Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.2 (focal adhesion kinase)
 44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dominant mutations in the erythropoietin receptor (EPOR) gene account for only about 15% of cases of primary congenital erythrocytosis. To search for molecular alterations in patients with this disorder. Sixteen patients with Epo <10 mU/mL were studied, 3 were related. Analyses included EPOR and JAK2 gene sequencing, quantitative PRV-1 RT-PCR, and erythroid colony assays. A novel sporadic EPOR 1453G->A (Trp439Stop) mutation was detected. All familial cases, varied in phenotype, presented the EPOR 1414C->G (Tyr426Stop) mutation. JAK2 mutations are not involved in the pathogenesis of primary congenital erythrocytosis.
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PMID:Molecular genetic analyses in familial and sporadic congenital primary erythrocytosis. 1748 92

Recent discoveries in the molecular pathogenesis of both polycythemia vera (PV) and congenital polycythemia (CP) underline the prospect of a genetic diagnosis in these disorders. At the forefront are the mutually exclusive exon 14 (JAK2V617F) and exon 12 JAK2 mutations that are almost always present in PV but not in polycythemias of other causes. Similarly, the molecular basis of CP is being unraveled, and several cases are now associated with germline mutations involving the von Hippel-Lindau (VHL) or erythropoietin receptor (EPOR) genes. Therefore, current diagnostic work-up for acquired polycythemia should start with peripheral blood JAK2 mutation screening, whereas VHL and/or EPOR mutations should be considered when CP is suspected. In all instances, serum erythropoietin measurement provides complementary information; the serum erythropoietin level is expected to be decreased in PV regardless of JAK2 mutation status, increased in VHL mutation-associated CP, and decreased or normal in the presence of an EPOR mutation.
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PMID:Evaluation of "increased" hemoglobin in the JAK2 mutations era: a diagnostic algorithm based on genetic tests. 1749 21

In the proposed revised World Health Organization (WHO) criteria for the diagnosis of BCR-ABL(-) myeloproliferative diseases (MPDs), exclusion criteria have been replaced by the presence of JAK2 mutations. We applied these criteria to 45 children with MPDs: 13 with polycythemia vera (PV) and 32 with essential thrombocythemia (ET). Among these 45 patients, 12 with ET and 5 with PV had a familial history of MPD, and had been investigated for hereditary mutations of the erythropoietin receptor, thrombopoietin, or MPL genes. We found that the JAK2(V617F) mutation in children occurs less frequently than in adults, and that exon 12 JAK2 mutations are absent. On the basis of the revised WHO criteria, a significant proportion of childhood PVs were misdiagnosed. Furthermore, all familial ET, including patients carrying the hereditary MPL(Ser505Asn) activating mutation, were erroneously diagnosed as MPDs. Our observations suggest that childhood MPDs require a set of specific diagnostic criteria.
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PMID:The revised WHO diagnostic criteria for Ph-negative myeloproliferative diseases are not appropriate for the diagnostic screening of childhood polycythemia vera and essential thrombocythemia. 1764 35

For many decades, myeloproliferative disorders (MPD) were largely neglected orphan diseases. The conceptual work of William Dameshek in 1951 provided the basis for understanding MPD as a continuum of related syndromes, possibly with a common pathogenetic cause. Recognition of the clonal origin of peripheral blood cells in MPD in 1976 and the ability to grow erythroid colonies in vitro in the absence of added growth factors in 1974 initiated the search for genetic alterations that might be responsible for myeloproliferation. Mutations in the genes for the erythropoietin receptor, thrombopoietin and the von Hippel-Lindau protein were found to cause familial syndromes resembling MPD, but despite their phenotypic similarities, none of these mutations were later found in patients with the sporadic form of MPD. The discovery of activating mutations in the Janus kinase 2 (JAK2) in most patients with MPD has fully transformed and energized the MPD field. Sensitive assays for detecting the JAK2-V617F mutation have become an essential part of the diagnostic work-up, and JAK2 now constitutes a prime target for developing specific inhibitors for the treatment of patients with MPD. Despite this progress, many questions remain unsolved, including how a single JAK2 mutation causes three different MPD phenotypes, what other genes might be involved in the pathogenesis, and what are the factors determining the progression to acute leukemia.
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PMID:The genetic basis of myeloproliferative disorders. 1802 2

