The respiratory syncytial virus small hydrophobic protein is phosphorylated via a mitogen-activated protein kinase p38-dependent tyrosine kinase activity during virus infection

The phosphorylation status of the small hydrophobic (SH) protein of respiratory syncytial virus (RSV) was examined in virus-infected Vero cells. The SH protein v.,as isolated from [S-35]methionine- and [P-33]orthophosphate-labelled IRSV-infected cells and analysed by SDS-PAGE. In each case, a protein product of the expected size for the SH protein was observed. Phosphoamino acid analysis and reactivity with the phosphotyrosine specific antibody PY20 showed that the SH protein was modified by tyrosine phosphorylation. The role or tyrosine kinase activity in SH protein phosphorylation was confirmed by the use of genistein, a broad-spectrum tyrosine kinase inhibitor, to inhibit SH protein phosphorylation. Further analysis showed that the different glycosylated forms of the SH protein were phosphorylated, as was the oligomeric form of the protein. Phosphorylation of the SH protein was specifically inhibited by the mitogen-activated protein kinase (MAPK) p38 inhibitor SB203580, suggesting that SH protein phosphorylation occurs via a MAPK p38-dependent pathway. Analysis of virus-infected cells using fluorescence microscopy showed that, although the SH protein was distributed throughout the cytoplasm, it appeared to accumulate, at low levels, in the endoplasmic reticulum/Golgi complex, confirming recent observations. However, in the presence of SB203580. an increased accumulation of the SH protein in the Golgi complex was observed, although other virus structures, such as virus filaments and inclusion bodies, remained largely unaffected. These results showed that during RSV infection, the SH protein is modified by an MAPK p38-dependant tyrosine kinase activity and that this modification influences its cellular distribution.

Chronic neutrophilic leukemia with an associated V617F JAK2 tyrosine kinase mutation

Chronic neutrophilic leukemia (CNL) is a rare disease and can cause considerable diagnostic difficulty. Although the V617F JAK2 mutation has been described by several groups to be associated with classical myeloproliferative disorders (MPD), this same mutation has been detected with a low incidence in atypical MPD, such as CNL. Here we report the presence of the V617F mutation in a CNL patient, who is unusual for having survived for more than 96 months, with little disease progression. It remains to be established what role this mutation, which gives cells a proliferative advantage, might play in the pathogenesis and prognosis of rare atypical MPD.

Characterisation of the Timing and Prevalence of Receptor Tyrosine Kinase Expression Changes in Esophageal Carcinogenesis

Despite being common in epithelial malignancies, the timing of receptor tyrosine kinase (RTK) up-regulation is poorly understood and therefore hampers the identification of the receptor to target for effective treatment. We aimed to determine if RTK expression changes were early events in carcinogenesis. Esophageal adenocarcinoma and its pre-invasive lesion, Barrett's esophagus, were used for immunohistochemical analysis of the RTK panel, EGFR, ErbB2, ErbB3, Met and FGFR2, by utilising a cohort of patients with invasive disease (n = 367) and two cohorts with pre-invasive disease, one cross-sectional (n = 110) and one longitudinal in time (n = 91). The results demonstrated that 51% of esophageal adenocarcinomas over-expressed at least one of the RTK panel; with 21% of these over-expressing multiple receptors. Up-regulation of RTK expression was an early event corresponding with low grade dysplasia development (25% in areas without dysplasia vs. 63% in low grade dysplasia, p

Synergistic effects of proteasome inhibitor carfilzomib in combination with tyrosine kinase inhibitors in imatinib-sensitive and -resistant chronic myeloid leukemia models

The tyrosine kinase inhibitor (TKI) imatinib has transformed the treatment and outlook of chronic myeloid leukemia (CML); however, the development of drug resistance and the persistence of TKI-resistant stem cells remain obstacles to eradicating the disease. Inhibition of proteasome activity with bortezomib has been shown to effectively induce apoptosis in TKI-resistant cells. In this study, we show that exposure to the next generation proteasome inhibitor carfilzomib is associated with a decrease in ERK signaling and increased expression of Abelson interactor proteins 1 and 2 (ABI-1/2). We also investigate the effect of carfilzomib in models of imatinib-sensitive and -resistant CML and demonstrate a potent reduction in proliferation and induction of apoptosis in a variety of models of imatinib-resistant CML, including primitive CML stem cells. Carfilzomib acts synergistically with the TKIs imatinib and nilotinib, even in imatinib-resistant cell lines. In addition, we found that the presence of immunoproteasome subunits is associated with an increased sensitivity to carfilzomib. The present findings provide a rational basis to examine the potential of carfilzomib in combination with TKIs as a potential therapy for CML, particularly in imatinib-resistant disease.

