL-3-dependent BaF/3 cells. Expression of DeltaPHGab-2 reduced IL-3-dependent proliferation and long-term activation of ERK1 and 2 and PKB by IL-3. While we demonstrate that the Gab-2 PH domain can bind PI(3,4,5)P3, it is dispensable for Gab-2 membrane localisation, tyrosine phosphorylation and signalsome formation. Rather, the proline-rich motifs of Gab-2 appear to contribute to the constitutive membrane localisation we observe, independently of tyrosine phosphorylation or the PH domain. Taken together, these findings suggest that once Gab-2 is tyrosine phosphorylated its PH domain is required for the optimal stabilisation of the signalsome, enabling full activation of downstream signals.
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PMID:The pleckstrin homology domain of Gab-2 is required for optimal interleukin-3 signalsome-mediated responses. 1627 30

Centaurin-alpha1 is known to be a phosphatidylinositol 3,4,5-triphosphate (PIP3)-binding protein that has two pleckstrin homology domains and a putative ADP ribosylation factor GTPase-activating protein domain. However, the physiological function of centaurin-alpha1 is still not understood. Here we have shown that transient expression of centaurin-alpha1 in COS-7 cells results in specific activation of ERK, and the activation is inhibited by co-expression of a dominant negative form of Ras. We have also found that a mutant form of centaurin-alpha1 that is unable to bind PIP3 fails to induce ERK activation and that a phosphatidylinositol 3-kinase inhibitor LY294002 inhibits centaurin-alpha1-dependent ERK activation. Furthermore, transient knockdown of centaurin-alpha1 by small interfering RNAs results in reduced ERK activation after epidermal growth factor stimulation in T-REx 293 cells. These results suggest that centaurin-alpha1 contributes to ERK activation in growth factor signaling, linking the PI3K pathway to the ERK mitogen-activated protein kinase pathway through its ability to interact with PIP3.
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PMID:Centaurin-alpha1 is a phosphatidylinositol 3-kinase-dependent activator of ERK1/2 mitogen-activated protein kinases. 1628 13

We demonstrate that recycling through the endocytic recycling compartment (ERC) is an essential step in Fc epsilonRI-induced activation of extracellular signal-regulated kinase (ERK)1/2. We show that ERK1/2 acquires perinuclear localization and colocalizes with Rab 11 and internalized transferrin in Fc epsilonRI-activated cells. Moreover, a close correlation exists between the amount of ERC-localized ERK1/2 and the amount of phospho-ERK1/2 that resides in the nucleus. We further show that by activating phosphatidylinositol 4-kinase beta (PI4Kbeta) and increasing the cellular level of phosphatidylinositol(4) phosphate, neuronal calcium sensor-1 (NCS-1), a calmodulin-related protein, stimulates recycling and thereby enhances Fc epsilonRI-triggered activation and nuclear translocation of ERK1/2. Conversely, NCS-1 short hairpin RNA, a kinase dead (KD) mutant of PI4Kbeta (KD-PI4Kbeta), the pleckstrin homology (PH) domain of FAPP1 as well as RNA interference of synaptotagmin IX or monensin, which inhibit export from the ERC, abrogate Fc epsilonRI-induced activation of ERK1/2. Consistently, NCS-1 also enhances, whereas both KD-PI4Kbeta and FAPP1-PH domain inhibit, Fc epsilonRI-induced release of arachidonic acid/metabolites, a downstream target of ERK1/2 in mast cells. Together, our results demonstrate a novel role for NCS-1 and PI4Kbeta in regulating ERK1/2 signaling and inflammatory reactions in mast cells. Our results further identify the ERC as a crucial determinant in controlling ERK1/2 signaling.
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PMID:Neuronal calcium sensor-1 and phosphatidylinositol 4-kinase beta stimulate extracellular signal-regulated kinase 1/2 signaling by accelerating recycling through the endocytic recycling compartment. 1683 55

Ste5, the prototypic mitogen-activated protein kinase (MAPK) scaffold protein, associates with plasma membrane-tethered Gbetagamma freed upon pheromone receptor occupancy, thereby initiating downstream signaling. We demonstrate that this interaction and membrane binding of an N-terminal amphipathic alpha-helix (PM motif) are not sufficient for Ste5 action. Rather, Ste5 contains a pleckstrin-homology (PH) domain (residues 388-518) that is essential for its membrane recruitment and function. Altering residues (R407S K411S) equivalent to those that mediate phosphoinositide binding in other PH domains abolishes Ste5 function. The isolated PH domain, but not a R407S K411S derivative, binds phosphoinositides in vitro. Ste5(R407S K411S) is expressed normally, retains Gbetagamma and Ste11 binding, and oligomerizes, yet is not recruited to the membrane in response to pheromone. Artificial membrane tethering of Ste5(R407S K411S) restores signaling. R407S K411S loss-of-function mutations abrogate the constitutive activity of gain-of-function Ste5 alleles, including one (P44L) that increases membrane affinity of the PM motif. Thus, the PH domain is essential for stable membrane recruitment of Ste5, and this association is critical for initiation of downstream signaling because it allows Ste5-bound Ste11 (MAPKKK) to be activated by membrane-bound Ste20 (MAPKKKK).
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PMID:Function of the MAPK scaffold protein, Ste5, requires a cryptic PH domain. 1684 50

