Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.1.137 (phosphatidylinositol 3-kinase)
11,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Syp is a protein tyrosine phosphatase implicated in insulin and growth factor signaling. To evaluate the role of syp in insulin's regulation of plasma glucose, we generated knockout mice. Homozygous knockout mice die prior to day 10.5 of embryonic development. Hemizygous mice express half the levels of syp protein compared with their wild type littermates but do not display any gross morphological changes. Total body weight (age 2-10 weeks) and plasma insulin and glucose levels both in fasting and glucose-challenged states were comparable in the wild type and the hemizygous mice. No differences were observed in insulin-induced glucose uptake in soleus muscle and epididymal fat; insulin inhibition of lipolysis was also similar. We injected insulin into the portal vein of the mice to examine upstream events of the insulin signaling cascade. Tyrosine phosphorylation of insulin receptor and insulin receptor substrate-1 (IRS-1) from hemizygous tissue was similar to that of wild type tissue. Association of the p85 subunit of phosphatidylinositol 3-kinase to IRS-1 increased an average of 2-fold in both groups. We did not observe an increase of IRS-1/syp association after insulin administration, but we did note a significant basal association in both wild type and hemizygous tissue. Our results do not support a major role for syp in the acute in vivo metabolic actions of insulin.
...
PMID:Insulin signaling in mice expressing reduced levels of Syp. 870 15

The families of tyrosine and serine/threonine kinases exhibit shared clusters of conserved amino acid residues. Some conserved residues are confined to the family of tyrosine kinases (TKs), like Tyr at position 1210 in the insulin receptor. Nearly all TKs have at this position Tyr, whereas Ser/Thr kinases generally have Phe at this site. The three-dimensional structure of the insulin receptor TK domain shows Tyr1210 to be located in the cleft, below bound ATP, in a region which potentially contributes to substrate binding. We have examined whether this specific Tyr residue contributes to the generation of TK-specific responses, such as Tyr phosphorylation of Shc, activation of Ras and Erk1,2, and stimulation of DNA synthesis. In addition, we have examined the contribution of Tyr1210 to insulin receptor-specific responses as Tyr phosphorylation of IRS1, stimulation of glycogen synthesis, and dephosphorylation of focal adhesion kinase (FAK). Wild-type and a mutant insulin receptor, in which Tyr1210 was replaced by Phe, were stably expressed in CHO cells, and clones expressing similar numbers of insulin receptors were selected. It was found that replacement of Tyr1210 by Phe resulted in a receptor which was nearly inactive in inducing dephosphorylation of FAK. The mutant receptor was able to induce RasGTP formation, glycogen synthesis, and activation of phosphatidylinositol 3-kinase, though the magnitude of stimulation of some responses was decreased. These findings indicate that Tyr1210 is not essential for the induction of tyrosine kinase-specific responses, such as activation of the Shc/Ras/Erk1,2 pathway and mitogenicity. On the other hand, the abrogation of insulin-induced FAK dephosphorylation indicates that Tyr1210 is involved in coupling of the activated receptor to some downstream targets. Thus, Tyr1210 may fine tune the signal generated by the activated insulin receptor.
...
PMID:Replacement of the conserved tyrosine 1210 by phenylalanine in the insulin receptor affects insulin-induced dephosphorylation of focal adhesion kinase but leaves other responses intact. 875 93

