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Simple Summary Neuroblastoma is a pediatric cancer that arises in the sympathetic nervous system. High-risk neuroblastoma is clinically challenging and identification of novel therapies, particularly those that offer a reduction in morbidity for these patients, is a high priority. Combining genetic analyses with investigation of molecular mechanisms, while considering recent advances in our understanding of key developmental events, provides avenues for future treatment. Here we review and highlight several recently published articles that address novel molecular mechanisms arising from chromosome 1p, 2p, and 11q aberrations, which likely contribute to high-risk neuroblastoma, and discusses their potential impact on treatment options. Abstract Neuroblastoma is the most common extracranial solid pediatric tumor, with around 15% childhood cancer-related mortality. High-risk neuroblastomas exhibit a range of genetic, morphological, and clinical heterogeneities, which add complexity to diagnosis and treatment with existing modalities. Identification of novel therapies is a high priority in high-risk neuroblastoma, and the combination of genetic analysis with increased mechanistic understanding—including identification of key signaling and developmental events—provides optimism for the future. This focused review highlights several recent findings concerning chromosomes 1p, 2p, and 11q, which link genetic aberrations with aberrant molecular signaling output. These novel molecular insights contribute important knowledge towards more effective treatment strategies for neuroblastoma.

Anaplastic lymphoma kinase (Alk) is an evolutionary conserved receptor tyrosine kinase belonging to the insulin receptor superfamily. In addition to its well-studied role in cancer, numerous studies have revealed that Alk-signaling is associated with a variety of complex traits such as: regulation of growth and metabolism, hibernation, regulation of neurotransmitters, synaptic coupling, axon targeting, decision making, memory formation and learning, alcohol use disorder, as well as steroid hormone metabolism. In this study, we used BioID-based in vivo proximity labeling to identify molecules that interact with Alk in the Drosophila CNS. To do this, we used CRISPR/Cas9 induced homology-directed repair (HDR) to modify the endogenous Alk locus to produce first and next generation Alk::BioID chimeras. This approach allowed identification of Alk proximitomes under physiological conditions and without overexpression. Our results show that the next generation of BioID proteins (TurboID and miniTurbo) outperform the first generation BirA* fusion in terms of labeling speed and efficiency. LC-MS3-based BioID screening of AlkTurboID and AlkminiTurbo larval brains revealed an extensive neuronal Alk proximitome identifying numerous potential components of Alk signaling complexes. Validation of Alk proximitome candidates further revealed co-expression of Stardust (Sdt), Discs large 1 (Dlg1), Syntaxin (Syx) and Rugose (Rg) with Alk in the CNS and identified the protein-tyrosine-phosphatase Corkscrew (Csw) as a modulator of Alk signaling.

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that is mutated in approximately 10% of pediatric neuroblastoma (NB). To shed light on ALK-driven signaling processes, we employed BioID-based in vivo proximity labeling to identify molecules that interact intracellularly with ALK. NB-derived SK-N-AS and SK-N-BE(2) cells expressing inducible ALK-BirA* fusion proteins were generated and stimulated with ALKAL ligands in the presence and absence of the ALK tyrosine kinase inhibitor (TKI) lorlatinib. LC/MS-MS analysis identified multiple proteins, including PEAK1 and SHP2, which were validated as ALK interactors in NB cells. Further analysis of the ALK-SHP2 interaction confirmed that the ALK-SHP2 interaction as well as SHP2-Y542 phosphorylation was dependent on ALK activation. Use of the SHP2 inhibitors, SHP099 and RMC-4550, resulted in inhibition of cell growth in ALK-driven NB cells. In addition, we noted a strong synergistic effect of combined ALK and SHP2 inhibition that was specific to ALK-driven NB cells, suggesting a potential therapeutic option for ALK-driven NB.

Development of the midgut visceral muscle ofDrosophilacrucially depends on Anaplastic Lymphoma Kinase (Alk) receptor tyrosine kinase (RTK) signalling, which is needed to specify founder cells (FCs) in the circular visceral mesoderm (VM). While activation of the Alk receptor by its ligand Jelly Belly (Jeb) is well characterized, only a small number of target molecules have been identified. Here, we assayed RNA polymerase II (Pol II) occupancy in VM cells by using the targeted DamID (TaDa) approach. To identify Alk targets we employed comparative analysis of embryos overexpressing Jebversusembryos with abrogated Alk activity, revealing differential expression of a number of genes, including the Snail/Scratch family transcription factorKahuli(Kah). Upon furtherin vivovalidation, we confirmed that Alk signalling regulatesKahmRNA expression in the VM. We show thatKahmutants display defects in the formation of midgut constrictions, similar to that ofpointed(pnt) mutants. Analysis of publicly available ChIP data defined a Kah target-binding site similar to that of Snail. In addition, we compared genes that were differentially expressed inKahmutants with publicly available Kah- and Pnt-ChIP datasets identifying a set of common target genes putatively regulated by Kah and Pnt in midgut constriction. Taken together, we (i) report a rich dataset of Alk responsive loci in the embryonic VM, (ii) provide the first functional characterization of the Kah transcription factor, identifying a role in embryonic midgut constriction, and (iii) suggest a model in which Kah and Pnt cooperate in embryonic midgut morphogenesis.

Simple Summary The anaplastic lymphoma kinase (ALK) and rearranged during transfection (RET) receptor tyrosine kinases (RTKs) are expressed in both the developing neural crest and the pediatric cancer neuroblastoma. Moreover, ALK is mutated in approximately 10% of neuroblastomas. Here, we investigated ALK and RET in neuroblastoma, with the aim of better understanding their respective contributions. Using neuroblastoma cell lines, we show that ALK modulates RET signaling at the level of RET phosphorylation, as well as at the level of transcription. Using CRISPR/Cas9, we generated RET knockout neuroblastoma cell lines and performed a multi-omics approach, combining RNA-Seq and proteomics to characterize the effect of deleting RET in a neuroblastoma context. Remarkably, we could show that loss of RET results in a striking epithelial-to-mesenchymal transition (EMT) phenotype, and we provide evidence that RET activity suppresses the mesenchymal phenotype in neuroblastoma. Abstract Aberrant activation of anaplastic lymphoma kinase (ALK) drives neuroblastoma (NB). Previous work identified the RET receptor tyrosine kinase (RTK) as a downstream target of ALK activity in NB models. We show here that ALK activation in response to ALKAL2 ligand results in the rapid phosphorylation of RET in NB cells, providing additional insight into the contribution of RET to the ALK-driven gene signature in NB. To further address the role of RET in NB, RET knockout (KO) SK-N-AS cells were generated by CRISPR/Cas9 genome engineering. Gene expression analysis of RET KO NB cells identified a reprogramming of NB cells to a mesenchymal (MES) phenotype that was characterized by increased migration and upregulation of the AXL and MNNG HOS transforming gene (MET) RTKs, as well as integrins and extracellular matrix components. Strikingly, the upregulation of AXL in the absence of RET reflects the development timeline observed in the neural crest as progenitor cells undergo differentiation during embryonic development. Together, these findings suggest that a MES phenotype is promoted in mesenchymal NB cells in the absence of RET, reflective of a less differentiated developmental status.

