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Morelli E.,IFOM The FIRC Institute of Molecular Oncology | Ginefra P.,IFOM The FIRC Institute of Molecular Oncology | Mastrodonato V.,IFOM The FIRC Institute of Molecular Oncology | Beznoussenko G.V.,IFOM The FIRC Institute of Molecular Oncology | And 5 more authors.
Autophagy | Year: 2014

How autophagic degradation is linked to endosomal trafficking routes is little known. Here we screened a collection of uncharacterized Drosophila mutants affecting membrane transport to identify new genes that also have a role in autophagy. We isolated a loss of function mutant in Snap29 (Synaptosomal-associated protein 29 kDa), the gene encoding the Drosophila homolog of the human protein SNAP29 and have characterized its function in vivo. Snap29 contains 2 soluble NSF attachment protein receptor (SNARE) domains and a asparagine-proline-phenylalanine (NPF motif) at its N terminus and rescue experiments indicate that both SNARE domains are required for function, whereas the NPF motif is in part dispensable. We find that Snap29 interacts with SNARE proteins, localizes to multiple trafficking organelles, and is required for protein trafficking and for proper Golgi apparatus morphology. Developing tissue lacking Snap29 displays distinctive epithelial architecture defects and accumulates large amounts of autophagosomes, highlighting a major role of Snap29 in autophagy and secretion. Mutants for autophagy genes do not display epithelial architecture or secretion defects, suggesting that the these alterations of the Snap29 mutant are unlikely to be caused by the impairment of autophagy. In contrast, we fi nd evidence of elevated levels of hop-Stat92E (hopscotch-signal transducer and activator of transcription protein at 92E) ligand, receptor, and associated signaling, which might underlie the epithelial defects. In summary, our findings support a role of Snap29 at key steps of membrane trafficking, and predict that signaling defects may contribute to the pathogenesis of cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma (CEDNIK), a human congenital syndrome due to loss of Snap29. © Elena Morelli, Pierpaolo Ginefra, Valeria Mastrodonato, Galina V Beznoussenko, Tor Erik Rusten, David Bilder, Harald Stenmark, Alexandre A Mironov, and Thomas Vaccari.


Zecchini S.,IFOM The FIRC Institute of Molecular Oncology | Bombardelli L.,IFOM The FIRC Institute of Molecular Oncology | Decio A.,Mario Negri Institute for Pharmacological Research | Bianchi M.,IFOM The FIRC Institute of Molecular Oncology | And 13 more authors.
EMBO Molecular Medicine | Year: 2011

Epithelial ovarian carcinoma (EOC) is an aggressive neoplasm, which mainly disseminates to organs of the peritoneal cavity, an event mediated by molecular mechanisms that remain elusive. Here, we investigated the expression and functional role of neural cell adhesion molecule (NCAM), a cell surface glycoprotein involved in brain development and plasticity, in EOC. NCAM is absent from normal ovarian epithelium but becomes highly expressed in a subset of human EOC, in which NCAM expression is associated with high tumour grade, suggesting a causal role in cancer aggressiveness. We demonstrate that NCAM stimulates EOC cell migration and invasion in vitro and promotes metastatic dissemination in mice. This pro-malignant function of NCAM is mediated by its interaction with fibroblast growth factor receptor (FGFR). Indeed, not only FGFR signalling is required for NCAM-induced EOC cell motility, but targeting the NCAM/FGFR interplay with a monoclonal antibody abolishes the metastatic dissemination of EOC in mice. Our results point to NCAM-mediated stimulation of FGFR as a novel mechanism underlying EOC malignancy and indicate that this interplay may represent a valuable therapeutic target. © 2011 EMBO Molecular Medicine.


PubMed | Yale Cardiovascular Research Center, IFOM the FIRC Institute of Molecular Oncology, Mario Negri Institute for Pharmacological Research, University of Zürich and 6 more.
Type: Journal Article | Journal: EMBO molecular medicine | Year: 2016

Cerebral cavernous malformations (CCMs) are vascular malformations located within the central nervous system often resulting in cerebral hemorrhage. Pharmacological treatment is needed, since current therapy is limited to neurosurgery. Familial CCM is caused by loss-of-function mutations in any of Ccm1, Ccm2, and Ccm3 genes. CCM cavernomas are lined by endothelial cells (ECs) undergoing endothelial-to-mesenchymal transition (EndMT). This switch in phenotype is due to the activation of the transforming growth factor beta/bone morphogenetic protein (TGF/BMP) signaling. However, the mechanism linking Ccm gene inactivation and TGF/BMP-dependent EndMT remains undefined. Here, we report that Ccm1 ablation leads to the activation of a MEKK3-MEK5-ERK5-MEF2 signaling axis that induces a strong increase in Kruppel-like factor 4 (KLF4) in ECs invivo. KLF4 transcriptional activity is responsible for the EndMT occurring in CCM1-null ECs. KLF4 promotes TGF/BMP signaling through the production of BMP6. Importantly, in endothelial-specific Ccm1 and Klf4 double knockout mice, we observe a strong reduction in the development of CCM and mouse mortality. Our data unveil KLF4 as a therapeutic target for CCM.


