Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously reported that reduction of autocrine IGF-I by polyinosinic-polycytidylic acid [poly(IC)] was permissive for the poly(IC)-mediated decrease in C6 rat glioma cell number. We now report that poly(IC) caused a block in G(1) to S transition in confluent C6 cultures, whereas in subconfluent cultures, poly(IC) decreased the percentage of cells in the G(2)/M phase. Addition of IGF-I to poly(IC)-treated cells decreased the percentage of cells in G(0)/G(1) phase and increased the percentage of cells in G(2)/M phase in confluent and subconfluent C6 cultures, indicating the reversal of cell cycle blocks. Inhibition of protein kinase R (PKR) activation partially prevented the poly(IC)-mediated cytostasis of C6 cells. Poly(IC) induced interferon-alpha in C6 cells. Both IGF-I and a blocking antibody against type I interferon (IFN) prevented the increase in PKR levels and the decrease in cell proliferation caused by poly(IC). We conclude that poly(IC) induces IFN, which mediates the cytostatic effect of poly(IC) on C6 cells at least in part through PKR. IGF-I prevents IFN from inducing PKR, thus explaining the ability of IGF-I to reverse the cell cycle blocks and the decreased C6 proliferation caused by poly(IC).
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PMID:Double-stranded ribonucleic acid decreases c6 rat glioma cell proliferation in part by activating protein kinase R and decreasing insulin-like growth factor I levels. 1202 Nov 78

FSH and IGF-I are both important determinants of testicular development and Sertoli cell function. The present studies were performed to determine the actions of FSH and IGF-I on PI3K/AKT protein kinase signaling in immature rat Sertoli cells. Primary cultures of rat Sertoli cells were prepared from 10-d-old rats. After 7 d in culture, Sertoli cells were treated with IGF-I, FSH, or IGF-I plus FSH. In some experiments cultures were treated with 8-bromo-cAMP (40 microM), (Bu)(2)cAMP (40 microM), or forskolin (10 microM). After treatments, cell lysates were prepared, and the activation state of AKT and cAMP response element-binding protein (CREB) was determined by Western blot analysis using phosphorylation site-specific antibodies. IGF-I had little effect on CREB phosphorylation, but rapidly increased the phosphorylation of AKT in a concentration-dependent manner. Maximal stimulatory effects of IGF-I were observed at 10-20 ng/ml. Treatment with FSH (0.9 IU/ml) or forskolin for 20 min increased CREB phosphorylation, but had little effect on AKT phosphorylation. However, FSH caused a concentration-dependent increase in IGF-I-induced AKT phosphorylation. Longer incubations (1-4 h) with FSH alone resulted in the elevation of AKT phosphorylation concomitant with an increased secretion of IGF-I and decreased production of IGF-binding protein-3, implicating endogenous IGF-I in the action of FSH on AKT phosphorylation. IGF-I- and FSH-dependent AKT phosphorylation was inhibited by LY29400 (10 microM), a PI3K inhibitor, and by IGF-binding protein 3, but not by a PKA inhibitor (H89). The present study demonstrates that immature rat Sertoli cells possess multiple protein kinase signaling cascades that are regulated by FSH. Furthermore, FSH amplifies IGF-I-mediated PI3K/AKT signaling in Sertoli cells. The results provide evidence for intracellular signaling mechanisms that may be required for the proliferation and differentiation of Sertoli cells.
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PMID:Follicle-stimulating hormone amplifies insulin-like growth factor I-mediated activation of AKT/protein kinase B signaling in immature rat Sertoli cells. 1202 Nov 90

