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)

PKB/Akt is a protein involved in control of apoptosis, proliferation and cellular metabolism, and it has been found to be activated in many cancers. Activation of PKB involves recruitment of the enzyme by its PH domain to the cell membrane, and phosphorylation at two residues, T308 and S473. To produce active PKB kinase from Escherichia coli, we constructed a derivative of PKB lacking the PH domain and mutated to glutamate at residues S124, T450 and the activating residue S473 (DeltaPH-PKB-EEE). DeltaPH-PKB-EEE was expressed in E. coli together with PDK1, the kinase responsible for phosphorylating PKB at T308, which was expressed as a GST-fusion. Full-length DeltaPH-PKB-EEE was obtained by using a double tag strategy: His6 at the N-terminus and FLAG at the C-terminus. The protein was purified by nickel affinity chromatography, followed by passage over an anti-FLAG column. The final purification step, anion exchange over a monoQ column, separated phosphorylated from unphosphorylated protein. Active recombinant PKB kinase was thus produced from E. coli, by a simple, reproducible procedure.
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PMID:Expression and purification of active PKB kinase from Escherichia coli. 1580 34

This article describes recent advances in the development and biological evaluation of small molecule inhibitors for the serine/threonine kinase Akt (PKB). Akt plays a pivotal role in cell survival and proliferation through a number of downstream effectors. Recent studies indicate that unregulated activation of the PI3K/Akt pathway is a prominent feature of many human cancers and Akt is over-expressed or activated in all major cancers. Akt is considered an attractive target for chemotherapy and it has been postulated that inhibition of Akt alone or in combination with standard cancer chemotherapeutics will reduce the apoptotic threshold and preferentially kill cancer cells. The development of specific and potent inhibitors will allow this hypothesis to be tested in animals. The majority of small molecule inhibitors in this nascent field are classic ATP-competitive inhibitors which provide little specificity. Phosphatidylinositol (PI) analogs have been reported to inhibit Akt, but these inhibitors may also have specificity problems with respect to other PH domain containing proteins and may have poor bioavailability. None of the inhibitors in these classes have been reported to have Akt isozyme specificity. Recently, novel allosteric inhibitors have been reported which are pleckstrin homology domain dependent and exhibit Akt isozyme selectivity. Inhibitors in this class may have sufficient potency and specificity to test for tumor efficacy in animal models and recently reported preliminary experiments are reviewed.
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PMID:The Akt/PKB family of protein kinases: a review of small molecule inhibitors and progress towards target validation. 1585 41

PDK1 and PKB/Akt have a pleckstrin homology (PH) domain at the C-terminus and N-terminus, respectively, which stabilizes an unphosphorylated, autoinhibited conformation. Binding of the PH domain to a phospholipid second messenger causes relief of autoinhibition, which results in kinase phosphorylation and activation. Baculovirus-mediated expression in Sf9 insect cells of both His(6)-PDK1 and His(6)-PKBbeta/Akt2 were optimized, which significantly improved the yields (5-fold) of the affinity purified enzymes over previously reported values. Isoelectric focusing (IEF) and Western analyses indicated that the apparent V(max)=192+/-13 U/mg and K(m) (PDK-Tide)=55+/-10 microM of purified His(6)-PDK1 results from a mixture of at least three different phospho-specific isoforms (pI values of 6.8, 6.5, and 6.4). A purely unphosphorylated isoform of His(6)-PDK1 (pI=6.8) was generated by treatment with lambda protein phosphatase (lambdaPP), which decreased V(max) to 2.4+/-0.4 U/mg and increased K(m) (PDK-Tide) to 217+/-61 microM. Isoelectric focusing and Western analyses indicated that the apparent V(max)=0.21+/-0.03 U/mg and K(m) (Crosstide)=87+/-30 microM of purified His(6)-PKBbeta/Akt2 results from a mixture of the enzyme monophosphorylated either at Ser-474 ( approximately 90%) or at Thr-309 ( approximately 10%). A purely unphosphorylated isoform of His(6)-PKBbeta/Akt2 (pI=6.4) was generated by treatment with lambdaPP, which decreased V(max) approximately 2-fold. The optimization of high-level production and detailed characterization of purified and lambdaPP-treated His(6)-PDK1 and His(6)-PKBbeta/Akt2 will facilitate detailed structural and kinetic studies aimed at understanding the mechanism of second messenger-induced activation.
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PMID:Improved yields for baculovirus-mediated expression of human His(6)-PDK1 and His(6)-PKBbeta/Akt2 and characterization of phospho-specific isoforms for design of inhibitors that stabilize inactive conformations. 1608 96