Tyrosine phosphorylation of cellular proteins is an early and key step after activation of the insulin receptor kinase (IRK). The study of the properties of these proteins should contribute to our understanding of insulin action. In rat hepatoma cells overexpressing human insulin receptors (HTC-IR), insulin treatment resulted in rapid tyrosine phosphorylation of proteins of 180, 94, 68, and 60 kDa. When lysates from insulin-treated cells were immunoprecipitated with anti-Syp antibody, subsequent immunoblotting identified p65 and p68, which reacted with anti-Syp, and p6O and p68, which reacted with antiphosphotyrosine antibody. Thus, insulin treatment yielded tyrosine phosphorylation of both Syp and a Syp-associated p6O molecule. When lysates from insulin-treated cells were adsorbed with a glutathione S-transferase (GST)-Syp-Src homology-2 (SH2) fusion protein, tyrosine- phosphorylated p6O was sequestered. After subjecting lysates to SDS-PAGE, the GST-SypSH2 fusion protein was found to bind to p18O, p94, and p6O. Thus, Syp associates directly with a 60-kDa IRK substrate via its SH2 domains. Syp-associated p6O differed from the 60- to 62-kDa proteins, associating with ras guanosine triphosphatase-activating protein, which also underwent modest tyrosine phosphorylation in response to insulin. Preadsorption of cell lystates with antibody against the 85-kDa subunit (p85) of phosphatidylinositol 3-kinase substantially reduced the amount of p60 subsequently immunoprecipitated by anti-Syp. Thus, p60 associates with both Syp and p85. The amount of tyrosine-phosphorylated p60 exceeded that of p180 in anti-Syp immunoprecipitates, whereas their proportion was comparable in anti-p85 immunoprecipitates. Grb2 was also observed in the anti-Syp immunoprecipitates. When lysates from insulin-treated cells were adsorbed with GST-p85SH2 domains or GST-Grb2, the subsequent eluates contained tyrosine-phosphorylated p60, as determined by immunoblotting with antiphosphotyrosine. Membrane binding assays using GST fusion proteins showed that these associations were direct. Studies in rat liver, muscle, and adipose tissue identified insulin-dependent association of Syp, Grb2, and p85 with tyrosine-phosphorylated p60 in adipose tissue only. We conclude that insulin treatment of HTC-IR cells and rat adipose tissue results in the tyrosine phosphorylation of p60, which might participate in the recruitment of downstream effectors involved in insulin signal transduction.
...
PMID:A 60-kilodalton protein in rat hepatoma cells overexpressing insulin receptor was tyrosine phosphorylated and associated with Syp, phophatidylinositol 3-kinase, and Grb2 in an insulin-dependent manner. 877 Aug 81

Rad is a Ras-like GTPase that was isolated by subtraction cloning of human muscle and shown to have increased expression in some individuals with Type II diabetes. To ascertain the potential role of Rad in insulin-mediated signaling, we have overexpressed Rad in myocyte and adipocyte cell lines. Expression of Rad resulted in a 50-90% reduction in insulin-stimulated 2-deoxyglucose glucose uptake in C2C12 murine myotubes, L6 rat myotubes, and 3T3-L1 adipocytes and a 25% reduction in 3-O-methylglucose uptake in 3T3-L1 adipocytes. This occurred despite unaltered levels of glucose transporter expression, with no detectable change in Glut4 translocation and with no alteration in insulin receptor or substrate phosphorylation or phosphatidylinositol 3-kinase activity. These data indicate that Rad is a negative regulator of glucose uptake and that this effect may be due to a decrease in the intrinsic activity of the transporter molecules, rather than an effect on the translocation of Glut4.
...
PMID:Overexpression of Rad inhibits glucose uptake in cultured muscle and fat cells. 879 2

Interaction domains located in the NH2 terminus of IRS-1 mediate its recognition by the insulin receptor. Alignment of IRS-1 and IRS-2 reveals two homology regions: the IH1(PH) contains a pleckstrin homology (PH) domain, and the IH2(PTB) contains a phosphotyrosine binding (PTB) domain. A third region in IRS-1 called SAIN was proposed to contain another functional PTB domain. Peptide competition experiments demonstrated that the IH2(PTB) in IRS-2, like the corresponding domain in IRS-1, binds directly to peptides containing NPXY motifs. In contrast, these peptides do not bind to IH1(PH) or the SAIN regions. In 32D cells the IH1(PH) was essential for insulin-stimulated tyrosine phosphorylation of IRS-1 and insulin-stimulated phosphatidylinositol 3-kinase activity and p70(s6k) phosphorylation. In contrast, the IH2(PTB) and the SAIN regions were not required for these insulin actions; however, the IH2(PTB) improved the coupling between IRS-1 and the insulin receptor. Overexpression of the insulin receptor in 32DIR cells increased IRS-1 tyrosine phosphorylation and mediated insulin-stimulated DNA synthesis. The sensitivity of these responses was partially reduced by deletion of either the IH1(PH) or the IH2(PTB) and significantly reduced when both regions were deleted together. Thus, the PH and PTB domains equally couple IRS-1 to high levels of insulin receptor normally expressed in most cells, whereas at low levels of insulin receptors the PTB domain is inefficient and the PH domain is essential for a productive interaction.
...
PMID:The pleckstrin homology domain is the principal link between the insulin receptor and IRS-1. 879 77

