Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P14784 (IL-2 receptor)
 3,849 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ADP ribosylation in the presence of cholera or pertussis toxin indicated the presence of G-proteins in Nb2 cell membranes. Two protein bands, with mol wt of 43.5K and 46.5K, were radiolabeled by cholera toxin, while a single protein (41.5K mol wt) was ADP ribosylated by pertussis toxin. Northern hybridization of total RNA from Nb2 cells with specific cDNA probes indicated the presence of mRNA transcripts encoding Gs, Gi2, Go, and, to a lesser extent, Gi3. A characteristic of receptors coupled to G-proteins is that their binding properties are regulated by guanine nucleotides. The binding of [125I]human GH to the lactogen receptor as well as the binding of [125I]IL-2 to the IL-2 receptor were decreased in a dose-dependent manner by GTP, GDP, and the analog guanosine 5'-O-(3-thiotriphosphate). GMP, however, had no effect. The addition of pyruvate kinase and phosphoenolpyruvate to regenerate GTP from GDP greatly increased the apparent potency of GTP. Cholera toxin inhibited PRL- and interleukin-2-stimulated DNA synthesis and cell proliferation in the Nb2 cells. In contrast, pertussis toxin had a differential effect on PRL- and IL-2-stimulated cells. Pertussis toxin, at an optimal concentration of 0.01 ng/ml, significantly enhanced the stimulatory effects of PRL on DNA synthesis (P less than or equal to 0.01; n = 9) and cell proliferation (P less than or equal to 0.05; n = 9) compared with the effect of PRL alone. However, at higher concentrations the toxin inhibited PRL-stimulated DNA synthesis and cell proliferation. Complete inhibition was achieved with 1000 ng/ml toxin. In contrast to the biphasic effect on PRL-stimulated cells, pertussis toxin was only weakly inhibitory to cells treated with IL-2. At the highest concentration tested, pertussis toxin (1000 ng/ml) inhibited IL-2-stimulated DNA synthesis and cell growth by only 30-35%. (Bu)2cAMP (IC50 = 0.019 mM) or methylxanthine (MIX; IC50 = 0.25 mM) also inhibited PRL-stimulated DNA synthesis. In the absence of mitogen, neither agent, from 0.0001-1 mM, had any effect on DNA synthesis. Similarly, IL-2-stimulated DNA synthesis in Nb2 cells was inhibited by (Bu)2cAMP (IC50 = 0.019 mM) or MIX (IC50 = 0.072 mM). However, MIX was approximately 3 times as potent in inhibiting the cell response to IL-2 as that to PRL. The susceptibility of Nb2 cells to both bacterial toxins suggests a role for G-proteins in regulating PRL- or IL-2-stimulated mitogenesis in these cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:G-proteins modulate prolactin- and interleukin-2-stimulated mitogenesis in rat Nb2 lymphoma cells. 246 72

Binding of interleukin-2 (IL-2) to the IL-2 receptor (IL-2R) stimulates Src family kinases, tyrosine phosphorylation of several proteins, conversion of Ras to its active GTP-bound form, and eventually c-fos, c-jun, and c-myc induction. The IL-2R beta chain plays a crucial role in IL-2R signaling. Within the cytoplasmic domain of the beta chain, a region essential for mitogenesis and another involved in binding the Src family kinase Lck have been defined. The beta chain itself is tyrosine-phosphorylated upon IL-2 stimulation. Since the adapter protein Shc acts upstream of Ras and is involved in T cell receptor-mediated Ras activation, we examined the role of Shc in IL-2 signaling. Shc was found to be tyrosine-phosphorylated upon IL-2 stimulation in CTLL-20 cells. After its phosphorylation, Shc interacted with another adapter protein, Grb2, and, via Grb2, with the Ras GTP/GDP exchange factor mSOS. After IL-2 stimulation, Shc also associated with the IL-2R beta chain. Thus, during IL-2 signaling, the interaction of Shc with the IL-2R beta chain and its simultaneous association with Grb2 and mSOS may couple IL-2R stimulation to Ras signaling.
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PMID:The adapter protein Shc interacts with the interleukin-2 (IL-2) receptor upon IL-2 stimulation. 829 3

Vav has been shown to activate Ras (1-3) and is regulated by tyrosine phosphorylation (1) or binding of diglycerides (3) to the cysteine rich domain. In the present study employing different Ras activation assay techniques using [3H]GDP release or [32P]alpha GTP-binding from membrane-bound or soluble recombinant Ras, we demonstrate that Ras activity can be increased by tyrosine phosphorylated Vav upon cellular stimulation via the IL-2 receptor or the TCR/CD3-complex. Increase of [32P]alpha GTP-binding to Ras catalyzed by phosphorylated Vav is similar to the activity of immunoprecipitated Sos. The activity of Vav measured by binding of [32P]alpha GTP to Ras was linear with respect to the concentration of Vav protein used. To study molecular characteristics of this Vav-Ras interaction, we used several Ras mutants and demonstrate that Vav activity towards Ras depends on the integrity of the same or similar domains as Ras activation by SDC 25 or CDC 25.
