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:2.7.10.2 (focal adhesion kinase)
44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The granulocyte/macrophage colony-stimulating factor (GM-CSF)/interleukin-3 (IL-3)/IL-5 receptors are a family of heterodimeric transmembrane proteins expressed by myeloid lineage cells. Each receptor has a unique ligand-binding alpha chain and they share a common beta chain (beta c chain). Binding of GM-CSF activates at least one receptor-associated tyrosine kinase, JAK2, and rapidly induces tyrosine phosphorylation of the GMR beta c chain (GMR beta), but not the GMR alpha chain (GMR alpha). Mutation of each of the 8 tyrosine residues in the cytoplasmic domain of the human GMR beta to phenylalanine (GMR beta-F8) reduced tyrosine phosphorylation of GMR beta, SHP2 and SHC, but not JAK2 or STAT5. Interestingly, GMR beta-F8 was still capable of inducing at least short-term proliferation and enhancing viability. The role of each individual tyrosine residue was explored by replacing each mutated phenylalanine with the wild-type tyrosine residue. Tyrosine 577 was found to be sufficient to regenerate GM-CSF-dependent phosphorylation of SHC, and any of Y577, Y612, or Y695 were sufficient to regenerate GM-CSF-inducible phosphorylation of SHP2. Next, a series of four internal deletion mutants were generated, which deleted small sections from aa 518 to 626. One of these, deleting residues 566-589 was profoundly defective in signaling and supporting viability, and may identify an important viability signaling domain for this receptor family. Overall, these results indicate that GMR beta tyrosine residues are not necessary for activation of the JAK/STAT pathway, or for proliferation, viability, or adhesion signaling in Ba/F3 cells, although tyrosine residues significantly affect the magnitude of the response. However, internal deletion mutant studies identify critical domains for viability and proliferation.
...
PMID:Signaling domains of the beta c chain of the GM-CSF/IL-3/IL-5 receptor. 1037 32

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.
...
PMID:Physician Education: The Erythropoietin Receptor and Signal Transduction. 1038 12

Receptor antagonists block all receptor-coupled signaling pathways indiscriminately. We introduce a novel class of peptide inhibitors that is designed to block a specific signal from a receptor while keeping other signals intact. This concept was tested in the model of IL-5 signaling via Lyn kinase. We have previously mapped the Lyn-binding site of the IL-5/GM-CSF receptor common beta (beta c) subunit. In the present study, we designed a peptide inhibitor using the Lyn-binding sequence. The peptide was N-stearated to enable cellular internalization. The stearated peptide blocked the binding of Lyn to the beta c receptor and the activation of Lyn. The lipopeptide did not affect the activation of Janus kinase 2 or its association with beta c. The inhibitor blocked the Lyn-dependent functions of IL-5 in vitro (e.g., eosinophil differentiation from stem cells and eosinophil survival). It did not affect eosinophil degranulation. When applied in vivo, the Lyn-binding peptide significantly inhibited airway eosinophil influx in a mouse model of asthma. The lipopeptide had no effect on basophil histamine release or on the proliferation of B cells and T cells. To our knowledge, this is the first report on an inhibitor of IL-5 that blocks eosinophil differentiation, survival, and airway eosinophilic inflammation. This novel strategy to develop peptide inhibitors can be applied to other receptors.
...
PMID:A novel Lyn-binding peptide inhibitor blocks eosinophil differentiation, survival, and airway eosinophilic inflammation. 1039 90

