Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rapamycin is a macrolide antifungal agent that exhibits potent immunosuppressive properties. In Saccharomyces cerevisiae, rapamycin sensitivity is mediated by a specific cytoplasmic receptor which is a homolog of human FKBP12 (hFKBP12). Deletion of the gene for yeast FKBP12 (RBP1) results in recessive drug resistance, and expression of hFKBP12 restores rapamycin sensitivity. These data support the idea that FKBP12 and rapamycin form a toxic complex that corrupts the function of other cellular proteins. To identify such proteins, we isolated dominant rapamycin-resistant mutants both in wild-type haploid and diploid cells and in haploid rbp1::URA3 cells engineered to express hFKBP12. Genetic analysis indicated that the dominant mutations are nonallelic to mutations in RBP1 and define two genes, designated DRR1 and DRR2 (for dominant rapamycin resistance). Mutant copies of DRR1 and DRR2 were cloned from genomic YCp50 libraries by their ability to confer drug resistance in wild-type cells. DNA sequence analysis of a mutant drr1 allele revealed a long open reading frame predicting a novel 2470-amino-acid protein with several motifs suggesting an involvement in intracellular signal transduction, including a leucine zipper near the N terminus, two putative DNA-binding sequences, and a domain that exhibits significant sequence similarity to the 110-kDa catalytic subunit of both yeast (VPS34) and bovine phosphatidylinositol 3-kinases. Genomic disruption of DRR1 in a mutant haploid strain restored drug sensitivity and demonstrated that the gene encodes a nonessential function. DNA sequence comparison of seven independent drr1dom alleles identified single base pair substitutions in the same codon within the phosphatidylinositol 3-kinase domain, resulting in a change of Ser-1972 to Arg or Asn. We conclude either that DRR1 (alone or in combination with DRR2) acts as a target of FKBP12-rapamycin complexes or that a missense mutation in DRR1 allows it to compensate for the function of the normal drug target.
Mol Cell Biol 1993 Oct
PMID:Dominant missense mutations in a novel yeast protein related to mammalian phosphatidylinositol 3-kinase and VPS34 abrogate rapamycin cytotoxicity. 841 4

In somatic cells, phosphatidylinositol 3-kinase (PI3 kinase) is a critical intermediary in growth factor-induced mitogenesis. We have examined the role of this enzyme in meiotic maturation of Xenopus laevis oocytes. PI3 kinase activity was present in immunoprecipitates of the p85 subunit of PI3 kinase from immature oocytes and markedly increased following progesterone stimulation. Injection of bacterially expressed protein corresponding to the C-terminal SH2 domain of p85 (SH2-C) inhibited progesterone-induced PI3 kinase activation and meiotic maturation. Injection of protein corresponding to the N-terminal SH2 domain or the SH3 domain of p85 did not inhibit PI3 kinase activation or maturation. SH2-C did not inhibit oocyte maturation induced by c-mos RNA injection. In addition, radiolabelled SH2-C was used to probe oocyte lysates, revealing that a novel 200-kDa protein bound to SH2-C. This protein may be an important mediator of progesterone-induced lipid metabolism in oocytes.
Mol Cell Biol 1993 Nov
PMID:Phosphatidylinositol 3-kinase activity is important for progesterone-induced Xenopus oocyte maturation. 841 62

