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Kinase Receptor (kinase + receptor)
Kinds of Kinase Receptor Selected AbstractsSignaling by Neuronal Tyrosine Kinase Receptors: Relevance for Development and RegenerationTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 12 2009Barbara Hausott Abstract Receptor tyrosine kinase activation by binding of neurotrophic factors determines neuronal morphology and identity, migration of neurons to appropriate destinations, and integration into functional neural circuits as well as synapse formation with appropriate targets at the right time and at the right place. This review summarizes the most important aspects of intraneuronal signaling mechanisms and induced gene expression changes that underlie morphological and neurochemical consequences of receptor tyrosine kinase activation in central and peripheral neurons. Anat Rec, 292:1976,1985, 2009. © 2009 Wiley-Liss, Inc. [source] Ret deficiency in mice impairs the development of A5 and A6 neurons and the functional maturation of the respiratory rhythmEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2005J. C. Viemari Abstract Although a normal respiratory rhythm is vital at birth, little is known about the genetic factors controlling the prenatal maturation of the respiratory network in mammals. In Phox2a mutant mice, which do not express A6 neurons, we previously hypothesized that the release of endogenous norepinephrine by A6 neurons is required for a normal respiratory rhythm to occur at birth. Here we investigated the role of the Ret gene, which encodes a transmembrane tyrosine kinase receptor, in the maturation of norepinephrine and respiratory systems. As Ret -null mutants (Ret,/,) did not survive after birth, our experiments were performed in wild-type (wt) and Ret,/, fetuses exteriorized from pregnant heterozygous mice at gestational day 18. First, in wt fetuses, quantitative in situ hybridization revealed high levels of Ret transcripts in the pontine A5 and A6 areas. Second, in Ret,/, fetuses, high-pressure liquid chromatography showed significantly reduced norepinephrine contents in the pons but not the medulla. Third, tyrosine hydroxylase immunocytochemistry revealed a significantly reduced number of pontine A5 and A6 neurons but not medullary norepinephrine neurons in Ret,/, fetuses. Finally, electrophysiological and pharmacological experiments performed on brainstem ,en bloc' preparations demonstrated impaired resting respiratory activity and abnormal responses to central hypoxia and norepinephrine application in Ret,/, fetuses. To conclude, our results show that Ret gene contributes to the prenatal maturation of A6 and A5 neurons and respiratory system. They support the hypothesis that the normal maturation of the respiratory network requires afferent activity corresponding to the A6 excitatory and A5 inhibitory input balance. [source] Inhibition of tyrosine kinase receptor type B synthesis blocks axogenic effect of estradiol on rat hypothalamic neurones in vitroEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004V. I. Brito Abstract 17-,-estradiol (E2) increases axonal growth and tyrosine kinase receptor (Trk)B levels of male-derived hypothalamic neurones in vitro. To investigate whether the axogenic response depends on the upregulation of TrkB, we analysed neuritic growth and neuronal polarization in cultures treated with an antisense oligonucleotide against TrkB mRNA. In cultures without E2, treatment with 7.5 or 10 µm antisense reduced TrkB levels and the percentage of neurones showing an identifiable axon; the number and length of minor processes were increased. In cultures treated with 5 µm antisense, morphometric parameters were normal although total TrkB levels were reduced. The same dose prevented the E2-dependent increase of TrkB levels and suppressed the axogenic effect of E2. These results indicate that TrkB is necessary for normal neuronal growth and maturation and further suggest that an increase in TrkB is necessary for E2 to exert its axogenic effect in male-derived neurones. [source] KIT and RAS signalling pathways in testicular germ cell tumours: new data and a review of the literatureINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 4 2007N. C. Goddard Summary Testicular germ cell tumours (TGCTs) are the leading cause of cancer deaths in young male Caucasians. Identifying changes in DNA copy number can pinpoint genes involved in tumour development. We defined the smallest overlapping regions of imbalance in TGCTs using array comparative genomic hybridization analysis. Novel regions, or regions which refined those previously reported, were identified. The expression profile of genes from 12p, which is invariably gained in TGCTs, and amplicons defined at 12p11.2-12.1 and 4q12, suggest KRAS and KIT involvement in TGCT and seminoma development, respectively. Amplification of these genes was not found in intratubular germ cell neoplasia adjacent to invasive disease showing these changes, suggesting their involvement in tumour progression. Activating mutations of RAS genes (KRAS or NRAS) and overexpression of KRAS were mutually exclusive events. These, correlations between the expression levels of KIT, KRAS and GRB7 (which encodes an adapter molecule known to interact with the KIT tyrosine kinase receptor) and other reported evidence reviewed here, are consistent with a role for activation of KIT and RAS signalling in TGCT development. In order to assess a role for KIT in seminomas, we