High‐risk neuroblastoma (NB) is responsible for a disproportionate number of childhood deaths due to cancer. One indicator of high‐risk NB is amplification of the neural MYC (MYCN) oncogene, which is currently therapeutically intractable. Identification of anaplastic lymphoma kinase (ALK) as an NB oncogene raised the possibility of using ALK tyrosine kinase inhibitors (TKIs) in treatment of patients with activating ALK mutations. 8–10% of primary NB patients are ALK‐positive, a figure that increases in the relapsed population. ALK is activated by the ALKAL2 ligand located on chromosome 2p, along with ALK and MYCN, in the “2p‐gain” region associated with NB. Dysregulation of ALK ligand in NB has not been addressed, although one of the first oncogenes described was v‐sis that shares > 90% homology with PDGF. Therefore, we tested whether ALKAL2 ligand could potentiate NB progression in the absence of ALK mutation. We show that ALKAL2 overexpression in mice drives ALK TKI‐sensitive NB in the absence of ALK mutation, suggesting that additional NB patients, such as those exhibiting 2p‐gain, may benefit from ALK TKI‐based therapeutic intervention., ALKAL2 misregulation facilitates ALK receptor tyrosine kinase signaling and drives ALK‐dependent cancer irrespective of oncogenic mutations.

Protein-protein interactions (PPIs) play essential roles in Anaplastic Lymphoma Kinase (ALK) signaling. Systematic characterization of ALK interactors helps elucidate novel ALK signaling mechanisms and may aid in the identification of novel therapeutics targeting related diseases. In this study, we used the Mammalian Membrane Two- Hybrid (MaMTH) system to map the phospho-dependent ALK interactome. By screening a library of 86 SH2 domain-containing full length proteins, 30 novel ALK interactors were identified. Many of their interactions are correlated to ALK phosphorylation activity: oncogenic ALK mutations potentiate the interactions and ALK inhibitors attenuate the interactions. Among the novel interactors, NCK2 was further verified in neuroblastoma cells using co-immunoprecipitation. Modulation of ALK activity by addition of inhibitors lead to concomitant changes in the tyrosine phosphorylation status of NCK2 in neuroblastoma cells, strongly supporting the functionality of the ALK/NCK2 interaction. Our study provides a resource list of potential novel ALK signaling components for further study. (C) 2021 The Authors. Published by Elsevier Ltd.

Anaplastic lymphoma kinase (Alk) is a receptor tyrosine kinase of the insulin receptor super-family that functions as oncogenic driver in a range of human cancers such as neuroblastoma. In order to investigate mechanisms underlying Alk oncogenic signaling, we conducted a genetic suppressor screen in Drosophila melanogaster. Our screen identified multiple loci important for Alk signaling, including members of Ras/Raf/ERK-, Pi3K-, and STAT-pathways as well as tailless (tll) and foxo whose orthologues NR2E1/TLX and FOXO3 are transcription factors implicated in human neuroblastoma. Many of the identified suppressors were also able to modulate signaling output from activated oncogenic variants of human ALK, suggesting that our screen identified targets likely relevant in a wide range of contexts. Interestingly, two misexpression alleles of wallenda (wnd, encoding a leucine zipper bearing kinase similar to human DLK and LZK) were among the strongest suppressors. We show that Alk expression leads to a growth advantage and induces cell death in surrounding cells. Our results suggest that Alk activity conveys a competitive advantage to cells, which can be reversed by over-expression of the JNK kinase kinase Wnd.

High-risk 11q deleted neuroblastomas typically display undifferentiated/poorly differentiated morphology. Neuroblastoma is thought to develop from Schwann cell precursors and undifferentiated neural crest (NC) derived cells. It is therefore vital to understand mechanisms involved in the block of differentiation. We identify an important role for oncogenic ALK-ERK1/2-SP1 signaling in maintenance of undifferentiated NC-derived progenitors via repression of DLG2, a tumor suppressor in neuroblastoma. DLG2 is expressed in the ‘bridge signature’ that represents the transcriptional transition state when neural crest cells or Schwann Cell Precursors become chromaffin cells of the adrenal gland. We show that restoration of DLG2 expression spontaneously drives neuroblastoma differentiation highlighting the importance of DLG2 in this process. Further, genetic analysis of high-risk 11q-deletion neuroblastomas identified genetic lesions in the DLG2 gene. Our data also suggest that further exploration of other ‘bridge genes’ may help elucidate the mechanisms underlying the differentiation of NC-derived progenitors and their contribution to neuroblastoma.

Gain of chromosome arm 2p is a previously described entity in neuroblastoma (NB). This genomic address is home to two important oncogenes in NB-MYCN and anaplastic lymphoma kinase (ALK). MYCN amplification is a critical prognostic factor coupled with poor prognosis in NB. Mutation of the ALK receptor tyrosine kinase has been described in both somatic and familial NB. Here, ALK activation occurs in the context of the full-length receptor, exemplified by activating point mutations in NB. ALK overexpression and activation, in the absence of genetic mutation has also been described in NB. In addition, the recently identified ALK ligand ALKAL2 (previously described as FAM150B and AUGα) is also found on the distal portion of 2p, at 2p25. Here we analyze 356 NB tumor samples and discuss observations indicating that gain of 2p has implications for the development of NB. Finally, we put forward the hypothesis that the effect of 2p gain may result from a combination of MYCN, ALK, and the ALK ligand ALKAL2.

SUMMARY Although activating mutations of the anaplastic lymphoma kinase (ALK) membrane receptor occur in ~10% of neuroblastoma (NB) tumors, the role of the wild-type (WT) receptor, which is aberrantly expressed in most non-mutated cases, is unclear. Both WT and mutant proteins undergo extracellular domain (ECD) cleavage. Here, we map the cleavage site to Asn654-Leu655 and demonstrate that cleavage inhibition of WT ALK significantly impedes NB cell migration with subsequent prolongation of survival in mouse models. Cleavage inhibition results in the downregulation of an epithelial-to-mesenchymal transition (EMT) gene signature, with decreased nuclear localization and occupancy of β-catenin at EMT gene promoters. We further show that cleavage is mediated by matrix metalloproteinase 9, whose genetic and pharmacologic inactivation inhibits cleavage and decreases NB cell migration. Together, our results indicate a pivotal role for WT ALK ECD cleavage in NB pathogenesis, which may be harnessed for therapeutic benefit., Graphical abstract, In brief Huang et al. show that extracellular domain (ECD) cleavage of the ALK cell surface tyrosine kinase receptor mediates neuroblastoma cell migration through induction of an EMT phenotype. ECD cleavage is caused by MMP-9 whose inhibition leads to decreased cell migration.

