| 1. |
- Amer, Ayad, et al.
(författare)
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YopN and TyeA Hydrophobic Contacts Required for Regulating Ysc-Yop Type III Secretion Activity by Yersinia pseudotuberculosis
- 2016
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Ingår i: Frontiers in Cellular and Infection Microbiology. - : Frontiers Media SA. - 2235-2988. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Yersinia bacteria target Yop effector toxins to the interior of host immune cells by the Ysc-Yop type III secretion system. A YopN-TyeA heterodimer is central to controlling Ysc-Yop targeting activity. A + 1 frameshift event in the 3-prime end of yopN can also produce a singular secreted YopN-TyeA polypeptide that retains some regulatory function even though the C-terminal coding sequence of this YopN differs greatly from wild type. Thus, this YopN C-terminal segment was analyzed for its role in type III secretion control. Bacteria producing YopN truncated after residue 278, or with altered sequence between residues 279 and 287, had lost type III secretion control and function. In contrast, YopN variants with manipulated sequence beyond residue 287 maintained full control and function. Scrutiny of the YopN-TyeA complex structure revealed that residue W279 functioned as a likely hydrophobic contact site with TyeA. Indeed, a YopNW279G mutant lost all ability to bind TyeA. The TyeA residue F8 was also critical for reciprocal YopN binding. Thus, we conclude that specific hydrophobic contacts between opposing YopN and TyeA termini establishes a complex needed for regulating Ysc-Yop activity.
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| 2. |
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| 3. |
- Blomberg, Jeanette, et al.
(författare)
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Inhibition of cellular FLICE-like inhibitory protein abolishes insensitivity to interferon-α in a resistant variant of the human U937 cell line
- 2011
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Ingår i: Apoptosis (London). - : Springer Science and Business Media LLC. - 1360-8185 .- 1573-675X. ; 16:8, s. 783-794
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Tidskriftsartikel (refereegranskat)abstract
- Type I interferons constitute a family of pleiotropic cytokines that have a key role in both adaptive and innate immunity. The interferon signalling pathways mediate transcriptional regulation of hundreds of genes, which result in mRNA degradation, decreased protein synthesis, cell cycle inhibition and induction of apoptosis. To elucidate regulatory networks important for interferon induced cell death, we generated interferon resistant U937 cells by selection in progressively increasing concentrations of interferon-α (IFN-α). The results show that IFN-α activates the death receptor signalling pathway and that IFN resistance was associated with cross-resistance to several death receptor ligands in a manner similar to previously described Fas resistant U937 cell lines. Increased expression of the long splice variant of the cellular FLICE-like inhibitor protein (cFLIP-L) was associated with the resistance to death receptor and IFN-α stimulation. Accordingly, inhibition of cFLIP-L expression with cycloheximide or through cFLIP short harpin RNA interference restored sensitivity to Fas and/or IFN-α. Thus, we now show that selection for interferon resistance can generate cells with increased expression of cFLIP, which protects the cells from both IFN-α and death receptor mediated apoptosis.
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| 4. |
- Blomberg, Jeanette, 1977-, et al.
(författare)
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Reduced FAS transcription in clones of U937 cells that have acquired resistance to Fas-induced apoptosis
- 2009
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 276:2, s. 497-508
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Tidskriftsartikel (refereegranskat)abstract
- Susceptibility to cell death is a prerequisite for the elimination of tumour cells by cytotoxic immune cells, chemotherapy or irradiation. Activation of the death receptor Fas is critical for the regulation of immune cell homeostasis and efficient killing of tumour cells by apoptosis. To define the molecular changes that occur during selection for insensitivity to Fas-induced apoptosis, a resistant variant of the U937 cell line was established. Individual resistant clones were isolated and characterized. The most frequently observed defect in the resistant cells was reduced Fas expression, which correlated with decreased FAS transcription. Clones with such reduced Fas expression also displayed partial cross-resistance to tumour necrosis factor-alpha stimulation, but the mRNA expression of tumour necrosis factor receptors was not decreased. Reintroduction of Fas conferred susceptibility to Fas but not to tumour necrosis factor-alpha stimulation, suggesting that several alterations could be present in the clones. The reduced Fas expression could not be explained by mutations in the FAS coding sequence or promoter region, or by silencing through methylations. Protein kinase B and extracellular signal-regulated kinase, components of signalling pathways downstream of Ras, were shown to be activated in some of the resistant clones, but none of the three RAS genes was mutated, and experiments using chemical inhibitors could not establish that the activation of these proteins was the cause of Fas resistance as described in other systems. Taken together, the data illustrate that Fas resistance can be caused by reduced Fas expression, which is a result of an unidentified mode of regulation.