modulated the level of KIT expression in TCam-2, a seminoma cell line. The likely seminomatous origin of this cell line was supported by demonstrating KIT and OCT3/4 overexpression and gain of 12p material. Reducing the expression of KIT in TCam-2 through RNA inhibition resulted in decreased cell viability. Further understanding of KIT and RAS signalling in TGCTs may lead to novel therapeutic approaches for these tumours. [source] Genetic mapping of dominant white (W), a homozygous lethal condition in the horse (Equus caballus)JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 6 2004C. Mau Summary Dominant white coat colour (W) is a depigmentation syndrome, known in miscellaneous species. When homozygous in the horse (similar in mice), the mutation responsible for the white phenotype is lethal in a very early stage of gestation. It seems, that the action of the dominant white allele is not always fully penetrant, resulting occasionally in spotted look alike offspring. These horses resemble a coat colour pattern known as sabino spotting. So far, it is not known whether dominant white (W) and sabino spotting (S) share a common genetic background. In this study, a pedigree consisting of 87 horses segregating for dominant white (W) was used to genetically localize the horse (W)-locus. Microsatellite ASB23 was found linked to (W), which allowed us to map dominant white to a region on horse chromosome 3q22. Tyrosine kinase receptor (KIT) was previously mapped to this same chromosome region (3q21,22). KIT and its ligand (KITLG) are responsible for the normal function of melanogenesis, haematopoiesis and gametogenesis. So far, sequence analysis of different KIT gene fragments did not lead to new polymorphisms, except for a SNP detected in KIT intron 3 (KITSNPIn3). Additional microsatellites from ECA3q (TKY353 and LEX7), together with KITSNPIn3 allowed us to state more precisely the (W)-mutation. The positional results and comparative functional data strongly suggest that KIT encodes for the horse (W)-locus. Zusammenfassung Die dominant weisse Fellfarbe (W) ist eine Form der Depigmentierung, die bei vielen Spezies auftritt. Beim Pferd wirkt die Mutation für Dominant Weiss (W) in homozygoter Form (analog zur Maus), bereits in einem sehr frühen Stadium der Trächtigkeit letal. Es scheint, dass die Wirkung des dominant weissen Allels nicht immer mit vollständiger Penetranz erfolgt. Dies führt gelegentlich zu Nachkommen mit einer Art Schecken-Fellzeichnung. Solche Pferde sind phänotypisch mit den sogenannten ,,Sabino-Schecken,, vergleichbar. Es ist bis jetzt nicht bekannt ob Dominant Weiss (W) und Sabino-Scheckung (S) einen gemeinsamen genetischen Hintergrund besitzen. Mittels eines Pedigrees aus 87 Pferden, in dem Dominant Weiss (W) segregiert, konnte in der vorliegenden Studie der equine (W)-Locus genetisch lokalisiert werden. Der Mikrosatellit ASB23 erwies sich als gekoppelt mit (W) und ermöglichte die Zuweisung des (W)-Locus auf eine Region von Chromosom ECA 3q22. Das Gen für den Tyrosinkinaserezeptor (KIT) liegt ebenfalls in dieser Chromosomenregion (3q21,22). Das KIT -Gen ist zusammen mit dem KIT -Liganden (KITLG) verantwortlich für einen normal funktionierenden Ablauf der Melanogenese, Hämatopoese und Gametogenese. Die direkte Sequenzierung von KIT -Genfragmenten führte bis jetzt zu keinen neuen Polymorphismen, ausser einem SNP in KIT Intron 3 (KITSNPIn3). Mittels weiterer Mikrosatelliten von ECA3q (TKY353 and LEX7) sowie KITSNPIn3 gelang es, die (W)-Mutation genauer zu positionieren. Die vorliegenden Lokalisierungsresultate und vergleichende funktionelle Erkenntnisse deuten stark darauf hin, dass KIT für den Pferde (W)-Locus kodiert. [source] Fluctuation analysis and accuracy of a large-scale in silico screenJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2004H. Merlitz Abstract Using a cascadic version of the stochastic tunneling method we perform an all-atom database screen over 186,000 flexible ligands of the NCI 3D database against the thymidine kinase receptor. By analyzing the errors in the binding energy we demonstrate how the cascadic technique is superior to conventional sequential docking techniques and how reliable results for the determination of the top-scoring ligands could be achieved. The substrate corresponding to the crystal structure used in the screen ranks in the upper 0.05% of the database, validating both docking methodology and the applicability of the scoring function to this substrate. Several high ranking ligands of the database display significant structural similarity with known substrates. A detailed analysis of the accuracy of the screening method is carried out, and its dependence on the flexibility of the ligand is quantified. