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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
189
PI4KII
and
sac1
mutants genetically interact with other trafficking complex mutants, such as those affecting AP-3 and HOPS. Indeed, we have found that
Sac1 is required for proper localization of the AP-3δ subunit Garnet. This suggests that altering PI4P levels affects multiple LRO trafficking pathways and
that correct PI4P levels is required for LRO formation.
209B
Notch signaling from
vps25
mutant cells confers apoptotic protection to neighboring cells via Yorkie activation in
Drosophila
.
Hillary K. Graves
1
,
Sarah E. Woodfield
1,2
, Georg Halder
1,2
, Andreas Bergmann
1,2,3
. 1) Biochemistry & Molecular Biology, MD Anderson Cancer Center, Houston, TX, USA; 2)
Baylor College of Medicine, Graduate Program in Developmental Biology, Houston, TX, USA; 3) Department of Cancer Biology, University of
Massachusetts Medical School, Worcester, MA, USA.
The microenvironment in which epithelial carcinomas arise can influence their progression. Often, epithelial cells with oncogenic transformations are
eliminated by apoptosis, suggesting that signaling between oncogenic and normal cells is a mechanism by which organisms eliminate aberrant cells from
epithelia. In light of this fact, untransformed cells likely have molecular cues that identify that they are normal and need not be eliminated, though little is
known about these cues. In
Drosophila
imaginal epithelia, clones of cells mutant for the endocytic neoplastic tumor suppressor gene
vps25
are eliminated by
cell death, but induce nearby untransformed cells to express Diap1, an important inhibitor of apoptosis. Here, we show that the non-autonomous apoptotic
resistance induced by
vps25
mutant cells is mediated at the transcriptional level by Yorkie, the conserved downstream effector of Hippo signaling.
Furthermore, we show that inhibiting ectopic Notch signaling from the vps25 mutant cells prevents the non-autonomous induction of Yorkie signaling.
Finally, we show that overactivation of Notch signaling is sufficient to induce non-autonomous apoptotic resistance via Diap1 expression. Our data indicate
that Notch signaling from cells mutant for enodcytic neoplastic tumor suppressor genes could be part of a mechanism by which animals protect
untransformed cells in tissues while eliminating epithelial malignancies.
210C
The molecular basis of airway maturation in Drosophila.
Chie Hosono, Rho Matsuda, Christos Samakovlis. Developmental Biology, The Wenner-Gren
Institute, Stockholm, Sweden.
The respiratory tubes of mammalian lungs and the Drosophila tracheal system undergo a series of maturation events at the end of embryogenesis. During
this period the nascent tubes acquire their mature size, clear the luminal liquid and transform into functional respiratory networks. Our laboratory has
recorded three precisely controlled transitions of cellular activities during airway maturation in living fly embryos: First, a secretion burst deposits
extracellular matrix into the lumen and expands tube diameter. Second, the activation of a massive apical endocytosis wave clears the matrix. Finally,
luminal liquid is evacuated and the network is filled with a gas within ten minutes. The mechanisms underlying the precise spatial and temporal regulation of
epithelial activities during airway maturation are unknown. We used a tracheal specific driver and ~20000 transgenic UAS-RNAi strains to first describe all
protein-coding genes involved in the process. We found 1461 genes, involved in airway maturation. Tracheal inactivation of 1935 of the remaining genes
caused lethality or adult phenotypes in >50% of the animals. To identify the developmental regulators of airway maturation, we preselected about 600 genes
encoding putative regulators like kinases, channels, GPCRs, transcription factors and proteins of unknown functions. We further classified these into 12
groups based on the defects in tube morphologies, apical secretion and protein clearance events caused by RNAi. The combination of this phenotypic
analysis with the data from protein interaction databases revealed a new gene regulatory network that controls tube planar cell polarity, and integrity during
airway liquid clearance.
211A
Searching for substrates of the MAST kinase homolog Drop out using SILAC based phospho-proteomics.
Alistair J Langlands, Daniel Hain, H.-Arno
J. Muller. Division of Cell & Developmental Biology, University of Dundee, Scotland, UK.
The maternal effect mutant
drop out
(
dop
) causes severe defects during cellularisation: inward growth of the cleavage membrane is slowed, protein
polarity complexes are mislocalised and the nuclei drop out during mid-cellularisation. We have established that
dop
encodes the single microtubule-
associated serine/threonine (MAST) kinase homolog in
Drosophila
. Although MAST kinases have been implicated in a number of human diseases such as
breast cancer, inflammatory bowel disease and neurodegenerative diseases, their function remains poorly understood. The highly conserved domain structure
makes Dop an excellent model to better understand MAST kinase function. We generated a range of EMS-induced
dop
alleles, the majority of which affect
the kinase domain, indicating that the kinase domain is essential for Dop function. Therefore, identifying the substrates of Dop will be an important step in
understanding its function. We utilise a SILAC (stable isotope labelling of amino acids in cell culture) and a phospho-proteomic approach to identify the
substrates of Dop. We are differentially labelling proteins in embryos with heavy isotopes followed by mass spectrometry to detect differences in phospho-
peptide patterns between
dop
mutants and wild type. One potential substrate of Dop is Dynein intermediate chain (Dic). We show that the phosphorylation
of Dic is dependent on Dop. Furthermore, we identified synergistic genetic interactions between
dop
mutations and mutations in genes encoding components
of the Dynein/Dynactin complex. Double mutants of
dop
with either Dic or P150/Glued also exhibit enhanced phenotypes in cellularlisation. These genetic
interactions support our biochemical data and indicate that mutations in
dop
affect Dynein-dependent transport processes.
212B
Moesin is required for trafficking of Crumbs in the follicular epithelium.
Kristin Sherrard, Richard Fehon. Molecular Genetics and Cell Biology,
University of Chicago, Chicago, IL.
Moesin, a FERM domain protein that directly binds actin, has been implicated in the organization of apical actin structures and in crosslinking the plasma
membrane to the cortex. Moesin also negatively regulates Rho1 activity in developing imaginal discs and other epithelial cells. The mechanisms of Moesin’s
activity and identity of its downstream partners have remained elusive, in part due to a large maternal contribution making Moesin hard to deplete in
embryonic tissue. In addition, in imaginal epithelia Moesin-depleted cells undergo JNK-mediated apoptosis (Neisch et al. 2010), making it difficult to assess
its other cellular functions. Our recent work in the follicular epithelium has uncovered a distinct and apparently Rho-independent trafficking defect in
Moesin-depleted cells. We have observed a strong accumulation of Rab5, Rab4, Rab11, and Hrs, as well as excess vesicular Crumbs in Moe deficient cells.
Our current working model is that Moesin promotes the recycling and/or degradation of Crumbs, a transmembrane protein which is essential for maintaining