Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

H19-7/IGF-IR cells are rat hippocampal cells expressing a human IGF-I receptor, which differentiate to a neuronal phenotype when stimulated by IGF-I at 39 degrees C. H19-7/IGF-IR cells have low levels of expression of insulin receptor substrate-l (IRS-1), a major substrate of the IGF-IR. IGF-I induces serine-phosphorylation and down-regulation of the endogenous IRS-1 upon differentiation of H19-7/IGF-IR cells. The profound influence of IRS-1 on differentiation of H19-7/IGF-IR cells was confirmed by transfecting these cells with a plasmid expressing mouse IRS-1. Over-expression of wild type IRS-1 in H19-7/IGF-IR cells abolishes IGF-I-induced differentiation at 39 degrees C. A mutant of IRS-1 lacking the PTB domain loses the ability to inhibit the differentiation program. H19-7/IGF-IR/IRS-1 cells at 39 degrees C show a stronger and prolonged activation of Akt, when compared to H19-7/IGF-IR cells. The role of Akt in the inhibition of the differentiation program was confirmed by using the inhibitor of Class I PI3 kinases LY29400, which restores IGF-I-induced differentiation of H19-7/IGF-IR/IRS-1 cells. H19-7/IGF-IR/IRS-1 cells show a strong reduction in MAP kinases signaling, which is related to the superactivation of Akt. This was confirmed by expressing in H19-7/IGF-IR cells a constitutively active Akt, which inhibited MAP kinases activation in these cells. These experiments confirm the importance of MAPK in the mechanism of IGF-I-mediated differentiation of H19-7/IGF-IR cells
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PMID:The role of the insulin receptor substrate-1 in the differentiation of rat hippocampal neuronal cells. 1152 Nov 95

Alterations in the degree of the phosphorylation of ERKI/2, Akt-1 and p70 S6K in mouse skeletal and cardiac muscle was examined in vivo following an intraperitoneal injection of des IGF-I. Plasma levels of insulin, IGF-I and glucose were measured. The administration of des IGF-I had no effect on plasma levels of insulin, or IGF-I, but plasma glucose levels were decreased about 50% (p < 0.01). In both skeletal and cardiac muscle, des IGF-I increased the phosphorylation of Akt-1 at Ser 473 (p < 0.01) with no change in the phosphorylation of p44 and p42 MAP kinases at Thr202/Tyr204. The phosphorylation of p70 S6K at Thr421/Ser424 was increased in skeletal muscle (p < 0.01), but not in cardiac muscle. The phosphorylation of the nuclear transcription factor CREB phosphorylation at Ser 133 was not significantly changed in either skeletal or cardiac muscle. Des IGF-I increased the phosphorylation of the transcription factor FKHR in cardiac muscle only (p < 0.05). These data demonstrate that the administration of des IGF-I had differential effects on the activation of the MAP kinase and PI 3-kinase pathways in mouse skeletal and cardiac muscle.
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PMID:Differential effects of des IGF-1 on Erks, AKT-1 and P70 S6K activation in mouse skeletal and cardiac muscle. 1219 Jan 9

