Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.26 (GSK)
 6,788 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The molecular pathogenesis of diabetic nephropathy (DN), the leading cause of end-stage renal disease worldwide, is complex and not fully understood. Transforming growth factor-beta (TGF-beta1) plays a critical role in many fibrotic disorders, including DN. In this study, we report protein kinase B (PKB/Akt) activation as a downstream event contributing to the pathophysiology of DN. We investigated the potential of PKB/Akt to mediate the profibrotic bioactions of TGF-beta1 in kidney. Treatment of normal rat kidney epithelial cells (NRK52E) with TGF-beta1 resulted in activation of phosphatidylinositol 3-kinase (PI3K) and PKB/Akt as evidenced by increased Ser473 phosphorylation and GSK-3beta phosphorylation. TGF-beta1 also stimulated increased Smad3 phosphorylation in these cells, a response that was insensitive to inhibition of PI3K or PKB/Akt. NRK52E cells displayed a loss of zona occludins 1 and E-cadherin and a gain in vimentin and alpha-smooth muscle actin expression, consistent with the fibrotic actions of TGF-beta1. These effects were blocked with inhibitors of PI3K and PKB/Akt. Furthermore, overexpression of PTEN, the lipid phosphatase regulator of PKB/Akt activation, inhibited TGF-beta1-induced PKB/Akt activation. Interestingly, in the Goto-Kakizaki rat model of type 2 diabetes, we also detected increased phosphorylation of PKB/Akt and its downstream target, GSK-3beta, in the tubules, relative to that in control Wistar rats. Elevated Smad3 phosphorylation was also detected in kidney extracts from Goto-Kakizaki rats with chronic diabetes. Together, these data suggest that TGF-beta1-mediated PKB/Akt activation may be important in renal fibrosis during diabetic nephropathy.
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PMID:Protein kinase B/Akt activity is involved in renal TGF-beta1-driven epithelial-mesenchymal transition in vitro and in vivo. 1849 98

Metastasis is responsible for 90% of cancer patient deaths. More information is needed about the molecular basis for its potential detection and treatment. The activated AKT kinase is necessary for many events of the metastatic pathway including escape of cells from the tumor's environment, into and then out of the circulation, activation of proliferation, blockage of apoptosis, and activation of angiogenesis. A series of steps leading to metastatic properties can be initiated upon activation of AKT by phosphorylation on Ser-473. These findings lead to the question of how this activation is connected to metastasis. Activated AKT phosphorylates GSK-3beta causing its proteolytic removal. This increases stability of the negative transcription factor SNAIL, thereby decreasing transcription of the transmembrane protein E-cadherin that forms adhesions between adjacent cells, thereby permitting their detachment. How is AKT hyperactivated in metastatic cells? Increased PI3K or TORC2 kinase activity- or decreased PHLPP phosphatase could be responsible. Furthermore, a positive feedback mechanism is that the decrease of E-cadherin lowers PTEN and thereby increases PIP3, further activating AKT and metastasis.
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PMID:Metastasis and AKT activation. 1881 26

Glycogen synthase kinase 3beta (GSK-3beta) represses cell cycle progression by directly phosphorylating cyclin D1 and indirectly regulating cyclin D1 transcription by inhibiting Wnt signaling. Recently, we reported that the Epm2a-encoded laforin is a GSK-3beta phosphatase and a tumor suppressor. The cellular mechanism for its tumor suppression remains unknown. Using ex vivo thymocytes and primary embryonic fibroblasts from Epm2a(-/-) mice, we show here a general function of laforin in the cell cycle regulation and repression of cyclin D1 expression. Moreover, targeted mutation of Epm2a increased the phosphorylation of Ser9 on GSK-3beta while having no effect on the phosphorylation of Ser21 on GSK-3alpha. In the GSK-3beta(+/+) but not the GSK-3beta(-/-) cells, Epm2a small interfering RNA significantly enhanced cell growth. Consistent with an increased level of cyclin D1, the phosphorylation of retinoblastoma protein (Rb) and the levels of Rb-E2F-regulated genes cyclin A, cyclin E, MCM3, and PCNA are also elevated. Inhibitors of GSK-3beta selectively increased the cell growth of Epm2a(+/+) but not of Epm2a(-/-) cells. Taken together, our data demonstrate that laforin is a selective phosphatase for GSK-3beta and regulates cell cycle progression by GSK-3beta-dependent mechanisms. These data provide a cellular basis for the tumor suppression activity of laforin.
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PMID:Laforin negatively regulates cell cycle progression through glycogen synthase kinase 3beta-dependent mechanisms. 1882 42