The apical and basolateral membranes of epithelia are insulated from each other, preventing the transfer of extracellular proteins from one side to the other1. Thus, a signalling protein produced apically is not expected to reach basolateral receptors. Evidence suggests that Wingless, the main Drosophila Wnt is secreted apically in the embryonic epidermis2, 3. However, in the wing imaginal disc epithelium, Wingless is mostly seen on the basolateral membrane where it spreads from secreting to receiving cells 4, 5. Here we examine the apico-basal movement of Wingless in Wingless-producing cells of wing imaginal discs. We find that it is presented first on the apical surface before making its way to the basolateral surface, where it is released and allowed to interact with signalling receptors. We show that Wingless transcytosis involves Dynamin-dependent endocytosis from the apical surface. Subsequent trafficking from early apical endosomes to the basolateral surface requires Godzilla, a member of the RNF family of membrane-anchored E3 ubiquitin ligases. Without such transport, Wingless signalling is strongly reduced in this tissue.

Over the last decade Anaplastic Lymphoma Kinase (ALK), a receptor tyrosine kinase (RTK), has been identified as a fusion partner in a diverse variety of translocation events resulting in oncogenic signaling in many different cancer types. In tumors where full-length ALK RTK itself is mutated, such as neuroblastoma, the picture regarding the role of ALK as an oncogenic driver is less clear. Neuroblastoma is a complex and heterogeneous tumor that arises from the neural crest-derived peripheral nervous system. Although high-risk neuroblastoma is rare, it often relapses and becomes refractory to treatment. Thus, neuroblastoma accounts for 10-15% of all childhood cancer deaths. Since most cases are in children under the age of two, understanding the role and regulation of ALK during neural crest development is an important goal in addressing neuroblastoma tumorigenesis. An impressive array of tyrosine kinase inhibitors (TKIs) that act to inhibit ALK have been FDA approved for using in ALK-driven cancers. ALK TKIs bind differently within the ATP-binding pocket of the ALK kinase domain and have been associated with different resistance mutations within ALK itself that arise in response to therapeutic use, particularly in ALK fusion-positive NSCLC. This patient population has highlighted the importance of considering the relevant ALK TKI to be used for a given ALK mutant variant. In this poster we discuss ALK in neuroblastoma, as well as the use of ALK TKIs and other strategies to inhibit tumor growth. Current efforts combining novel approaches and increasing our understanding of the oncogenic role of ALK in neuroblastoma are aimed at improving efficacy of ALK TKIs as precision medicine options in the clinic. Citation Format: Jikui Guan, Diana Cervantes-Madrid, Joachim Siaw, Wasi Alam, Ganesh Umapathy, Marcus Borenäs, Dan Lind, Joanna Szydzik, Kathrin Pfeifer, Patricia Mendoza-Garcia, Ruth Palmer, Bengt Hallberg. Targeting anaplastic lymphoma kinase in neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr A36.

Basement membranes (BMs) are specialized layers of extracellular matrix (ECM) mainly composed of Laminin, type IV Collagen, Perlecan and Nidogen/entactin (NDG). While the essential and evolutionary conserved functions of Laminin, Collagen and Perlecan are well documented inDrosophilaand other species, the proposed role of NDG as the major ECM linker molecule has been challenged by severalin vivostudies revealing that NDG is dispensable for viability and BM formation. Here, we report the characterization of the singleNdggene inDrosophila.EmbryonicNdgexpression differed from that of other BM components and was primarily observed in mesodermal tissues and the chordotonal organs, whereas NDG protein localized to all BMs. While loss of Laminin strongly affected BM-localization of NDG,Ndgnull mutants exhibited no overt changes in the distribution of BM core components. However, loss of NDG led to ultrastructural BM defects compromising barrier function and stabilityin vivo.AlthoughNdgmutants were viable, loss of NDG led to decreased fecundity in flies as well as impaired crawling behavior and reduced response to vibrational stimuli in larvae. Further morphological analysis revealed accompanying defects in the larval peripheral nervous system especially in the chordotonal organs and the neuromuscular junction (NMJ), whereNdggenetically interacted with theLeukocyte-antigen-related-like (Lar) receptorgene to regulate NMJ extension and synaptic differentiation. Taken together, our analysis suggests that NDG is not essential for BM assembly but mediates BM stability and ECM-dependent neural plasticity duringDrosophiladevelopment.Summary StatementIn this study we characterizeDrosophila Nidogen/Entactin (Ndg)mutants revealing that loss of Ndg impairs basement membrane (BM) stability and permeability as well as proper function of the nervous system.

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that is a clinical target of major interest in cancer. Mutations and rearrangements in ALK trigger the activation of the encoded receptor and its downstream signaling pathways. ALK mutations have been identified in both familial and sporadic neuroblastoma cases as well as in 30 to 40% of relapses, which makes ALK a bona fide target in neuroblastoma therapy. Tyrosine kinase inhibitors (TKIs) that target ALK are currently in clinical use for the treatment of patients with ALK-positive non-small cell lung cancer. However, monotherapy with the ALK inhibitor crizotinib has been less encouraging in neuroblastoma patients with ALK alterations, raising the question of whether combinatorial therapy would be more effective. In this study, we established both phosphoproteomic and gene expression profiles of ALK activity in neuroblastoma cells exposed to first- and third-generation ALK TKIs, to identify the underlying molecular mechanisms and identify relevant biomarkers, signaling networks, and new therapeutic targets. This analysis has unveiled various important leads for novel combinatorial treatment strategies for patients with neuroblastoma and an increased understanding of ALK signaling involved in this disease.

Basement membranes (BMs) are specialized layers of extracellular matrix (ECM) mainly composed of Laminin, type IV Collagen, Perlecan and Nidogen/entactin (NDG). Recent in vivo studies challenged the initially proposed role of NDG as major ECM linker molecule by revealing dispensability for viability and BM formation. Here, we report the characterization of the single Ndg gene in Drosophila. Embryonic Ndg expression was primarily observed in mesodermal tissues and the chordotonal organs, whereas NDG protein localized to all BMs. While loss of Laminin strongly affected BM-localization of NDG, Ndg null mutants exhibited no overt changes in the distribution of BM components. Although Drosophila Ndg mutants were viable, loss of NDG led to ultrastructural BM defects compromising barrier function and stability in vivo. Moreover, loss of NDG impaired larval crawling behavior and reduced responses to vibrational stimuli. Further morphological analysis revealed accompanying defects in the larval peripheral nervous system especially in the chordotonal organs and the neuromuscular junction (NMJ). Taken together, our analysis suggests that NDG is not essential for BM assembly but mediates BM stability and ECM-dependent neural plasticity during Drosophila development.