Primorac I.,Max Planck Institute of Molecular Physiology | Weir J.R.,Max Planck Institute of Molecular Physiology | Chiroli E.,IFOM The FIRC Institute of Molecular Oncology | Gross F.,IFOM The FIRC Institute of Molecular Oncology | And 5 more authors.
eLife | Year: 2013

Regulation of macromolecular interactions by phosphorylation is crucial in signaling networks. In the spindle assembly checkpoint (SAC), which enables errorless chromosome segregation, phosphorylation promotes recruitment of SAC proteins to tensionless kinetochores. The SAC kinase Mps1 phosphorylates multiple Met-Glu-Leu-Thr (MELT) motifs on the kinetochore subunit Spc105/Knl1. The phosphorylated MELT motifs (MELTP) then promote recruitment of downstream signaling components. How MELTP motifs are recognized is unclear. In this study, we report that Bub3, a 7-bladed β-propeller, is the MELTP reader. It contains an exceptionally well-conserved interface that docks the MELTP sequence on the side of the β-propeller in a previously unknown binding mode. Mutations targeting the Bub3 interface prevent kinetochore recruitment of the SAC kinase Bub1. Crucially, they also cause a checkpoint defect, showing that recognition of phosphorylated targets by Bub3 is required for checkpoint signaling. Our data provide the first detailed mechanistic insight into how phosphorylation promotes recruitment of checkpoint proteins to kinetochores. © Primorac et al.


PubMed | St Anna Hospital, IFOM The FIRC Institute of Molecular Oncology, CNR Institute of Molecular Genetics, Fondazione IRCCS Ca Granda and University of Milan
Type: Journal Article | Journal: Oncotarget | Year: 2015

The vacuolar H+ ATPase (V-ATPase) is a proton pump responsible for acidification of cellular microenvironments, an activity exploited by tumors to survive, proliferate and resist to therapy. Despite few observations, the role of V-ATPase in human tumorigenesis remains unclear.We investigated the expression of ATP6V0C, ATP6V0A2, encoding two subunits belonging to the V-ATPase V0 sector and ATP6V1C, ATP6V1G1, ATPT6V1G2, ATP6V1G3, which are part of the V1 sector, in series of adult gliomas and in cancer stem cell-enriched neurospheres isolated from glioblastoma (GBM) patients. ATP6V1G1 expression resulted significantly upregulated in tissues of patients with GBM and correlated with shorter patients overall survival independent of clinical variables.ATP6V1G1 knockdown in GBM neurospheres hampered sphere-forming ability, induced cell death, and decreased matrix invasion, a phenotype not observed in GBM monolayer cultures. Treating GBM organotypic cultures or neurospheres with the selective V-ATPase inhibitor bafilomycin A1 reproduced the effects of ATP6V1G1 siRNA and strongly suppressed expression of the stem cell markers Nestin, CD133 and transcription factors SALL2 and POU3F2 in neurospheres.These data point to ATP6V1G1 as a novel marker of poor prognosis in GBM patients and identify V-ATPase inhibition as an innovative therapeutic strategy for GBM.


Giampietro C.,University of Milan | Giampietro C.,IFOM The FIRC Institute of Molecular Oncology
Tissue Barriers | Year: 2016

The vascular endothelium is a selective barrier that separates the organs from the circulating blood. The endothelium has a wide variety of functions controlled by cell-to-cell junctions and in particular by Vascular Endothelial cadherin (VE-cadherin) complexes. Recent research identified the epidermal growth factor receptor kinase substrate 8 (EPS8) and the co-transcriptional regulator yes-associated protein (YAP) as new components of the adherens junction complexes. The binding of these 2 proteins to VE-cadherin determines the formation of different specialized adhesive structures contributing to the dynamic control of vascular permeability. This commentary will summarize what is currently known about the role of EPS8 and YAP in the modification of molecular organization and intracellular signaling of adherens junction complexes, and their potential multiple effects on vascular homeostasis. © 2016 Taylor & Francis


Vinod P.K.,University of Oxford | Freire P.,University of Oxford | Freire P.,Instituto Gulbenkian Of Ciencia | Rattani A.,University of Oxford | And 3 more authors.
Journal of the Royal Society Interface | Year: 2011

