Biomedical subjects

Anne Plessis

Publications and source records attributed to Anne Plessis.

6 recordsLinked to original sources

PubMed2006

The last 59 amino acids of Smoothened cytoplasmic tail directly bind the protein kinase Fused and negatively regulate the Hedgehog pathway.

The Hedgehog (HH) signaling pathway is crucial for the development of many organisms and its inappropriate activation is involved in numerous cancers. HH signal controls the traffic and activity of the seven-pass transmembrane protein Smoothened (SMO), leading to the transcriptional regulation of HH-responsive genes. In Drosophila, the intracellular transduction events following SMO activation depend on cytoplasmic multimeric complexes that include the Fused (FU) protein kinase. Here we show that the regulatory domain of FU physically interacts with the last 52 amino acids of SMO and that the two proteins colocalize in vivo to vesicles. The deletion of this region of SMO leads to a constitutive activation of SMO, promoting the ectopic transcription of HH target genes. This activation is partially dependent of FU activity. Thus, we identify a novel link between SMO and the cytoplasmic complex(es) and reveal a negative role of the SMO C-terminal region that interacts with FU. We propose that FU could act as a switch, activator in presence of HH signal or inhibitor in absence of HH.

Animals↗

PubMed2006

Modulation of the Suppressor of fused protein regulates the Hedgehog signaling pathway in Drosophila embryo and imaginal discs.

The Suppressor of fused (Su(fu)) protein is known to be a negative regulator of Hedgehog (Hh) signal transduction in Drosophila imaginal discs and embryonic development. It is antagonized by the kinase Fused (Fu) since Su(fu) null mutations fully suppress the lack of Fu kinase activity. In this study, we overexpressed the Su(fu) gene in imaginal discs and observed opposing effects depending on the position of the cells, namely a repression of Hh target genes in cells receiving Hh and their ectopic expression in cells not receiving Hh. These effects were all enhanced in a fu mutant context and were suppressed by cubitus interruptus (Ci) overexpression. We also show that the Su(fu) protein is poly-phosphorylated during embryonic development and these phosphorylation events are altered in fu mutants. This study thus reveals an unexpected role for Su(fu) as an activator of Hh target gene expression in absence of Hh signal. Both negative and positive roles of Su(fu) are antagonized by Fused. Based on these results, we propose a model in which Su(fu) protein levels and isoforms are crucial for the modulation of the different Ci states that control Hh target gene expression.

Animals↗

PubMed2006

Characterization of the Drosophila myeloid leukemia factor.

In human, the myeloid leukemia factor 1 (hMLF1) has been shown to be involved in acute leukemia, and mlf related genes are present in many animals. Despite their extensive representation and their good conservation, very little is understood about their function. In Drosophila, dMLF physically interacts with both the transcription regulatory factor DREF and an antagonist of the Hedgehog pathway, Suppressor of Fused, whose over-expression in the fly suppresses the toxicity induced by polyglutamine. No connection between these data has, however, been established. Here, we show that dmlf is widely and dynamically expressed during fly development. We isolated and analyzed the first dmlf mutants: embryos lacking maternal dmlf product have a low viability with no specific defect, and dmlf(-)- adults display weak phenotypes. We monitored dMLF subcellular localization in the fly and cultured cells. We were able to show that, although generally nuclear, dMLF can also be cytoplasmic, depending on the developmental context. Furthermore, two differently spliced variants of dMLF display differential subcellular localization, allowing the identification of regions of dMLF potentially important for its localization. Finally, we demonstrate that dMLF can act developmentally and postdevelopmentally to suppress neurodegeneration and premature aging in a cerebellar ataxia model.

Alternative Splicing↗

PubMed2005

Protein interaction mapping: a Drosophila case study.

The Drosophila (fruit fly) model system has been instrumental in our current understanding of human biology, development, and diseases. Here, we used a high-throughput yeast two-hybrid (Y2H)-based technology to screen 102 bait proteins from Drosophila melanogaster, most of them orthologous to human cancer-related and/or signaling proteins, against high-complexity fly cDNA libraries. More than 2300 protein-protein interactions (PPI) were identified, of which 710 are of high confidence. The computation of a reliability score for each protein-protein interaction and the systematic identification of the interacting domain combined with a prediction of structural/functional motifs allow the elaboration of known complexes and the identification of new ones. The full data set can be visualized using a graphical Web interface, the PIMRider (http://pim.hybrigenics.com), and is also accessible in the PSI standard Molecular Interaction data format. Our fly Protein Interaction Map (PIM) is surprisingly different from the one recently proposed by Giot et al. with little overlap between the two data sets. Analysis of the differences in data sets and methods suggests alternative strategies to enhance the accuracy and comprehensiveness of the post-genomic generation of broad-scale protein interaction maps.

Animals↗

PubMed2003

Over-expression of a novel nuclear interactor of Suppressor of fused, the Drosophila myelodysplasia/myeloid leukaemia factor, induces abnormal morphogenesis associated with increased apoptosis and DNA synthesis.

BACKGROUND: In Drosophila and vertebrates, suppressor of fused (Su(fu)) proteins act as negative regulators of the Gli/Ci transcription factors, which mediate the transcriptional effects of Hh signalling. RESULTS: We sought for novel partners of Su(fu) in fly using the two-hybrid method. Most of the Su(fu) interactors thus identified are (or are likely to be) able to enter the nucleus. We focused on one of these putative partners, dMLF, which resembles vertebrate myelodysplasia/myeloid leukaemia factors 1 and 2. We demonstrate that dMLF binds specifically to Su(fu) in vitro and in vivo. Using a novel anti-dMLF antibody, we showed, that dMLF is a nuclear, chromosome-associated protein. We over-expressed a dMLF transgene in fly using an inducible expression system and showed that dMLF over-expression disrupts normal development, leading to either a lethal phenotype or adult structural defects associated with apoptosis and increased DNA synthesis. Furthermore, the dMLF-induced eye phenotype is enhanced by the loss of Su(fu) function, suggesting a genetic interaction between Su(fu) and dMLF. CONCLUSION: We propose that dSu(fu) and dMLF act together at the transcriptional level to coordinate patterning and proliferation during development.

Animals↗

PubMed2002

Hedgehog signal transduction proteins: contacts of the Fused kinase and Ci transcription factor with the kinesin-related protein Costal2.

BACKGROUND: Hedgehog signaling proteins play important roles in development by controlling growth and patterning in various animals including Drosophila and mammals. Hedgehog signaling triggers changes in responsive cells through a novel transduction mechanism that ultimately controls the transcription of specific target genes via the activity of zinc finger transcription factors of the Cubitus interruptus/GLI family. In flies, key Hedgehog signal transduction components have been identified including the kinesin-related protein Costal2, the serinethreonine kinase Fused, and the PEST-containing protein Suppressor of Fused. These proteins control Cubitus interruptus cleavage, nucleo-cytoplasmic localization and activation. In fly embryos, Costal2, Fused, Suppressor of Fused and Cubitus interruptus are associated in at least one cytoplasmic complex, which interacts with the microtubules in a Hedgehog-dependent manner. RESULTS: Here we identified and mapped direct interactions between Cos2, Fu, and Ci using an in vitro affinity assay and the yeast two-hybrid system. CONCLUSIONS: Our results provide new insights into the possible mechanism of the cytosolic steps of Hedgehog transduction.

Animals↗