Nyk/Mer is a recently identified receptor tyrosine kinase with neural cell adhesion molecule-like structure (two immunoglobulin G-like domains and two fibronectin III-like domains) in its extracellular region and belongs to the Ufo/Axl family of receptors. The ligand for Nyk/Mer is presently unknown, as are the signal transduction pathways mediated by this receptor. We constructed and expressed a chimeric receptor (Fms-Nyk) composed of the extracellular domain of the human colony-stimulating factor 1 receptor (Fms) and the transmembrane and cytoplasmic domains of human Nyk/Mer in NIH 3T3 fibroblasts in order to investigate the mitogenic signaling and biochemical properties of Nyk/Mer. Colony-stimulating factor 1 stimulation of the Fms-Nyk chimeric receptor in transfected NIH 3T3 fibroblasts leads to a transformed phenotype and generates a proliferative response in the absence of other growth factors. We show that phospholipase C gamma, phosphatidylinositol 3-kinase/p70 S6 kinase, Shc, Grb2, Raf-1, and mitogen-activated protein kinase are downstream components of the Nyk/Mer signal transduction pathways. In addition, Nyk/Mer weakly activates p90rsk, while stress-activated protein kinase, Ras GTPase-activating protein (GAP), and GAP-associated p62 and p190 proteins are not activated or tyrosine phosphorylated by Nyk/Mer. An analysis comparing the Nyk/Mer signal cascade with that of the epidermal growth factor receptor indicates substrate preferences by these two receptors. Our results provide a detailed description of the Nyk/Mer signaling pathways. Given the structural similarity between the Ufo/Axl family receptors, some of the information may also be applied to other members of this receptor tyrosine kinase family.
Mol Cell Biol 1995 Dec
PMID:Mitogenic signals and transforming potential of Nyk, a newly identified neural cell adhesion molecule-related receptor tyrosine kinase. 852 23

T-cell activation involves two distinct signal transduction pathways. Antigen-specific signaling events are initiated by T-cell receptor recognition of cognate peptide presented by major histocompatibility complex molecules. Costimulatory signals, which are required for optimal T-cell activation and for overcoming the induction of anergy, can be provided by the homodimeric T-cell glycoprotein CD28 through its interaction with the counterreceptors B7-1 and B7-2 on antigen-presenting cells. Ligation of CD28 results in its phosphorylation on tyrosines and the subsequent recruitment and activation of phosphatidylinositol 3-kinase (PI 3-kinase). It has been suggested that the induced association of CD28 and PI 3-kinase is required for costimulation. We report here that ligation of CD19, a heterologous B-cell receptor that also associates with and activates PI 3-kinase upon ligation, failed to costimulate interleukin-2 production. Moreover, pharmacological inhibition of PI 3-kinase activity failed to block costimulation mediated by CD28. By mutational analysis, we demonstrate that disruption of PI 3-kinase association with CD28 also did not abrogate costimulation. These results argue that PI 3-kinase association with CD28 is neither necessary nor sufficient for costimulation of interleukin-2 production. Finally, we identify specific amino acid residues required for CD28-mediated costimulatory activity.
Mol Cell Biol 1995 Dec
PMID:CD28-mediated costimulation in the absence of phosphatidylinositol 3-kinase association and activation. 852 48

Activation of phosphatidylinositol 3-kinase (PI 3-kinase) appears to be part of the signaling mechanism by which insulin stimulates cellular glucose uptake. We have investigated the involvement of PI 3-kinase in the regulation of glucose uptake in 3T#-L1 adipocytes by comparing the effects of platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and insulin. Stimulation of [14C]deoxyglucose uptake by PDGF and EGF was 29% and 70%, respectively, while that by insulin was 5-fold. Wortmannin, a PI 3-kinase inhibitor, completely blocked the effects of all three agonists. The relative effects of the growth factors on phosphatidlyinositoltriphosphate (PIP3) synthesis were also determined. Insulin caused a large increase in this phosphoinositide. The effect of PDGF was much smaller, in fact barely detectable, while EGF had no detectable effect. The results suggest a role for PI 3-kinase in stimulation of glucose uptake by PDGF and EGF. However, the degree of PI 3-kinase by these growth factors appears to be much smaller than that by insulin, consistent with smaller stimulations of glucose transport.
Biochem Mol Biol Int 1995 Jul
PMID:Involvement of phosphatidylinositol 3-kinase in stimulation of glucose transport by growth factors in 3T3-L1 adipocytes. 852 46