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PMID:Molecular analysis of Ras activation by tyrosine phosphorylated Vav. 855 11

Stimulation via the T-cell growth factor interleukin 2 (IL-2) leads to tyrosine phosphorylation of Shc, the interaction of Shc with Grb2, and the Ras GTP/GDP exchange factor, mSOS. Shc also coprecipitates with the IL-2 receptor (IL-2R), and therefore, may link IL-2R to Ras activation. We have further characterized the Shc-IL-2R interaction and have made the following observations. (i) Among the two phosphotyrosine-interaction domains present in Shc, the phosphotyrosine-binding (PTB) domain, rather than its SH2 domain, interacts with the tyrosine-phosphorylated IL-2R beta chain. Moreover, the Shc-PTB domain binds a phosphopeptide derived from the IL-2R beta chain (corresponding to residues surrounding Y338, SCFTNQGpYFF) with high affinity. (ii) In vivo, mutant IL-2R beta chains lacking the acidic region of IL-2Rbeta (which contains Y338) fail to phosphorylate Shc. Furthermore, when wild type or mutant Shc proteins that lack the PTB domain were expressed in the IL-2-dependent CTLL-20 cell line, an intact Shc-PTB domain was required for Shc phosphorylation by the IL-2R, which provides further support for a Shc-PTB-IL-2R interaction in vivo. (iii) PTB and SH2 domains of Shc associate with different proteins in IL-2- and T-cell-receptor-stimulated lysates, suggesting that Shc, through the concurrent use of its two different phosphotyrosine-binding domains, could assemble multiple protein complexes. Taken together, our in vivo and in vitro observations suggest that the PTB domain of Shc interacts with Y338 of the IL-2R and provide evidence for a functional role for the Shc-PTB domain in IL-2 signaling.
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PMID:Evidence for a role for the phosphotyrosine-binding domain of Shc in interleukin 2 signaling. 864 66

ERYTHROPOIETIN (EPO): Erythropoietin (EPO) is a hormone that promotes the proliferation and differentiation of erythroid progenitor cells and regulates the number of erythrocytes in peripheral blood. EPO is produced mainly by the kidneys, and transcription of the EPO gene is promoted by a reduction in the oxygen concentration in the blood. The existence of EPO was suggested near the end of the 19th century by the discovery that hypoxia increases the production of red blood cells. EPO was identified as a serum factor in the 1950s, and in 1970 Miyake and coworkers succeeded in purifying it by using the urine of patients with aplastic anemia as a starting material. The human EPO gene was cloned in 1985 using a partial amino acid sequence from this purified EPO, and it is well known that recombinant EPO is currently used as a drug to treat anemia associated with chronic renal failure and other illnesses. ACTION OF EPO: When human bone marrow cells are cultured in a semisolid medium containing EPO, they form small erythroblast colonies in five to seven days, and by day 10 large erythroblast colonies appear that resemble fireworks ("burst" colonies). The original cells in the former colonies are called colony forming units-erythroid (CFU-E) or late-stage erythroblast progenitor cells and in the latter colonies they are called burst forming units-erythroid (BFU-E) or early-stage erythroblast progenitor cells. As shown in Figure 1, red blood cells are produced through differentiation from stem cells to BFU-E, CFU-E, and erythroblasts. Although EPO acts on both BFU-E and CFU-E cells, CFU-E cells show greater sensitivity to EPO, and other factors such as stem cell factor (SCF), interleukin (IL)-3, IL-4, and granulocyte macrophage colony-stimulating factor (GM-CSF) must be present together with EPO for BFU-E cell proliferation. In erythroblasts beyond the CFU-E stage, sensitivity to EPO decreases as the cells mature. THE EPO RECEPTOR AND THE CYTOKINE RECEPTOR FAMILY: The EPO receptor gene was cloned by D'Andrea and coworkers in 1989 from murine erythroleukemia cells [1]. It became clear that the EPO receptor belongs to the cytokine receptor family that comprises receptors for the various interleukins, GM-CSF, granulocyte colony-stimulating factor (G-CSF), growth hormone and prolactin. The special characteristic of this family of receptors is that they are switched on (i.e., the receptor is activated) and transduce signals to the interior of the cell by the formation of homo- or hetero-oligomers (dimers or trimers). Moreover, hetero-oligomers of these receptors share a common receptor subunit. As shown in Figure 2, the IL-3, IL-5 and GM-CSF receptors have a common &bgr; subunit, and their ligand specificity is determined by the &agr; subunit. In the same manner, the IL-6, LIF and oncostatin M (OSM) receptors all share gp130, which is the &bgr; subunit of the IL-6 receptor. The IL-2, IL-4 and IL-7 receptors all share the &ggr; subunit of the IL-2 receptor. All the above receptors are