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1568,1575, 2004 [source] Neuroprotection by stem cell factor in rat cortical neurons involves AKT and NF,BJOURNAL OF NEUROCHEMISTRY, Issue 1 2005Krishnan M. Dhandapani Abstract Stem cell factor (SCF) is a highly expressed cytokine in the central nervous system. In the present study, we demonstrate a neuroprotective role for SCF and its tyrosine kinase receptor, c-kit, against camptothecin-induced apoptosis and glutamate excitotoxicity in rat cortical neurons. This protection was blocked by pharmacological or molecular inhibition of either the MEK/ERK or PI3K/Akt signaling pathways. The importance of these pathways was further confirmed by the activation of both ERK, in a MEK-dependent manner, and Akt, via PI3K. Activation of Akt increased the binding of the p50 and p65 subunits of NF,B, which was also important for neuroprotection. Akt inhibition prevented NF,B binding, suggesting a role for Akt in SCF-induced NF,B. Pharmacological inhibition of NF,B or dominant negative I,B also prevented neuroprotection by SCF. SCF up-regulated the anti-apoptotic genes, bcl-2 and bcl-xL in an NF,B-dependent manner. Together, these findings demonstrate a neuroprotective role for SCF in cortical neurons, an effect that was mediated by Akt and ERK, as well as NF,B-mediated gene transcription. SCF represents a novel therapeutic target in the treatment of neurodegenerative disease. [source] A novel inducible tyrosine kinase receptor to regulate signal transduction and neurite outgrowthJOURNAL OF NEUROSCIENCE RESEARCH, Issue 12 2009Ronald W. Alfa Abstract Nervous system growth factor gene delivery can promote axonal growth and prevent cell death in animal models of CNS trauma and neurodegenerative diseases. The ability to regulate growth factor expression or signaling pathways downstream from growth factor receptors remains a desirable goal for in vivo gene transfer. To achieve precise pharmacological modulation of neurotrophin activity, we have generated a chimeric trkA receptor (ItrkA) by fusing the entire intracellular domain of the trkA high-affinity NGF receptor to two intracellular, modified FK506 binding domains for the synthetic small molecule dimerization ligand AP20187. Rat PC12 cells were transduced with lentiviral vectors containing ItrkA and green fluorescent protein (GFP; via an internal ribosome entry site). Treatment of ItrkA-expressing PC12 cells with AP20187 induced neurite outgrowth and differentiation in a time- and dose-dependent fashion, with a half-maximal response at a concentration of 1 nM AP20187. Seventy percent of cells responded to AP20187 by day 3. Western blots demonstrated that AP20187 treatment resulted in phosphorylation of Erk1/2 and Akt in ItrkA-transduced PC12 cells but not in nontransduced, naļve cells. Phosphorylation levels were comparable to levels obtained with 50 ng/ml nerve growth factor (NGF). In addition, ItrkA lentiviral transduction of primary E15 dorsal root ganglion neurons significantly increased neurite growth three- to fourfold in the presence of AP20187 compared with control GFP transduced and naļve neurons. These results demonstrate that small ligand-induced dimerization of the intracellular domain of trkA can efficiently simulate the biological activity of NGF and provide a means to regulate intracellular neurotrophin receptor signaling. © 2009 Wiley-Liss, Inc. [source] Differential Effects of Ethanol on Insulin-Like Growth Factor-I Receptor SignalingALCOHOLISM, Issue 2 2000Andrea E.M. Seiler Background: Activation of the insulin-like growth factor I receptor (IGF-IR) by its ligands IGF-I and IGF-II induces cell proliferation and protects against apoptosis. Ethanol inhibits IGF-IR tyrosine autophosphorylation, which subsequently interferes with the activation of key downstream signaling mediators including insulin-receptor substrate-1, phosphatidylinositol 3-kinase, and mitogen-activated protein (MAP) kinase. The ethanol-induced inhibition of IGF-IR signaling reduces mitogenesis and enhances apoptosis. In the current study, we demonstrate that the antiproliferative action of ethanol can be modulated by differential sensitivity of the autophosphorylation of the IGF-IR to ethanol. Methods: A series of subclones was generated from 3T3 cells that express the human IGF-IR. Results: There was considerable variability in the ability of ethanol to inhibit IGF-I-dependent IGF-IR tyrosine autophosphorylation and MAP kinase activation, despite equivalent IGF-IR expression. The IGF-IR was completely resistant to a high concentration of ethanol (150 mM) in several subclones. The sensitivity of IGF-IR autophosphorylation to ethanol correlated directly with the inhibition of IGF-I-mediated MAP kinase activation and cell proliferation. Resistant subclones exhibited features of the transformed phenotype including high MAP kinase activity, partial loss of contact inhibition, and the development of foci at confluency. The IGF-IR isolated from ethanol-resistant cells was similarly resistant to ethanol in autophosphorylation reactions in vitro, whereas ethanol inhibited the autophosphorylation of IGF-IR obtained from sensitive cells. Conclusions: Our findings are the first to demonstrate the modulation of ethanol sensitivity of a tyrosine kinase receptor, and they provide a molecular basis for differential effects of ethanol on cell proliferation. [source] NMR methods for studying the structure and dynamics of oncogenic and antihistaminic peptides in biomembranesMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2004Christina Sizun Abstract We present several applications of both wide-line and magic angle spinning (MAS) solid-state NMR of bicelles in which are embedded fragments of a tyrosine kinase receptor or enkephalins. The magnetically orientable bicelle membranes are shown to be of particular interest for studying the functional properties of lipids and proteins in a state that is very close to their natural environment. Quadrupolar, dipolar and chemical shielding interactions can be used to determine minute alterations of internal membrane dynamics and the orientation of peptides with respect to the membrane plane. MAS of bicelles can in turn lead to high-resolution proton spectra of hydrated