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

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

Pleckstrin homology (PH) domains comprised of loosely conserved sequences of approximately 100 amino acid residues are a functional protein motif found in many signal-transducing and cytoskeletal proteins. We recently demonstrated that the PH domains of Tec family protein-tyrosine kinases Btk and Emt (equal to Itk and Tsk) interact with protein kinase C (PKC) and that PKC down-regulates Btk by phosphorylation. In this study we have characterized the PKC-BtkPH domain interaction in detail. Using pure PKC preparations, it was shown that the Btk PH domain interacts with PKC with high affinity (KD = 39 nM). Unlike other tested phospholipids, phosphatidylinositol 4,5-bisphosphate, which binds to several PH domains, competed with PKC for binding to the PH domain apparently because their binding sites on the amino-terminal portion of the PH domains overlap. The minimal PKC-binding sequence within the Btk PH domain was found to correspond roughly to the second and third beta-sheets of the PH domains of known tertiary structures. On the other hand, the C1 regulatory region of PKCepsilon containing the pseudosubstrate and zinc finger-like sequences was found to be sufficient for strong binding to the Btk PH domain. Phorbol 12-myristate 13-acetate (PMA), a potent activator of PKC that interacts with the C1 region of PKC, inhibited the PKC-PH domain interaction, whereas the bioinactive PMA (4-alpha-PMA) was ineffective. The zeta isoform of PKC, which has a single zinc finger-like motif instead of the two tandem zinc finger-like sequences present in conventional and novel PKC isoforms, does not bind PMA. Thus, as expected, PH domain binding with PKCzeta was not interfered with by PMA. Further, inhibitors that are known to attack the catalytic domains of serine/threonine kinases did not affect this PKC-PH domain interaction. In contrast, the presence of physiological concentrations of Ca2+ induced less than a 2-fold increase in PKC-PH domain binding. These results indicate that PKC binding to PH domains involve the beta2-beta3 region of the Btk PH domain and the C1 region of PKC, and agents that interact with either of these regions (i.e. phosphatidylinositol 4,5-bisphosphate binding to the PH domain and PMA binding to the C1 region of PKC) might act to regulate PKC-PH domain binding.
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PMID:Interactions between protein kinase C and pleckstrin homology domains. Inhibition by phosphatidylinositol 4,5-bisphosphate and phorbol 12-myristate 13-acetate. 914 13

Mutations of the Bruton's tyrosine kinase (Btk) gene cause X linked agammaglobulinaemia (XLA). This inherited immunodeficiency disease causes an arrest in B cell differentiation of pre-B cells to mature B cells. In this study we report the characterisation of mutations in the Btk gene in 10 unrelated XLA families. The screening approach we used was based on reverse transcriptase PCR and direct cycle sequencing of the amplified products followed by analysis of the observed mutations at the level of genomic DNA. The single strand confirmation polymorphism (SSCP) technique was used for assessment of the carriers in some of these families. Various mutations throughout the coding gene were observed, including missense and nonsense mutations, a deletion, and several splicing defects. None of the mutations except one has been previously described. There were three point mutations resulting in a single amino acid substitution. One of these missense mutations was observed in a conserved region of the PH domain, the other two were found in the src homology domain 2 that is involved in phosphotyrosyl peptide binding. Two mutations were single base pair substitutions resulting in premature stop codons. In four patients abnormal Btk transcripts were found that were the result of aberrant splicing. One small deletion was observed causing a frameshift and a secondary premature termination signal. Characterisation of the mutations responsible for XLA allowed us to diagnose the disease conclusively and identify the phenotypically normal female carriers.
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PMID:Identification of novel Bruton's tyrosine kinase mutations in 10 unrelated subjects with X linked agammaglobulinaemia. 919 69

Bruton's tyrosine kinase (Btk) is an enzyme which is involved in maturation of B cells. It is a target for mutations causing X-linked agammaglobulinaemia (XLA) in man. We have determined the structure of the N-terminal part of Btk by X-ray crystallography at 1.6 A resolution. This part of the kinase contains a pleckstrin homology (PH) domain and a Btk motif. The structure of the PH domain is similar to those published previously: a seven-stranded bent beta-sheet with a C-terminal alpha-helix. Individual point mutations within the Btk PH domain which cause XLA can be classified as either structural or functional in the light of the three-dimensional structure and biochemical data. All functional mutations cluster into the positively charged end of the molecule around the predicted binding site for phosphatidylinositol lipids. It is likely that these mutations inactivate the Btk pathway in cell signalling by reducing its affinity for inositol phosphates, which causes a failure in translocation of the kinase to the cell membrane. A small number of signalling proteins contain a Btk motif that always follows a PH domain in the sequence. This small module has a novel fold which is held together by a zinc ion bound by three conserved cysteines and a histidine. The Btk motif packs against the second half of the beta-sheet of the PH domain, forming a close contact with it. Our structure opens up new ways to study the role of the PH domain and Btk motif in the cellular function of Btk and the molecular basis of its dysfunction in XLA patients.
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PMID:Structure of the PH domain and Btk motif from Bruton's tyrosine kinase: molecular explanations for X-linked agammaglobulinaemia. 921 82