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| 5. |
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| 6. |
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| 7. |
- Chand, Damini, 1986, et al.
(författare)
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Cell culture and Drosophila model systems define three classes of anaplastic lymphoma kinase mutations in neuroblastoma.
- 2013
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Ingår i: Disease models & mechanisms. - Cambridge, UK : The Company of Biologists. - 1754-8411 .- 1754-8403. ; 6:2, s. 373-82
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Tidskriftsartikel (refereegranskat)abstract
- Neuroblastoma is a childhood extracranial solid tumor which is associated with a number of genetic changes. Included in these genetic alterations are mutations in the kinase domain of the Anaplastic Lymphoma Kinase (ALK) receptor tyrosine kinase (RTK), which have been found in both somatic and familial neuroblastoma. In order to treat patients accordingly required characterisation of these mutations in terms of their response to ALK tyrosine kinase inhibitors (TKIs). Here, we report the identification and characterisation of two novel neuroblastoma ALK mutations (A1099T and 1464STOP) which we have investigated together with several previously reported but uncharacterised ALK mutations (T1087I, D1091N, T1151M, M1166R, F1174I and A1234T). In order to understand the potential role of these ALK mutations in neuroblastoma progression we have employed cell culture based systems together with the model organism Drosophila as a readout for ligand-independent activity. Mutation of ALK at position F1174I generates a gain-of-function receptor capable of activating intracellular targets, such as ERK (extracellular signal regulated kinase) and STAT3 (signal transducer and activator of transcription 3) in a ligand independent manner. Analysis of these previously uncharacterised ALK mutants and comparison with ALK(F1174) mutants suggests that ALK mutations observed in neuroblastoma fall into three classes. These are: (i) gain-of-function ligand independent mutations such as ALK(F1174), (ii) kinase-dead ALK mutants, e.g. ALK(I1250T)(Schonherr et al 2011a) or (iii) ALK mutations which are ligand-dependent in nature. Irrespective of the nature of the observed ALK mutants, in every case the activity of the mutant ALK receptors could be abrogated by the ALK inhibitor crizotinib (PF-02341066, Xalkori), albeit with differing levels of sensitivity.
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| 8. |
- Fransson, Susanne, 1975, et al.
(författare)
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Intragenic anaplastic lymphoma kinase (ALK) rearrangements: Translocations as a novel mechanism of ALK activation in neuroblastoma tumors.
- 2015
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Ingår i: Genes, chromosomes & cancer. - : Wiley. - 1098-2264 .- 1045-2257. ; 54:2, s. 99-109
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Tidskriftsartikel (refereegranskat)abstract
- Anaplastic lymphoma kinase (ALK) has been demonstrated to be deregulated in sporadic as well as in familiar cases of neuroblastoma (NB). Whereas ALK-fusion proteins are common in lymphoma and lung cancer, there are few reports of ALK rearrangements in NB indicating that ALK mainly exerts its oncogenic capacity via activating mutations and/or overexpression in this tumor type. In this study, 332 NB tumors and 13 cell lines were screened by high resolution single nucleotide polymorphism microarray. Gain of 2p was detected in 23% (60/332) of primary tumors and 46% (6/13) of cell lines, while breakpoints at the ALK locus were detected in four primary tumors and two cell lines. These were further analyzed by next generation sequencing and a targeted enrichment approach. Samples with both ALK and MYCN amplification displayed complex genomic rearrangements with multiple breakpoints within the amplicon. None of the translocations characterized in primary NB tumors are likely to result in a chimeric protein. However, immunohistochemical analysis reveals high levels of phosphorylated ALK in these samples despite lack of initial exons, possibly due to alternative transcription initiation sites. Both ALK proteins predicted to arise from such alterations and from the abnormal ALK exon 4-11 deletion observed in the CLB-BAR cell line show strong activation of downstream targets STAT3 and extracellular signal-regulated kinase (ERK) when expressed in PC12 cells. Taken together, our data indicate a novel, although rare, mechanism of ALK activation with implications for NB tumorigenesis.