The adaptor protein Gab-2 coordinates the assembly of the IL-3 signalsome comprising Gab-2, Grb2, Shc, SHP-2 and PI3K. To investigate the role of the pleckstrin homology domain of Gab-2 in this process, epitope-tagged wild type Gab-2 (WTGab-2), Gab-2 lacking its PH domain (DeltaPHGab-2) and the Gab-2 PH domain alone (PHGab-2) were inducibly expressed in IL-3-dependent BaF/3 cells. Expression of DeltaPHGab-2 reduced IL-3-dependent proliferation and long-term activation of ERK1 and 2 and PKB by IL-3. While we demonstrate that the Gab-2 PH domain can bind PI(3,4,5)P3, it is dispensable for Gab-2 membrane localisation, tyrosine phosphorylation and signalsome formation. Rather, the proline-rich motifs of Gab-2 appear to contribute to the constitutive membrane localisation we observe, independently of tyrosine phosphorylation or the PH domain. Taken together, these findings suggest that once Gab-2 is tyrosine phosphorylated its PH domain is required for the optimal stabilisation of the signalsome, enabling full activation of downstream signals.
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PMID:The pleckstrin homology domain of Gab-2 is required for optimal interleukin-3 signalsome-mediated responses. 1627 30

TFII-I is a transcription factor and a target of phosphorylation by Bruton's tyrosine kinase. In humans, deletions spanning the TFII-I locus are associated with a cognitive defect, the Williams-Beuren cognitive profile. We report an unanticipated role of TFII-I outside the nucleus as a negative regulator of agonist-induced calcium entry (ACE) that suppresses surface accumulation of TRPC3 (transient receptor potential C3) channels. Inhibition of ACE by TFII-I requires phosphotyrosine residues that engage the SH2 (Src-homology 2) domains of phospholipase C-g (PLC-g) and an interrupted, pleckstrin homology (PH)-like domain that binds the split PH domain of PLC-g. Our observations suggest a model in which TFII-I suppresses ACE by competing with TRPC3 for binding to PLC-g.
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PMID:Action of TFII-I outside the nucleus as an inhibitor of agonist-induced calcium entry. 1702 38

Phosphoinositide 3-kinases (PI3Ks) generate several distinct lipid second messengers including phosphatidylinositol (3,4,5) trisphosphate (PIP3) and phosphatidylinositol (3,4) bisphosphate PI(3,4)P2. PI(3,4)P2 is produced with distinct kinetics and binds to distinct PH domain effector proteins; however, the regulation of this signaling pathway is poorly understood. Superoxides such as hydrogen peroxide are transiently produced after activation through various cell surface receptors and play important roles in immune and inflammatory responses. Here we use quantitative microscopy to examine the effect of peroxide on PI(3,4)P2-mediated mobilization of signaling proteins in B lymphocytes. Peroxide was found to induce dose-dependant membrane recruitment of the PI(3,4)P2-binding PH domain proteins Bam32, TAPP2 and Akt/PKB but not the PIP3-binding PH domain of Btk. Peroxide-induced membrane recruitment was found to be dependant on PI3K activity, with the p110delta isoform contributing much of the activity in the BJAB human B lymphoma model. Strikingly, peroxide co-stimulation enhanced antigen receptor-induced membrane recruitment of Bam32 and TAPP2, with combined stimulation exceeding the maximum achievable with either stimulus alone. Expression of the lipid phosphatase PTEN led to reduction of antigen receptor-induced membrane recruitment of TAPP2; however, peroxide costimulation could overcome the inhibitory effect of PTEN. Inhibition of the NADPH oxidase led to reduction of antigen receptor-induced membrane recruitment of TAPP2. Our results indicate that exogenous and endogenous superoxides can modulate the quality of the PI3K signal in lymphocytes by selectively increasing PI(3,4)P2-dependant signaling.
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PMID:Regulation of phosphoinositide 3-kinase signaling by oxidants: hydrogen peroxide selectively enhances immunoreceptor-induced recruitment of phosphatidylinositol (3,4) bisphosphate-binding PH domain proteins. 1721 4