Endosomal localization and receptor dynamics determine tyrosine phosphorylation of hepatocyte growth factor-regulated tyrosine kinase substrate

Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is a prominent substrate for activated tyrosine kinase receptors that has been proposed to play a role in endosomal membrane trafficking. The protein contains a FYVE domain, which specifically binds to the lipid phosphatidylinositol (PI) 3-phosphate (PI 3-P). We show that this interaction is required both for correct localization of the protein to endosomes that only partially coincides with early endosomal autoantigen 1 and for efficient tyrosine phosphorylation of the protein in response to epidermal growth factor stimulation. Treatment with wortmannin reveals that Hrs phosphorylation also requires PI 3-kinase activity, which is necessary to generate the PI 3-P required for localization. We have used both hypertonic media and expression of a dominant-negative form of dynamin (K44A) to inhibit endocytosis; under which conditions, receptor stimulation fails to elicit phosphorylation of Hrs. Our results provide a clear example of the coupling of a signal transduction pathway to endocytosis, from which we propose that activated receptor (or associated factor) must be delivered to the appropriate endocytic compartment in order for Hrs phosphorylation to occur.

The dual EGFR/HER-2 tyrosine kinase inhibitor lapatinib sensitizes colon and gastric cancer cells to the irinotecan active metabolite SN-38

Members of the human epidermal receptor (HER) family are frequently associated with aggressive disease and poor prognosis in multiple malignancies. Lapatinib is a dual tyrosine kinase inhibitor targeting the epidermal growth factor receptor (EGFR) and HER-2. This study evaluated the therapeutic potential of lapatinib, alone and in combination with SN-38, the active metabolite of irinotecan (CPT-11), in colon and gastric cancer cell lines. Concentration-dependent antiproliferative effects of both lapatinib and SN-38 were observed in all colon and gastric cancer cell lines tested but varied significantly between individual cell lines (lapatinib range 0.08-11.7 muM; SN-38 range 3.6-256 nM). Lapatinib potently inhibited the growth of a HER-2 overexpressing gastric cancer cell line and demonstrated moderate activity in gastric and colon cancer cells with detectable HER-2 expression. The combination of lapatinib and SN-38 interacted synergistically to inhibit cell proliferation in all colon and gastric cancer cell lines tested. Cotreatment with lapatinib and SN-38 also resulted in enhanced cell cycle arrest and the induction of apoptosis with subsequent cellular pharmacokinetic analysis demonstrating that lapatinib promoted the increased intracellular accumulation and retention of SN-38 when compared to SN-38 treatment alone. Finally, the combination of lapatinib and CPT-11 demonstrated synergistic antitumor efficacy in the LoVo colon cancer mouse xenograft model with no apparent increase in toxicity compared to CPT-11 monotherapy. These results provide compelling preclinical rationale indicating lapatinib to be a potentially efficacious chemotherapeutic combination partner for irinotecan in the treatment of gastrointestinal carcinomas.

Prognostic role of lemur tyrosine kinase-3 germline polymorphisms in adjuvant gastric cancer in Japan and the United States