The growth-promoting effects of gastrin on normal and neoplastic gastrointestinal tissues have been shown to be mediated by the gastrin/CCKB receptor, which belongs to the family of G protein-coupled receptors. However, the downstream signaling pathways activated by gastrin are not well characterized. In the present study, we demonstrate that gastrin stimulates tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1), the major cytoplasmic substrate of the insulin receptor. The gastrin-induced phosphorylation of IRS-1 was rapid and transient, occurring within 30 s of treatment and diminishing thereafter. IRS-1 binds several proteins containing Src homology 2 domains through its multiple tyrosine phosphorylation sites. Following gastrin stimulation, we observed a time- and dose-dependent association of IRS-1 with the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI 3-kinase). In addition, activation of PI 3-kinase was detected in anti-IRS-1 immunoprecipitates from gastrin-treated cells, suggesting that tyrosine phosphorylation of IRS-1, which leads to the rapid recruitment of p85, might be one mechanism used by gastrin to activate PI 3-kinase. We have previously reported that tyrosine phosphorylation of Shc and its association with the Grb2-Sos complex may contribute to the activation of the mitogen-activated protein kinase pathway by gastrin. We report here that Grb2 also interacts with tyrosine-phosphorylated IRS-1 in response to gastrin. Taken together, our results suggest that IRS-1 may serve as a converging target in the signaling pathways stimulated by receptors that belong to different families, such as the gastrin/CCKB G protein-coupled receptor and the insulin receptor.
...
PMID:Gastrin stimulates tyrosine phosphorylation of insulin receptor substrate 1 and its association with Grb2 and the phosphatidylinositol 3-kinase. 882 90

Pervanadate mimics several distinct insulin effects, including stimulation of hexose uptake in the in vitro system, and reduces the blood glucose level in streptozotocin-treated diabetic rats. It has been proposed that pervanadate induces insulin-like effects mediated through autophosphorylation and activation of insulin receptor (IR) even in the absence of insulin by inhibiting protein tyrosine phosphatases. This study focused on the mechanism of pervanadate action on hexose uptake. Both insulin (100 nM) and pervanadate (100 microM), a protein tyrosine phosphatase inhibitor, induced a marked increase in the phosphorylation at tyrosine residues of IR and insulin receptor substrate 1 (IRS-1) and in 2-deoxyglucose uptake in 3T3-L1 adipocytes. Wortmannin (1 microM), a specific phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, inhibited the increased 2-deoxyglucose uptake by insulin completely but that by pervanadate only partially. On the other hand, both insulin- and pervanadate-stimulated PI 3-kinase activities were inhibited completely by wortmannin (100 nM), suggesting that the pervanadate-induced wortmannin-resistant effect on hexose uptake may be mediated through a PI 3-kinase-independent pathway. This pervanadate-induced wortmannin-resistant effect was abolished by ST-638, a specific tyrosine kinase inhibitor. These data suggest that at least two distinct tyrosine phosphorylation pathways may be involved in the insulin-like effect of pervanadate.
...
PMID:Pervanadate stimulation of wortmannin-sensitive and -resistant 2-deoxyglucose transport in adipocytes. 886 28