Human Sin1 (SAPK-interacting protein 1) is a member of a conserved family of orthologous proteins that have an essential role in signal transduction in yeast and Dictyostelium. This study demonstrates that most Sin1 orthologues contain both a Raf-like Ras-binding domain (RBD) and a pleckstrin homology (PH) domain. These domains are functional in the human Sin1 protein, with the PH domain involved in lipid and membrane binding by Sin1, and the RBD able to bind activated H-and K-Ras. Sin1 and Ras co-immunoprecipitated and co-localised, showing that these proteins associate with each other in vivo. Overexpression of Sin1 inhibited the activation of ERK, Akt and JNK signalling pathways by Ras. In contrast, siRNA knockdown of endogenous Sin1 protein expression in HEK293 cells enhanced the activation of ERK1/2 by Ras. These data suggest that Sin1 is a mammalian Ras-inhibitor.
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PMID:Human Sin1 contains Ras-binding and pleckstrin homology domains and suppresses Ras signalling. 1730 83

Adipocyte differentiation is regulated by insulin and IGF-I, which transmit signals by activating their receptor tyrosine kinase. SH2-B is an adaptor protein containing pleckstrin homology and Src homology 2 (SH2) domains that have been implicated in insulin and IGF-I receptor signaling. In this study, we found a strong link between SH2-B levels and adipogenesis. The fat mass and expression of adipogenic genes including peroxisome proliferator-activated receptor gamma (PPARgamma) were reduced in white adipose tissue of SH2-B-/- mice. Reduced adipocyte differentiation of SH2-B-deficient mouse embryonic fibroblasts (MEFs) was observed in response to insulin and dexamethasone, whereas retroviral SH2-B overexpression enhanced differentiation of 3T3-L1 preadipocytes to adipocytes. SH2-B overexpression enhanced mRNA level of PPARgamma in 3T3-L1 cells, whereas PPARgamma levels were reduced in SH2-B-deficient MEFs in response to insulin. SH2-B-mediated up-regulation of PPARgamma mRNA was blocked by a phosphatidylinositol 3-kinase inhibitor, but not by a MAPK kinase inhibitor. Insulin-induced Akt activation and the phosphorylation of forkhead transcription factor (FKHR/Foxo1), a negative regulator of PPARgamma transcription, were up-regulated by SH2-B overexpression, but reduced in SH2-B-deficient MEFs. These data indicate that SH2-B is a key regulator of adipogenesis both in vivo and in vitro by regulating the insulin/IGF-I receptor-Akt-Foxo1-PPARgamma pathway.
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PMID:Adaptor protein SH2-B linking receptor-tyrosine kinase and Akt promotes adipocyte differentiation by regulating peroxisome proliferator-activated receptor gamma messenger ribonucleic acid levels. 1731 74

The proapoptotic protein Bad is a key player in cell survival decisions, and is regulated post-translationally by several signaling networks. We expressed Bad in mouse embryonic fibroblasts to sensitize them to apoptosis, and tested cell lines derived from knock-out mice to establish the significance of the interaction between the adaptor protein Grb10 and the Raf-1 protein kinase in anti-apoptotic signaling pathways targeting Bad. When compared with wild-type cells, both Grb10 and Raf-1-deficient cells exhibit greatly enhanced sensitivity to apoptosis in response to Bad expression. Structure-function analysis demonstrates that, in this cellular model, the SH2, proline-rich, and pleckstrin homology domains of Grb10, as well as its Akt phosphorylation site and consequent binding by 14-3-3, are all necessary for its anti-apoptotic functions. As for Raf-1, its kinase activity, its ability to be phosphorylated by Src on Tyr-340/341 and the binding of its Ras-associated domain to the Grb10 SH2 domain are all necessary to promote cell survival. Silencing the expression of either Grb10 or Raf-1 by small interfering RNAs as well as mutagenesis of specific serine residues on Bad, coupled with signaling inhibitor studies, all indicate that Raf-1 and Grb10 are required for the ability of both the phosphatidylinositol 3-kinase/Akt and MAP kinase pathways to modulate the phosphorylation and inactivation of Bad. Because total Raf-1, ERK, and Akt kinase activities are not impaired in the absence of Grb10, we propose that this adapter protein creates a subpopulation of Raf-1 with specific anti-apoptotic activity.
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PMID:Grb10 and active Raf-1 kinase promote Bad-dependent cell survival. 1753 12

