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)

The gene responsible for X-linked agammaglobulinemia (XLA) has been recently identified to code for a cytoplasmic tyrosine kinase (Bruton's agammaglobulinemia tyrosine kinase, BTK), required for normal B cell development. BTK, like many other cytoplasmic tyrosine kinases, contains Src homology domains (SH2 and SH3), and catalytic kinase domain. SH3 domains are important for the targeting of signaling molecules to specific subcellular locations. We have identified a family with XLA whose affected members have a point mutation (g-->a) at the 5' splice site of intron 8, resulting in the skipping of coding exon 8 and loss of 21 amino acids forming the COOH-terminal portion of the BTK SH3 domain. The study of three generations within this kinship, using restriction fragment length polymorphism and DNA analysis, allowed identification of the mutant X chromosome responsible for XLA and the carrier status in this family. BTK mRNA was present in normal amounts in Epstein-Barr virus-induced B lymphoblastoid cell lines established from affected family members. Although the SH3 deletion did not alter BTK protein stability and kinase activity of the truncated BTK protein was normal, the affected patients nevertheless have a severe B cell defect characteristic for XLA. The mutant protein was modeled using the normal BTK SH3 domain. The deletion results in loss of two COOH-terminal beta strands containing several residues critical for the formation of the putative SH3 ligand-binding pocket. We predict that, as a result, one or more crucial SH3 binding proteins fail to interact with BTK, interrupting the cytoplasmic signal transduction process required for B cell differentiation.
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PMID:Deletion within the Src homology domain 3 of Bruton's tyrosine kinase resulting in X-linked agammaglobulinemia (XLA). 751 38

Bruton tyrosine kinase (EC 2.7.1.112) [Btk, encoded by Btk in mice and BTK in humans (formerly known as atk, BPK, or emb)], which is variously mutated in chromosome X-linked agammaglobulinemia patients and X-linked immunodeficient (xid) mice, has the pleckstrin homology (PH) domain at its amino terminus. The PH domain of Btk expressed as a bacterial fusion protein directly interacts with protein kinase C in mast cell lysates. Evidence was obtained that Btk is physically associated with protein kinase C in intact murine mast cells as well. Both Ca(2+)-dependent (alpha, beta I, and beta II) and Ca(2+)-independent protein kinase C isoforms (epsilon and zeta) in mast cells interact with the PH domain of Btk in vitro, and protein kinase C beta I is associated with Btk in vivo. Btk served as a substrate of protein kinase C, and its enzymatic activity was down-regulated by protein kinase C-mediated phosphorylation. Furthermore, depletion or inhibition of protein kinase C with pharmacological agents resulted in an enhancement of the tyrosine phosphorylation of Btk induced by mast cell activation.
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PMID:The pleckstrin homology domain of Bruton tyrosine kinase interacts with protein kinase C. 752 30

Interleukin 5 (IL-5) induces proliferation and differentiation of B cells and eosinophils by interacting with its receptor (IL-5R) which consists of two distinct polypeptide chains, alpha and beta (beta c). Although both IL-5R alpha and beta c lack a kinase catalytic domain, IL-5 is capable of inducing tyrosine phosphorylation of cellular proteins. We investigated the role of IL-5R alpha in tyrosine phosphorylation of molecules involved in IL-5 signal transduction, using an IL-5-dependent early B cell line, Y16 and transfectants expressing intact or mutant IL-5R alpha together with intact beta c. The results revealed that the transfectants expressing truncated IL-5R alpha, which entirely lacks a cytoplasmic domain, together with beta c, showed neither protein-tyrosine phosphorylation nor proliferation in response to IL-5. This confirms that IL-5R alpha plays a critical role in protein-tyrosine phosphorylation which triggers cell growth. IL-5 stimulation results in rapid tyrosine phosphorylation of beta c and proteins containing Src homology 2 (SH2) and/or SH3 domains such as phosphatidyl-inositol-3 kinase, Shc, Vav, and HS1, suggesting their involvement in IL-5-mediated signal transduction. IL-5 stimulation significantly enhanced activities of Janus 2 and B cell-specific Bruton's tyrosine kinases (JAK2 and Btk) and increased the tyrosine phosphorylation of JAK2 kinase. These results and recent data on signaling of growth factors taken together, multiple biochemical pathways driven by tyrosine kinases such as JAK2 and Btk are involved in IL-5 signal transduction.
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PMID:IL-5 receptor-mediated tyrosine phosphorylation of SH2/SH3-containing proteins and activation of Bruton's tyrosine and Janus 2 kinases. 752 47