The insulin-like growth factor (IGF) axis is a complex system composed of 2 mitogenic ligands, IGF-I and -II, 2 receptors, IGF-1R and IGF-2R, and 6 binding proteins, IGFBP-1 to -6. The IGFBPs exert their actions through their regulation of IGF bioavailability for IGF receptors. In addition, some IGFBPs have also been found to have direct cellular actions independent of IGFs. IGFBP-2 is a major IGFBP in the prostate and in seminal fluid. IGFBP-2 levels, which are elevated in many malignancies, are markedly increased in prostate cancer, and show a positive correlation with prostate specific antigen (PSA) and prostate tumor aggressiveness. We investigated the potential role of IGFBP-2 in the pathogenesis of prostate cancer by evaluating its ability to stimulate growth and the expression and activity of the nuclear enzyme, telomerase. We found IGFBP-2 to have a modest suppressive effect on the growth of primary cultures of normal prostate epithelial cells and a potent IGF-antagonistic effect in these cells, similar to previous reports on the inhibitory nature of this molecule. Surprisingly, IGFBP-2 had a potent stimulatory effect on growth of LAPC-4 prostate cancer cells, an effect that was more pronounced in the absence of androgens. IGFBP-2 growth stimulation of LAPC-4 cells was completely blocked by MAP-kinase inhibitors and partially blocked by PI3-kinase inhibitors. IGFBP-2 stimulation of LAPC-4 cell growth seen in serum-free conditions was lost in the presence of 10% FBS. IGFBP-2 also had a growth stimulatory effect on DU 145 prostate cancer cells. IGFBP-2 significantly stimulated telomerase activity in LAPC-4 cells in the absence of androgens. In addition, IGFBP-2 significantly stimulated hTERT expression and telomerase activity in DU 145 cells. Thus, we demonstrated an inhibitory effect of IGFBP-2 on non-malignant prostate cells, but showed it to be stimulatory for prostate cancer cells in a MAP-kinase and androgen-modulated process. In conclusion, IGFBP-2 may play a role in the progression, but not in the initiation of the prostate cancer disease process, suggesting the existence of a molecular switch transitioning IGFBP-2 from a growth inhibitor to a pro-carcinogenic molecule.
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PMID:Novel stimulatory role for insulin-like growth factor binding protein-2 in prostate cancer cells. 1267 24

Dehydroepiandrosterone (DHEA) is synthesized in the brain, but whether DHEA is involved in modulating neuronal cell survival is not yet fully understood. Herein we show that when deprived of trophic support, GT1-7 hypothalamic neurons undergo apoptosis following exposure to DHEA, as demonstrated both by morphological and biochemical criteria. This proapoptotic effect appeared to be specific to DHEA itself, and not through conversion of DHEA to other steroids such as androgen or estrogen. Importantly, we determined that IGF-I protects GT1-7 neurons from DHEA-induced cell death. DHEA-induced apoptosis was associated with increased activation of caspase 3 and decreased PARP, which were both attenuated with addition of IGF-I. Addition of DHEA prevented phosphorylation of both Akt and glycogen synthase kinase-3 beta (GSK-3beta), downstream effector molecules of the phosphatidylinositol 3-kinase (PI3K) pathway. Further IGF-I was able to sustain Akt activity and thus preventing GSK-3beta activation in the presence of DHEA. On the other hand, the MAP kinases, ERK, p38, and JNK, were not affected by DHEA. These findings suggest that in GT1-7 hypothalamic neurons, DHEA acts detrimentally to induce cell death and IGF-I is able to rescue the neurons by preserving the activity of Akt, and therefore maintaining the proapoptotic kinase GSK-3beta, in a phosphorylated catalytically inactive state.
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PMID:IGF-I signaling prevents dehydroepiandrosterone (DHEA)-induced apoptosis in hypothalamic neurons. 1506 51

The neoplastic production of the insulin-like growth factor binding protein (IGFBP)-2 often correlates with tumor malignancy and aggressiveness. Since IGFBP-2 contains an RGD motif in its C-terminus, it was hypothesized that this protein may act independently of IGF on tumor cells through integrins. To investigate this, integrin binding, intracellular signaling and the impact of IGFBP-2 on cell adhesion and proliferation were examined in two tumor cell lines. In tracer displacement studies, up to 30% of the added (125)I-hIGFBP-2 specifically bound to the cells. Bound (125)I-hIGFBP-2 was reversibly displaced by IGFBP-2, IGFBP-1 and RGD-(Gly-Arg-Asp)-containing peptides, but not by IGFBP-3, -4, -5, -6 and RGE-(Gly-Arg-Glu)-containing peptides. Blocking with antibodies directed against different integrins and with fibronectin demonstrated that IGFBP-2 cell surface binding is specific for alpha5beta1-integrin. Incubation of IGFBP-2 with equimolar quantities of IGF-I and IGF-II annihilated RGD-specific binding. IGFBP-2 binding at the cell surface led to dephosphorylation of the focal adhesion-kinase (FAK) of up to 37% (P<0.01), and of the p42/44 MAP-kinases of up to 40% (P<0.01). In addition, IGFBP-2 promoted de-adhesion of the cells dose-dependently by up to 30% (P<0.05), and reduced proliferation by 24% (P<0.01). Since one of the cell lines used does not express a functional IGF-I receptor, these data demonstrate that IGFBP-2 can act in an IGF-independent manner, at least in part by an interaction with alpha5beta1-integrin.
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PMID:Integrin-mediated action of insulin-like growth factor binding protein-2 in tumor cells. 1517 17