Significance Neuroblastoma is a pediatric tumor arising from the neural crest. Dysregulation of the receptor tyrosine kinase ALK has been linked to neuroblastoma, making it important to understand its function in native conditions. In zebrafish, a related receptor—Ltk—is also expressed in neural crest and regulates development of specific pigment cells—iridophores. Ligands activating human ALK were recently identified as the ALKAL proteins (FAM150, AUG) by biochemical means. Our data show that this ligand–receptor pair functions in vivo in the neural crest of zebrafish to drive development of iridophores. Removal of Ltk or all three zebrafish ALKALs results in larvae completely lacking these cells. Using Drosophila and human cell lines, we show evolutionary conservation of this important interaction., Mutations in anaplastic lymphoma kinase (ALK) are implicated in somatic and familial neuroblastoma, a pediatric tumor of neural crest-derived tissues. Recently, biochemical analyses have identified secreted small ALKAL proteins (FAM150, AUG) as potential ligands for human ALK and the related leukocyte tyrosine kinase (LTK). In the zebrafish Danio rerio, DrLtk, which is similar to human ALK in sequence and domain structure, controls the development of iridophores, neural crest-derived pigment cells. Hence, the zebrafish system allows studying Alk/Ltk and Alkals involvement in neural crest regulation in vivo. Using zebrafish pigment pattern formation, Drosophila eye patterning, and cell culture-based assays, we show that zebrafish Alkals potently activate zebrafish Ltk and human ALK driving downstream signaling events. Overexpression of the three DrAlkals cause ectopic iridophore development, whereas loss-of-function alleles lead to spatially distinct patterns of iridophore loss in zebrafish larvae and adults. alkal loss-of-function triple mutants completely lack iridophores and are larval lethal as is the case for ltk null mutants. Our results provide in vivo evidence of (i) activation of ALK/LTK family receptors by ALKALs and (ii) an involvement of these ligand–receptor complexes in neural crest development.

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.

The Jelly belly (Jeb)/Anaplastic Lymphoma Kinase (Alk) signalling pathway regulates myoblast fusion in the circular visceral mesoderm (VM) of Drosophila embryos via specification of founder cells. However, only a limited number of target molecules for this pathway are described. We have investigated the role of the Lame Duck (Lmd) transcription factor in VM development in relationship to Jeb/Alk signal transduction. We show that Alk signalling negatively regulates Lmd activity post-transcriptionally through the MEK/MAPK (ERK) cascade resulting in a relocalisation of Lmd protein from the nucleus to cytoplasm. It has previously been shown that downregulation of Lmd protein is necessary for the correct specification of founder cells. In the visceral mesoderm of lmd mutant embryos, fusion-competent myoblasts seem to be converted to ‘founder-like’ cells that are still able to build a gut musculature even in the absence of fusion. The ability of Alk signalling to downregulate Lmd protein requires the N-terminal 140 amino acids, as a Lmd141-866 mutant remains nuclear in the presence of active ALK and is able to drive robust expression of the Lmd downstream target Vrp1 in the developing VM. Our results suggest that Lmd is a target of Jeb/Alk signalling in the VM of Drosophila embryos.

Activation of the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase is a key oncogenic mechanism in a growing number of tumor types. In the majority of cases, ALK is activated by fusion with a dimerizing partner protein as a result of chromosomal translocation events, most studied in the case of the nucleophosmin-ALK and echinoderm microtubule-associated protein-like 4-ALK oncoproteins. It is now also appreciated that the full-length ALK receptor can be activated by point mutations and by deletions within the extracellular domain, such as those observed in neuroblastoma. Several studies have employed phosphoproteomics approaches to find substrates of ALK fusion proteins. In this study, we used MS-based phosphotyrosine profiling to characterize phosphotyrosine signaling events associated with the full-length ALK receptor. A number of previously identified and novel targets were identified. One of these, signal transducer and activator of transcription 3 (STAT3), has previously been observed to be activated in response to oncogenic ALK signaling, but the significance of this in signaling from the full-length ALK receptor has not been explored further. We show here that activated ALK robustly activates STAT3 on Tyr705 in a number of independent neuroblastoma cell lines. Furthermore, knockdown of STAT3 by RNA interference resulted in a reduction in myelocytomatosis neuroblastom (MYCN) protein levels downstream of ALK signaling. These observations, together with a decreased level of MYCN and inhibition of neuroblastoma cell growth in the presence of STAT3 inhibitors, suggest that activation of STAT3 is important for ALK signaling activity in neuroblastoma. Special Issue: Frontiers in Cell Signalling, and Ca2+-Signalling and Transport in Health and Disease

Folliculitis is a common inflammatory skin syndrome. Several microbial organisms have been put forward as causative agents, but few studies visualized microbes directly in inflamed hair follicles. This retrospective study investigated bacterial and fungal colonization of inflamed hair follicles in patients with clinically diagnosed non-infectious folliculitis. Skin biopsies from 39 folliculitis patients and 27 controls were screened by fluorescence in situ hybridization (FISH) using broad-range bacterial and fungal probes and by immunofluorescence microscopy using a monoclonal antibody towards Gram-positive bacteria. Specific monoclonal and polyclonal antibodies towards Staphylococcus spp. and Propionibacterium acnes were applied for further species identification. Inflamed follicles were associated with bacterial colonization in 10 samples (26%) and fungal colonization in three samples (8%). Staphylococcus spp. were observed in inflamed follicles in seven samples (18%). Two samples were positive for P. acnes, which were identified as either type II or type IB/type III. Both Staphylococcus spp. and P. acnes were seen in macrocolonies/biofilm structures. In conclusion, one-third of patients with clinically diagnosed, non-infectious folliculitis exhibited microbial colonization with predominance of Staphylococcus spp.

SummaryNeuroblastoma 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 1174 (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 ALKF1174 mutants suggests that ALK mutations observed in neuroblastoma fall into three classes. These are: (i) gain-of-function ligand independent mutations such as ALKF1174, (ii) kinase-dead ALK mutants, e.g. ALKI1250T(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.

A vast array of oncogenic variants has been identified for anaplastic lymphoma kinase (ALK). Therefore, there is a need to better understand the role of ALK in cancer biology in order to optimise treatment strategies. This review summarises the latest research on the receptor tyrosine kinase ALK, and how this information can guide the management of patients with cancer that is ALK-positive. A variety of ALK gene alterations have been described across a range of tumour types, including point mutations, deletions and rearrangements. A wide variety of ALK fusions, in which the kinase domain of ALK and the amino-terminal portion of various protein partners are fused, occur in cancer, with echinoderm microtubule-associated protein-like 4 (EML4)-ALK being the most prevalent in non-small-cell lung cancer (NSCLC). Different ALK fusion proteins can mediate different signalling outputs, depending on properties such as subcellular localisation and protein stability. The ALK fusions found in tumours lack spatial and temporal regulation, which can also affect dimerisation and substrate specificity. Two ALK tyrosine kinase inhibitors (TKIs), crizotinib and ceritinib, are currently approved in Europe for use in ALK-positive NSCLC and several others are in development. These ALK TKIs bind slightly differently within the ATP-binding pocket of the ALK kinase domain and are associated with the emergence of different resistance mutation patterns during therapy. This emphasises the need to tailor the sequence of ALK TKIs according to the ALK signature of each patient. Research into the oncogenic functions of ALK, and fast paced development of ALK inhibitors, has substantially improved outcomes for patients with ALK-positive NSCLC. Limited data are available surrounding the physiological ligand-stimulated activation of ALK signalling and further research is needed. Understanding the role of ALK in tumour biology is key to further optimising therapeutic strategies for ALK-positive disease.