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| 9. |
- Guan, Jikui, et al.
(författare)
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Clinical response of the novel activating ALK-I1171T mutation in neuroblastoma to the ALK inhibitor ceritinib.
- 2018
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Ingår i: Cold Spring Harbor molecular case studies. - : Cold Spring Harbor Laboratory. - 2373-2873. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Tumors with Anaplastic Lymphoma Kinase (ALK) fusion rearrangements, including non-small cell lung cancer and anaplastic large cell lymphoma, are highly sensitive to ALK tyrosine kinase inhibitors (TKIs), underscoring the notion that such cancers are addicted to ALK activity. While mutations in ALK are heavily implicated in childhood neuroblastoma, response to the ALK TKI crizotinib has been disappointing. Embryonal tumors in patients with DNA repair defects such as Fanconi anemia (FA) often have a poor prognosis, due to lack of therapeutic options. Here we report a child with underlying FA and ALK mutant high-risk neuroblastoma responding strongly to precision therapy with the ALK TKI ceritinib. Conventional chemotherapy treatment caused severe, life-threatening toxicity. Genomic analysis of the initial biopsy identified germ-line FANCA mutations as well as a novel ALK-I1171T variant. ALK-I1171T generates a potent gain-of-function mutant, as measured in PC12 cell neurite outgrowth and NIH3T3 transformation. Pharmacological inhibition profiling of ALK-I1171T in response to various ALK TKIs identified an 11-fold improved inhibition of ALK-I1171T with ceritinib when compared with crizotinib. Immunoaffinity-coupled LC-MS/MS phosphoproteomics analysis indicated a decrease in ALK signaling in response to ceritinib. Ceritinib was therefore selected for treatment in this child. Mono-therapy with ceritinib was well tolerated and resulted in normalized catecholamine markers and tumor shrinkage. After 7.5 months treatment, residual primary tumor was surgically removed and exhibited hallmarks of differentiation together with reduced Ki67 levels. Clinical follow-up after 21 months treatment revealed complete clinical remission including all metastatic sites. Therefore, ceritinib presents a viable therapeutic option for ALK-positive neuroblastoma.
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| 10. |
- Guan, Jikui, et al.
(författare)
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Novel mechanisms of ALK activation revealed by analysis of the Y1278S neuroblastoma mutation
- 2017
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Ingår i: Cancers. - : MDPI. - 2072-6694. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Numerous mutations have been observed in the Anaplastic Lymphoma Kinase (ALK) receptor tyrosine kinase (RTK) in both germline and sporadic neuroblastoma. Here, we have investigated the Y1278S mutation, observed in four patient cases, and its potential importance in the activation of the full length ALK receptor. Y1278S is located in the 1278-YRASYY-1283 motif of the ALK activation loop, which has previously been reported to be important in the activation of the ALK kinase domain. In this study, we have characterized activation loop mutations within the context of the full length ALK employing cell culture and Drosophila melanogaster model systems. Our results show that the Y1278S mutant observed in patients with neuroblastoma harbors gain-of-function activity. Secondly, we show that the suggested interaction between Y1278 and other amino acids might be of less importance in the activation process of the ALK kinase than previously proposed. Thirdly, of the three individual tyrosines in the 1278-YRASYY-1283 activation loop, we find that Y1283 is the critical tyrosine in the activation process. Taken together, our observations employing different model systems reveal new mechanistic insights on how the full length ALK receptor is activated and highlight differences with earlier described activation mechanisms observed in the NPM-ALK fusion protein, supporting a mechanism of activation more in line with those observed for the Insulin Receptor (InR).
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