In previous studies we demonstrated that IGF-I induces proliferation of pituitary lactotrophs. In addition to its mitotrophic actions, IGF-I is known to prevent apoptosis induced by diverse stimuli in several cell types. In this study, we investigated the action of IGF-I on pituitary cell survival and the intracellular signaling transduction pathway implicated in this effect. Treatment of cultured male rat pituitary cells with IGF-I (10(-7) M) for 24 h prevented pituitary cell death induced by serum deprivation. The protective effect of IGF-I was blocked by phosphoinositide 3-kinase (PI3-kinase) inhibitor, LY294002, but was unaffected by PD98059, which inhibits MAP/ERK kinase (MEK1). IGF-I activation of PI3-kinase induced the phosphorylation and activation of the serine/threonine kinase Akt. Moreover, IGF-I increased the phosphorylation of the pro-apoptotic factor Bad and the levels of the anti-apoptotic protein Bcl-2 through the PI3-kinase pathway in primary pituitary cells.
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PMID:IGF-I inhibits apoptosis through the activation of the phosphatidylinositol 3-kinase/Akt pathway in pituitary cells. 1529 50

Under usual conditions, the role of IGF-I in vascular cell types is to maintain cellular protein synthesis and cell size, and even excess IGF-I does not stimulate proliferation. In pathophysiologic states, such as hyperglycemia, smooth muscle cells (SMC) dedifferentiate and change their responsiveness to IGF-I. During hyperglycemia IGF-I stimulates both SMC migration and proliferation. Our laboratory has investigated the molecular mechanism by which this change is mediated. During hyperglycemia SMC secrete increased concentrations of thrombospondin, vitronectin and osteopontin, ligands for the integrin alphaVbeta3. Activation of alphaVbeta3 stimulates recruitment of a tyrosine phosphatase, SHP-2. Exposure of SMC to IGF-I results in phosphorylation of the transmembrane protein, SHPS-1, which provides a docking site for alphaVbeta3-associated SHP-2. After IGF-I stimulation SHP-2 associates with Src kinase, which associates with the signaling protein Shc. Src phosphorylates Shc, resulting in activation of MAP kinases, which are necessary both for stimulation of cell proliferation and migration. Blocking activation of alphaVbeta3 results in an inability of IGF-I to stimulate Shc phosphorylation. Under conditions of normoglycemia, there are insufficient alphaVbeta3 ligands to recruit SHP-2, and no increase in Shc phosphorylation can be demonstrated in SMC. In contrast, if alphaVbeta3 ligands are added to cells in normal glucose, the signaling events that are necessary for Shc phosphorylation can be reconstituted. Therefore when SMC are exposed to normal glucose they are protected from excessive stimulation of mitogenesis by IGF-I. With hyperglycemia there is a marked increased in alphaVbeta3 ligands and Shc phosphorylation in response to IGF-I is sustained. These findings indicate that in SMC hyperglycemic stress leads to altered IGF-I signaling, which allows the cells to undergo a mitogenic response, and which may contribute to the development of atherosclerosis.
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PMID:Role of the integrin alphaVbeta3 in mediating increased smooth muscle cell responsiveness to IGF-I in response to hyperglycemic stress. 1741 27