The first-in-class inhibitor of ALK, c-MET and ROS1, crizotinib (Xalkori), has shown remarkable clinical efficacy in treatment of ALK-positive non-small cell lung cancer. However, in neuroblastoma, activating mutations in the ALK kinase domain are typically refractory to crizotinib treatment, highlighting the need for more potent inhibitors. The next-generation ALK inhibitor PF-06463922 is predicted to exhibit increased affinity for ALK mutants prevalent in neuroblastoma. We examined PF-06463922 activity in ALK-driven neuroblastoma models in vitro and in vivo. In vitro kinase assays and cell-based experiments examining ALK mutations of increasing potency show that PF-06463922 is an effective inhibitor of ALK with greater activity towards ALK neuroblastoma mutants. In contrast to crizotinib, single agent administration of PF-06463922 caused dramatic tumor inhibition in both subcutaneous and orthotopic xenografts as well as a mouse model of high-risk neuroblastoma driven by Th-ALKF1174L/MYCN. Taken together, our results suggest PF-06463922 is a potent inhibitor of crizotinib-resistant ALK mutations, and highlights an important new treatment option for neuroblastoma patients., Summary: Our results suggest that PF-06463922 is a potent inhibitor of crizotinib-resistant ALK mutations, and highlights an important new treatment option for neuroblastoma patients.

Summary Background Acne vulgaris is a disorder of the sebaceous follicles. Propionibacterium acnes can be involved in inflammatory acne. Objectives This case-control study aimed at investigating ...

Neuroblastoma is a neural crest-derived embryonal tumour of the postganglionic sympathetic nervous system and a disease with several different chromosomal gains and losses, which include MYCN-amplified neuroblastoma on chromosome 2, deletions of parts of the chromosomes 1p and 11q, gain of parts of 17q and triploidy. Recently, activating mutations of the ALK (Anaplastic Lymphoma Kinase) RTK (Receptor Tyrosine Kinase) gene have been described in neuroblastoma. A meta-analysis of neuroblastoma cases revealed that ALK mutations (49 of 709 cases) in relation to genomic subtype were most frequently observed in MYCN amplified tumours (8.9%), correlating with a poor clinical outcome. MYCN proteins target proliferation and apoptotic pathways, and have an important role in the progression of neuroblastoma. Here, we show that both wild-type and gain-of-function mutants in ALK are able to stimulate transcription at the MYCN promoter and initiate mRNA transcription of the MYCN gene in both neuronal and neuroblastoma cell lines. Further, this stimulation of MYCN gene transcription and de novo MYCN protein expression is abrogated by specific ALK inhibitors, such as crizotinib (PF-2341066), NVP-TAE684, and by small interfering RNA to ALK resulting in a decrease in proliferation rate. Finally, co-transfection of ALK gain-of-function mutations together with MYCN leads to an increase in transformation potential. Taken together, our results indicate that ALK signalling regulates initiation of transcription of the MYCN gene providing a possible explanation for the poor clinical outcome observed when MYCN is amplified together with activated ALK.

Mutations in the kinase domain of ALK (anaplastic lymphoma kinase) have recently been shown to be important for the progression of the childhood tumour neuroblastoma. In the present study we investigate six of the putative reported constitutively active ALK mutations, in positions G1128A, I1171N, F1174L, R1192P, F1245C and R1275Q. Our analyses were performed in cell-culture-based systems with both mouse and human ALK mutant variants and subsequently in a Drosophila melanogaster model system. Our investigation addressed the transforming potential of the putative gain-of-function ALK mutations as well as their signalling potential and the ability of two ATP-competitive inhibitors, Crizotinib (PF-02341066) and NVP-TAE684, to abrogate the activity of ALK. The results of the present study indicate that all mutations tested are of an activating nature and thus are implicated in tumour initiation or progression of neuroblastoma. Importantly for neuroblastoma patients, all ALK mutations used in the present study can be blocked by the inhibitors, although some mutants exhibited higher levels of drug sensitivity than others.

Activating mutations in the kinase domain of anaplastic lymphoma kinase (ALK) have recently been shown to be an important determinant in the genetics of the childhood tumor neuroblastoma. Here we discuss an in-depth analysis of one of the reported gain-of-function ALK mutations-ALK(I1250T)-identified in the germ line DNA of one patient. Our analyses were performed in cell culture-based systems and subsequently confirmed in a Drosophila model. The results presented here indicate that the germ line ALK(I1250T) mutation is most probably not a determinant for tumor initiation or progression and, in contrast, seems to generate a kinase-dead mutation in the ALK receptor tyrosine kinase (RTK). Consistent with this, stimulation with agonist ALK antibodies fails to lead to stimulation of ALK(I1250T) and we were unable to detect tyrosine phosphorylation under any circumstances. In agreement, ALK(I1250T) is unable to activate downstream signaling pathways or to mediate neurite outgrowth, in contrast to the activated wild-type ALK receptor or the activating ALK(F1174S) mutant. Identical results were obtained when the ALK(I1250T) mutant was expressed in a Drosophila model, confirming the lack of activity of this mutant ALK RTK. We suggest that the ALK(I1250T) mutation leads to a kinase-dead ALK RTK, in stark contrast to assumed gain-of-function status, with significant implications for patients reported to carry this particular ALK mutation.

Introduction Receptor tyrosine kinases (RTKs) play important roles in cellular proliferation and differentiation. In addition, RTKs reveal oncogenic potential when their kinase activities are constitutively enhanced by point mutation, amplification, or rearrangement of the corresponding genes. We are investigating ALK (Anaplastic Lymphoma Kinase) tyrosine kinase in neuroblastoma (NB) - the most frequently occurring extracranial tumour in children, where ALK activating mutations are found. In this study we performed phosphoproteomic and a gene signature profiling of ALK activity from several different neuroblastoma cells comparing treatment with the first and third generations ALK inhibitors. Material and methods Crizotinib was one of the first ALK TKIs to be described; however the response in patients with ALK positive NB was poor. In contrast, robust and sustained clinical responses we seen in ALK rearranged IMT. Lorlatinib is a third generation ALK TKI with very positive responses in NSCLC. We treated two ALK addicted (CLB-BAR, CLB-GE) and one ALK non-addicted (SK-N-AS) NB cell lines with either crizotinib or lorlatinib and performed phosphoproteomic and RNAseq profiling to identify common targets for future combinational treatment for patients. Results and discussions Profiling of ALK addicted CLB-BAR and CLB-GE cell lines led to the identification of 3345 and 2252 phosphoproteins, respectively. Phosphorylation of the ALK receptor itself was decreased in both lines upon treatment with crizotinib or lorlatinib. Parallel RNAseq profiling was performed at 24 hours. Comparison with non-treated controls revealed 19 232 differently expressed genes. In ALK addicted cells phosphoproteomic analysis revealed more than 50 proteins that were dephosphorylated upon treatment with ALK TKIs. More than 400 genes were downregulated, and more than 600 were upregulated, upon treatment with either crizotinib or lorlatinib. As an outcome we obtained a list of predicted targets for further analysis. We focused on validation of downstream signalling molecules such as: FOXO3a/4, DUSP4 and ETV3/4. Conclusion In this study we established and compared phosphoproteomic and gene signature profiles of ALK activity in NB cells employing first and third generation ALK TKIs. This analysis has unveiled a number of leads for novel combinatorial treatment strategies for NB patients as well as an increased understanding ALK dependant signalling processes.