membranes. Using deuterium,proton contrast methods one can then obtain pseudo-high-resolution proton spectra of peptides or proteins embedded in deuterated membranes and determine their atomic 3D structure using quasi-conventional liquid-state NMR methods. Copyright © 2004 John Wiley & Sons, Ltd. [source] Tyrosine protein kinases and spermatogenesis: truncation mattersMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2006Abraham L. Kierszenbaum Abstract Protein phosphorylation on serine/threonine or tyrosine residues represents a significant regulatory mechanism in signal transduction during spermatogenesis, oogenesis, and fertilization. There are several families of tyrosine protein kinases operating during spermatogenesis: the Src family of tyrosine protein kinases; the Fujinami poultry sarcoma/feline sarcoma (Fps/Fes) and Fes-related protein (Fer) subfamily of non-receptor proteins; and c-kit, the transmembrane tyrosine kinase receptor that belongs to the family of the PDGF receptor. A remarkable characteristic is the coexistence of full-length and truncated tyrosine kinases in testis. Most of the truncated forms are present during spermiogenesis. Examples include the truncated forms of Src tyrosine kinase hematopoietic cell kinase (Hck), FerT, and tr-kit. A feature of FerT and tr-kit is the kinase domain that ensures the functional properties of the truncated protein. FerT, a regulator of actin assembly/disassembly mediated by cortactin phosphorylation, is present in the acroplaxome, a cytoskeletal plate containing an F-actin network and linking the acrosome to the spermatid nuclear envelope. This finding suggests that Fer kinase represents one of the tyrosine protein kinases that may contribute to spermatid head shaping. The c-kit ligand, stem cell factor (SCF), which induces c-kit dimerization and autophosphorylation, exists as both membrane-associated and soluble. Although tyrosine protein kinases are prominent in spermatogenesis, a remarkable observation is the paucity of phenotypic alterations in spermatogenic cells in male mice targeted with Fer kinase-inactivating mutation. It is possible that the redundant functions of the tyrosine protein kinase pool present during spermatogenesis may explain the limited phenotypes of single mutant mice. The production of compound and viable mutant mice, lacking the expression of two or more tyrosine kinases, may shed light on this intriguing issue. Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source] Developmental expression of glial cell-line derived neurotrophic factor, neurturin, and their receptor mRNA in the rat urinary bladderNEUROUROLOGY AND URODYNAMICS, Issue 1 2003Takahiro Kawakami Abstract Aims: Glial cell-line derived neurotrophic factor (GDNF) and related factors neurturin (NRTN), artemin, and persephin are members of the GDNF family of neurotrophic factors. GDNF and NRTN bind to the tyrosine kinase receptor Ret and the receptors GFR,1 and GFR,2. The objective was to examine the developmental expression of GDNF, NRTN, and their receptors within the rat urinary bladder. Methods: Rat bladders dissected from embryonic day (E) 15, postnatal day (P) 0, P14, P28, and adult rats (P60) were investigated by semiquantitative reverse transcriptase polymerase chain reaction. Embryos (E15, E16, and E17) were immunohistochemically stained for neurofilament. Results: GDNF and Ret mRNA levels at E15 were the highest of all the stages we examined and then immediately decreased. In contrast, NRTN mRNA levels did not change between E15 and postnatal day 14; thereafter, they gradually but insignificantly increased. GFR,1 and GFR,2 mRNA levels were high at E15, after which their signal intensities decreased. In whole-mounted specimens, neurofilament-positive axons were first detected in the bladder at E16. Conclusions: Our results suggest that GDNF and NRTN may act as trophic factors for neural in-growth to the bladder and/or for the maintenance of mature neurons innervating the bladder. These factors might also be involved in bladder morphogenesis. Neurourol. Urodynam. 22:83,88, 2003. © 2003 Wiley-Liss, Inc. [source] Identification of secreted proteins regulated by cAMP in glioblastoma cells using glycopeptide capture and label-free quantificationPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2009Jennifer J. Hill Dr. Abstract Exposure of glioblastoma U87MG cells to a cAMP analog leads to a decrease in proliferation, invasion, and angiogenic potential. Here, we apply a label-free MS-based approach to identify formerly N -linked glycopeptides that change in abundance upon cAMP treatment. Over 150 unique glycopeptides in three biological repetitions were quantified, leading to the identification of 14 upregulated proteins and 21 downregulated proteins due to cAMP treatment. Of these, eight have been validated, either through comparison with microarray data or by Western blot. We estimate our ability to identify differentially expressed peptides at greater than 85% in a single biological repetition, while the analysis of multiple biological repetitions lowers the false positive rate to ,2%. Many of the proteins identified in this study are involved in cell signaling and some, such as Tenascin C, Cathepsin L, Neuroblastoma suppressor of tumorigenicity, and AXL/UFO tyrosine,protein kinase receptor, have been previously shown to be involved in glioblastoma progression. We also identify several semitryptic peptides that increase in abundance upon cAMP treatment, suggesting