Four novel dinuclear platinum(II) complexes of formula [Pt2L4(berenil)2]Cl4 (Pt1-Pt4) where L is piperazine (Pt1), 4-picoline (Pt2), 3-picoline (Pt3) or isopropylamine (Pt4) were compared to cisplatin in respect to collagen biosynthesis, beta1- integrin receptor, IGF-I receptor, phosphorylated MAP-kinases (ERK1/ERK2 and p38), phosphorylated Akt kinase expression and appearance of apoptosis in MCF-7 breast cancer cells. It was found that Pt1-Pt4 were more active inhibitor of collagen biosynthesis than cisplatin. The expression of IGF-I and beta1 integrin receptor, as well as phosphorylated MAPK, (ERK1 and ERK2 and p38) was significantly increased in cells incubated for 24 h with 20 muM Pt1-Pt4 compared to the control, not treated cells. The phenomenon was related to the increase expresion of NFkappaB by Pt1-Pt4 as shown by Western immunoblot analysis. Experiments made with annexin V-FITC and detection of apoptosis by a fluorescent microscopy assay revealed that novel dinuclear platinum(II) complexes (Pt1-Pt4) inhibited the proliferation of MCF-7 breast cancer cells by increasing the number of apoptotic and necrotic cells.
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PMID:Novel dinuclear platinum(II) complexes targets NFkappaB signaling pathway to induce apoptosis and inhibit metabolism of MCF-7 breast cancer cells. 2006 86

By promoting cell proliferation, survival and maturation insulin-like growth factor (IGF)-I is essential to the normal growth and development of the central nervous system. It is clear that IGF-I actions are primarily mediated by the type I IGF receptor (IGF1R), and that phosphoinositide 3 (PI3)-Akt kinases and MAP kinases signal many of IGF-I-IGF1R actions in neural cells, including oligodendrocyte lineage cells. The precise downstream targets of these signaling pathways, however, remain to be defined. We studied oligodendroglial cells to determine whether beta-catenin, a molecule that is a downstream target of glycogen synthase kinase-3beta (GSK3beta) and plays a key role in the Wnt canonical signaling pathway, mediates IGF-I actions. We found that IGF-I increases beta-catenin protein abundance within an hour after IGF-I-induced phosphorylation of Akt and GSK3beta. Inhibiting the PI3-Akt pathway suppressed IGF-I-induced increases in beta-catenin and cyclin D1 mRNA, while suppression of GSK3beta activity simulated IGF-I actions. Knocking-down beta-catenin mRNA by RNA interference suppressed IGF-I-stimulated increases in the abundance of cyclin D1 mRNA, cell proliferation, and cell survival. Our data suggest that beta-catenin is an important downstream molecule in the PI3-Akt-GSK3beta pathway, and as such it mediates IGF-I upregulation of cyclin D1 mRNA and promotion of cell proliferation and survival in oligodendroglial cells.
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PMID:beta-catenin mediates insulin-like growth factor-I actions to promote cyclin D1 mRNA expression, cell proliferation and survival in oligodendroglial cultures. 2023 20

IGF-I is structurally related to proinsulin and when administered to human subjects it enhances insulin sensitivity. However because of its growth promoting properties and its relationship to growth hormone, it has been proposed as a etiologic factor in the development of diabetic complications. This review discusses recently published data regarding the ability of hyperglycemia to sensitize cells that are capable of dedifferentiating to the growth promoting effects of IGF-I. Under normoglycemic conditions vascular smooth muscle and endothelial cells are cystostatic and stimulation of the IGF-I receptor activates the adaptor protein IRS-1 which leads to PI-3 kinase pathway activation. Following exposure to hyperglycemia these cell types undergo a signaling switch whereby an entirely different mechanism is utilized to activate both the PI-3 kinase and the MAP pathways. This leads to increased cell proliferation and migration. This molecular mechanism involves the coordinate regulation of signaling molecules and scaffolding proteins. Activation of this alternative signaling mechanism is directly linked to the stimulation of pathophysiologic processes that are involved in the pathogenesis of both diabetic retinopathy and atherosclerosis. Inhibition of activation of these intermediates has been shown to attenuate glucose induced pathophysiologic changes and results in the inhibition of both atherosclerotic lesion progression and diabetic retinopathy. In summary, hyperglycemia induces a signaling switch in vascular endothelial and smooth muscle cells that results in enhanced sensitivity to the growth promoting effects of IGF-I. This may be an important variable for determining the progression of atherosclerosis in poorly controlled diabetes and in the development of retinopathy.
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PMID:Igf-I signaling in response to hyperglycemia and the development of diabetic complications. 2170 34


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