Sequence randomization through functional phage display of single chain human interleukin (IL)-5 was used to investigate the limits of replaceability of the Glu(110) residues that form a part of the receptor-binding epitope. Mutational analysis revealed unexpected affinity for IL-5 receptor alpha chain with variants containing E110W or E110Y. Escherichia coli-expressed Glu(110) variants containing E110W in the otherwise sequence-intact N-terminal half, including a variant with an E110A replacement in the sequence-disabled C-terminal half, were shown by their CD spectra to be folded into secondary structures similar to that of single chain human IL-5 (scIL-5). Biosensor kinetics analysis revealed that (E110W/A5)scIL-5 and (E110W/A6)scIL-5 had receptor alpha chain binding affinities similar to that of (wt/A5)scIL-5. However, (E110W/A6)scIL-5 had a significantly reduced bioactivity in TF-1 cell proliferation compared with both (wt/A5)scIL-5 and (E110W/A5)scIL-5, and this activity reduction was disproportionately greater than the much smaller effect of Glu(110) mutation on receptor binding affinity. The marked and disproportionate decrease in TF-1 proliferation observed with (E110W/A6)scIL-5 suggests a role for Glu(110) in the biological activity mediated by the signal transducing receptor betac subunit of the IL-5 receptor. This is also consistent with the lack of stimulation of JAK2 phosphorylation by the (E110W/A6)scIL-5 mutant in recombinant 293T cells, as compared with the concentration-dependent stimulation seen for scIL-5. The results reveal the dispensability of charge in the Glu(110) locus of IL-5 for receptor alpha chain binding and, in contrast, its heretofore underappreciated importance for receptor activation.
...
PMID:Epitope randomization redefines the functional role of glutamic acid 110 in interleukin-5 receptor activation. 1070 7

Granulocyte-macrophage colony stimulating factor (GM-CSF), Interleukin-3 (IL-3) and Interleukin-5 (IL-5) have overlapping, pleiotropic effects on hematopoietic cells, including neutrophils, eosinophils, monocytes and early progenitor cells. The high-affinity receptors for human GM-CSF, IL-3, and IL-5 share a common beta-subunit (hbeta(c)), which is essential for signalling and plays a major role in recruiting intracellular signalling molecules. While activation of the cytoplasmic tyrosine kinase JAK2 appears to be the initiating event for signalling, the immediate events that trigger this are still unclear. We have isolated a number of activated mutants of hbeta(c), which can be grouped into classes defined by their state of receptor phosphorylation, their requirement for alpha subunit as a cofactor, and their activities in primary cells and cell lines. We discuss these findings with regard to the stoichiometry, activation, and signalling of the normal GM-CSF/IL-3/IL-5 receptor complexes. Specifically, this work has implications for the role of the ligand-specific alpha-subunits in initiating the signalling through the beta-subunit, the role of beta subunit dimerization as a receptor trigger, and the function of receptor tyrosine phosphorylation in generating growth and survival signals. Based on the properties of the activated mutants and the recent structures of erythropoietin receptor (Epo-R) complexes, we propose a model in which (1) activation of hbeta(c) can occur via alternative states that differ with respect to stoichiometry and subunit assembly, but which all mediate proliferative responses, and (2) each of the different classes of activated mutants mimics one of these alternative states.
...
PMID:A model for assembly and activation of the GM-CSF, IL-3 and IL-5 receptors: insights from activated mutants of the common beta subunit. 1072 Jun 88

We studied the effect of tyrphostin AG-490, a specific Janus kinase 2 (JAK2) inhibitor, on antigen-induced eosinophil recruitment into the airways of sensitized mice and on IL-5-induced chemokinesis and adhesiveness of eosinophils. The in vivo administration of AG-490 prevented antigen-induced eosinophil infiltration in the airways of sensitized mice in a dose-dependent manner. However, the administration of AG-490 did not affect antigen-induced IL-5 production in the airways nor in vitro antigen-induced IL-5 production and T cell proliferation of spleen cells. Furthermore, AG-490 inhibited IL-5-induced chemokinesis and beta1-integrin adhesiveness of eosinophils in vitro. Because antigen-induced eosinophil recruitment into the airways is mediated by IL-5, these results indicate that JAK2 activation is critical for antigen-induced, IL-5-dependent mobilization of eosinophils into the tissue.
...
PMID:Blockade of JAK2 by tyrphostin AG-490 inhibits antigen-induced eosinophil recruitment into the mouse airways. 1073 29

gp130 is the common signal-transducing receptor chain of interleukin (IL)-6-type cytokines. Here we describe, for the first time, a single amino acid substitution (Trp(666)-->Ala) in the membrane-proximal interbox1/2 region that abrogates activation of STAT (signal transducer and activator of transcription) transcription factors and the proliferative response of pro-B-cell transfectants. Moreover, association of the Janus kinase JAK1 is prevented. No signalling of heterodimeric IL-5 receptor (IL-5R)/gp130 chimaeras occurs in COS-7 cells, even when only a single cytoplasmic chain of a gp130 dimer contains the Trp(666)Ala mutation, indicating that it acts dominantly.
...
PMID:A single amino acid substitution (Trp(666)-->Ala) in the interbox1/2 region of the interleukin-6 signal transducer gp130 abrogates binding of JAK1, and dominantly impairs signal transduction. 1086 Dec 37