Fractionation of 3T3-L1 adipocyte membranes revealed that PDE3B (phosphodiesterase 3B) was associated with PM (plasma membrane) and ER (endoplasmic reticulum)/Golgi fractions, that insulin-induced phosphorylation/activation of PDE3B was greater in internal membranes than PM fractions, and that there was no significant translocation of PDE3B between membrane fractions. Insulin also induced formation of large macromolecular complexes, separated during gel filtration (Superose 6 columns) of solubilized membranes, which apparently contain phosphorylated/activated PDE3B and signalling molecules potentially involved in its activation by insulin, e.g. IRS-1 (insulin receptor substrate-1), IRS-2, PI3K p85 [p85-subunit of PI3K (phosphoinositide 3-kinase)], PKB (protein kinase B), HSP-90 (heat-shock protein 90) and 14-3-3. Expression of full-length recombinant FLAG-tagged murine (M) PDE3B and M3BDelta604 (MPDE3B lacking N-terminal 604 amino acids) indicated that the N-terminal region of MPDE3B was necessary for insulin-induced activation and recruitment of PDE3B. siRNA (small interfering RNA) knock-down of PDE3B indicated that PDE3B was not required for formation of insulin-induced complexes. Wortmannin inhibited insulin-induced assembly of macromolecular complexes, as well as phosphorylation/activation of PKB and PDE3B, and their co-immunoprecipitation. Another PI3K inhibitor, LY294002, and the tyrosine kinase inhibitor, Genistein, also inhibited insulin-induced activation of PDE3B and its co-immunoprecipitation with PKB. Confocal microscopy indicated co-localization of PDE3B and PKB. Recombinant MPDE3B co-immunoprecipitated, and co-eluted during Superose 12 chromatography, to a greater extent with recombinant pPKB (phosphorylated/activated PKB) than dephospho-PKB or p-DeltaPKB [pPKB lacking its PH domain (pleckstrin homology domain)]. Truncated recombinant MPDE3B proteins and pPKB did not efficiently co-immunoprecipitate, suggesting that structural determinants for their interaction reside in, or are regulated by, the N-terminal portion of MPDE3B. Recruitment of PDE3B in macromolecular complexes may be critical for regulation of specific cAMP pools and signalling pathways by insulin, e.g. lipolysis.
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PMID:Insulin-induced formation of macromolecular complexes involved in activation of cyclic nucleotide phosphodiesterase 3B (PDE3B) and its interaction with PKB. 1732 23

Protein kinase B (PKB/Akt) plays a key role in cell signaling. The PH domain of PKB binds phosphatidylinositol 3,4,5-trisphosphate translocating PKB to the plasma membrane for activation by 3-phosphoinositide-dependent protein kinase 1. The crystal structure of the headgroup inositol 1,3,4,5-tetrakisphosphate Ins(1,3,4,5)P4-PKB complex facilitates in silico ligand design. The novel achiral analogue benzene 1,2,3,4-tetrakisphosphate (Bz(1,2,3,4)P4) possesses phosphate regiochemistry different from that of Ins(1,3,4,5)P4 and surprisingly binds with similar affinity as the natural headgroup. Bz(1,2,3,4)P4 co-crystallizes with the PKBalpha PH domain in a fashion also predictable in silico. The 2-phosphate of Bz(1,2,3,4)P4 does not interact with any residue, and the D5-phosphate of Ins(1,3,4,5)P4 is not mimicked by Bz(1,2,3,4)P4. Bz(1,2,3,4)P4 is an example of a simple inositol phosphate surrogate crystallized in a protein, and this approach could be applied to design modulators of inositol polyphosphate binding proteins.
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PMID:Novel inositol phospholipid headgroup surrogate crystallized in the pleckstrin homology domain of protein kinase Balpha. 1743 22