SummaryCytokinesis, the final step of cell division, conventionally proceeds to cell separation by abscission, or complete cytokinesis [1, 2], but may in certain tissues be incomplete, yielding daughter cells that are interconnected in syncytia by stable intercellular bridges [3]. The mechanisms that determine complete versus incomplete cytokinesis are not known. Here we report a novel in vivo role of the Drosophila CD2AP/CIN85 ortholog Cindr in both complete and incomplete cytokinesis. We also show evidence for the presence of persistent intercellular bridges in the major larval imaginal disc epithelia. During conventional division of both cultured and embryonic cells, Cindr localizes to cleavage furrows, intercellular bridges, and midbodies. Moreover, in cells undergoing incomplete cytokinesis in the female germline and the somatic ovarian follicle cell and larval imaginal disc epithelia, Cindr localizes to arrested cleavage furrows and stable intercellular bridges, respectively. In these structures, Cindr colocalizes with the essential cytokinesis regulator Anillin. We show that Cindr interacts with Anillin and that depletion of either Cindr or Anillin gives rise to binucleate cells and fewer intercellular bridges in vivo. We propose that Cindr and Anillin cooperate to promote intercellular bridge stability during incomplete cytokinesis in Drosophila melanogaster.

Antibacterial peptides of the innate immune system combat pathogenic microbes, but often have additional roles in promoting inflammation and as growth factors during tissue repair. Midkine (MK) and pleiotrophin (PTN) are the only two members of a family of heparin-binding growth factors. They show restricted expression during embryogenesis and are up-regulated in neoplasia. In addition, MK shows constitutive and inflammation-dependent expression in some non-transformed tissues of the adult. In the present study, we show that both MK and PTN display strong antibacterial activity, present at physiological salt concentrations. Electron microscopy of bacteria and experiments using artificial lipid bilayers suggest that MK and PTN exert their antibacterial action via a membrane disruption mechanism. The predicted structure of PTN, employing the previously solved MK structure as a template, indicates that both molecules consist of two domains, each containing three antiparallel β-sheets. The antibacterial activity was mapped to the unordered C-terminal tails of both molecules and the last β-sheets of the N-terminals. Analysis of the highly conserved MK and PTN orthologues from the amphibian Xenopus laevis and the fish Danio rerio suggests that they also harbor antibacterial activity in the corresponding domains. In support of an evolutionary conserved function it was found that the more distant orthologue, insect Miple2 from Drosophila melanogaster, also displays strong antibacterial activity. Taken together, the findings suggest that MK and PTN, in addition to their earlier described activities, may have previously unrealized important roles as innate antibiotics.

Many different types of cancer originate from aberrant signaling from the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase (RTK), arising through different translocation events and overexpression. Further, activating point mutations in the ALK domain have been recently reported in neuroblastoma. To characterize signaling in the context of the full-length receptor, we have examined whether ALK is able to activate Rap1 and contribute to differentiation/proliferation processes. We show that ALK activates Rap1 via the Rap1-specific guanine-nucleotide exchange factor C3G, which binds in a constitutive complex with CrkL to activated ALK. The activation of the C3G/Rap1 pathway results in neurite outgrowth of PC12 cells, which is inhibited by either overexpression of Rap1GAP or siRNA-mediated knockdown of Rap1 itself or the guanine nucleotide exchange factor C3G. Significantly, this pathway also appears to function in the regulation of proliferation of neuroblastoma cells such as SK-N-SH and SH-SY5Y, because abrogation of Rap1 activity by Rap1-specific siRNA or overexpression of Rap1GAP reduces cellular growth. These results suggest that ALK activation of Rap1 may contribute to cell proliferation and oncogenesis of neuroblastoma driven by gain-of-function mutant ALK receptors.

Mutations in the kinase domain of Anaplastic Lymphoma Kinase (ALK) have been suggested to be important players in the genetics and progression of the childhood tumor neuroblastoma. Here we report the appearance of a novel ALK mutation in neuroblastoma together with other chromosomal aberrations that mediate neuroblastoma initiation and progression. Analyses of genomic tumor DNA from biopsy samples initially showed an 11q minus, 17q gain with a mutation of the ALK gene at protein position 1171, which mediate an amino acid change from isoleucine to threonine. We show that mutation of I1171 to threonine generates a potent gain-of-function mutant, as observed in two independent systems. Firstly, in PC12 cell lines expressing ALKI1171T display ligand independent activation of ALK, neurite outgrowth and further downstream signaling activation. Secondly, ALKI1171T meditate foci formation in a NIH3T3 transformation analysis. Finally, pharmacological inhibition of ALKI1171T employing ceritinib, an FDA approved ALK inhibitor show 14-fold better ability to abrogate ALKI1171T compared with crizotinib. Citation Format: Joachim T. Siaw, Jikui Guan, Tommy Martinsson, Magnus Hansson, Per Kogner, Ruth Palmer. A novel activating I1171T ALK mutation in neuroblastoma responds better to ceritinib compare to the first generation inhibitor crizotinib [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B40.

RTKs (receptor tyrosine kinases) play important roles in cellular proliferation and differentiation. In addition, RTKs reveal oncogenic potential when their kinase activities are constitutively enhanced by point mutation, amplification or rearrangement of the corresponding genes. The ALK (anaplastic lymphoma kinase) RTK was originally identified as a member of the insulin receptor subfamily of RTKs that acquires transforming capability when truncated and fused to NPM (nucleophosmin) in the t(2;5) chromosomal rearrangement associated with ALCL (anaplastic large cell lymphoma). To date, many chromosomal rearrangements leading to enhanced ALK activity have been described and are implicated in a number of cancer types. Recent reports of the EML4 (echinoderm microtubule-associated protein like 4)–ALK oncoprotein in NSCLC (non-small cell lung cancer), together with the identification of activating point mutations in neuroblastoma, have highlighted ALK as a significant player and target for drug development in cancer. In the present review we address the role of ALK in development and disease and discuss implications for the future.

SummaryAnaplastic lymphoma kinase (Alk) has been proposed to regulate neuronal development based on its expression pattern in vertebrates and invertebrates; however, its function in vivo is unknown. We demonstrate that Alk and its ligand Jelly belly (Jeb) play a central role as an anterograde signaling pathway mediating neuronal circuit assembly in the Drosophila visual system. Alk is expressed and required in target neurons in the optic lobe, whereas Jeb is primarily generated by photoreceptor axons and functions in the eye to control target selection of R1–R6 axons in the lamina and R8 axons in the medulla. Impaired Jeb/Alk function affects layer-specific expression of three cell-adhesion molecules, Dumbfounded/Kirre, Roughest/IrreC, and Flamingo, in the medulla. Moreover, loss of flamingo in target neurons causes some R8-axon targeting errors observed in jeb and Alk mosaic animals. Together, these findings suggest that Jeb/Alk signaling helps R-cell axons to shape their environment for target recognition.