We have investigated the effects of wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI 3-kinase), on antigen-mediated signaling in the RBL-2H3 mast cell model. In RBL-2H3 cells, the cross-linking of high affinity IgE receptors (Fc epsilon R1) activates at least two cytoplasmic protein tyrosine kinases, Lyn and Syk, and stimulates secretion, membrane ruffling, spreading, pinocytosis, and the formation of actin plaques implicated in increased cell-substrate adhesion. In addition, Fc epsilon R1 cross-linking activates PI 3-kinase. It was previously shown that wortmannin causes a dose-dependent inhibition of PI 3-kinase activity and also inhibits antigen-stimulated degranulation. We report that the antigen-induced synthesis of inositol(1,4,5)P3 is also markedly inhibited by wortmannin. Consistent with evidence in other cell systems implicating phosphatidylinositol(3,4,5)P3 in ruffling, pretreatment of RBL-2H3 cells with wortmannin inhibits membrane ruffling and fluid pinocytosis in response to Fc epsilon R1 cross-linking. However, wortmannin does not inhibit antigen-induced actin polymerization, receptor internalization, or the actin-dependent processes of spreading and adhesion plaque formation that follow antigen stimulation in adherent cells. Wortmannin also fails to inhibit either of the Fc epsilon R1-coupled tyrosine kinases, Lyn or Syk, or the activation of mitogen-activated protein kinase as measured by in vitro kinase assays. Strikingly, there is substantial in vitro serine/threonine kinase activity in immunoprecipitates prepared from Fc epsilon R1-activated cells using antisera to the p85 subunit of PI 3-kinase. This activity is inhibited by pretreatment of the cells with wortmannin or by the direct addition of wortmannin to the kinase assay, suggesting that PI 3-kinase itself is capable of acting as a protein kinase. We conclude that Fc epsilon R1 cross-linking activates both lipid and protein kinase activities of PI 3-kinase and that inhibiting these activities with wortmannin results in the selective block of a subset of Fc epsilon R1-mediated signaling responses.
Mol Biol Cell 1995 Sep
PMID:Wortmannin blocks lipid and protein kinase activities associated with PI 3-kinase and inhibits a subset of responses induced by Fc epsilon R1 cross-linking. 853 12

The role of phosphatidylinositol 3-kinase (PI 3-kinase) was investigated in human platelets exposed to varying doses of 5-hydroxytryptamine (5-HT) and subthreshold doses of epinephrine. The synergistic effect of 5-HT on epinephrine-induced aggregation was blocked by a specific inhibitor of PI 3-kinase, wortmannin, in a dose-dependent manner. However, there was no effect of inhibitors of protein kinase A (PKA) or protein kinase C (PKC). These studies suggest a role of PI 3-kinase in the 5-HT induced potentiation of epinephrine-mediated platelet aggregation.
Res Commun Mol Pathol Pharmacol 1995 Aug
PMID:Phosphatidylinositol 3-kinase inhibitor, wortmannin, inhibits 5-hydroxytryptamine-mediated potentiation of platelet aggregation induced by epinephrine. 855 70

Infection of mouse fibroblasts by wild-type polyomavirus results in increased phosphorylation of ribosomal protein S6 (D.A. Talmage, J. Blenis, and T.L. Benjamin, Mol. Cell. Biol. 8:2309-2315, 1988). Here we identify pp70 S6 kinase (pp70S6K) as a target for signal transduction events leading from polyomavirus middle tumor antigen (mT). Two partially transforming virus mutants altered in different mT signalling pathways have been studied to elucidate the pathway leading to S6 phosphorylation. An upstream role for mT-phosphatidylinositol 3-kinase (PI3K) complexes in pp70S6K activation is implicated by the failure of 315YF, a mutant unable to promote PI3K binding, to elicit a response. This conclusion is supported by studies using wortmannin, a known inhibitor of PI3K. In contrast, stable interaction of mT with Shc, a protein thought to be involved upstream of Ras, is dispensable for pp70S6K activation. 250YS, a mutant mT which retains a binding site for PI3K but lacks one for Shc, stimulates pp70S6K to wild-type levels. Mutants 315YF and 250YS induce partial transformation of rats fibroblasts with distinct phenotypes, as judged from morphological and growth criteria. Neither mutant induces growth in soft agar, indicating that an increase in S6 phosphorylation, while necessary for cell cycle progression in normal mitogenesis, is not sufficient for anchorage-independent cell growth. In the polyomavirus systems, the latter requires integration of signals from mT involving both Shc and PI3K.
Mol Cell Biol 1996 Jun
PMID:Studies of partially transforming polyomavirus mutants establish a role for phosphatidylinositol 3-kinase in activation of pp70 S6 kinase. 864 80