that cAMP regulates protease activity in these cells. Overall, these results demonstrate the benefits of using a highly specific enrichment method for quantitative proteomic experiments. [source] Molecular mechanisms utilized by alternative c-kit gene products in the control of spermatogonial proliferation and sperm-mediated egg activationANDROLOGIA, Issue 1 2003P. Rossi Summary. The c-kit proto-oncogene plays a dual role in the control of male fertility in mice through two alternative gene products: (1) c-kit [the transmembrane tyrosine kinase receptor for stem cell factor (SCF)], which is expressed and functional in differentiating spermatogonia of the postnatal testis, in which c-kit is essential for pre-meiotic proliferation; and (2) tr-kit, an intracellular protein which is specifically accumulated during spermiogenesis through the use of an alternative intronic promoter, and which is able to trigger mouse egg activation when microinjected into the cytoplasm of metaphase II arrested oocytes. Here, we summarize the most recent findings about the molecular pathways through which c-kit regulates cell cycle progression in mitotic germ cells, and those through which sperm-derived tr-kit triggers parthenogenetic completion of meiosis II and pronuclear formation in microinjected mouse eggs. [source] Identification of a novel germline MET mutation in dogsANIMAL GENETICS, Issue 3 2006A.T. Liao Summary The MET proto-oncogene encodes a transmembrane tyrosine kinase receptor that mediates multiple functions such as migration, cycling and survival by binding to hepatocyte growth factor (HGF). Dysregulation of MET through inappropriate expression or mutation has been shown to play an important role in human cancers. Furthermore, inherited mutations in MET are known to contribute to the development of gastric and renal cancer in humans. Lastly, mouse models of MET mutations lead to the development of a wide variety of cancers including lymphomas, sarcomas and some forms of carcinoma. In the process of cloning canine MET, a novel germline point mutation was found in the juxtamembrane domain (G966S) in two of the templates used for cloning, both of which were derived from Rottweiler dogs, a breed believed to be at high risk for the development of several cancers. Screening of germline DNA from a variety of breeds revealed that this mutation was present in approximately 70% of Rottweiler dogs and <5% of all other breeds examined, suggesting a breed-specific heritable mutation. Stable transfection of the G966S mutant form of MET into NIH3T3 cells resulted in enhanced baseline scattering and migration of the cells, which was further increased in the presence of HGF. This study supports the notion that particular dog breeds may carry germline mutations that contribute to high rates of cancer in a manner similar to heritable, cancer-associated mutations in humans. [source] Attenuation of osteoarthritis progression by reduction of discoidin domain receptor 2 in miceARTHRITIS & RHEUMATISM, Issue 9 2010Lin Xu Objective To investigate whether the reduction of discoidin domain receptor 2 (DDR-2), a cell membrane tyrosine kinase receptor for native type II collagen, attenuates the progression of articular cartilage degeneration in mouse models of osteoarthritis (OA). Methods Double-heterozygous (type XI collagen,deficient [Col11a1+/,] and Ddr2 -deficient [Ddr2+/,]) mutant mice were generated. Knee joints of Ddr2+/, mice were subjected to microsurgical destabilization of the medial meniscus. Conditions of the articular cartilage from the knee joints of the double-heterozygous mutant and surgically treated mice were examined by histology, evaluated using a modified Mankin scoring system, and characterized by immunohistochemistry. Results The rate of progressive degeneration in knee joints was dramatically reduced in the double-heterozygous mutant mice compared with that in the type XI collagen,deficient mice. The progression in the double-heterozygous mutant mice was delayed by ,6 months. Following surgical destabilization of the medial meniscus, the progressive degeneration toward OA was dramatically delayed in the Ddr2+/, mice compared with that in their wild-type littermates. The articular cartilage damage present in the knee joints of the mice was directly correlated with the expression profiles of DDR-2 and matrix metalloproteinase 13. Conclusion Reduction of DDR-2 expression attenuates the articular cartilage degeneration of knee joints induced either by type XI collagen deficiency or by surgical destabilization of the medial meniscus. [source] Anti-epidermal growth factor receptor monoclonal antibodies in cancer therapyCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2009E. Martinelli Summary The epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor involved in the proliferation and survival of cancer cells. EGFR is the first molecular target against which monoclonal antibodies (mAb) have been developed for cancer therapy. Here we review the mechanisms underlying the effects of EGFR-specific mAb in cancer therapy. The efficacy of EGFR-specific mAb in cancer occurs thanks to inhibition of EGFR-generated signalling; furthermore, the effects of antibodies on the immune system seem to play an important role in determining the overall anti-tumour response. In this review, attention is focused on cetuximab and panitumumab, two mAb introduced recently into clinical practice for treatment of metastatic colorectal and head and neck cancer