Tsk/Itk and Btk are members of the pleckstrin-homology (PH) domain-containing tyrosine kinase family. The PH domain has been demonstrated to be able to interact with beta gamma subunits of heterotrimeric guanine nucleotide-binding proteins (G proteins) (G beta gamma) and phospholipids. Using cotransfection assays, we show here that the kinase activities of Tsk and Btk are stimulated by certain G beta gamma subunits. Furthermore, using an in vitro reconstitution assay with purified bovine brain G beta gamma subunits and the immunoprecipitated Tsk, we find that Tsk kinase activity is increased by G beta gamma subunits and another membrane factor(s). These results indicate that this family of tyrosine kinases could be an effector of heterotrimeric G proteins.
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PMID:Activation of Tsk and Btk tyrosine kinases by G protein beta gamma subunits. 756 82

X-linked agammaglobulinaemia (XLA) is an inherited immunodeficiency resulting from mutations in the gene for a cytoplasmic protein tyrosine kinase (Btk). We have utilised reverse-transcription-based PCR in combination with the chemical cleavage and mismatch technique (CCM) to screen for Btk mutations in 42 unrelated patients having classical XLA or 'leaky' XLA-like phenotypes. A variety of mutations, including point mutations, large deletions and splicing defects were detected using this strategy. In total, 20 mutations were found in these patients. All the mutations were different with the exception of three unrelated patients who all showed the same Arg-->His amino acid substitution (R641H) at a highly-conserved residue in the kinase domain. We have also used structural modelling of the Btk kinase domain to predict how two different amino acid substitution mutations at highly-conserved residues are likely to affect the Btk kinase activity.
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PMID:Identification of Btk mutations in 20 unrelated patients with X-linked agammaglobulinaemia (XLA). 763 20

The identification of the BTK (Bruton's tyrosine kinase) gene defective in human immunoglobulin deficiency X-linked agammaglobulinaemia (XLA) and characterisation of BTK exon-intron boundaries has now allowed the analysis of mutations and polymorphisms at the level of genomic DNA. Using Southern blot analysis and the polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) assay, amplifying all 19 exons and the putative promoter region with a single annealling temperature, mutations have been identified in 19 out of 24 unrelated patients diagnosed as having XLA. Apart from a large deletion involving exon 19, nine missense (F25S, R288W, 1370M, M509V, R525P, N526K, R562W, A582V and G594R), two nonsense (E277X and R525X), five frameshift and two splice site mutations have been found affecting most coding exons and all major enzyme domains. No mutations or polymorphisms were detected in the putative promoter region. A single nucleotide deletion located in the last exon, resulting in a truncation of the eight C-terminal residues of Btk and a typical XLA phenotype, indicates structural and/or functional importance of Btk helix I in the catalytic domain. Although allelic heterogeneity at the BTK locus may partly explain clinical variability in families with XLA, compensatory and redundant mechanisms involved in B-cell development must play a role in the phenotypic diversity of the disease.
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PMID:DNA-based mutation analysis of Bruton's tyrosine kinase gene in patients with X-linked agammaglobulinaemia. 771 34

