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)

Irreversible inhibitors of proteases have proven themselves useful tools for determining which proteases are active under given conditions in tissues or cells and for studying the functional role that a protease plays in physiological processes. The application of such techniques to the study of the activity and function of protein-protein interactions has been hindered by the lack of guiding principles for the mechanistic design of irreversible inhibitors targeting the "active site" of a protein interaction. We report herein the first example of a mechanism-based irreversible inhibitor of a protein interaction that has been specifically targeted to one member of the PDZ family of protein interaction domains: the second PDZ domain of the membrane-associated guanylate kinase MAGI3. This inhibitor was designed using rationally directed computational evaluation to take advantage of a conserved histidine in the PDZ domain by introducing an ionizable group that will be held in close proximity to that nucleophile during binding. The novel compound exhibits all of the characteristics of an irreversible inhibitor of the interaction of the tumor suppressor PTEN with MAGI3 in in vitro models. In cells, the inhibitor can be shown to release PTEN from sequestration by MAGI3 and consequently upregulate the PKB signaling pathway.
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PMID:A selective irreversible inhibitor targeting a PDZ protein interaction domain. 1451 76

The tumor-suppressor gene PTEN encodes a multifunctional phosphatase that is mutated in a variety of human cancers. PTEN inhibits the phosphatidylinositol 3-kinase pathway and downstream functions, including activation of Akt/protein kinase B (PKB), cell survival, and cell proliferation in tumor cells carrying mutant- or deletion-type PTEN. In such tumor cells, enforced expression of PTEN decreases cell proliferation through cell-cycle arrest at G1 phase accompanied, in some cases, by induction of apoptosis. More recently, the tumor-suppressive effect of PTEN has been reported in ovarian and thyroid tumors that are wild type for PTEN. In the present study, we examined the tumor-suppressive effect of PTEN in human colorectal cancer cells that are wild type for PTEN. Adenoviral-mediated transfer of PTEN (Ad-PTEN) suppressed cell growth and induced apoptosis significantly in colorectal cancer cells (DLD-1, HT29, and SW480) carrying wtPTEN than in normal colon fibroblast cells (CCD-18Co) carrying wtPTEN. This suppression was induced through downregulation of the Akt/PKB pathway, dephosphorylation of focal adhesion kinase (FAK) and mitogen-activated protein kinase (MAPK) and cell-cycle arrest at the G2/M phase, but not the G1 phase. Furthermore, treatment of human colorectal tumor xenografts (HT-29, and SW480) with Ad-PTEN resulted in significant (P=0.01) suppression of tumor growth. These results indicate that Ad-PTEN exerts its tumor-suppressive effect on colorectal cancer cells through inhibition of cell-cycle progression and induction of cell death. Thus Ad-PTEN may be a potential therapeutic for treatment of colorectal cancers.
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PMID:Adenovirus-mediated transfer of the PTEN gene inhibits human colorectal cancer growth in vitro and in vivo. 1452 20

The tumour suppressor PTEN is a PtdIns(3,4,5)P(3) phosphatase that regulates many cellular processes through direct antagonism of PI 3-kinase signalling. Here we show that oxidative stress activates PI 3-kinase-dependent signalling via the inactivation of PTEN. We use two assay systems to show that cellular PTEN phosphatase activity is inhibited by oxidative stress induced by 1 mM hydrogen peroxide. PTEN inactivation by oxidative stress also causes an increase in cellular PtdIns(3,4,5)P(3) levels and activation of the downstream PtdIns(3,4,5)P(3) target, PKB/Akt, that does not occur in cells lacking PTEN. We then show that endogenous oxidant production in RAW264.7 macrophages inactivates a fraction of the cellular PTEN, and that this is associated with an oxidant-dependent activation of downstream signalling. These results show that oxidants, including those produced by cells, can activate downstream signalling via the inactivation of PTEN. This demonstrates a novel mechanism of regulation of the activity of this important tumour suppressor and the signalling pathways it regulates. These results may have significant implications for the many cellular processes in which PtdIns(3,4,5)P(3) and oxidants are produced concurrently.
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PMID:Redox regulation of PI 3-kinase signalling via inactivation of PTEN. 1453 22

