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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
198
The Drosophila cAMP-dependent protein kinase (PKA) has been identified as one of the key proteins that regulate Hedgehog signaling, which is involved
in multiple developmental decisions including segment formation during embryogenesis, and the growth/patterning of imaginal discs. However, little is
known about the role of PKA in the larval fat body, a nutrient storage organ that functions equivalently to mammalian liver. By manipulating the level of the
PKA-C1 catalytic subunit in individual fat body cells, we have observed an increased cell size in PKA loss-of-function clones and severe size reduction in
PKA-overexpressing cells, indicating that PKA negatively regulates cell growth in a cell-autonomous manner. Previous studies have revealed that
autophagy, a catabolic process that degrades cellular components to recycle materials and to provide energy, is quickly triggered in the fat body in response
to nutrient deprivation. We find that loss of PKA activity impairs the induction of autophagy in starved larvae, and that overexpression of PKA induces
autophagy in well-fed animals, indicating that PKA has an essential and sufficient role in autophagy regulation. Genetic analyses further show that PKA is
involved in insulin and target of rapamycin (TOR) signaling pathways, which demonstrates a new model in which PKA coordinates cell growth and
autophagy in Drosophila.
246C
Characterization of a novel testis-specific mitochondrial protein in sperm formation.
Jieyan Chen, Timothy Megraw. Biomedical Sciences, Florida
State University, Tallahassee, FL.
Mitochondria are the energy centers in the cell. In testes, the normal functions of mitochondria are required for sperm formation. The Nebenkern is a
remarkable mitochondrial form in the Drosophila sperm. Right after meiosis is completed, the mitochondria of the spermatid collect on one side of the
haploid pronucleus and fuse together into two giant aggregates which then wrap around one another to produce the spherical Nebenkern. Failure of
mitochondrion fusion may affect the sperm tail elongation and motility and lead to the male sterility. Previous studies have shown that mitochondria play a
role in sperm tail elongation by providing a structural platform for microtubule reorganization to support the elongation at the tip of sperm tail. We have
identified a new protein (CG14128) containing a Ran binding protein 1 (RanBP1) domain, that localizes to the sperm mitochondria, especially the
Nebenkerns. RT-PCR and Western Blot results show that CG14128 protein is testis-specific. Previously published yeast two hybrid data suggests that
CG14128 interacts with centrosomin (Cnn), indicating a possible role of CG14128 with Cnn in the testis. We will test the genetic interaction between
CG14128 and fuzzy onion (fzo), mutation of which results in failure of mitochondrion fusion that leads to male sterility. We will also assay the CG14128
and Cnn interaction during sperm formation, and test the role of CG14128 in sperm tail elongation with a mutant allele.
247A
Natural variation provides a rich source of new genes for ER stress response.
Clement Y. Chow, Mariana F. Wolfner, Andrew G. Clark. Dept Mol Bio
& Gen, Cornell Uiv, Ithaca, NY.
The endoplasmic reticulum (ER) is responsible for synthesis and maturation of many proteins. ER stress occurs when misfolded proteins accumulate in the
ER. Cells respond by increasing transcription of ER chaperones, attenuating translation and degrading misfolded proteins. ER stress is a primary cause or a
secondary exacerbating effect of many diseases. To understand its effect on cells and organisms, we measured the extent of natural variation in ER stress
response. We compared the survival of 120 wild-derived lines from the DGRP (Drosophila Genetic Reference Panel) on food containing tunicamycin (TM),
a drug that causes ER stress. Mortality rates varied across lines by >100 fold. Thus, extensive genetic variation in ER stress response is present in a single
population. To understand how ER stress response is buffered by natural variation, we searched for genes whose expression varied with survival to ER
stress. Using Agilent microarrays, we compared gene expression during TM exposure in 4 lines that showed high ER stress resistance to 4 that showed low
resistance. Genes involved in the cellular response to ER stress, such as chaperones, showed a strong response across all 8 lines; thus the survival differences
did not reflect variation in basic ER stress transcriptional responses. However, we found that transcriptome responses between lines with high or low
sensitivity to ER stress differed qualitatively and quantitatively. For example, before the strong common response is fully initiated, genes associated with the
proteasome and immune response are upregulated in resistant lines, but not in susceptible lines. Many genes showing different responses in high vs. low
sensitivity lines had not previously been implicated in ER stress, yet our preliminary RNAi data show their importance to this fundamental cellular response.
We demonstrate that there is a large amount of natural variation in ER stress response. This variation is a powerful tool for uncovering new expression
patterns and genes involved in ER stress and understanding how natural variation can impact disease processes.
248B
Cell signalling mechanisms in epithelial stress and immune responses.
Shireen A Davies, Gayle Overend, Sujith Sebastian, Pablo Cabrero, Selim
Terhzaz. Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom.
The Drosophila Malpighian tubule is an epithelial model for cell-specific, organotypic ion transport and cell signalling studies, functional genomics and
gene discovery. The tubule is critical for fluid homeostasis and and detoxification in the fly (Beyenbach, Skaer et al. 2010). Fluid transport is modulated by
neuroendocrine control and second messengers (Dow and Davies, 2003; Nassel and Winther 2010). As barriers between the external and internal
environment, epithelia play key roles in stress defence; and the Drosophila tubule is critical for organismal defence against salt and oxidative stress
(Overend, Cabrero et al., 2011; Terhzaz, Finlayson et al., 2010; Stergiopoulos, Cabrero et al., 2009). Tubules are also immune tissues (Tzou, Ohresser et al.,
2000; McGettigan, McLennan et al., 2005; Kaneko, Yano et al., 2006), expressing anti-microbial peptides via the IMD and Toll pathways. We now show
that a tubule principal cell-specific cGMP-kinase (cGK) ‘switch’ modulates NF-kB orthologue (Relish) and IMD pathway activation. This cGK ‘switch’
modulates the survival of immune-challenged whole flies, the first evidence for cyclic nucleotide modulation of innate immunity. The tubule cGK switch
also influences the response of the gut to bacteria; thus, response to infection may be dependent on tubule/gut communication. The high rates of metabolic
activity in tubules and the associated production of reactive oxygen species results in specific adaptations to counter this, including the enriched expression
of ‘antioxidant’ genes. We show that the manipulation of specific genes in only tubule principal cells is sufficient to modulate organismal stress and immune
responses. Thus, the tubule is a key stress-sensing tissue for the whole organism.
249C
Multiple screening approaches suggest novel interaction partners for Eyes absent in the nucleus and cytoplasm.
Trevor L. Davis
1,2
, Ilaria Rebay
1,2
. 1)
Ben May Department for Cancer Research, University of Chicago, Chicago, IL; 2) Committee on Development, Regeneration, and Stem Cell Biology,