Lemur tyrosine kinase-3 (LMTK3) was recently identified as an estrogen receptor (ER)-α modulator related to endocrine therapy resistance, and its polymorphisms rs9989661 (T>C) T/T genotype and rs8108419 (G>A) G/G or A/G genotype predicted improved outcomes in breast cancer. Because different predominant ER distributions link to breast and gastric cancer and little is known of the prognostic role of LMTK3 in gastric cancer, this study was carried out to clarify the prognostic role of these polymorphisms in gastric cancer. One-hundred and sixty-nine Japanese and 137 U.S. patients with localized gastric adenocarcinoma were enrolled. Genomic DNA was extracted from blood or tissue, and all samples were analyzed by PCR-based direct DNA sequencing. Overall, these polymorphisms were not associated with survival in both cohorts. When gender was considered, in multivariate analysis, harboring rs9989661 T/T genotype was associated with disease-free survival [HR, 4.37; 95% confidence interval (CI), 2.08-9.18; P < 0.0001] and overall survival (OS; HR, 3.69; 95% CI, 1.65-8.24; P = 0.0014) in the Japanese males and time to recurrence (HR, 7.29; 95% CI, 1.07-49.80; P = 0.043) in the U.S. females. Meanwhile, harboring rs8108419 G/G genotype was associated with OS in the Japanese females (HR, 3.04; 95% CI, 1.08-8.56; P = 0.035) and the U.S. males (HR, 3.39; 95% CI, 1.31-8.80; P = 0.012). The prognostic role of these polymorphisms may be negative in gastric cancer. These findings suggest that the estrogen pathway may play a prognostic role in patients with gastric cancer but this may be dependent on the regional differences both in physiology and genetic alterations of gastric cancer.

Synthesis, characterization, electrochemical behavior and in vitro protein tyrosine kinase inhibitory activity of the cymene-halogenobenzohydroxamato [Ru(eta(6)-cymene)(bha)Cl] complexes

The ruthenium(II)-cymene complexes [Ru(eta(6)-cymene)(bha)Cl] with substituted halogenobenzohydroxamato (bha) ligands (substituents = 4-F, 4-Cl, 4-Br, 2,4-F-2, 3,4-F-2, 2,5-F-2, 2,6-F-2) have been synthesized and characterized by elemental analysis, IR, H-1 NMR, C-13 NMR, cyclic voltammetry and controlled-potential electrolysis, and density functional theory (DFT) studies. The compositions of their frontier molecular orbitals (MOs) were established by DFT calculations, and the oxidation and reduction potentials are shown to follow the orders of the estimated vertical ionization potential and electron affinity, respectively. The electrochemical E-L Lever parameter is estimated for the first time for the various bha ligands, which can thus be ordered according to their electron-donor character. All complexes exhibit very strong protein tyrosine kinase (PTK) inhibitory activity, even much higher than that of genistein, the clinically used PTK inhibitory drug. The complex containing the 2,4-difluorobenzohydroxamato ligand is the most active one, and the dependences of the PTK activity of the complexes and of their redox potentials on the ring substituents are discussed. (C) 2012 Elsevier B.V. All rights reserved.

Distribution intracellulaire et trafic des récepteurs à tyrosine kinase EphA4 et EphB2 à la synapse mature dans le système nerveux central murin

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Rôle du récepteur EphA4 dans la plasticité structurale neurono-gliale du noyau supraoptique à la suite d’un régime à l’eau salée