The PTEN (phosphatase and tensin homologue deleted on chromosome 10) tumor suppressor is a phosphatidylinositol 3,4,5-trisphosphate (PtdInsP3) 3-phosphatase that plays a crucial role in regulating many cellular processes by antagonizing the phosphoinositide 3-kinase signaling pathway. Although able to metabolize soluble inositol phosphates in vitro, the question of their significance as physiological substrates is unresolved. We show that inositol phosphates are not regulated by wild type PTEN, but that a synthetic mutant, PTEN M-CBR3, previously thought to be inactive toward inositides, can selectively regulate inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P5). Transfection of U87-MG cells with PTEN M-CBR3 lowered Ins(1,3,4,5,6)P5 levels by 60% without detectable effect on PtdInsP3. Although PTEN M-CBR3 is a 3-phosphatase, levels of myo-inositol 1,4,5,6-tetrakisphosphate were not increased, whereas myo-inositol 1,3,4,6-tetrakisphospate levels increased by 80%. We have used PTEN M-CBR3 to study the physiological function of Ins(1,3,4,5,6)P5 and have found that Ins(1,3,4,5,6)P5 does not modulate PKB phosphorylation, nor does it regulate clathrin-mediated epidermal growth factor receptor internalization. By contrast, PTEN M-CBR3 expression, and the subsequent lowering of Ins(1,3,4,5,6)P5, are associated with reduced anchorage-independent colony formation and anchorage-dependent proliferation in U87-MG cells. Our results, together with previously published data, suggest that Ins(1,3,4,5,6)P5 has a role in proliferation.
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PMID:PTEN M-CBR3, a versatile and selective regulator of inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P5). Evidence for Ins(1,3,4,5,6)P5 as a proliferative signal. 1456 49

The protein kinase PKB/Akt plays a pivotal role in promoting cell survival and proliferation. This study investigated the regulation of PKB/Akt activity in breast cancer cells. In primary invasive breast cancers PKB/Akt exhibited elevated phosphorylation at regulatory site Ser473 in 80% of cases, using immunohistochemistry. The degree of phospho-PKB/Akt immunoreactivity was positively correlated with the extent of its nuclear accumulation. Moderate/strong staining was seen in 31% of the samples but was absent in tumour-associated normal breast epithelia. To examine the mechanisms of PKB/Akt activation, we studied its phosphorylation in a panel of breast cancer cell lines. PKB/Akt was constitutively phosphorylated on both regulatory sites (Thr308 and Ser473) in the absence of serum growth factors in 7 of 8 lines but not in two cell lines derived from normal breast epithelia. Further analysis revealed that constitutive PKB/Akt phosphorylation was associated with loss of PTEN phosphatase expression (CAL51, MDA-MB-468, BT549 cells) and constitutive activation of erbB2 (SKBR3, BT474 cells). In two further breast cancer lines (T47D and HS578T) PKB/Akt phosphorylation was dependent upon autocrine factors acting primary through the epidermal growth factor receptor (EGFR) and erbB2. Conditioned medium from HS578T cells stimulated EGFR-dependent PKB/Akt phosphorylation in normal breast cells. These results demonstrate that PKB/Akt is frequently activated in breast cancer through diverse mechanisms, including autocrine signalling via erbB receptors.
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PMID:Autocrine signalling through erbB receptors promotes constitutive activation of protein kinase B/Akt in breast cancer cell lines. 1457 54

Glioblastomas frequently carry mutations in the PTEN tumor suppressor gene on 10q23.3. The tumor suppressor properties of Pten are closely related to its inhibitory effect on the phosphatidyl-inositol-3'-kinase (Pi3k)-dependent activation of protein kinase B (Akt) signalling. Here, we report on the analysis of 17 genes related to the Pi3k/Akt signalling pathway for genetic alteration and aberrant expression in a series of 103 glioblastomas. Mutation, homozygous deletion or loss of expression of PTEN was detected in 32% of the tumors. In contrast, we did not find any aberrations in the inositol polyphosphate phosphatase like-1 gene (INPPL1), whose gene product may also counteract Pi3k-dependent Akt activation. Analysis of genes encoding proteins that may activate the pathway upstream of Pi3k revealed variable fractions of tumors with EGFR amplification (31%), PDGFRA amplification (8%), and IRS2 amplification (2%). The protein tyrosine kinase 2 (PTK2/FAK1) gene was neither amplified nor overexpressed at the mRNA level. Investigation of three genes encoding catalytic subunits of Pi3k (PIK3CA, PIK3CD, and PIK3C2B) revealed amplification of PIK3C2B (1q32) in 6 tumors (6%). Overexpression of PIK3C2B mRNA was detected in 4 of these cases. PIK3CD (1p36.2) and PIK3CA (3q26.3) were not amplified but PIK3CD mRNA was overexpressed in 6 tumors (6%). Amplification and overexpression of AKT1 was detected in a single case of gliosarcoma. The IRS1, PIK3R1, PIK3R2, AKT2, AKT3, FRAP1, and RPS6KB1 genes were neither amplified nor overexpressed in any of the tumors. Taken together, our data indicate that different genes related to the Pi3k/Akt signalling pathway may be aberrant in glioblastomas.
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PMID:Genetic alterations and aberrant expression of genes related to the phosphatidyl-inositol-3'-kinase/protein kinase B (Akt) signal transduction pathway in glioblastomas. 1465 56