activated by the formation of hetero-oligomers, but the G-CSF receptor, EPO receptor, and growth hormone receptor are activated by the formation of homodimers of the same types of molecules [2]. We can see that groups of cytokines such as the interleukins that affect a relatively wide range of cells and have redundant biological activity create this redundancy through the common use of a single receptor subunit. On the other hand, EPO and G-CSF act with high specificity on a relatively limited range of cells, so it was probably unnecessary for their receptors to share one of the subunits. EPO RECEPTOR AND JAK2 KINASE: The signal for cellular proliferation and differentiation into erythroblasts is thought to originate at the EPO receptor. The cytoplasmic domain of the EPO receptor can be divided into two major regions. Roughly half of the cytoplasmic domain, the part lying nearest the plasma membrane, is required for generating the signals for proliferation and differentiation such as the induction of globin synthesis [3, 4]. The remaining half is not required for this signaling, and, conversely, it acts to dampen the signals. It is known that a tyrosine kinase called JAK2 associates with the region near the plasma membrane, undergoes autophosphorylation, and phosphorylates the EPO receptor, and a transcription factor called a STAT [5]. It is thought that JAK2 plays an important role in promoting cellular proliferation. The STAT is activated by the phosphorylation, and it then translocates to the nucleus, recognizes a specific base sequence in the promoter region of its target gene, and initiates transcription. At present, we know that the STAT whose activation is mediated by the EPO receptor is STAT5, and the target genes are CIS [6], which has an SH2 domain (a molecular structure that recognizes a phosphorylated tyrosine) and OSM [7], which is a pleiotropic cytokine. However, activation of STAT5 and activation of the target genes are not unique to the EPO receptor, and they also occur with the IL-2 and IL-3 receptors. Moreover, the JAK2 substrate that is directly linked to cellular proliferation is still unknown. At present, studies are under way to determine the transcription factors specific to EPO and their target genes, as well as the substrates of JAK2. RECEPTOR PHOSPHORYLATION AND CESSATION OF THE SIGNAL: On the other hand, tyrosine phosphorylation of the receptor is necessary at the cytoplasmic tail region far from the plasma membrane, and the signal transduction pathway that originates with this phosphorylated tyrosine and is mediated by proteins with SH2 domains becomes activated. First, a GTP/GDP exchange factor called SOS, which is mediated by Shc and Grb2, migrates to the plasma membrane and converts a ras protein to its GTP form. The activated ras protein then activates the Raf-MAP kinase kinase-MAP kinase cascade, and ultimately initiates the transcription of oncogenes such as c-fos and c-jun. An enzyme called PI3 kinase binds to the tyrosine phosphorylation site of the receptor and a second messenger is born. It is known that this pathway is a requirement for DNA synthesis in certain types of fibroblasts. However, these signal transduction pathways are not unique to the EPO receptor, and they are also activated by most growth factor receptors, so they are not necessarily required for EPO-induced proliferation. Conversely, the tyrosine phosphatase SH-PTP1 (also called HCP) that has an SH2 domain and is specific to blood cells associates with the tyrosine phosphorylation site of the receptor and promotes the dephosphorylation of JAK2. In other words, the role of SH-PTP1 is to stop generation of the signal [8]. Therefore, in mutations lacking this cytoplasmic tail region of the receptor far from the plasma membrane, the receptors do not undergo tyrosine phosphorylation, JAK2 activation continues for a longer period of time, and thus the signal is generated more efficiently. In fact, in one patient with a mild case of familial erythrocytosis a mutation was discovered in which the C-terminus of the EPO receptor was missing 70 amino acids [9]. This was a dominant genetic trait, and the patient's erythroblasts showed an increased sensitivity to EPO. In this family the impairment was not severe enough to be called an illness, and in fact it is said that this patient was proficient enough athletically to compete for a gold medal at the Olympics. More specifically, the reason that athletes undergo training at high altitudes is to boost EPO production because of the lower oxygen partial pressure, and this brings about the desired effect of sustained athletic capability due to a resultant increase in red blood cells. However, the same effect has occurred naturally in this athlete thanks to accelerated receptor capability.
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PMID:Physician Education: The Erythropoietin Receptor and Signal Transduction. 1038 12