which target the external part of EGFR. [source] Measurement of the soluble angiopoietin receptor tie-2 in patients with coronary artery disease: development and application of an immunoassayEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 7 2003N. A. Y. Chung Abstract Background The angiopoietin family has emerged as a group of crucial growth factors to normal angiogenesis. They are essential to the development of the mature vessel wall and interact with the endothelium via endothelial cell-specific tyrosine kinase receptors, tie-1 and tie-2. The role of the tie-2 receptor has been extensively examined in neovascularization associated with malignancy, but little is known about the role it may play in atherosclerosis, a condition whose pathophysiology also involves angiogenesis. Soluble tie-2 has been detected in the plasma of healthy controls, but this has yet to be applied to patients in the clinical setting. Materials and methods We developed an ELISA to detect plasma tie-2 levels and applied these to a clinical setting. The intra- and interassay coefficients of variation for the assay were 4·7% and 9·6%, respectively. We then measured levels of tie-2, vascular endothelial growth factor (VEGF), another factor associated with angiogenesis, and the soluble VEGF receptor Flt-1 (sFlt-1) in 75 patients with coronary artery disease [25 with acute myocardial infarction (AMI), 25 with acute coronary syndromes (ACS) and 25 with stable angina] and 25 healthy controls. Results Median [IQR, interquartile range] levels of tie-2 were significantly higher in the coronary artery disease patients (AMI 12 [10,17] ng mL,1, ACS 10 [9,14] ng mL,1, stable angina 9 [3,11] ng mL,1) when compared with the controls (7·5 [7,9] ng mL,1P = 0·004). As expected, levels of VEGF and sFlt were significantly different from those in the healthy controls (P = 0·011 and P < 0·001, respectively). Significant correlations were found between levels of tie-2 and VEGF (Spearman r = 0·59, P < 0·001), tie-2 and sFlt-1 (r = 0·45, P < 0·001) and VEGF and sFlt-1 (r = 0·56, P < 0·001) in the whole study group. Conclusion We suggest that tie-2 may be potentially used as a marker of angiogenesis in atherosclerosis and may help elucidate the role of the angiopoietin/tie-2 system in atherogenesis. [source] Two major Smad pathways in TGF-, superfamily signallingGENES TO CELLS, Issue 12 2002Keiji Miyazawa Members of the transforming growth factor-, (TGF-,) superfamily bind to two different serine/threonine kinase receptors, i.e. type I and type II receptors. Upon ligand binding, type I receptors specifically activate intracellular Smad proteins. R-Smads are direct substrates of type I receptors; Smads 2 and 3 are specifically activated by activin/nodal and TGF-, type I receptors, whereas Smads 1, 5 and 8 are activated by BMP type I receptors. Nearly 30 proteins have been identified as members of the TGF-, superfamily in mammals, and can be classified based on whether they activate activin/TGF-,-specific R-Smads (AR-Smads) or BMP-specific R-Smads (BR-Smads). R-Smads form complexes with Co-Smads and translocate into the nucleus, where they regulate the transcription of target genes. AR-Smads bind to various proteins, including transcription factors and transcriptional co-activators or co-repressors, whereas BR-Smads interact with other proteins less efficiently than AR-Smads. Id proteins are induced by BR-Smads, and play important roles in exhibiting some biological effects of BMPs. Understanding the mechanisms of TGF-, superfamily signalling is thus important for the development of new ways to treat various clinical diseases in which TGF-, superfamily signalling is involved. [source] Differential erbB signaling in astrocytes from the cerebral cortex and the hypothalamus of the human brainGLIA, Issue 4 2009Ariane Sharif Abstract Studies in rodents have shown that astroglial erbB tyrosine kinase receptors are key regulatory elements in neuron,glia communication. Although both astrocytes and deregulation of erbB functions have been implicated in the pathogenesis of many common human brain disorders, erbB signaling in native human brain astrocytes has never been explored. Taking advantage of our ability to perform primary cultures from the cortex and the hypothalamus of human fetuses, we conducted a thorough analysis of erbB signaling in human astrocytes. We showed that human cortical astrocytes express erbB1, erbB2, and erbB3, whereas human hypothalamic astrocytes express erbB1, erbB2, and erbB4 receptors. Ligand-dependent activation of different erbB receptor heterodimeric complexes in these two populations of astrocytes translated into different morphological and proliferative responses. Although morphological plasticity was more pronounced in hypothalamic astrocytes than in cortical astrocytes, the former showed a lower mitogenic potential. Decreasing erbB4 expression via siRNA-mediated gene knockdown revealed that erbB4 constitutively restrains basal proliferative activity in hypothalamic astrocytes. We further show that treatment of human astrocytes with a protein kinase C activator results in rapid tyrosine phosphorylation of erbB receptors that involves cleavage of endogenous membrane bound erbB ligands by metalloproteinases. Together, these results indicate that erbB signaling in primary human brain astrocytes is functional, region-specific, and can be activated in a paracrine and/or autocrine manner. In addition, by revealing that some aspects of astroglial