The serine-threonine protein kinases PDK1 and PKB each contain a pleckstrin homology (PH) domain that binds the membrane-bound phosphatidylinositol 3,4,5-triphosphate [PI(3,4,5)P3] second messenger and is required for PDK1-catalyzed phosphorylation and activation of PKB. While X-ray structures have been reported for the individual regulatory PH and catalytic kinase domain constructs of both PDK1 and PKB, diffraction quality crystals of full length constructs have yet to be obtained, likely due to conformational heterogeneity. In developing alternative approaches to understanding the potential role of conformational dynamics in regulating PKB phosphorylation by PDK1, an efficient in vitro method for protein trans-splicing was developed, which utilizes the N- and C-terminal split inteins of the gene dnaE from Nostoc punctiforme [(N)NpuDnaE] and Synechocystis sp. strain PCC6803 [(C)SspDnaE], respectively. For conjugating the regulatory PH domain to the catalytic kinase domain of PDK1, the recombinant trans-splicing fusion constructs KINASE(AEY)-(N)NpuDnaE-His6 and GST-His6-(C)SspDnaE-(CMN)PH were designed, PCR assembled, overexpressed, and affinity purified. The cross-reacting (N)NpuDnaE and (C)SspDnaE inteins generated full length spliced-PDK1 with kobs = (2.8 +/- 0.3) x 10(-5) s(-1) and with < or =5% of any competing trans-cleavage reactions. Spliced-PDK1 was efficiently purified to > or =95% homogeneity from the reaction mixture by subsequent His6 affinity and ion exchange chromatography steps. In vitro kinase assays and phosphopeptide mapping studies confirmed that spliced-PDK1 retained the ability to colocalize and selectively phosphorylate Thr-309 of PKBbeta in a PI(3,4,5)P3-dependent manner. The high-level production and reconstitution of functional spliced-PDK1 establishes the feasibility of incorporating domain-specific biophysical probes for spectroscopic studies of regulatory PH domain mediated catalytic specificity.
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PMID:Reconstitution of modular PDK1 functions on trans-splicing of the regulatory PH and catalytic kinase domains. 1750 May 9

This article describes recent advances in the development and biological evaluation of small molecule inhibitors for the serine/threonine kinase Akt (PKB). Akt plays a pivotal role in cell survival and proliferation through a number of downstream effectors. Recent studies indicate that unregulated activation of the PI3K/Akt pathway is a prominent feature of many human cancers and Akt is over-expressed or activated in all major cancers. Akt is considered an attractive target for cancer therapy and inhibition of Akt alone or in combination with standard cancer chemotherapeutics has been postulated to reduce the apoptotic threshold and preferentially kill cancer cells. The development of specific and potent inhibitors will allow this hypothesis to be tested in animals. Recently, several series of small molecule, ATP-competitive inhibitors have been reported with a range of Akt potencies and selectivities. Phosphatidylinositol (PI) analogs have been reported to inhibit Akt, but these inhibitors may also have specificity problems with respect to other pleckstrin homology (PH) domain containing proteins and may have poor bioavailability. In addition, novel allosteric inhibitors have been reported which are PH domain dependent, exhibit selectivity for the individual Akt isozymes and inhibit the activity and the activation of Akt. Compounds within these classes Akt inhibitors have sufficient potency and specificity to test for tumor efficacy in animal models and recently reported preliminary experiments are reviewed.
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PMID:Recent progress in the development of ATP-competitive and allosteric Akt kinase inhibitors. 1769 25


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