Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Essential to signal transduction are mechanisms of "cross-talk" to coordinate different pathways. This study shows that stimulation of serine/threonine protein kinases activates protein-tyrosine phosphatase (PTPase; protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48). More than 95% of intracellular PTPase was in the particulate fraction of various cell lines and was extracted with detergent as a 150-kDa complex that contained a 55-kDa catalytic subunit. The complex was activated by protease digestion, which changed its substrate specificity coincident with reduction in size. The complex was dissociated by treatment of the membrane fraction with 3 M LiBr. Treatment of intact cells with isoproterenol, forskolin, or cAMP analogues to stimulate cAMP-dependent protein kinase (PKA) or with phorbol ester or dioctanoylglycerol to stimulate Ca2+/phospholipid-dependent protein kinase (PKC) produced activation of membrane PTPase complex without a change in its size. Inhibition of protein-serine/threonine phosphatases with okadaic acid or fluoride also resulted in activation of the membrane PTPase. These results support a model for regulation of PTPase by phosphorylation and dephosphorylation of serine/threonine residues in a regulatory component complexed with the 55-kDa PTPase catalytic subunit. This mechanism may be important in regulating sensitivity to extracellular signals transduced via tyrosine phosphorylation and in the synchronization of events during the cell cycle.
 ...
PMID:Activation of membrane protein-tyrosine phosphatase involving cAMP- and Ca2+/phospholipid-dependent protein kinases. 165 Apr 78

Dehydroepiandrosterone (DHEA) treatment is effective in preventing or delaying the onset of various genetic and induced disorders of mice and rats. Associated with the beneficial therapeutic effects exerted by action of this steroid is the development of hepatomegaly. To determine whether the changes associated with hepatomegaly also involve alterations in activities of tissue enzymes, we evaluated the effects of DHEA (0.45% in food, w/w) on hepatic protein kinases, phosphatases, and lipogenic enzymes in mice of various strains. The rates of fatty acid and cholesterol syntheses also were evaluated. DHEA administration resulted in profound changes in the sodium dodecylsulfate-polyacrylamide gel electrophoresis patterns of endogenous radiophosphorylated proteins obtained by incubation of liver homogenates with (gamma-32P]ATP. These changes were dependent upon the medium used for homogenization. Thus, when homogenates of liver tissue of DHEA-treated mice were prepared in Tris buffer containing sucrose (0.25 M) there was a marked decrease in phosphorylation of the proteins of relative molecular weight approximately 116,000 (Mr approximately 116,000), approximately 82,000, approximately 80,000, approximately 58,000, approximately 56,000, approximately 48,000, approximately 34,000, and approximately 31,000 compared with controls. With liver homogenates of DHEA-treated mice prepared in Tris buffer alone, there was a marked increase in phosphorylation of the proteins of Mr approximately 70,000, approximately 49,000, approximately 34,000, approximately 31,000, and 28,000 compared with controls. Moreover, the specific activity of kinases for endogenous protein acceptors in liver of control mice was higher than that in liver of DHEA-treated animals. The specific activities of casein kinase, cAMP-dependent protein kinase, and cGMP-dependent protein kinase remained unchanged with DHEA treatment, but the specific activity of histone kinase was increased approximately 30%. Long-term administration of DHEA also was associated with increases in the specific activities of liver AMPase and GTPase (approximately two times), but not of other nucleotidases, alkaline phosphatase, acid phosphatase, glucose-6-phosphatase, or phosphotyrosine phosphatase. The activity of hepatic NADP-linked malic enzyme was increased significantly (two to three times) by DHEA treatment of female mice of three different strains, but was unchanged in male C57BL/6 mice. The specific activities of hepatic glucose-6-phosphate dehydrogenase, NADP-linked isocitrate dehydrogenase, and ATP-citrate lyase were not affected significantly by DHEA treatment of mice. The rate of hepatic lipogenesis, determined by incorporation of tritium from 3H2O into fatty acids, was decreased approximately 70% in DHEA-treated mice, while the rate of cholesterol synthesis was increased approximately 44% compared with controls.
 ...
PMID:Dehydroepiandrosterone feeding and protein phosphorylation, phosphatases, and lipogenic enzymes in mouse liver. 215 82

Stimulation of fibroblasts with serum growth factors results in the rapid activation of a set of immediate-early genes, among them 3CH134. We have purified a bacterially expressed form of the 3CH134-encoded polypeptide and demonstrated that it has intrinsic protein-tyrosine-phosphatase (PTPase; protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48) activity in vitro. This activity is optimal at pH 7.5, is sensitive to vanadate and cysteinyl modifying agents, and is insensitive to a panel of serine/threonine phosphatase inhibitors. Purified 3CH134 protein displays a high degree of selectivity among the tyrosine-phosphorylated polypeptide substrates tested. Under our assay conditions, the rates of dephosphorylation are in the order EDNDYINASL peptide < myelin basic protein < reduced, carboxyamidomethylated, and maleylated lysozyme (RCML) < p42mapk. There is a 200-fold range in rates for these substrates, with p42mapk dephosphorylated 15-fold more rapidly than RCML. Although 3CH134 is most closely related to the tyrosine/serine dual-specificity phosphatase VH1, we failed to detect any 3CH134-directed activity on casein or RCML phosphorylated on serine/threonine residues by cAMP-dependent protein kinase. Since 3CH134 expression is controlled transcriptionally and posttranscriptionally, it may represent a class of PTPases whose activity is regulated at the level of protein synthesis and degradation.
 ...
PMID:The growth factor-inducible immediate-early gene 3CH134 encodes a protein-tyrosine-phosphatase. 838 79