HLA-G5 is secreted by erythroblasts in all hematopoietic organs, suggesting a role for this protein in erythropoiesis. To examine this, we analyzed whether HLA-G5 affects the proliferation of UT7/EPO and HEL erythroleukemia cells and characterized the mechanism by which HLA-G5 influences erythropoietin receptor (EPOR) signaling. We show that HLA-G5 inhibits the proliferation of UT7/EPO cells, the EPOR signaling of which is similar to that of normal erythroid progenitors. HLA-G5-mediated inhibition was associated with reduced phosphorylation of JAK2 kinase and that of the downstream signaling proteins STAT-5 and STAT-3. Involvement of JAK2 in erythroid cell proliferation has been highlighted by the role of JAK2 V617F mutation in polycythemia vera (PV), a myeloproliferative disorder characterized by erythroid lineage overproduction. We demonstrate that HLA-G5 downregulates EPOR constitutive signaling of JAK2 V617F-expressing HEL cells, leading to inhibition of cell proliferation through G1 cell cycle arrest. Combination of HLA-G5 with JAK inhibitor I further decreases HEL cell growth. Clinical relevance is provided by analysis of PV patients who carry JAK2 V617F mutation, showing that HLA-G5 inhibits the formation of erythropoietin-independent erythroid colonies. Such HLA-G5-mediated inhibition constitutes a new parameter to be considered in the design of future approaches aimed at treating JAK2 V617F-positive myeloproliferative disorders.
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PMID:HLA-G turns off erythropoietin receptor signaling through JAK2 and JAK2 V617F dephosphorylation: clinical relevance in polycythemia vera. 1805 84

Explaining the uniqueness of the acquired somatic JAK2 V617F mutation, which is present in more than 95% of polycythemia vera patients, has been a challenge. The V617F mutation in the pseudokinase domain of JAK2 renders the unmutated kinase domain constitutively active. We have performed random mutagenesis at position 617 of JAK2 and tested each of the 20 possible amino acids for ability to induce constitutive signaling in Ba/F3 cells expressing the erythropoietin receptor. Four JAK2 mutants, V617W, V617M, V617I, and V617L, were able to induce cytokine independence and constitutive downstream signaling. Only V617W induced a level of constitutive activation comparable with V617F. Also, only V617W stabilized tyrosine-phosphorylated suppressor of cytokine signaling 3 (SOCS3), a mechanism by which JAK2 V617F overcomes inhibition by SOCS3. The V617W mutant induced a myeloproliferative disease in mice, mainly characterized by erythrocytosis and megakaryocytic proliferation. Although JAK2 V617W would predictably be pathogenic in humans, the substitution of the Val codon, GTC, by TTG, the codon for Trp, would require three base pair changes, and thus it is unlikely to occur. We discuss how the predicted conformations of the activated JAK2 mutants can lead to better screening assays for novel small molecule inhibitors.
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PMID:Substitution of pseudokinase domain residue Val-617 by large non-polar amino acids causes activation of JAK2. 1832 42

Thirty-six unrelated cases with erythrocytosis of unknown origin were investigated. Exons 5-8 of the erythropoietin receptor gene (EPOR), the von Hippel-Lindau gene, and the prolyl hydroxylase domain protein 2 gene (PHD2) were screened by direct DNA sequencing. The Janus kinase 2 mutation, JAK2 (Val617Phe), was screened by allele specific PCR. In this study, three new mutations of EPOR causing deletions in exon 8 were found: the first led directly to a stop codon [g.5957_5958delTT (p.Phe424X)], the second to a stop codon after one residue [g.5828_5829delCC (p.Pro381GlnfsX1)] and the third to a stop codon following a frameshift sequence of 23 residues [g.5971delC (p.Leu429TrpfsX23)]. One patient had a previously reported EPOR mutation [g.6146A>G (p.Asn487Ser)] and another, a silent one (g.5799G>A). All were heterozygotes. In addition, 2 patients were positive for JAK2 (Val617Phe), and 2 reported elsewhere, were mutated in the PHD2 gene [c.606delG (p.Met202IlefsX71).
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PMID:A study of 36 unrelated cases with pure erythrocytosis revealed three new mutations in the erythropoietin receptor gene. 1849 94