We were interested in the elucidation of the interaction between the heparan sulfate proteoglycan, perlecan, and PTEN in the regulation of vascular smooth muscle cell (SMC) growth. We verified serum-stimulated DNA synthesis, and Akt and FAK phosphorylation were significantly reduced in SMCs overexpressing wild-type PTEN. Our previous studies showed perlecan is a potent inhibitor of serum-stimulated SMC growth. We report in the present study, compared with SMCs plated on fibronectin, serum-stimulated SMCs plated on perlecan exhibited increased PTEN activity, decreased FAK and Akt activities, and high levels of p27, consistent with SMC growth arrest. Adenoviral-mediated overexpression of constitutively active Akt reversed perlecan-induced SMC growth arrest while morpholino antisense-mediated loss of endogenous PTEN resulted in increased growth and phosphorylation of FAK and Akt of SMCs on perlecan. Immunohistochemical and Western analyses of balloon-injured rat carotid artery tissues showed a transient increase in phosphoPTEN (inactive) after injury, correlating to high rates of neointimal cell replication; phosphoPTEN was largely limited to actively replicating SMCs. Similarly, in the developing rat aorta, we found increased PTEN activity associated with increased perlecan deposition and decreased SMC replication rates. However, significantly decreased PTEN activity was detected in aortas of perlecan-deficient mouse embryos, consistent with SMC hyperplasia observed in these animals, compared with E17.5 heterozygous controls that produce abundant amounts of perlecan at this developmental time point. Our data show PTEN is a potent endogenously produced inhibitor of SMC growth and increased PTEN activity mediates perlecan-induced suppression of SMC proliferation.
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PMID:Perlecan-induced suppression of smooth muscle cell proliferation is mediated through increased activity of the tumor suppressor PTEN. 1465 29

In glioma cells, the stimulatory input of extracellular matrix components and an increased sensitivity to growth factors result in a high proliferative and migratory behaviour. Cell surface receptor interactions play pivotal roles in converging information about conditions in the environment immediately outside the cell. The transduced signal, in turn induces a response within the cell that provokes a specific behaviour. Cellular migration and cell proliferation are interwoven processes that share several common intracellular pathways. The major cross-links are the phosphoinositol phosphate regulating enzymes, PI-3 kinase and PTEN, the focal adhesion kinase (FAK) and the tumour suppressor p53. An understanding of the interaction between the molecular participants involved in migration and proliferation will promote the design of new treatments. A full understanding of the basis of the invasiveness of tumour cells remains elusive. Gene and protein expression are being studied, using modern techniques such as microarray analysis, SAGE and 2-D protein gels. Transient and permanent protein-protein interactions and recruitment of proteins to specialised cellular domains are equally important in regulating cellular invasion and presumably will attract more attention in future.
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PMID:Molecular approaches to brain tumour invasion. 1466 59

Cowden disease, also known as multiple hamartoma syndrome, is a rare disease inherited in an autosomal dominant pattern, which confers a high risk of developing breast and thyroid carcinomas. Mutations in PTEN, a tumor suppressor gene located on chromosome 10q23, have been identified in patients with Cowden disease. In this work, the direct sequencing of all coding regions of the PTEN gene led us to the identification of N48K, a new germline PTEN missense mutation, in a patient suffering from Cowden disease. The genetic analysis of 200 chromosomes from healthy individuals revealed that the variant was not common in our population. Moreover, by functional analysis we found that the ability of PTEN N48K mutant protein to inhibit the activation of the proto-oncogene PKB/Akt was impaired, supporting the involvement of N48K mutation in Cowden disease. Loss of heterozygosity using three microsatellites (D10S215, D10S541, and D10S564) and the complete sequence analysis of PTEN exons in breast and endometrial tumor samples from the same patient were also carried out in an attempt to identify additional PTEN somatic mutations. The lack of loss of heterozygosity or additional mutations in tumor samples suggests that abnormalities of the regulatory regions of the PTEN gene or haplo-insufficiency might occur in tumors from Cowden disease patients.
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PMID:A novel loss-of-function mutation (N48K) in the PTEN gene in a Spanish patient with Cowden disease. 1467 82

We show in this study that endogenous NEP and PTEN associate in cells directly through electrostatic interactions between a highly basic residue stretch in the intracellular domain of NEP and the major phosphorylation site in PTEN's tail. NEP binds and engages in higher order complexes both phosphorylated and unphosphorylated PTEN. NEP recruits PTEN to the plasma membrane and enhances its stability and phosphatase activity. As a result, an enzymatically inactive NEP mutant preserves the ability to bind PTEN, inactivates the Akt/PKB kinase, and partially suppresses the growth of PC cells. This study demonstrates a molecular cooperation between NEP and PTEN tumor suppressors in which NEP constitutively recruits and activates PTEN to inhibit the PI3K/Akt oncogenic pathway.
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PMID:Synergy in tumor suppression by direct interaction of neutral endopeptidase with PTEN. 1474 27


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