erbB signaling are different between human and rodents, our results provide a molecular framework to explore the potential involvement of astroglial erbB signaling deregulation in human brain disorders. © 2008 Wiley-Liss, Inc. [source] Expression of oncogenic K-ras and loss of Smad4 cooperate to induce the expression of EGFR and to promote invasion of immortalized human pancreas ductal cellsINTERNATIONAL JOURNAL OF CANCER, Issue 9 2010Shujie Zhao Abstract Activating mutation of K-ras and inactivation of DPC4 are two common genetic alterations that occur in the development and progression of pancreatic ductal adenocarcinomas (PDAC). A separate common event in PDAC progression is increased expression of phosphotyrosine kinase receptors (PTKRs). In our study, we examined whether activating mutations of K-ras and loss of Smad4 play a role in causing the aberrant expression of PTKRs. Immortalized human pancreas ductal cells (HPNE) were genetically modified by expressing oncogenic K-ras and/or by shRNA knockdown of Smad4. EGFR and erbB2 protein levels but not Ron or IGF-1R were substantially upregulated in HPNE cells that express K-ras(GD12). The increased expression of EGFR in HPNE cells that expressed K-ras(GD12) was mediated by both stabilizing EGFR protein and by increasing EGFR transcription. TGF-, signaling partially suppressed K-ras(GD12) induced EGFR transcription in Smad4 intact HPNE cells; whereas knockdown of Smad4 in cells expressing K-ras(GD12) further enhanced expression of EGFR and erbB2. The upregulation of EGFR and erbB2 was associated with an increase of invasion, which was blocked by a kinase inhibitor of EGFR. Our study indicates for the first time, that oncogenic ras and loss of Smad signaling cooperate to upregulate EGFR and erbB2, which plays a role in promoting invasion. [source] Potentiation of angiogenic response by ischemic and hypoxic reconditioning of the heartJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 1 2002Nilanjana Maulik Abstract This review is intended to discuss the newly discovered role of preconditioning which should make it an attractive therapeutic stimulus for repairing the injured myocardium. We recently found that apart from rendering the myocardium tolerant to ischemic reperfusion injury, preconditioning also potentiates angiogenesis. Our study demonstrated for the first time that both ischemic and hypoxic preconditioning triggered myocardial angiogenesis at the capillary and arteriolar levels which nicely corroborated with the improved myocardial contractile function.Hypoxic preconditioning resulted in the stimulation of VEGF, the most potent angiogenic factor known to date. In concert, endothelial cell specific tyrosine kinase receptors, Tie 1, Tie 2 and Flt-1 and Flk-1 were also significantly enhanced in the preconditioned myocardium. The redox-regulated transcription factor NFkB was found to play an essential role in the preconditioning regulation of angiogenesis [source] Flavonoids as RTK inhibitors and potential anticancer agentsMEDICINAL RESEARCH REVIEWS, Issue 5 2008Florence Teillet Abstract Tyrosine kinase receptors (RTKs) play a crucial role in the regulation of the cell division cycle. Currently more than 50 RTKs divided into several subfamilies have been described. The inhibition of these enzymes has emerged as an important research-area. Compounds able to inhibit the activity of these enzymes are expected to display antiproliferative properties. Flavonoids are representative of various small molecules acting as RTK inhibitors. These naturally occurring compounds are able to bind to the ATP-binding site of several kinases. The most plausible current hypothesis explaining the action of these substances on kinases is that the chromenone moiety of the flavonoid acts as a mimetic of the adenine moiety of ATP, the receptor co-factor. In this review, we report recent results on the activity of natural and synthetic derivatives of flavonoids as inhibitors of RTKs. Mechanistic aspects, the therapeutic usefulness, and the potential clinical use are discussed. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 5, 715,745, 2008 [source] Structure of the ligand-binding domain of the EphB2 receptor at 2,Å resolutionACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Yehuda Goldgur Eph tyrosine kinase receptors, the largest group of receptor tyrosine kinases, and their ephrin ligands are important mediators of cell,cell communication regulating cell attachment, shape and mobility. Recently, several Eph receptors and ephrins have also been found to play important roles in the progression of cancer. Structural and biophysical studies have established detailed information on the binding and recognition of Eph receptors and ephrins. The initial high-affinity binding of Eph receptors to ephrin occurs through the penetration of an extended G,H loop of the ligand into a hydrophobic channel on the surface of the receptor. Consequently, the G,H loop-binding channel of Eph receptors is the main target in the search for Eph antagonists that could be used in the development of anticancer drugs and several peptides have been shown to specifically bind Eph receptors and compete with the cognate ephrin ligands. However, the molecular details of the conformational changes upon Eph/ephrin binding have remained speculative, since two of the loops were unstructured in the original model of the free EphB2 structure and their conformational changes upon ligand binding could consequently not