We previously reported that the pleckstrin homology (PH) domain of Bruton's tyrosine kinase (Btk) binds Ins(1,3,4,5)P4 and that missense mutations in this domain which cause either human X-linked agammaglobulinemia (XLA) or murine X-linked immunodeficiency (Xid) also dramatically reduce the Ins(1,3,4,5)P4 binding activity. In this paper, we describe the inositol phosphate binding specificity of the Btk PH domain and different inositol polyphosphate binding properties among the PH domains of Tec family kinases. Our results suggest that certain inositol phosphates and/or phosphoinositides are physiological ligands of some Tec family kinases and that Tec family members are differently regulated by inositol molecules.
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PMID:Characterization of the pleckstrin homology domain of Btk as an inositol polyphosphate and phosphoinositide binding domain. 924 Apr 35

Pleckstrin homology (PH) and phosphotyrosine binding (PTB) domains are structurally related regulatory modules that are present in a variety of proteins involved in signal transduction, such as kinases, phospholipases, GTP exchange proteins, and adapter proteins. Initially these domains were shown to mediate protein-protein interactions, but more recently they were also found to bind phosphoinositides. Most studies to date have focused on binding of PH domains to phosphatidylinositol (PtdIns)-4-P and PtdIns-4,5-P2 and have not considered the lipid products of phosphoinositide 3-kinase: PtdIns-3-P, PtdIns-3,4-P2, and PtdIns-3,4,5-P3. Here we have compared the phosphoinositide specificity of six different PH domains and the Shc PTB domain using all five phosphoinositides. We show that the Bruton's tyrosine kinase PH domain binds to PtdIns-3,4, 5-P3 with higher affinity than to PtdIns-4,5-P2, PtdIns-3,4-P2 or inositol 1,3,4,5-tetrakisphosphate (Ins-1,3,4,5-P4). This selectivity is decreased by the xid mutation (R28C). Selective binding of PtdIns-3,4,5-P3 over PtdIns-4,5-P2 or PtdIns-3,4-P2 was also observed for the amino-terminal PH domain of T lymphoma invasion and metastasis protein (Tiam-1), the PH domains of Son-of-sevenless (Sos) and, to a lesser extent, the PH domain of the beta-adrenergic receptor kinase. The oxysterol binding protein and beta-spectrin PH domains bound PtdIns-3,4,5-P3 and PtdIns-4,5-P2 with similar affinities. PtdIns-3,4,5-P3 and PtdIns-4,5-P2 also bound to the PTB domain of Shc with similar affinities and lipid binding was competed with phosphotyrosine (Tyr(P)-containing peptides. These results indicate that distinct PH domains select for different phosphoinositides.
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PMID:A comparative analysis of the phosphoinositide binding specificity of pleckstrin homology domains. 926 46

Tec family protein tyrosine kinases have in their N-terminus two domains. The PH domain is followed by Tec homology (TH) domain, which consists of two motifs. The first pattern, Btk motif, is also present in some Ras GAP molecules. C-terminal half of the TH domain, a proline-rich region, has been shown to bind to SH3 domains. Mutations in Bruton's tyrosine kinase (Btk) belonging to the Tec family cause X-linked agammaglobulinemia (XLA) due to developmental arrest of B cells. Here we present the first missense mutations in the TH domain. The substitutions affect a conserved pair of cysteines, residues 154 and 155, involved in Zn2+ binding and thereby the mutations alter protein folding and stability.
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PMID:Missense mutations affecting a conserved cysteine pair in the TH domain of Btk. 928 Feb 83

Bruton's tyrosine kinase (Btk) is essential for normal B lymphocyte development and function. The activity of Btk is partially regulated by transphosphorylation within its kinase domain by Src family kinases at residue Tyr-551 and subsequent autophosphorylation at Tyr-223. Activation correlates with Btk association with cellular membranes. Based on specific loss of function mutations, the Btk pleckstrin homology (PH) domain plays an essential role in this activation process. The Btk PH domain can bind in vitro to several lipid end products of the phosphatidylinositol 3-kinase (PI 3-kinase) family including phosphatidylinositol 3,4,5-trisphosphate. Activation of Btk as monitored by elevation of phosphotyrosine content and a cellular transformation response was dramatically enhanced by coexpressing a weakly activated allele of Src (E378G) and the two subunits of PI 3-kinase-gamma. This activation correlates with new sites of phosphorylation on Btk identified by two-dimensional phosphopeptide mapping. Activation of Btk was dependent on the catalytic activity of all three enzymes and an intact Btk PH domain and Src transphosphorylation site. These combined data define Btk as a downstream target of PI 3-kinase-gamma and Src family kinases.
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PMID:Phosphatidylinositol 3-kinase-gamma activates Bruton's tyrosine kinase in concert with Src family kinases. 939 Nov 11