Les noyaux supraoptiques (NSO) et paraventriculaires (NPV) de l’hypothalamus montrent un phénomène réversible de plasticité structurale neurono-gliale dans diverses conditions physiologiques telles que la parturition, l’allaitement ou lors d’une surcharge en sel. En effet, les feuillets astrocytaires qui enveloppent normalement les somas et dendrites des neurones à ocytocine (OT) ou à vasopressine (AVP) se rétractent alors, autour des neurones à OT, laissant place à la formation de nouvelles synapses, surtout GABAergiques. Nous avons émis l’hypothèse voulant que ces mouvements cellulaires soient régulés par des molécules connues pour leurs rôles dans l’adhérence et la motilité cellulaires, notamment les récepteurs Eph et les éphrines (Efn). Nous avons étudié le rôle de l’un de ces récepteurs, EphA4, un récepteur à tyrosine kinase reconnaissant l’ensemble des Efn, A ou B, puis tenté d’identifier les Efn partenaires dans le NSO, à la suite d’une surcharge en sel. Pour démontrer la présence d’EphA4 dans le NSO et déterminer l’effet d’une surcharge en sel sur son expression et sa localisation, nous avons utilisé l’hybridation in situ et l’immunohistochimie en microscopie électronique, sur des coupes de cerveaux de souris ou rats traités ou non à l’eau salée pendant 1-7 j, avec des ribosondes ou des anticorps spécifiques pour EphA4. Ces travaux ont démontré une augmentation de l’expression d’EphA4 dans le NSO, notamment dans des dendrites, après le régime salé. La distribution de cette expression correspondait à celle des neurones OT et était absente de la glia limitans. Nous avons ensuite déterminé l’effet d’une absence d’EphA4 sur les mouvements astrocytaires et la synaptogènese autour des dendrites à OT et AVP, en utilisant des souris EphA4 knockouts et des souris de type sauvage des mêmes portées. Nous avons ainsi mesuré la couverture astrocytaire des dendrites OT ou AVP, identifiées par immunocytochimie anti-OT ou anti-AVP, en microscopie électronique. Ces mesures ont confirmé la rétraction des feuillets astrocytaires et la synaptogenèse autour des dendrites OT, mais pas autour des dendrites AVP, chez les souris de type sauvage, et démontré que la rétraction des feuillets astrocytaires et la synaptogenèse sur les dendrites OT ne se produisait pas chez les souris knockouts soumises à la surcharge en sel. L’ensemble de ces résultats démontre un rôle d’EphA4 dans cette plasticité structurale neurono-gliale. Afin d’identifier l’Efn partenaire d’EphA4 dans cette fonction, nous avons utilisé l’hybridation in situ et l’immunohistochimie pour les EfnB3 et -A3. L’hybridation in situ n’a pas démontré d’expression de l’EfnB3 dans le NSO, tandis que les résultats pour l’EfnA3 restent à quantifier. Cependant, l’immunohistochimie anti-EfnA3 montre un marquage d’astrocytes dans le NSO et la glia limitans, marquage qui semble augmenter après surcharge en sel, mais il reste à démontrer que l’anticorps anti-EfnA3 est bien spécifique et à quantifier les éventuels changements sur un plus grand nombre d’animaux. L’ensemble de ces observations démontre un rôle du récepteur EphA4 dans les mécanismes à la base des changements structuraux neurono-gliaux du NSO et pointe vers l’EfnA3 comme partenaire d’EphA4 dans ce modèle.

Role of the Protein Tyrosine Kinase 7 gene in human neural tube defects

Les anomalies du tube neural (ATN) sont des anomalies développementales où le tube neural reste ouvert (1-2/1000 naissances). Afin de prévenir cette maladie, une connaissance accrue des processus moléculaires est nécessaire. L’étiologie des ATN est complexe et implique des facteurs génétiques et environnementaux. La supplémentation en acide folique est reconnue pour diminuer les risques de développer une ATN de 50-70% et cette diminution varie en fonction du début de la supplémentation et de l’origine démographique. Les gènes impliqués dans les ATN sont largement inconnus. Les études génétiques sur les ATN chez l’humain se sont concentrées sur les gènes de la voie métabolique des folates du à leur rôle protecteur dans les ATN et les gènes candidats inférés des souris modèles. Ces derniers ont montré une forte association entre la voie non-canonique Wnt/polarité cellulaire planaire (PCP) et les ATN. Le gène Protein Tyrosine Kinase 7 est un membre de cette voie qui cause l’ATN sévère de la craniorachischisis chez les souris mutantes. Ptk7 interagit génétiquement avec Vangl2 (un autre gène de la voie PCP), où les doubles hétérozygotes montrent une spina bifida. Ces données font de PTK7 comme un excellent candidat pour les ATN chez l’humain. Nous avons re-séquencé la région codante et les jonctions intron-exon de ce gène dans une cohorte de 473 patients atteints de plusieurs types d’ATN. Nous avons identifié 6 mutations rares (fréquence allélique <1%) faux-sens présentes chez 1.1% de notre cohorte, dont 3 sont absentes dans les bases de données publiques. Une variante, p.Gly348Ser, a agi comme un allèle hypermorphique lorsqu'elle est surexprimée dans le modèle de poisson zèbre. Nos résultats impliquent la mutation de PTK7 comme un facteur de risque pour les ATN et supporte l'idée d'un rôle pathogène de la signalisation PCP dans ces malformations.