Among cytoplasmic protein-tyrosine kinases (PTKs) Tec now forms a novel subfamily with recently identified Tec-related PTKs (Btk and Itk/Tsk). Tec is known to be abundantly expressed in myeloid cells, and multiple forms of Tec protein can be generated via the mechanism of alternative splicing. In this report, we have investigated 5'-terminal diversity of the tec messages to demonstrate a predominant form of the Tec protein in mouse hematopoietic cell lines. Using anti-Tec serum, we could show that stimulation with interleukin-3 (IL-3) can induce tyrosine phosphorylation of Tec both in myeloid and pro-B-cell lines. IL-3 stimulation was also shown to induce kinase activity of Tec. Furthermore, we could demonstrate that Tec is constitutively associated with the Shc protein in vivo. Thus, we conclude that Tec is involved in the signaling pathway of IL-3.
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PMID:Tec protein-tyrosine kinase is involved in interleukin-3 signaling pathway. 781 91

The protein-tyrosine kinase gene Itk is expressed preferentially in T lymphoid cells of the mouse and is induced by IL-2. A related gene, Btk, is expressed in the murine B lymphoid and myeloid lineages. Because mutations in Btk and the corresponding human gene are associated with X-linked immunodeficiency syndromes, it was of interest to map Itk and its human counterpart. By Southern blot analysis of DNA from the progeny of two multilocus crosses, murine Itk was mapped to Chromosome 11. By fluorescence in situ hybridization, human ITK was mapped to 5q32-q33. Murine Itk and its human homologue lie within regions of conserved synteny that include several growth factor and growth factor receptor genes. This region in humans is frequently deleted in the myelodysplastic syndrome, suggesting possible involvement of ITK in this disorder.
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PMID:Mapping of the gene for the tyrosine kinase Itk to a region of conserved synteny between mouse chromosome 11 and human chromosome 5q. 782 87

The control of phosphorylation by protein tyrosine kinases represents an important regulatory mechanism in T cell growth, function, and differentiation. We have identified a 62-kDa murine protein tyrosine kinase predominantly expressed within the T cell lineage, which we have termed Rlk (for Resting lymphocyte kinase). rlk mRNA was found to be expressed in the fetal thymus as early as day 13 of embryonic development as well as in adult thymus and mature resting peripheral T cells. The sequence of rlk showed that it is most closely related to the subfamily of cytoplasmic tyrosine kinases that includes the Btk, Itk, and Tec proteins. However, Rlk differs from these kinases by virtue of its unique aminoterminal domain, which lacks a region of pleckstrin homology common to the other members of this protein subfamily. Examination of rlk abundance within different T cell subpopulations revealed preferential expression in Th1 relative to Th2 T cell clones, suggesting a possible role in signal transduction pathways that selectively regulate cytokine production in mature CD4+ T cell subsets. Rlk thus represents a novel cytoplasmic tyrosine kinase with potential functions in intrathymic T cell development and mature T cell signaling.
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PMID:Identification of Rlk, a novel protein tyrosine kinase with predominant expression in the T cell lineage. 782 30

The defective gene responsible for the recessively inherited immunodeficiency X-linked agammaglobulinemia (XLA) has been shown to encode a cytoplasmic protein tyrosine kinase of the Src family designated Btk (Bruton's tyrosine kinase). To facilitate the search for germline mutations of the Btk gene, we have characterized its genomic structure. Eighteen introns were positioned within the approximately 37 kb gene. Each of the exon/intron boundaries were defined and sequenced, and all but two conform to consensus sequences. We have utilized the genomic organization of Btk and the intervening sequence data to design an assay for amplifying each of the 19 exons from XLA patient DNA for single strand conformation polymorphism (SSCP) analysis. By using this method we have identified mutations in 12 of 14 unrelated affected males: seven different base substitutions and two small deletions. Two of the mutations described in exon 15 of the kinase domain were found in more than one patient and may represent a mutation hot spot. Exon scanning has proven to be a valuable method for identifying the patient mutations in genomic DNA without the use of cDNA. The mutations are easily confirmed with direct sequencing of the amplified exons. This approach will greatly benefit XLA family studies involving carrier detection and prenatal diagnosis. In addition, the mutations identified may reveal residues involved in the specific protein interactions necessary in the B-cell developmental pathway, of which Btk is an integral component.
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PMID:Genomic organization of the Btk gene and exon scanning for mutations in patients with X-linked agammaglobulinemia. 788 Mar 20


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