be analyzed in detail. In this study, the X-ray structure of unbound EphB2 is reported at a considerably higher 2,Å resolution, the conformational changes that the important receptor loops undergo upon ligand binding are described and the consequences that these findings have for the development of Eph antagonists are discussed. [source] Macrophage Stimulating Protein (MSP) evokes superoxide anion production by human macrophages of different originBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2001Sandra Brunelleschi Macrophage Stimulating Protein (MSP), a serum factor related to Hepatocyte Growth Factor, was originally discovered to stimulate chemotaxis of murine resident peritoneal macrophages. MSP is the ligand for Ron, a member of the Met subfamily of tyrosine kinase receptors. The effects of MSP on human macrophages and the role played in human pathophysiology have long been elusive. We show here that human recombinant MSP (hrMSP) evokes a dose-dependent superoxide anion production in human alveolar and peritoneal macrophages as well as in monocyte-derived macrophages, but not in circulating human monocytes. Consistently, the mature Ron protein is expressed by the MSP responsive cells but not by the unresponsive monocytes. The respiratory burst evoked by hrMSP is quantitatively higher than the one induced by N-formylmethionyl-leucyl-phenylalanine and similar to phorbol myristate acetate-evoked one. To investigate the mechanisms involved in NADPH oxidase activation, leading to superoxide anion production, different signal transduction inhibitors were used. By using the non selective tyrosine kinase inhibitor genistein, the selective c-Src inhibitor PP1, the tyrosine phosphatase inhibitor sodium orthovanadate, the phosphatidylinositol 3-kinase inhibitor wortmannin, the p38 inhibitor SB203580, the MEK inhibitor PD098059, we demonstrate that hrMSP-evoked superoxide production is mediated by tyrosine kinase activity, requires the activation of Src but not of PI 3-kinase. We also show that MAP kinase and p38 signalling pathways are involved. These results clearly indicate that hrMSP induces the respiratory burst in human macrophages but not in monocytes, suggesting for the MSP/Ron complex a role of activator as well as of possible marker for human mature macrophages. British Journal of Pharmacology (2001) 134, 1285,1295; doi:10.1038/sj.bjp.0704356 [source] Regulation of TGF-, family signaling by E3 ubiquitin ligasesCANCER SCIENCE, Issue 11 2008Yasumichi Inoue Members of the transforming growth factor-, (TGF-,) family, including TGF-,, activin and bone morphogenetic proteins (BMPs), are multifunctional proteins that regulate a wide variety of cellular responses, such as proliferation, differentiation, migration and apoptosis. Alterations in their downstream signaling pathways are associated with a range of human diseases like cancer. TGF-, family members transduce signals through membrane serine/threonine kinase receptors and intracellular Smad proteins. The ubiquitin,proteasome pathway, an evolutionarily conserved cascade, tightly regulates TGF-, family signaling. In this pathway, E3 ubiquitin ligases play a crucial role in the recognition and degradation of target proteins by the 26S proteasomes. Smad degradation regulates TGF-, family signaling; HECT (homologous to the E6-accessory protein C-terminus)-type E3 ubiquitin ligases, Smad ubiquitin regulatory factor 1 (Smurf1), Smurf2, and a RING-type E3 ubiquitin ligase, ROC1-SCFFbw1a have been implicated in Smad degradation. Smurf1 and Smurf2 bind to TGF-, family receptors via the inhibitory Smads, Smad6 and Smad7, to induce their ubiquitin-dependent degradation. Arkadia, a RING-type E3 ubiquitin ligase, induces the ubiquitination and degradation of Smad7 and corepressors, c-Ski and SnoN, to enhance TGF-, family signaling. Abnormalities in E3 ubiquitin ligases that control components of TGF-, family signaling may lead to the development and progression of various cancers. (Cancer Sci 2008; 99: 2107,2112) [source] Signaling networks guiding epithelial,mesenchymal transitions during embryogenesis and cancer progressionCANCER SCIENCE, Issue 10 2007Aristidis Moustakas Epithelial,mesenchymal transition (EMT) describes the differentiation switch between polarized epithelial cells and contractile and motile mesenchymal cells, and facilitates cell movements and generation of new tissue types during embryogenesis. Many secreted polypeptides are implicated in the EMT process and their corresponding intracellular transduction pathways form highly interconnected networks. Transforming growth factor-,, Wnt, Notch and growth factors acting through tyrosine kinase receptors induce EMT and often act in a sequential manner. Such growth factors orchestrate the concerted regulation of an elaborate gene program and a complex protein network, needed for establishment of new mesenchymal phenotypes after disassembly of the main elements of epithelial architecture, such as desmosomes, as well as tight, adherens and gap junctions. EMT of tumor cells occurs during cancer progression and possibly generates cell types of the tumor stroma, such as cancer-associated myofibroblasts. EMT contributes to new tumor cell properties required for invasiveness and vascular intravasation during metastasis. Here we present some of the current mechanisms that mediate the process of EMT and discuss their relevance to cancer progression. (Cancer Sci 2007; 98: 1512,1520) [source] | ||||||||||||||||||||||||||||