The operating principles of complex regulatory networks are best understood with the help of mathematical modelling rather than by intuitive reasoning. Hereby, we study the dynamics of the mitotic exit (ME) control system in budding yeast by further developing the Queralt's model. A comprehensive systems view of the network regulating ME is provided based on classical experiments in the literature. In this picture, Cdc20-APC is a critical node controlling both cyclin (Clb2 and Clb5) and phosphatase (Cdc14) branches of the regulatory network. On the basis of experimental situations ranging from single to quintuple mutants, the kinetic parameters of the network are estimated. Numerical analysis of the model quantifies the dependence of ME control on the proteolytic and non-proteolytic functions of separase. We show that the requirement of the non-proteolytic function of separase for ME depends on cyclin-dependent kinase activity. The model is also used for the systematic analysis of the recently discovered Cdc14 endocycles. The significance of Cdc14 endocycles in eukaryotic cell cycle control is discussed as well. © 2011 The Royal Society.


PubMed | Moscow State University and IFOM the FIRC Institute of Molecular Oncology
Type: Journal Article | Journal: Biochemical and biophysical research communications | Year: 2016

Liver plays a key role in controlling body carbohydrate homeostasis by switching between accumulation and production of glucose and this way maintaining constant level of glucose in blood. Increased blood glucose level triggers release of insulin from pancreatic -cells. Insulin represses hepatic glucose production and increases glucose accumulation. Insulin resistance is the main cause of type 2 diabetes and hyperglycemia. Currently thiazolidinediones (TZDs) targeting transcriptional factor PPAR are used as insulin sensitizers for treating patients with type 2 diabetes. However, TZDs are reported to be associated with cardiovascular and liver problems and stimulate obesity. Thus, it is necessary to search new approaches to improve insulin sensitivity. A promising candidate is transcriptional factor Prep1, as it was shown earlier it could affect insulin sensitivity in variety of insulin-sensitive tissues. The aim of the present study was to evaluate a possible involvement of transcriptional factor Prep1 in control of hepatic glucose accumulation and production. We created mice with liver-specific Prep1 knockout and discovered that hepatocytes derived from these mice are much more sensitive to insulin, comparing to their WT littermates. Incubation of these cells with 100nM insulin results in almost complete inhibition of gluconeogenesis, while in WT cells this repression is only partial. However, Prep1 doesnt affect gluconeogenesis in the absence of insulin. Also, we observed that nuclear content of gluconeogenic transcription factor FOXO1 was greatly reduced in Prep1 knockout hepatocytes. These findings suggest that Prep1 may control hepatic insulin sensitivity by targeting FOXO1 nuclear stability.


PubMed | IFOM The Firc Institute of Molecular Oncology
Type: | Journal: FEBS letters | Year: 2017

Coordination between DNA replication and DNA repair ensures maintenance of genome integrity, which is lost in cancer cells. Emerging evidence has linked Homologous Recombination (HR) proteins RAD51, BRCA1 and BRCA2 to the stability of nascent DNA. This function appears to be distinct from Double Strand Break (DSB) repair and is in part due to the prevention of MRE11-mediated degradation of nascent DNA at stalled forks. The role of RAD51 in fork protection resembles the activity described for its prokaryotic ortholog RecA, which prevents nuclease-mediated degradation of DNA and promotes replication fork restart in cells challenged by DNA damaging agents. Here, we examine the mechanistic aspects of HR-mediated fork protection, addressing the crosstalk between HR and replication proteins. This article is protected by copyright. All rights reserved.


PubMed | IFOM The FIRC Institute of Molecular Oncology
Type: Journal Article | Journal: EMBO molecular medicine | Year: 2011

Epithelial ovarian carcinoma (EOC) is an aggressive neoplasm, which mainly disseminates to organs of the peritoneal cavity, an event mediated by molecular mechanisms that remain elusive. Here, we investigated the expression and functional role of neural cell adhesion molecule (NCAM), a cell surface glycoprotein involved in brain development and plasticity, in EOC. NCAM is absent from normal ovarian epithelium but becomes highly expressed in a subset of human EOC, in which NCAM expression is associated with high tumour grade, suggesting a causal role in cancer aggressiveness. We demonstrate that NCAM stimulates EOC cell migration and invasion in vitro and promotes metastatic dissemination in mice. This pro-malignant function of NCAM is mediated by its interaction with fibroblast growth factor receptor (FGFR). Indeed, not only FGFR signalling is required for NCAM-induced EOC cell motility, but targeting the NCAM/FGFR interplay with a monoclonal antibody abolishes the metastatic dissemination of EOC in mice. Our results point to NCAM-mediated stimulation of FGFR as a novel mechanism underlying EOC malignancy and indicate that this interplay may represent a valuable therapeutic target.

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