An update of the mechanisms of resistance to EGFR-tyrosine kinase inhibitors in breast cancer: gefitinib (Iressatrade mark)-induced changes in the expression and nucleo-cytoplasmic trafficking of HER-ligands (Review)

Intrinsic resistance to the epidermal growth factor receptor (EGFR; HER1) tyrosine kinase inhibitor (TKI) gefitinib, and more generally to EGFR TKIs, is a common phenomenon in breast cancer. The availability of molecular criteria for predicting sensitivity to EGFR-TKIs is, therefore, the most relevant issue for their correct use and for planning future research. Though it appears that in non-small-cell lung cancer (NSCLC) response to gefitinib is directly related to the occurrence of specific mutations in the EGFR TK domain, breast cancer patients cannot be selected for treatment with gefitinib on the same basis as such EGFR mutations have been reported neither in primary breast carcinomas nor in several breast cancer cell lines. Alternatively, there is a general agreement on the hypothesis that the occurrence of molecular alterations that activate transduction pathways downstream of EGFR (i.e., MEK1/MEK2 - ERK1/2 MAPK and PI-3'K - AKT growth/survival signaling cascades) significantly affect the response to EGFR TKIs in breast carcinomas. However, there are no studies so far addressing a role of EGF-related ligands as intrinsic breast cancer cell modulators of EGFR TKI efficacy. We recently monitored gene expression profiles and sub-cellular localization of HER-1/-2/-3/-4 related ligands (i.e., EGF, amphiregulin, transforming growth factor-α, ß-cellulin, epiregulin and neuregulins) prior to and after gefitinib treatment in a panel of human breast cancer cell lines. First, gefitinibinduced changes in the endogenous levels of EGF-related ligands correlated with the natural degree of breast cancer cell sensitivity to gefitinib. While breast cancer cells intrinsically resistant to gefitinib (IC50 ≥15 μM) markedly up-regulated (up to 600 times) the expression of genes codifying for HERspecific ligands, a significant down-regulation (up to 106 times) of HER ligand gene transcription was found in breast cancer cells intrinsically sensitive to gefitinib (IC50 ≤1 μM). Second, loss of HER1 function differentially regulated the nuclear trafficking of HER-related ligands. While gefitinib treatment induced an active import and nuclear accumulation of the HER ligand NRG in intrinsically gefitinib-resistant breast cancer cells, an active export and nuclear loss of NRG was observed in intrinsically gefitinib-sensitive breast cancer cells. In summary, through in vitro and pharmacodynamic studies we have learned that, besides mutations in the HER1 gene, oncogenic changes downstream of HER1 are the key players regulating gefitinib efficacy in breast cancer cells. It now appears that pharmacological inhibition of HER1 function also leads to striking changes in both the gene expression and the nucleo-cytoplasmic trafficking of HER-specific ligands, and that this response correlates with the intrinsic degree of breast cancer sensitivity to the EGFR TKI gefitinib. The relevance of this previously unrecognized intracrine feedback to gefitinib warrants further studies as cancer cells could bypass the antiproliferative effects of HER1-targeted therapeutics without a need for the overexpression and/or activation of other HER family members and/or the activation of HER-driven downstream signaling cascades

Hepatitis C virus NS5A protein binds the SH3 domain of the Fyn tyrosine kinase with high affinity: mutagenic analysis of residues within the SH3 domain that contribute to the interaction

Background: The hepatitis C virus (HCV) non-structural 5A protein (NS5A) contains a highly conserved C-terminal polyproline motif with the consensus sequence Pro-X-X- Pro-X-Arg that is able to interact with the Src-homology 3 (SH3) domains of a variety of cellular proteins. Results: To understand this interaction in more detail we have expressed two N-terminally truncated forms of NS5A in E. coli and examined their interactions with the SH3 domain of the Src-family tyrosine kinase, Fyn. Surface plasmon resonance analysis revealed that NS5A binds to the Fyn SH3 domain with what can be considered a high affinity SH3 domain-ligand interaction (629 nM), and this binding did not require the presence of domain I of NS5A (amino acid residues 32-250). Mutagenic analysis of the Fyn SH3 domain demonstrated the requirement for an acidic cluster at the C-terminus of the RT-Src loop of the SH3 domain, as well as several highly conserved residues previously shown to participate in SH3 domain peptide binding. Conclusion: We conclude that the NS5A: Fyn SH3 domain interaction occurs via a canonical SH3 domain binding site and the high affinity of the interaction suggests that NS5A would be able to compete with cognate Fyn ligands within the infected cell.