The proliferation, apoptosis and protein kinase A (PKA) in porcine cumulus oophorus (CO) before and after 40 h of culture together with oocytes in the presence of IGF-I, IGF-II and EGF (all at 10 ng x mL(-1) medium) were compared. Cellular proliferation, apoptosis and PKA contents were evaluated by immunocytochemistry using specific antibodies against PCNA, TUNEL and catalytic (C-alpha) and regulatory (RI) subunits of PKA. The in-vitro culture of oocyte-CO complexes in a basal medium was accompanied by a decrease in the proportion of PCNA-positive CO cells (from 51 to 36%, p < 0.05). The addition of either IGF-I or EGF to the culture medium prevented this process and increased the proliferation rate (64 and 67% respectively, p < 0.001). During culture, the percentage of apoptotic (TUNEL-positive) CO cells increased from 42 to 57% (p < 0.01). The addition of IGF-I or EGF resulted in the inhibition of apoptosis to 36 and 12% respectively (p < 0.001). IGF-II and EGF reduced the amount of PKA catalytic subunits in the CO (percentage of cells with immunoreactive PKA catalytic subunits (28%, p < 0.05 and 27%, p < 0.05 respectively; versus control -41%), whilst the effect of IGF-I on this index was insignificant (31%). The expression of the PKA regulatory subunit was increased by EGF (51% compared with 29% in the control, p < 0.05), but not by IGF-I or IGF-II (30 and 29%). Our observations demonstrate that 40 h of culture of porcine CO resulted in a decrease in the proliferation and development of apoptosis in CO cells. IGF-I or EGF can stimulate proliferation and inhibit apoptosis. The influence of growth factors on the PKA content of the CO suggests that cAMP/PKA may be a mediator of the action of growth factors on these cells. The differential effects of IGFs and EGF on the regulatory subunit of PKA may indicate differences between their mechanisms of action.
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PMID:Effect of growth factors on proliferation, apoptosis and protein kinase A expression in cultured porcine cumulus oophorus cells. 1219 74

To begin to determine whether IGF-I treatment represents a potential means of enhancing the survival of islet cell grafts after transplantation, the present studies established a model of beta-cell death secondary to loss of trophic support and examined the ability of IGF-I to prevent cell death. The studies were performed using the rat pancreatic beta-cell line, INS-1. Incubating INS-1 cells in RPMI 1640 and 0.25% BSA for 48 h increased cell death, as determined by lactate dehydrogenase release, compared with that of cells maintained in RPMI and 10% fetal calf serum. Addition of 100 ng/ml IGF-I to the serum-free medium decreased lactate dehydrogenase release to a level comparable to that found in cells maintained in fetal calf serum. Similar results were seen using a mouse beta-cell line, MIN6, infected with an adenovirus expressing IGF-I. Examination of IGF-I-stimulated signaling demonstrated that IGF-I increased the phosphorylation of protein kinase B in both cell lines, whereas IGF-I-induced phosphorylation of the MAPKs, ERK1 and -2, was observed only in INS-1 cells. The effect of IGF-I on phosphorylation of substrates of phosphatidylinositol 3-kinase (PI 3-kinase) or protein kinase B was also examined in INS-1 cells. IGF-I increased the phosphorylation of glycogen synthase kinase 3beta, BAD, FKHR, and p70(S6) kinase. Another pathway that has been shown to mediate the protective of IGF-I in some cell types is activation of cAMP response element-binding protein (CREB). IGF-I increased CREB phosphorylation at a concentration as low as 10 ng/ml, and this effect was inhibited by H89, a PKA inhibitor, and PD98059, a MAPK kinase inhibitor. Consistent with the effect of IGF-I on CREB phosphorylation, IGF-I increased the transcriptional activity of CREB, although it had no effect on CREB binding to DNA. Use of inhibitors of the PI 3-kinase (LY 294002) or ERK (PD98059) pathways or CREB phosphorylation (H89) in the cell death assay demonstrated partial abrogation of the protective effect of IGF-I with LY 294002. These data demonstrate that IGF-I protects pancreatic beta-cells from cell death secondary to loss of trophic support and that, although IGF-I activates several signaling pathways that contribute to its protective effect in other cell types, only activation of PI 3-kinase contributes to this effect in beta-cells.
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PMID:Activation of phosphatidylinositol 3-kinase contributes to insulin-like growth factor I-mediated inhibition of pancreatic beta-cell death. 1223 91