Recent data suggest involvement of the Janus tyrosine kinase-2 (JAK2) in human GH-induced tyrosine phosphorylation of the GH receptor and the insulin receptor substrates 1 and 2 (IRS-1 and IRS-2), leading to activation of the phosphatidylinositol 3-kinase and the acute insulin-like effects in primary rat adipocytes. To investigate the functional role of this kinase, we screened a number of tyrosine kinase inhibitors for their ability to inhibit three rapid effects of GH on primary adipocytes: increased lipogenesis, inhibition of noradrenaline-induced lipolysis, and promotion of JAK2 tyrosine phosphorylation. Only staurosporine was found to inhibit all three effects. The inhibition of lipogenesis and antilipolysis exhibited the same staurosporine dose dependency (IC50, approximately 40 nM) as inhibition of JAK2 and IRS-1 tyrosine phosphorylation as well as binding of the p85 subunit of phosphatidylinositol 3-kinase to IRS-1 and IRS-2. The unidentified cytosolic tyrosine-phosphorylated protein pp95, in contrast, was not affected, suggesting that it is not phosphorylated primarily by JAK2. Protein kinase C does not seem to be directly involved in the insulin-like effects, because the selective protein kinase C inhibitor calphostin C had no effect at levels up to 100 nM above which unspecific cellular effects occurred. Methyl-2,5-dihydroxy cinnamate inhibited GH-induced lipogenesis from [3-3H]glucose and nonstimulated lipogenesis from [2-14C]-pyruvate and [3H]acetate, but was without effect on GH-induced 2-deoxy-D-[1-3H]glucose uptake, JAK2 phosphorylation and antilipolysis, suggesting unspecific effects on mitochondrial metabolism rather than a direct effect on the GH-mediated signal. Tyrphostin 25 and herbimycin A had no effect on any of the parameters studied, except for a slight increase in JAK2 phosphorylation in response to tyrphostin 25. In summary, these data support the role for JAK2 in mediating the insulin-like effects of GH in adipocytes.
...
PMID:Effects of tyrosine kinase inhibitors on tyrosine phosphorylations and the insulin-like effects in response to human growth hormone in isolated rat adipocytes. 889 29

Rat-1 fibroblasts overexpressing the human insulin receptor undergo rapid actin rearrangement in response to insulin. Breakdown of stress fibers present in quiescent cells is followed by transient membrane ruffling and a return of stress fibers. We investigated the signaling pathways that mediate this insulin-stimulated reorganization of the actin cytoskeleton, which was visualized with rhodamine-phalloidin. Treatment of cells with the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor wortmannin prevented insulin action at the preliminary step of stress fiber breakdown. Cellular microinjection of a polyclonal antibody directed against the p85 subunit of PI3-kinase as well as a purified recombinant p85-SH2 domain protein also inhibited actin reorganization. Transient expression of a constitutively active form of PI3-kinase (p110*) was sufficient to cause both stress fiber breakdown and membrane ruffling in the absence of insulin. Microinjection of a polyclonal anti-Shc antibody or dominant negative N17-Ras protein did not affect actin dynamics, and although constitutively active V12-Ras caused modest cytoskeletal reorganization, this effect was blocked by pretreatment with wortmannin. In summary, activation of PI3-kinase is necessary and sufficient to stimulate actin rearrangement, indicating that PI3-kinase may initiate the only signaling cascade required for insulin to induce cytoskeletal restructuring.
...
PMID:Phosphatidylinositol 3-kinase is necessary and sufficient for insulin-stimulated stress fiber breakdown. 889 79

Angiotensin II (AII), acting via its G-protein linked receptor, is an important regulator of cardiac, vascular, and renal function. Following injection of AII into rats, we find that there is also a rapid tyrosine phosphorylation of the major insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) in the heart. This phenomenon appears to involve JAK2 tyrosine kinase, which associates with the AT1 receptor and IRS-1/IRS-2 after AII stimulation. AII-induced phosphorylation leads to binding of phosphatidylinositol 3-kinase (PI 3-kinase) to IRS-1 and IRS-2; however, in contrast to other ligands, AII injection results in an acute inhibition of both basal and insulin-stimulated PI 3-kinase activity. The latter occurs without any reduction in insulin receptor or IRS phosphorylation or in the interaction of the p85 and p110 subunits of PI 3-kinase with each other or with IRS-1/IRS-2. These effects of AII are inhibited by AT1 receptor antagonists. Thus, there is direct cross-talk between insulin and AII signaling pathways at the level of both tyrosine phosphorylation and PI 3-kinase activation. These interactions may play an important role in the association of insulin resistance, hypertension, and cardiovascular disease.
...
PMID:Cross-talk between the insulin and angiotensin signaling systems. 890 9


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---