Receptor tyrosine kinase (RTK) c-Kit signalling is crucial for the proliferation, survival and differentiation of haematopoietic stem cells (HSCs). To further understand the mechanisms underlying these events we explored how the downstream mediators interact. The present study investigated the function of conventional protein kinase Cs (c-PKC) in c-Kit mediated signalling pathways in HSC-like cell lines. This analysis supported earlier findings, that steel factor (SF) activates c-PKC, extracellular signal-regulated kinase (Erk) and protein kinase B (PKB). The present results were consistent with an important role of c-PKC in the positive activation of Erk and for proliferation. Further, it was observed that c-PKC negatively regulated PKB activity upon SF stimulation, indicating that c-PKC acts as a suppressor of c-Kit signalling. Finally, these observations were extended to show that c-PKC mediated the phosphorylation of the endogenous c-Kit receptor on serine 746, resulting in decreased overall tyrosine phosphorylation of c-Kit upon SF stimulation. This report showed that this specific feedback mechanism of c-PKC mediated phosphorylation of the c-Kit receptor has consequences for both proliferation and survival of HSC-like cell lines.

Aberrant activation of anaplastic lymphoma kinase (ALK) has been described in a range of human cancers, including non-small cell lung cancer and neuroblastoma (Hallberg and Palmer, 2013). Vertebrate ALK has been considered to be an orphan receptor and the identity of the ALK ligand(s) is a critical issue. Here we show that FAM150A and FAM150B are potent ligands for human ALK that bind to the extracellular domain of ALK and in addition to activation of wild-type ALK are able to drive 'superactivation' of activated ALK mutants from neuroblastoma. In conclusion, our data show that ALK is robustly activated by the FAM150A/B ligands and provide an opportunity to develop ALK-targeted therapies in situations where ALK is overexpressed/activated or mutated in the context of the full length receptor. DOI: http://dx.doi.org/10.7554/eLife.09811.001, eLife digest Cells have receptor proteins on their surface that enable them to detect changes in their environment and communicate with other cells. Signal molecules bind to a segment of the receptor called the extracellular domain that faces out from the cell. This can result in the activation of another domain in the receptor that is just inside the cell, which, in turn, activates signaling pathways that relay the information around the cell. However, these communication systems are often disrupted in cancer cells. This helps the cells to override the strict growth controls imposed upon them by other (healthy) cells in the body. The gene that encodes a receptor protein called Anaplastic Lymphoma Kinase (or ALK for short) is often mutated in some types of human cancer so that the protein is always active. However, we still do not know what signal molecules bind to the ALK protein to activate it in normal cells. Guan, Umapathy et al. used a variety of cell biology and biochemical techniques to study the role of ALK. The experiments show that when either of two proteins called FAM150A and FAM150B are produced in rat nerve cells alongside ALK, the nerve cells rapidly respond and form outgrowths. Experiments using cancer cells derived from human nerve cells also yielded similar results. Guan, Umapathy et al. found that the extracellular domain of ALK can physically interact with FAM150A and FAM150B. The eyes of fruit flies that had been genetically modified to produce the human ALK protein alongside either FAM150A or FAM150B grew more than normal, giving the eyes an abnormal "rough" appearance. Further experiments showed that FAM150A and FAM150B are also able to increase the level of activation of an ALK mutant protein that is already active. Therefore, in future, the development of drugs that stop FAM150A and FAM150B from binding to ALK may be useful for treating cancers that are driven by high levels of ALK activity. Many challenging questions lie ahead to better understand how FAM150A and FAM150B interact with ALK. DOI: http://dx.doi.org/10.7554/eLife.09811.002

Mice lacking ALK activity have previously been reported to exhibit subtle behavioral phenotypes. In this study of ALK of loss of function mice we present data supporting a role for ALK in hypogonadotropic hypogonadism in male mice. We observed lower level of serum testosterone at P40 in ALK knock-out males, accompanied by mild disorganization of seminiferous tubules exhibiting decreased numbers of GATA4 expressing cells. These observations highlight a role for ALK in testis function and are further supported by experiments in which chemical inhibition of ALK activity with the ALK TKI crizotinib was employed. Oral administration of crizotinib resulted in a decrease of serum testosterone levels in adult wild type male mice, which reverted to normal levels after cessation of treatment. Analysis of GnRH expression in neurons of the hypothalamus revealed a significant decrease in the number of GnRH positive neurons in ALK knock-out mice at P40 when compared with control littermates. Thus, ALK appears to be involved in hypogonadotropic hypogonadism by regulating the timing of pubertal onset and testis function at the upper levels of the hypothalamic-pituitary gonadal axis.

Anaplastic Lymphoma Kinase (ALK), a receptor tyrosine kinase, was first described as the fusion product causing a subtype of non-Hodgkin's lymphoma. To date Alk has been reported to be mainly expressed in CNS and other parts of the brain. Here we describe an extensive characterization of the mRNA and protein expression of ALK during mouse development. We show that mRNA and ALK protein show overlapping expressing patterns in specific regions of the central and the peripheral nervous systems. Furthermore, ALK is also expressed in the eye, nasal epithelium, olfactory nerve, tongue, skin, tissue surrounding the esophagus, stomach and midgut but not the hindgut. Expression of ALK is also found in testis and ovary.

Intracellular targeting of the Pseudomonas aeruginosa toxins, such as exoenzyme S (ExoS), cause cell death, as well as morphological and physiological changes in various tissue culture cells and animal models. In this report we have investigated the mechanism behind ExoS-mediated cell death. In order to address this issue, we have used cell lines expressing activated forms of various components of the Ras signalling pathway in order to evaluate the importance of the Ras pathway for viability and survival upon ExoS infection. Here we show that activated Ras is able to protect cells against cell death, regardless of whether it has been ADP-ribosylated by ExoS. Further, an activated form of protein kinase B (PKB)/Akt also leads to decreased level of cell death in response to ExoS infection, indicating that an important ExoS survival target is located upstream of Raf-1 and PKB/Akt. Moreover, we show that ExoS infection inhibits phosphorylation of FOXO3a, and induces caspase-3 activity, which are hallmarks for induction of cell death. In conclusion, we suggest that Ras proteins are an important cellular target for the P. aeruginosa toxin ExoS, which induces cell death during pathogenesis as a means of defending the bacterium against eukaryotic phagocytosis.