During activation of adrenocortical cells by adrenocorticotrophic hormone (ACTH), tyrosine dephosphorylation of paxillin is stimulated and this correlates with protrusion of filopodial structures and a decreased number of focal adhesions. These effects are inhibited by Na(3)VO(4), a phosphotyrosine phosphatase inhibitor [Vilgrain, Chinn, Gaillard, Chambaz and Feige (1998) Biochem. J. 332, 533-540]. However, the tyrosine phosphatases involved in these processes remain to be identified. In this study, we provide evidence that the Src homology domain (SH)2-containing phosphotyrosine phosphatase (SHP)2, but not SHP1, is expressed in adrenocortical cells and is phosphorylated upon ACTH challenge. ACTH (10(-8) M) treatment of (32)P-labelled adrenocortical cells resulted in an increase in phosphorylated SHP2. By probing SHP2-containing immunoprecipitates with an antibody to phosphoserine we found that SHP2 was phosphorylated on serine in ACTH-treated cells in a dose- and time-dependent manner. Furthermore, using an in vitro kinase assay, we showed that SHP2 was a target for cAMP-dependent protein kinase (PKA). Serine was identified as the only target amino acid phosphorylated in SHP2. Phosphorylation of SHP2 by PKA resulted in a dramatic stimulation of phosphatase activity measured either with insulin receptor substrate-1 or with the synthetic peptide [(32)P]poly(Glu/Tyr) as substrate. In an in-gel assay of SHP2-containing immunoprecipitates, phosphorylated in vitro by PKA or isolated from adrenocortical cells treated with 10 nM ACTH, a pronounced activation of SHP2 activity was shown. These observations clearly support the idea that a PKA-mediated signal transduction pathway contributes to SHP2 regulation in adrenocortical cells and point to SHP2 as a possible mediator of the effects of ACTH.
 ...
PMID:Adrenocorticotrophic hormone stimulates phosphotyrosine phosphatase SHP2 in bovine adrenocortical cells: phosphorylation and activation by cAMP-dependent protein kinase. 1108 42

cAMP-dependent transcription of steroid hydroxylase genes involves activation of cAMP-dependent protein kinase (PKA) and subsequent phosphorylation of downstream target proteins. Although the requirement for the activation of PKA is well established, none of the transcription factors required for steroid hydroxylase gene transcription have been found to be PKA phosphoproteins. In this study we examined the role of changes in phosphorylation state on the expression and transcriptional activity of the human CYP17 gene (hCYP17). Using inhibitors of serine/threonine phosphatase activity (okadaic acid) and phosphotyrosine phosphatase activity (peroxyvanadate), we can inhibit the cAMP-inducible binding of the steroidogenic factor-1 (SF-1), p54(nrb)/NonO, and polypyrimidine tract-binding protein-associated splicing factor (PSF) complex required for regulation of transcription to the promoter of hCYP17. Further, both okadaic acid and peroxyvanadate attenuate cAMP-stimulated increases in endogenous hCYP17 mRNA expression and in hCYP17 promoter-reporter construct luciferase activity. In vivo phosphorylation and immunoprecipitation of SF-1 show a cAMP-stimulated decrease in (32)P-labeled SF-1. Our findings demonstrate that activation of protein phosphatase(s) is essential for cAMP-dependent transcription of hCYP17 in H295R cells and suggest a role for PKA in phosphatase activation, which leads to dephosphorylation of SF-1 and increased gene transcription.
 ...
PMID:Adrenocorticotropin/cyclic adenosine 3',5'-monophosphate-mediated transcription of the human CYP17 gene in the adrenal cortex is dependent on phosphatase activity. 1195 59

The VEGF/VEGFR2/Akt/eNOS/NO pathway is essential to VEGF-induced angiogenesis. We have previously discovered a novel role of calpain in mediating VEGF-induced PI3K/AMPK/Akt/eNOS activation through Ezrin. Here, we sought to identify possible feedback regulation of VEGFR2 by calpain via its substrate protein phosphotyrosine phosphatase 1B (PTP1B), and the relevance of this pathway to VEGF-induced angiogenesis, especially in diabetic wound healing. Overexpression of PTP1B inhibited VEGF-induced VEGFR2 and Akt phosphorylation in bovine aortic endothelial cells, while PTP1B siRNA increased both, implicating negative regulation of VEGFR2 by PTP1B. Calpain inhibitor ALLN induced VEGFR2 activation, which can be completely blocked by PTP1B overexpression. Calpain activation induced by overexpression or Ca/A23187 resulted in PTP1B cleavage, which can be blocked by ALLN. Moreover, calpain activation inhibited VEGF-induced VEGFR2 phosphorylation, which can be restored by PTP1B siRNA. These data implicate calpain/PTP1B negative feedback regulation of VEGFR2, in addition to the primary signaling pathway of VEGF/VEGFR2/calpain/PI3K/AMPK/Akt/eNOS. We next examined a potential role of PTP1B in VEGF-induced angiogenesis. Endothelial cells transfected with PTP1B siRNA showed faster wound closure in response to VEGF. Aortic discs isolated from PTP1B siRNA-transfected mice also had augmented endothelial outgrowth. Importantly, PTP1B inhibition and/or calpain overexpression significantly accelerated wound healing in STZ-induced diabetic mice. In conclusion, our data for the first time demonstrate a calpain/PTP1B/VEGFR2 negative feedback loop in the regulation of VEGF-induced angiogenesis. Modulation of local PTP1B and/or calpain activities may prove beneficial in the treatment of impaired wound healing in diabetes.
 ...
PMID:Protein Phosphotyrosine Phosphatase 1B (PTP1B) in Calpain-dependent Feedback Regulation of Vascular Endothelial Growth Factor Receptor (VEGFR2) in Endothelial Cells: IMPLICATIONS IN VEGF-DEPENDENT ANGIOGENESIS AND DIABETIC WOUND HEALING. 2787 90