To define the specific role of IGF-I receptor (IGF-IR) in adipogenic and thermogenic differentiation of brown adipocytes during late fetal life, we have established immortalized brown adipocyte cell lines from fetuses of IGF-IR-deficient mice (IGF-IR(-/-)) as well as from wild-type mice (IGF-IR(+/+)). IGF-IR(-/-) cells showed an increased insulin sensitivity regarding insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation despite a substantial reduction in IRS-1 protein content. Furthermore, insulin-induced total and IRS-1-associated phosphatidylinositol 3-kinase activities were augmented in IGF-IR-deficient cells compared with wild-type cells. Downstream phosphatidylinositol 3-kinase activation of Akt, but not p70s6 kinase, were elicited at lower doses of insulin in IGF-IR(-/-) brown adipocytes. Activation of protein kinase Czeta by insulin was similar in both cell types as was insulin-induced glucose uptake. Treatment of wild-type brown adipocytes with insulin for 12 h up-regulated fatty acid synthase (FAS) and adipocyte determination and differentiation (ADD1/SREBP) mRNAs; this effect was impaired in the absence of IGF-IR. At the protein level, insulin increased FAS content and the amount of the mature form of adipocyte determination and differentiation (ADD1/SREBP) in the nucleus in wild-type cells, but not in IGF-IR(-/-) cells. Furthermore, 24 h of insulin stimulation induced the expression of both uncoupling protein-1 and CCAAT/enhancer-binding protein alpha (C/EBPalpha) in wild-type brown adipocytes; these effects were abolished in IGF-I-R(-/-) cells. Retrovirus-mediated reexpression of peroxisomal proliferator-activated receptor gamma (PPARgamma) in IGF-IR(-/-) brown adipocytes could overcome FAS mRNA impairment, bypassing insulin signaling. However, insulin further increased FAS mRNA expression in C/EBPalpha-IGF-IR(-/-) cells, but not in PPARgamma-IGF-IR(-/-) cells. In addition, fetal brown adipocytes lacking IGF-IR up-regulated uncoupling protein-1 expression in the absence of insulin when PPARgamma, but not C/EBPalpha, was overexpressed. These data provide strong evidence for a critical role of IGF-IR in the differentiation of the brown adipocyte phenotype in fetal life; this effect is mimicked by PPARgamma in an insulin-independent manner.
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PMID:Essential role of insulin-like growth factor I receptor in insulin-induced fetal brown adipocyte differentiation. 1253 20

The abnormal accumulation of methylglyoxal (MG), a physiological glucose metabolite, is strongly related to the development of diabetic complications by affecting the metabolism and functions of organs and tissues. These disturbances could modify the cell response to hormones and growth factors, including insulin-like growth factor-1 (IGF-I). In this study, we investigated the effect of MG on IGF-I-induced cell proliferation and the mechanism of the effect in two cell lines, a human embryonic kidney cell line (HEK293), and a mouse fibroblast cell line (NIH3T3). MG rendered these cells resistant to the mitogenic action of IGF-I, and this was associated with stronger and prolonged activation of ERK and over-expression of P21(Waf1/Cip1). The synergistic effect of MG with IGF-I in activation of ERK was completely abolished by PD98059 but not by a specific PI3K inhibitor, LY294002, or a specific PKC inhibitor, bisindolylmaleimide. Blocking of Raf-1 activity by expression of a dominant negative form of Raf-1 did not reduce the enhancing effect of MG on IGF-I-induced activation of ERK. However, transfection of a catalytically inactive form of MEKK1 resulted in inactivation of the MG-induced activation of ERK and partial inhibition of the enhanced activation of ERK and over-expression of p21(Waf1/Cip1) induced by co-stimulation of MG and IGF-I. These results suggested that the alteration of intracellular milieu induced by MG through a MEKK1-mediated and PI3K/PKC/Raf-1-independent pathway resulted in the modification of cell response to IGF-I for p21(Waf1/Cip1)-mediated growth arrest, which may be one of the crucial mechanisms for MG to promote the development of chronic clinical complications in diabetes.
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PMID:Involvement of MEKK1/ERK/P21Waf1/Cip1 signal transduction pathway in inhibition of IGF-I-mediated cell growth response by methylglyoxal. 1264 5