Down-regulation of E-cadherin plays an important role in epithelial-mesenchymal transition (EMT), which is critical in normal development and disease states such as tissue fibrosis and metastasis. Snail, a key transcription repressor of E-cadherin, is a labile protein with a short half-life and is regulated through phosphorylation, ubiquitination, and degradation. Previously, we showed that GSK-3beta phosphorylated two stretches of serine residues within the nuclear export signal and the destruction box of Snail, provoking its cytoplasmic export for ubiquitin-mediated proteasome degradation. However, the mechanism of Snail dephosphorylation and the identity of the Snail-specific phosphatase remain elusive. Using a functional genomic screening, we found that the small C-terminal domain phosphatase (SCP) is a specific phosphatase for Snail. SCP interacted and co-localized with Snail in the nucleus. We also found that SCP expression induced Snail dephosphorylation and stabilization in vitro and in vivo. However, a catalytically inactive mutant of SCP had no effect on Snail. Furthermore, we found that Snail stabilization induced by SCP enhanced snail activity in the suppression of E-cadherin and increased cell migration. Thus, our findings indicate that SCP functions as a Snail phosphatase to control its phosphorylation and stabilization, and our study provides novel insights for the regulation of Snail during EMT and cancer metastasis.
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PMID:Small C-terminal domain phosphatase enhances snail activity through dephosphorylation. 1900 23

The protein kinase-mediated actions of peptide growth factors such as IGF-1 and bFGF protect cultured neurons from being killed by the oxygen and glucose deprivations (OGD) that prevail in the 'stroked brain'. Here, we show that neuroprotection by IGF-1 is mediated by PI-3K/Akt, whereas that of bFGF is mediated by MAPK. IGF-1 and bFGF together did not further increase protection suggesting a downstream convergence of their pathways. Since protein kinases mediated the protection, a phosphatase inhibitor such as okadaic acid (OA) might be as protective as the growth factors against OGD. Here, we show that OA is actually a much more effective protector. It increased the phosphorylation of both PI-3K/Akt and MAPK, and stimulated new protein synthesis. OA also acted independently of the CREB activation and FKHRL1 and GSK-3 inactivation which have been implicated in IGF-1 actions.
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PMID:The phosphatase inhibitor, okadaic acid, strongly protects primary rat cortical neurons from lethal oxygen-glucose deprivation. 1902 14

Inhibitor of differentiation-1 (Id-1) has been accepted as a putative oncogene to promote oncogenic processes through inactivation of tumor suppressors and activation of growth promoting pathways. Here, we show that Id-1 activates the Akt pathway by inhibition of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) transcription through downregulation of p53. Id-1 negatively regulated both p53 and PTEN at the transcriptional level. In promoter assay with serial deletion and chromatin immunoprecipitation assay, the binding of p53 to the PTEN promoter was reduced by Id-1, suggesting that Id-1 regulates PTEN transcription through its p53 modulation. This led to Akt phosphorylation at Ser473 and the activation of the Akt-mediated canonical Wnt signaling pathway. The glycogen synthase kinase-3beta phosphorylation at Ser9, stabilization and nuclear localization of beta-catenin, T-cell factor (TCF)/lymphoid enhancer factor transactivation activity and cyclin D1 expression were enhanced by Id-1. On the other hand, Akt-mediated p27(Kip1) phosphorylation at Thr157 and its cytosolic localization were also increased in Id-1 overexpressing MCF7 cells. In conclusion, our results disclose Id-1 as a novel PTEN inhibitor that could activate the Akt pathway and its downstream effectors, the Wnt/TCF pathway and p27(Kip1) phosphorylation and suggest that the oncogenic function of Id-1 may be partly attributed to its PTEN inhibition in human breast carcinogenesis.
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PMID:Id-1 activates Akt-mediated Wnt signaling and p27(Kip1) phosphorylation through PTEN inhibition. 1907 42

Regulators of calcineurin (RCANs) in fungi and mammals have been shown to stimulate and inhibit calcineurin signaling in vivo through direct interactions with the catalytic subunit of the phosphatase. The dual effects of RCANs on calcineurin were examined by performing structure-function analyses on yeast Rcn1 and human RCAN1 (a.k.a. DSCR1, MCIP1, and calcipressin 1) proteins expressed at a variety of different levels in yeast. At high levels of expression, the inhibitory effects required a degenerate PxIxIT-like motif and a novel LxxP motif, which may be related to calcineurin-binding motifs in human NFAT proteins. The conserved glycogen synthase kinase 3 (GSK-3) phosphorylation site was not required for inhibition, suggesting that RCANs can simply compete with other substrates for docking onto calcineurin. In addition to these docking motifs, two other highly conserved motifs plus the GSK-3 phosphorylation site in RCANs, along with the E3 ubiquitin ligase SCF(Cdc4), were required for stimulation of calcineurin signaling in yeast. These findings suggest that RCANs may function primarily as chaperones for calcineurin biosynthesis or recycling, requiring binding, phosphorylation, ubiquitylation, and proteasomal degradation for their stimulatory effect. Finally, another highly divergent yeast RCAN, termed Rcn2 (YOR220w), was identified through a functional genetic screen. Rcn2 lacks all stimulatory motifs, though its expression was still strongly induced by calcineurin signaling through Crz1 and it competed with other endogenous substrates when overexpressed, similar to canonical RCANs. These findings suggest a primary role for canonical RCANs in facilitating calcineurin signaling, but canonical RCANs may secondarily inhibit calcineurin signaling by interfering with substrate interactions and enzymatic activity.
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PMID:Domain architecture of the regulators of calcineurin (RCANs) and identification of a divergent RCAN in yeast. 1927 87