Signal transduction through phosphoinositide 3-OH kinase (PI 3-kinase) has been implicated in the regulation of lymphocyte adhesion mediated by integrin receptors. Cellular phosphorylation products of PI 3-kinases interact with a subset of pleckstrin homology (PH) domains, a module that has been shown to recruit proteins to cellular membranes. We have recently identified cytohesin-1, a cytoplasmic regulator of beta2 integrin adhesion to intercellular adhesion molecule 1. We describe here that expression of a constitutively active PI 3-kinase is sufficient for the activation of Jurkat cell adhesion to intercellular adhesion molecule 1, and for enhanced membrane association of cytohesin-1. Up-regulation of cell adhesion by PI 3-kinase and membrane association of endogenous cytohesin-1 is abrogated by overexpression of the isolated cytohesin-1 PH domain, but not by a mutant of the PH domain which fails to associate with the plasma membrane. The PH domain of Bruton's tyrosine kinase (Btk), although strongly associated with the plasma membrane, had no effect on either membrane recruitment of cytohesin-1 or on induction of adhesion by PI 3-kinase. Having delineated the critical steps of the beta2 integrin activation pathway by biochemical and functional analyses, we conclude that PI 3-kinase activates inside-out signaling of beta2 integrins at least partially through cytohesin-1.
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PMID:Phosphoinositide 3-OH kinase activates the beta2 integrin adhesion pathway and induces membrane recruitment of cytohesin-1. 961 87

Recruitment of intracellular proteins to the plasma membrane is a commonly found requirement for the initiation of signal transduction events. The recently discovered pleckstrin homology (PH) domain, a structurally conserved element found in approximately 100 signaling proteins, has been implicated in this function, because some PH domains have been described to be involved in plasma membrane association. Furthermore, several PH domains bind to the phosphoinositides phosphatidylinositol-(4,5)-bisphosphate and phosphatidylinositol-(3,4,5)-trisphosphate in vitro, however, mostly with low affinity. It is unclear how such weak interactions can be responsible for observed membrane binding in vivo as well as the resulting biological phenomena. Here, we investigate the structural and functional requirements for membrane association of cytohesin-1, a recently discovered regulatory protein of T cell adhesion. We demonstrate that both the PH domain and the adjacent carboxyl-terminal polybasic sequence of cytohesin-1 (c domain) are necessary for plasma membrane association and biological function, namely interference with Jurkat cell adhesion to intercellular adhesion molecule 1. Biosensor measurements revealed that phosphatidylinositol-(3,4,5)-trisphosphate binds to the PH domain and c domain together with high affinity (100 nM), whereas the isolated PH domain has a substantially lower affinity (2-3 microM). The cooperativity of both elements appears specific, because a chimeric protein, consisting of the c domain of cytohesin-1 and the PH domain of the beta-adrenergic receptor kinase does not associate with membranes, nor does it inhibit adhesion. Moreover, replacement of the c domain of cytohesin-1 with a palmitoylation-isoprenylation motif partially restored the biological function, but the specific targeting to the plasma membrane was not retained. Thus we conclude that two elements of cytohesin-1, the PH domain and the c domain, are required and sufficient for membrane association. This appears to be a common mechanism for plasma membrane targeting of PH domains, because we observed a similar functional cooperativity of the PH domain of Bruton's tyrosine kinase with the adjacent Bruton's tyrosine kinase motif, a novel zinc-containing fold.
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PMID:The PH domain and the polybasic c domain of cytohesin-1 cooperate specifically in plasma membrane association and cellular function. 969 61

Phosphatidylinositol 3-kinase (PI3K) mediates a variety of cellular responses by generating PtdIns(3,4)P2 and PtdIns(3,4,5)P3. These 3-phosphoinositides then function directly as second messengers to activate downstream signaling molecules by binding pleckstrin homology (PH) domains in these signaling molecules. We have established a novel assay in the yeast Saccharomyces cerevisiae to identify proteins that bind PtdIns(3,4)P2 and PtdIns(3,4,5)P3 in vivo which we have called TOPIS (Targets of PI3K Identification System). The assay uses a plasma membrane-targeted Ras to complement a temperature-sensitive CDC25 Ras exchange factor in yeast. Coexpression of PI3K and a fusion protein of activated Ras joined to a PH domain known to bind PtdIns(3,4)P2 (AKT) or PtdIns(3,4,5)P3 (BTK) rescues yeast growth at the non-permissive temperature of 37 degreesC. Using this assay, we have identified several amino acids in the beta1-beta2 region of PH domains that are critical for high affinity binding to PtdIns(3,4)P2 and/or PtdIns(3,4,5)P3, and we have proposed a structural model for how these PH domains might bind PI3K products with high affinity. From these data, we derived a consensus sequence which predicts high-affinity binding to PtdIns(3, 4)P2 and/or PtdIns(3,4,5)P3, and we have identified several new PH domain-containing proteins that bind PI3K products, including Gab1, Dos, myosinX, and Sbf1. Use of this assay to screen for novel cDNAs which rescue yeast at the non-permissive temperature should provide a powerful approach for uncovering additional targets of PI3K.
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PMID:Identification and analysis of PH domain-containing targets of phosphatidylinositol 3-kinase using a novel in vivo assay in yeast. 973 15


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