Insulin rapidly stimulates protein synthesis in a wide variety of tissues. This stimulation is associated with phosphorylation of several translational initiation and elongation factors, but little is known about the signaling pathways to these events. To study these pathways, we have used a myeloid progenitor cell line (32D) which is dependent on interleukin 3 but insensitive to insulin because of the very low levels of insulin receptor (IR) and the complete lack of insulin receptor substrate (IRS)-signaling proteins (IRS-1 and IRS-2). Expression of more IR permits partial stimulation of mitogen-activated protein kinase by insulin, and expression of IRS-1 alone mediates insulin stimulation of the 70-kDa S6 kinase (pp70S6K) by the endogenous IR. However, expression of both IR and IRS-1 is required for stimulation of protein synthesis. Moreover, this effect requires activation of phosphatidylinositol 3-kinase (PI3K), as determined by wortmannin inhibition and the use of an IRS-1 variant lacking all Tyr residues except those which activate PI3K. Stimulation of general protein synthesis does not involve activation by IRS-1 of GRB-2-SOS-p21ras or SH-PTP2, since IRS-1 variants lacking the SH2-binding Tyr residues for these proteins are fully active. Nor does it involve pp70S6K, since rapamycin, while strongly inhibiting the synthesis of a small subset of growth-regulated proteins, only slightly inhibits total protein synthesis. Recruitment of mRNAs to the ribosome is enhanced by phosphorylation of eIF4E, the cap-binding protein, and PHAS-I, a protein that specifically binds eIF4E. The behavior of cell lines containing IRS-1 variants and inhibition by wortmannin and rapamycin indicate that the phosphorylation of both proteins requires IRS-1-mediated stimulation of PI3K and pp70S6K but not mitogen-activated protein kinase or SH-PTP2.
Mol Cell Biol 1996 Jun
PMID:Stimulation of protein synthesis, eukaryotic translation initiation factor 4E phosphorylation, and PHAS-I phosphorylation by insulin requires insulin receptor substrate 1 and phosphatidylinositol 3-kinase. 864 95

We and others recently generated mice with a targeted disruption of the insulin receptor substrate 1 (IRS-1) gene and demonstrated that they exhibited growth retardation and had resistance to the glucose-lowering effect of insulin. Insulin initiates its biological effects by activating at least two major signalling pathways, one involving phosphatidylinositol 3-kinase (PI3-kinase) and the other involving a ras/mitogen-activated protein kinase (MAP kinase) cascade. In this study, we investigated the roles of IRS-1 and IRS-2 in the biological action in the physiological target organs of insulin by comparing the effects of insulin in wild-type and IRS-1-deficient mice. In muscles from IRS-1-deficient mice, the responses to insulin-induced PI3-kinase activation, glucose transport, p70 S6 kinase and MAP kinase activation, mRNA translation, and protein synthesis were significantly impaired compared with those in wild-type mice. Insulin-induced protein synthesis was both wortmannin sensitive and insensitive in wild-type and IRS-1 deficient mice. However, in another target organ, the liver, the responses to insulin-induced PI3-kinase and MAP kinase activation were not significantly reduced. The amount of tyrosine-phosphorylated IRS-2 (in IRS-1-deficient mice) was roughly equal to that of IRS-1 (in wild-type mice) in the liver, whereas it only 20 to 30% of that of IRS-1 in the muscles. In conclusion, (i) IRS-1 plays central roles in two major biological actions of insulin in muscles, glucose transport and protein synthesis; (ii) the insulin resistance of IRS-1-deficient mice is mainly due to resistance in the muscles; and (iii) the degree of compensation for IRS-1 deficiency appears to be correlated with the amount of tyrosine-phosphorylated IRS-2 (in IRS-1-deficient mice) relative to that of IRS-1 (in wild-type mice).
Mol Cell Biol 1996 Jun
PMID:Insulin signalling and insulin actions in the muscles and livers of insulin-resistant, insulin receptor substrate 1-deficient mice. 864 19


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