Energy restriction (ER) results in a profound inhibition of chemically induced mammary carcinogenesis. The cancer inhibitory activity of ER has been shown to be associated with lower rates of cell proliferation during both premalignant and malignant stages of this disease process. Moreover, inhibition of carcinogenesis and suppression of cell proliferation occur in animals in which plasma concentrations of insulin-like growth factor (IGF)-I are reduced, and plasma corticosterone levels are increased concomitantly. Given the role of both hormones in signal transduction pathways that can modulate cell cycle progression, albeit via different regulatory mechanisms, we report experiments conducted to determine whether hypothesized effects of changes in plasma levels of IGF-I and corticosterone on cell cycle regulation could be detected in mammary carcinomas occurring in 40% ER rats in comparison to ad libitum fed control rats or 40% ER rats that were energy repleted for 7 days (ER-REP). As determined by appropriate combinations of immunoprecipitations, Western blots, and kinase activity assays, it was found that levels of phosphorylated retinoblastoma and E2F-1 were significantly reduced by ER (approximately 40 and 75%, respectively; P < 0.01), an effect that was partially reversed by ER-REP. Reductions in cyclin-dependent kinase (CDK)2 (82%) and CDK4 (77%) kinase activity in ER carcinomas were likely to account for the observed effects on retinoblastoma and E2F-1. Both Cip1/p21 and Kip1/p27 and levels of these proteins complexed with CDK2 were significantly elevated in ER carcinomas (P < 0.01), and levels of cyclin E were reduced. On the other hand, regulation of CDK4 kinase activity by ER was likely attributable to effects on cyclin D1 as well as increased binding of P16 and P19 to CDK4. The majority of changes induced by ER were reversed by ER-REP. These observations are consistent with the hypothesis that ER exerts its profound cancer inhibitory activity, in part, by multifaceted regulation of cell cycle machinery, possibly via concomitant changes in corticosterone and IGF-1 metabolism, although the role of other hormones and growth factors should not be dismissed.
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PMID:Effect of energy restriction on cell cycle machinery in 1-methyl-1-nitrosourea-induced mammary carcinomas in rats. 1264 81

In osteoblasts, hormones such as prostaglandin E2 that activate protein kinase A increase the translocation of transcription factor CCAAT/enhancer binding protein delta (C/EBPdelta) from the cytoplasm to the nucleus where it rapidly induces IGF-I gene expression. In this study, we identified activation and suppression domains in C/EBPdelta using native and heterologous gene promoter assay systems. We demonstrated functional interactions between C/EBPdelta and trans-gene-expressed cAMP response element binding protein-binding protein, and showed that the ability of C/EBPdelta to promote gene expression was suppressed by viral protein E1A, which blocks the activity of native cAMP response element binding protein-binding protein. Site-directed mutations at serines 62 or 191 within C/EBPdelta reduced its basal transcriptional activity, whereas mutation at serine 191 suppressed the stimulatory effect of prostaglandin E2 on C/EBPdelta function as well as its DNA binding potential. These results are consistent with the location of serine 191 in the DNA binding domain of C/EBPdelta. Our studies provide the first evidence for regions of C/EBPdelta that are important for basal and for hormone-induced transcriptional activity, and for its interactions with other enhancers and suppressers of gene expression.
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PMID:Activation domains of CCAAT enhancer binding protein delta: regions required for native activity and prostaglandin E2-dependent transactivation of insulin-like growth factor I gene expression in rat osteoblasts. 1279 69