The transcription factor Egr-1 is encoded by an immediate early response gene and has been shown to be a key regulator in the induction of apoptosis, mitogenesis and differentiation. It is rapidly induced by different stimuli including the glycoprotein hormone erythropoietin. In this report, we analyse the role of different erythropoietin receptor substructures for the activation of Egr-1 and the functional consequences of Egr-1 overexpression in the erythroleukemic cell line ELM-I-1. The investigation of receptor variants revealed that the activity of JAK2 and the phosphorylation of receptor tyrosine residues are essential preconditions for the ability to target Egr-1. Furthermore, we observed a close correlation of the abilities of receptors to activate the Ras-MAPK pathway and Egr-1. Using mass spectrometry we identified the Ras-GTPase-activating protein-SH3-domain-binding protein 1 (G3BP-1), a component of the Ras network of proteins, as an Egr-1 interacting protein in EPO stimulated ELM-I-1 cells. The overexpression of Egr-1 in these cells resulted in an enhanced rate of spontaneous erythroid differentiation.
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PMID:Erythropoietin receptor-mediated Egr-1 activation: structural requirements and functional implications. 1862 90

Erythropoiesis strictly depends on signal transduction through the erythropoietin receptor (EpoR)-Janus kinase 2 (Jak2)-signal transducer and activator of transcription 5 (Stat5) axis, regulating proliferation, differentiation, and survival. The exact role of the transcription factor Stat5 in erythropoiesis remained puzzling, however, since the first Stat5-deficient mice carried a hypomorphic Stat5 allele, impeding full phenotypical analysis. Using mice completely lacking Stat5--displaying early lethality--we demonstrate that these animals suffer from microcytic anemia due to reduced expression of the antiapoptotic proteins Bcl-x(L) and Mcl-1 followed by enhanced apoptosis. Moreover, transferrin receptor-1 (TfR-1) cell surface levels on erythroid cells were decreased more than 2-fold on erythroid cells of Stat5(-/-) animals. This reduction could be attributed to reduced transcription of TfR-1 mRNA and iron regulatory protein 2 (IRP-2), the major translational regulator of TfR-1 mRNA stability in erythroid cells. Both genes were demonstrated to be direct transcriptional targets of Stat5. This establishes an unexpected mechanistic link between EpoR/Jak/Stat signaling and iron metabolism, processes absolutely essential for erythropoiesis and life.
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PMID:Stat5 regulates cellular iron uptake of erythroid cells via IRP-2 and TfR-1. 1869 96

Erythropoietin has emerged as a potential therapy for the treatment of ischemic tissue injury. In erythroid cells, the JAK2/Y343/STAT5 signaling axis has been shown to be necessary for stress but not steady-state erythropoiesis. The requirement for STAT5 activation in erythropoietin-mediated protection from ischemic injury has not been well-studied. To answer this question, we induced reproducible necrotic ischemic injury in primary mouse renal tubular epithelial cells (RTEC) in vitro. Using RTEC from erythropoietin receptor mutant mice with differential STAT5 signaling capabilities, we demonstrated first, that EPO administration either before or during injury significantly protects against mild-moderate but not severe necrotic cell death; and second, the JAK2/Y343/STAT5 signaling axis is required for protection against ischemic injury in primary mouse RTEC. In addition, we identified Pim-3, a prosurvival STAT5 target gene, as responsive to EPO in the noninjured kidney both in vitro and in vivo.
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PMID:JAK2/Y343/STAT5 signaling axis is required for erythropoietin-mediated protection against ischemic injury in primary renal tubular epithelial cells. 1881 18


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