Grb10 is a pleckstrin homology and Src homology 2 domain-containing protein that interacts with a number of phosphorylated receptor tyrosine kinases, including the insulin receptor. In mice, Grb10 gene expression is imprinted with maternal expression in all tissues except the brain. While the interaction between Grb10 and the insulin receptor has been extensively investigated in cultured cells, whether this adaptor protein plays a positive or negative role in insulin signaling and action remains controversial. In order to investigate the in vivo role of Grb10 in insulin signaling and action in the periphery, we generated Grb10 knockout mice by the gene trap technique and analyzed mice with maternal inheritance of the knockout allele. Disruption of Grb10 gene expression in peripheral tissues had no significant effect on fasting glucose and insulin levels. On the other hand, peripheral-tissue-specific knockout of Grb10 led to significant overgrowth of the mice, consistent with a role for endogenous Grb10 as a growth suppressor. Loss of Grb10 expression in insulin target tissues, such as skeletal muscle and fat, resulted in enhanced insulin-stimulated Akt and mitogen-activated protein kinase phosphorylation. Hyperinsulinemic-euglycemic clamp studies revealed that disruption of Grb10 gene expression in peripheral tissues led to increased insulin sensitivity. Taken together, our results provide strong evidence that Grb10 is a negative regulator of insulin signaling and action in vivo.
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PMID:Peripheral disruption of the Grb10 gene enhances insulin signaling and sensitivity in vivo. 1762 Apr 12

Inositol phospholipids phosphorylated on D3-position of their inositol rings (3-phosphoinositides) are known to play important roles in various cellular events. Activation of PI (phosphatidylinositol) 3-kinase is essential for aspects of insulin-induced glucose metabolism, including translocation of GLUT4 to the cell surface and glycogen synthesis. The enzyme exists as a heterodimer containing a regulatory subunit and one of two widely-distributed isoforms of the p110 catalytic subunit: p110alpha or p110beta. Activation of PI 3-kinase and its downstream AKT has been demonstrated to be essential for almost all of the insulin-induced glucose and lipid metabolism such as glucose uptake, glycogen synthesis, suppression of glucose output and triglyceride synthesis as well as insulin-induced mitogenesis. Accumulated PI(3,4,5)P(3) activates several serine/threonine kinases containing a PH (pleckstrin homology) domain, including Akt, atypical PKCs, p70S6 kinase and GSK. In the obesity-induced insulin resistant condition, JNK and p70S6K are activated and phosphorylate IRS-proteins, which diminishes the insulin-induced tyrosine phosphorylation of IRS-proteins and thereby impairs the PI 3-kinase/AKT activations. Thus, the drugs which restore the impaired insulin-induced PI 3-kinase/AKT activation, for example, by suppressing JNK or p70S6K, PTEN or SHIP2, could be novel agents to treat diabetes mellitus.
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PMID:Role of phosphatidylinositol 3-kinase activation on insulin action and its alteration in diabetic conditions. 1782 8

Trafficking of H-Ras was examined to determine whether it can enter cells through clathrin-independent endocytosis (CIE). H-Ras colocalized with the CIE cargo protein, class I major histocompatibility complex, and it was sequestered in vacuoles that formed upon expression of an active mutant of Arf6, Q67L. Activation of Ras, either through epidermal growth factor stimulation or the expression of an active mutant of Ras, G12V, induced plasma membrane ruffling and macropinocytosis, a stimulated form of CIE. Live imaging of cells expressing H-RasG12V and fluorescent protein chimeras with pleckstrin homology domains that recognize specific phosphoinositides showed that incoming macropinosomes contained phosphatidylinositol 4,5-bisphosphate (PIP(2)) and phosphatiylinositol 3,4,5-trisphosphate (PIP(3)). PIP(2) loss from the macropinosome was followed by the recruitment of Rab5, a downstream target of Ras, and then PIP(3) loss. Our studies support a model whereby Ras can signal on macropinosomes that pass through three distinct stages: PIP(2)/PIP(3), PIP(3)/Rab5, and Rab5. Vacuoles that form in cells expressing Arf6Q67L trap Ras signaling in the first stage, recruiting the active form of the Ras effectors extracellular signal-regulated kinase and protein kinase B (Akt) but not Rab5. Arf6 stimulation of macropinocytosis also involves passage through the distinct lipid phases, but recruitment of Akt is not observed.
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PMID:A unique platform for H-Ras signaling involving clathrin-independent endocytosis. 1809 44


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