NFAT transcription factors are highly phosphorylated proteins residing in the cytoplasm of resting cells. Upon dephosphorylation by the phosphatase calcineurin, NFAT proteins translocate to the nucleus, where they orchestrate developmental and activation programs in diverse cell types. NFAT is rephosphorylated and inactivated through the concerted action of at least 3 different kinases: CK1, GSK-3, and DYRK. The major docking sites for calcineurin and CK1 are strongly conserved throughout vertebrate evolution, and conversion of either the calcineurin docking site to a high-affinity version or the CK1 docking site to a low-affinity version results in generation of hyperactivable NFAT proteins that are still fully responsive to stimulation. In this study, we generated transgenic mice expressing hyperactivable versions of NFAT1 from the ROSA26 locus. We show that hyperactivable NFAT increases the expression of NFAT-dependent cytokines by differentiated T cells as expected, but exerts unexpected signal-dependent effects during T cell differentiation in the thymus, and is progressively deleterious for the development of B cells from hematopoietic stem cells. Moreover, progressively hyperactivable versions of NFAT1 are increasingly deleterious for embryonic development, particularly when normal embryos are also present in utero. Forced expression of hyperactivable NFAT1 in the developing embryo leads to mosaic expression in many tissues, and the hyperactivable proteins are barely tolerated in organs such as brain, and cardiac and skeletal muscle. Our results highlight the need for balanced Ca/NFAT signaling in hematopoietic stem cells and progenitor cells of the developing embryo, and emphasize the evolutionary importance of kinase and phosphatase docking sites in preventing inappropriate activation of NFAT.
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PMID:Requirement for balanced Ca/NFAT signaling in hematopoietic and embryonic development. 1935 96

Glycogen synthase kinase-3beta (GSK-3beta)-modulated IFN-gamma-induced inflammation has been reported; however, the mechanism that activates GSK-3beta and the effects of activation remain unclear. Inhibiting GSK-3beta decreased IFN-gamma-induced inflammation. IFN-gamma treatment rapidly activated GSK-3beta via neutral sphingomyelinase- and okadaic acid-sensitive phosphatase-regulated dephosphorylation at Ser(9), and proline-rich tyrosine kinase 2 (Pyk2)-regulated phosphorylation at Tyr(216). Pyk2 was activated through phosphatidylcholine-specific phospholipase C (PC-PLC)-, protein kinase C (PKC)-, and Src-regulated pathways. The activation of PC-PLC, Pyk2, and GSK-3beta was potentially regulated by IFN-gamma receptor 2-associated Jak2, but it was independent of IFN-gamma receptor 1. Furthermore, Jak2/PC-PLC/PKC/cytosolic phospholipase A(2) positively regulated neutral sphingomyelinase. Inhibiting GSK-3beta activated Src homology-2 domain-containing phosphatase 2 (SHP2), thereby preventing STAT1 activation in the late stage of IFN-gamma stimulation. All these results showed that activated GSK-3beta synergistically affected IFN-gamma-induced STAT1 activation by inhibiting SHP2.
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PMID:Glycogen synthase kinase-3beta facilitates IFN-gamma-induced STAT1 activation by regulating Src homology-2 domain-containing phosphatase 2. 1954 64

Through acute enteric infection, Salmonella invades host enterocytes and reproduces intracellularly into specialized vacuolae. This involves changes in host cell signaling elicited by bacterial proteins delivered via type III secretion systems (TTSS). One of the two TTSSs of Salmonella enterica serovar Typhimurium encoded by the Salmonella pathogenicity island-1, triggers bacterial internalization. Among the effector proteins translocated by this TTSS, the GTPase modulator SopE/E2 and the phosphoinositide phosphatase SigD are known to play key roles in these processes. To better understand their contribution to re-programming host cell pathways, we used ZeptoMARK reverse-phase protein array technology, which allows printing 32-sample lysate arrays that can be analyzed with phospho-specific antibodies to evaluate the phosphorylation of signaling proteins. Lysates were obtained at different times after infection of HeLa cells with WT, TTSS-deficient, sopE/E2 and sigD single and double deletants, as well as different sigD Salmonella mutants. Our analysis detected activation of p38, JNK and ERK mitogen-activated protein kinases, mainly dependent on SopE/E2, as well as SigD-dependent phosphorylation of PKB/Akt and its targets GSK-3beta and FKHR/FoxO. This is the first time that reverse-phase protein array technology is used in the cellular microbiology field, demonstrating its value to screen for host signaling events through bacterial infection.
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PMID:Addressing the effects of Salmonella internalization in host cell signaling on a reverse-phase protein array. 1960 73


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