14-3-3 proteins belong to a family of conserved molecules expressed in all eukaryotic cells, which play an important role in a multitude of signaling pathways. 14-3-3 proteins bind to phosphoserine/phosphothreonine motifs in a sequence-specific manner. More than 200 14-3-3 binding partners have been found that are involved in cell cycle regulation, apoptosis, stress responses, cell metabolism and malignant transformation. A phosphorylation-independent interaction has been reported to occur between 14-3-3 and a C-terminal domain within exoenzyme S (ExoS), a bacterial ADP-ribosyltransferase toxin from Pseudomonas aeruginosa. In this study, we have investigated the effect of amino acid mutations in this C-terminal domain of ExoS on ADP-ribosyltransferase activity and the 14-3-3 interaction. Our results suggest that leucine-428 of ExoS is the most critical residue for ExoS enzymatic activity, as cytotoxicity analysis reveals that substitution of this leucine significantly weakens the ability of ExoS to mediate cell death. Leucine-428 is also required for the ability of ExoS to modify the eukaryotic endogenous target Ras. Finally, single amino acid substitutions of positions 426-428 reduce the interaction potential of 14-3-3 with ExoS in vitro.

Anaplastic lymphoma kinase (ALK) is an important molecular target in neuroblastoma. Although tyrosine kinase inhibitors abrogating ALK activity are currently in clinical use for the treatment of ALK-positive (ALK(+)) disease, monotherapy with ALK tyrosine kinase inhibitors may not be an adequate solution for ALK(+) neuroblastoma patients. Increased expression of the gene encoding the transcription factor MYCN is common in neuroblastomas and correlates with poor prognosis. We found that the kinase ERK5 [also known as big mitogen-activated protein kinase (MAPK) 1 (BMK1)] is activated by ALK through a pathway mediated by phosphoinositide 3-kinase (PI3K), AKT, MAPK kinase kinase 3 (MEKK3), and MAPK kinase 5 (MEK5). ALK-induced transcription of MYCN and stimulation of cell proliferation required ERK5. Pharmacological or RNA interference-mediated inhibition of ERK5 suppressed the proliferation of neuroblastoma cells in culture and enhanced the antitumor efficacy of the ALK inhibitor crizotinib in both cells and xenograft models. Together, our results indicate that ERK5 mediates ALK-induced transcription of MYCN and proliferation of neuroblastoma, suggesting that targeting both ERK5 and ALK may be beneficial in neuroblastoma patients.

The mammalian focal adhesion kinase (FAK) family of non-receptor protein-tyrosine kinases has been implicated in controlling a multitude of cellular responses to the engagement of cell-surface integrins and G-protein-coupled receptors. The high level of sequence conservation between the mammalian proteins and the Drosophila homologue of FAK, Fak56,suggested that it would have similar functions. However, we show here that Drosophila Fak56 is not essential for integrin functions in adhesion,migration or signaling in vivo. Furthermore, animals lacking Fak56 are viable and fertile, demonstrating that Fak56 is not essential for other developmental or physiological functions. Despite this, overexpressed Fak56 is a potent inhibitor of integrins binding to the extracellular matrix, suggesting that Fak56 may play a subtle role in the negative regulation of integrin adhesion.

The Drosophila melanogaster gene Anaplastic lymphoma kinase (Alk) is homologous to mammalian Alk, a member of the Alk/Ltk family of receptor tyrosine kinases (RTKs)1. We have previously shown that the Drosophila Alk RTK is crucial for visceral mesoderm development during early embryogenesis2. Notably, observed Alk visceral mesoderm defects are highly reminiscent of the phenotype reported for the secreted molecule Jelly belly (Jeb)3. Here we show that Drosophila Alk is the receptor for Jeb in the developing visceral mesoderm, and that Jeb binding stimulates an Alk-driven, extracellular signal-regulated kinase-mediated signalling pathway, which results in the expression of the downstream gene duf (also known as kirre)4,5—needed for muscle fusion. This new signal transduction pathway drives specification of the muscle founder cells, and the regulation of Duf expression by the Drosophila Alk RTK explains the visceral-mesoderm-specific muscle fusion defects observed in both Alk and jeb mutant animals.

The Drosophila melanogaster gene Anaplastic lymphoma kinase (Alk) is homologous to mammalian Alk, which encodes a member of the Alk/Ltk family of receptor tyrosine kinases (RTKs). In humans, the t(2;5) translocation, which involves the ALK locus, produces an active form of ALK, which is the causative agent in non-Hodgkin's lymphoma. The physiological function of the Alk RTK, however, is unknown. In this paper, we describe loss-of-function mutants in the Drosophila Alk gene that cause a complete failure of the development of the gut. We propose that the main function of Drosophila Alk during early embryogenesis is in visceral mesoderm development.

14-3-3 proteins play an important role in a multitude of signalling pathways. The interactions between 14-3-3 and other signalling proteins, such as Raf and KSR (kinase suppressor of Ras), occur in a phospho-specific manner. Recently, a phosphorylation-independent interaction has been reported to occur between 14-3-3 and several proteins, for example 5-phosphatase, p75NTR-associated cell death executor (NADE) and the bacterial toxin Exoenzyme S (ExoS), an ADP-ribosyltransferase from Pseudomonas aeruginosa. In this study we have identified the amino acid residues on ExoS, which are responsible for its specific interaction with 14-3-3. Furthermore, we show that a peptide derived from ExoS, containing the 14-3-3 interaction site, effectively competes out the interaction between ExoS and 14-3-3. In addition, competition with this peptide blocks ExoS modification of Ras in our Ras modification assay. We show that the ExoS protein interacts with all isoforms of the 14-3-3 family tested. Moreover, in vivo an ExoS protein lacking the 14-3-3 binding site has a reduced capacity to ADP ribosylate cytoplasmic proteins, e.g. Ras, and shows a reduced capacity to change the morphology of infected cells.

Diverse cellular processes depend on endocytosis, intracellular vesicle trafficking, sorting and exocytosis, and processes that are regulated post-transcriptionally by modifications such as phosphorylation and ubiquitylation. The PA (protease-associated) domain E3 ligases, such as GodzillaCG10277 in Drosophila melanogaster and RNF167 (RING finger protein 167) in humans, have been implicated in the regulation of cellular endosome trafficking. In the present study, we have characterized point mutations in the RING (really interesting new gene) domain of human RNF13 and RNF167, which have been identified in human tumour samples, that abrogate ubiquitin ligase activity as well as function. In the present study, we have also identified a functional role for the PA domain, which is required for endosomal localization of these proteins. Although the PA domain point mutations of RNF13 and RNF167 identified in human tumours are ligase active, the resultant mutant proteins are mislocalized within the cell. Thus the PA domain E3 ligases examined in the present study appear to require both E3 ligase activity as well as an intact PA domain to efficiently target and ubiquitylate their cellular substrates.

Midkine (MDK) and Pleiotrophin (PTN) are small heparin-binding cytokines with closely related structures. The Drosophila genome harbours two genes encoding members of the MDK/PTN family of proteins, known as miple1 and miple2. We have investigated the role of Miple proteins in vivo, in particular with regard to their proposed role as ligands for the Alk receptor tyrosine kinase (RTK). Here we show that Miple proteins are neither required to drive Alk signaling during Drosophila embryogenesis, nor are they essential for development in the fruit fly. Additionally we show that neither MDK nor PTN can activate hALK in vivo when ectopically co-expressed in the fly. In conclusion, our data suggest that Alk is not activated by MDK/PTN related growth factors Miple1 and Miple 2 in vivo.