The purpose of this study was to determine whether interferon-gamma (IFN-gamma) induced CD69 expression by eosinophil precursors. Eosinophil precursors were induced from CD34+ cord blood cells using recombinant human interleukin-3 (IL-3) and interleukin-5 (IL-5). On day 14 of culture, cells constitutively expressed CD69 and the IFN-gamma receptor (IFN-gammaR). Stimulation with IFN-gamma for 24 h did not affect IFN-gammaR expression by the cells. On the other hand, IFN-gamma significantly upregulated CD69 expression by the precursors after 24 h of incubation. A specific JAK2 inhibitor (AG-490) caused a concentration-dependent suppression of IFN-gamma-induced CD69 expression by the precursors. In conclusion, these results indicate that IFN-gamma induces CD69 expression by eosinophil precursors via the activation of JAK2.
...
PMID:Regulation of CD69 expression on eosinophil precursors by interferon-gamma. 1086 4

Rat eosinophil survival was prolonged by recombinant rat IL-5 prepared by the baculovirus expression system. The IL-5-induced prolongation of eosinophil survival was dose-dependently inhibited by the protein synthesis inhibitor cycloheximide, the DNA-dependent RNA synthesis inhibitor actinomycin D, and the tyrosine kinase inhibitor herbimycin A. The MEK-1 inhibitor PD98059 inhibited IL-5-induced phosphorylation of both p44 and p42 MAP kinases, but the IL-5-induced prolongation of eosinophil survival was not inhibited. In contrast, the JAK2 inhibitor AG490 inhibited the IL-5-induced prolongation of eosinophil survival. Treatment of eosinophils with IL-5 resulted in phosphorylation of STAT5 but not STAT1, and the IL-5-induced phosphorylation of STAT5 was inhibited by AG490. These findings suggest that recombinant rat IL-5 activates JAK2 tyrosine kinase, which phosphorylates STAT5, and induces protein synthesis required for the prolongation of rat eosinophil survival.
...
PMID:Analysis of the prolongation of rat eosinophil survival induced by recombinant rat interleukin-5. 1086 6

The survival and apoptosis of eosinophils is of pivotal importance for controlling allergic diseases such as asthma and rhinitis. In this study we have investigated the role for cAMP in regulating eosinophil survival and apoptosis in the absence of eosinophil-active cytokines. The treatment with dibutyryl cyclic AMP (dbcAMP) increased eosinophil survival with a concomitant decrease of apoptosis in a dose-dependent manner. The pretreatment with a protein kinase A (PKA) inhibitor blocked the effects of dbcAMP on survival and apoptosis of eosinophils. The catalytic subunit of PKA was translocated to nucleus in parallel with a robust increase of intracellular cAMP levels upon exposure to dbcAMP but not IL-5, suggesting the separation of PKA activation from the IL-5-induced suppression of eosinophil apoptosis. When eosinophils were treated with pharmacological inhibitors of protein kinases prior to exposure to dbcAMP or IL-5, only the mitogen-activating protein kinase (MAPK) inhibitor, PD098059, was partly able to block dbcAMP-induced augmentation of eosinophil viability, whereas both Janus kinase 2 and MAPK inhibitors effectively interrupted the IL-5-induced prolongation of eosinophil survival. The effects of dbcAMP and these protein kinase inhibitors on eosinophil apoptosis were confirmed by morphologic analysis. We propose that a cAMP-dependent pathway may constitute an important component for regulating eosinophil survival/apoptosisand that cAMP may inhibit eosinophil apoptosis through the activation of PKA and of subsequent MAPK in part.
...
PMID:Role of cAMP-dependent pathway in eosinophil apoptosis and survival. 1091 59


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

---