Cross-linking of nonglycosylated biotinylated IGF binding protein (IGFBP)-3 to T-47D cell membranes identifies complexes with Mr of 32, 50, 70, and 100 kDa. Nonbiotinylated glycosylated IGFBP-3 competed for binding to each of these sites. The 32-kDa band approximated the size of intact nonglycosylated IGFBP-3, but its abundance was enhanced by cross-linking, and it had a more acidic isoelectric point on isoelectric focusing, suggesting that it had undergone phosphorylation. Immobilized IGFBP-3 was phosphorylated in the presence of (32)P-gamma ATP by both T-47D cell membranes and by intact cells treated with phenylarsine oxide to inhibit internalization. MCF-7 and COS-1 cells were also able to bind and phosphorylated IGFBP-3. IGF-I inhibited both IGFBP-3 binding to membranes and phosphorylation. However, incubation of T-47D cells with IGFBP-3 enhanced binding of (125)I-IGF-I to the cell monolayer indicating that membrane bound IGFBP-3 was able to bind IGF-I. Immobilized IGFBP-3 when phosphorylated by T-47D membranes bound significantly more (125)I-IGF-I than nonphosphorylated IGFBP-3. Treatment with alkaline phosphatase significantly reduced (125)I-IGF-I binding to phosphorylated immobilized IGFBP-3 and also reduced (125)I-IGF-I to T-47D cell monolayers preincubated with IGFBP-3. Phosphorylation of IGFBP-3 by T-47D membranes was partially blocked by inhibitors of both protein kinase A and C. These data demonstrate that binding of IGFBP-3 to breast cancer membranes is accompanied by phosphorylation at the plasma membrane and that both processes are inhibited by IGF-I. However, once phosphorylated the ability of IGFBP-3 to bind IGF-I is enhanced, resulting in increased association of the IGF-I with the cell membrane.
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PMID:Phosphorylation of insulin-like growth factor (IGF) binding protein-3 by breast cancer cell membranes enhances IGF-I binding. 1293 78

Src homology domain 2 (SH2)-containing inositol phosphatase 2 (SHIP2) possesses 5-phosphatase activity and an SH2 domain. The role of SHIP2 in platelet-derived growth factor (PDGF) and IGF-I signaling was studied by expressing wild-type (WT-) and a catalytically defective (Delta IP-) SHIP2 into rat aortic smooth muscle cells by adenovirus-mediated gene transfer. PDGF- and IGF-I-induced tyrosine phosphorylation of their respective receptors and phosphatidylinositol 3-kinase (PI3-kinase) activity were not affected by the expression of either WT- or Delta IP-SHIP2. SHIP2 possessed 5'-phosphatase activity to hydrolyze the PI3-kinase product phosphatidylinositol 3,4,5-trisphosphate in vivo. Akt and glycogen synthase kinase 3beta are known to be downstream molecules of PI3-kinase, leading to the antiapoptotic effect. Overexpression of WT-SHIP2 inhibited PDGF- and IGF-I-induced phosphorylation of these molecules and the protective effect of poly(ADP-ribose) polymerase degradation, whereas these phosphorylations and the protective effect were enhanced by the expression of Delta IP-SHIP2, which functions in a dominant negative fashion. Regarding the Ras-MAPK pathway, PDGF- and IGF-I-induced tyrosine phosphorylation of Shc was not affected by the expression of either WT- or Delta IP-SHIP2, whereas both expressed SHIP2 associated with Shc. Importantly, PDGF and IGF-I stimulation of Shc/Grb2 binding, MAPK activation, and 5-bromo-2'-deoxyuridine incorporation were all decreased in both WT- and Delta IP-SHIP2 expression. These results indicate that SHIP2 plays a negative regulatory role in PDGF and IGF-I signaling in vascular smooth muscle cells. As the bifunctional role, our results suggest that SHIP2 regulates PDGF- and IGF-I-mediated signaling downstream of PI3-kinase, leading to the antiapoptotic effect via 5-phosphatase activity, and that SHIP2 regulates the growth factor-induced Ras-MAPK pathway mainly via the SH2 domain.
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PMID:Dual role of SRC homology domain 2-containing inositol phosphatase 2 in the regulation of platelet-derived growth factor and insulin-like growth factor I signaling in rat vascular smooth muscle cells. 1293 96


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