ALIX
The Interactive Fly, Drosophila
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What's new in edition 75
January 2016
Gene sites new with this edition |
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The Interactive Fly was first released July/August 1996, with updates provided at approximately one month intervals, through September 1997 (edition 13). Updating quarterly started with edition 14. With edition 40, the Interactive Fly began to schedule updates three times a year: fall, winter and spring.
- Gene sites new with this edition of the Interactive Fly:
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- Dopamine 1-like receptor 2
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Dopaminergic neurons in Drosophila play critical roles in diverse
brain functions such as motor control, arousal, learning, and memory.
Using genetic and behavioral approaches, it has been firmly established
that proper dopamine signaling is required for olfactory classical
conditioning (e.g., aversive and appetitive learning). Dopamine mediates
its functions through interaction with its receptors. There are two
different types of dopamine receptors in Drosophila: 1) Dopamine 1-like, including Dopamine 1-like receptor 1 and
Dopamine 1-like receptor 2 (DDR2, the subject of this report) and 2) Dopamine 2-like receptor. Currently, no study has attempted to characterize the role
of DD2R in Drosophila learning and memory. Using a DD2R-RNAi transgenic
line, this study has examined the role of DD2R, expressed in dopamine
neurons (i.e., the presynaptic DD2R autoreceptor), in larval olfactory
learning. The function of postsynaptic DD2R expressed in mushroom body (MB) was also studied as
MB is the center for Drosophila learning, with a function analogous to
that of the mammalian hippocampus. These results showed that suppression
of presynaptic DD2R autoreceptors impairs both appetitive and aversive
learning. Similarly, postsynaptic DD2R in MB neurons appears to be
involved in both appetitive and aversive learning. The data confirm, for
the first time, that DD2R plays an important role in Drosophila
olfactory learning (Qi, 2014).
- Lipin
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Lipin proteins have key functions in lipid
metabolism, acting as both phosphatidate phosphatases (PAPs) and nuclear
regulators of gene expression. This study shows that the insulin and TORC1 pathways independently
control functions of Drosophila dLipin. Reduced
signaling through the insulin receptor strongly enhances defects caused
by dLipin deficiency in fat body
development, whereas reduced signaling through TORC1 leads to
translocation of dLipin into the nucleus. Reduced expression of dLipin
results in decreased signaling through the insulin receptor-controlled
PI3K/Akt pathway and increased hemolymph sugar levels. Consistent
with this, downregulation of dLipin in fat body cell clones causes a
strong growth defect. The PAP, but not the nuclear activity of dLipin is
required for normal insulin pathway activity. Reduction of other enzymes
of the glycerol-3 phosphate pathway similarly affects insulin pathway
activity, suggesting an effect mediated by one or more metabolites
associated with the pathway. Together, these data show that dLipin is
subject to intricate control by the insulin and TORC1 pathways and that
the cellular status of dLipin impacts how fat body cells respond to
signals relayed through the PI3K/Akt pathway (Schmitt, 2015).
- Pasiflora1 and Pasiflora2
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Epithelial sheets play essential roles as selective barriers insulating the body from the environment and establishing distinct chemical compartments within it. In invertebrate epithelia, septate junctions (SJs) consist of large multi-protein complexes that localize at the apicolateral membrane and mediate barrier function. This study reports the identification of two novel SJ components, Pasiflora1 (CG7713) and Pasiflora2 (CG8121), through a genome-wide glial RNAi screen in Drosophila. Pasiflora mutants show permeable blood-brain and tracheal barriers, overelongated tracheal tubes and mislocalization of SJ proteins. Consistent with the observed phenotypes, the genes are co-expressed in embryonic epithelia and glia and are required cell-autonomously to exert their function. Pasiflora1 and Pasiflora2 belong to a previously uncharacterized family of tetraspan membrane proteins conserved across the protostome-deuterostome divide. Both proteins localize at SJs and their apicolateral membrane accumulation depends on other complex components. In fluorescence recovery after photobleaching experiments, pasiflora proteins were found to be core SJ components as they are required for complex formation and exhibit restricted mobility within the membrane of wild-type epithelial cells, but rapid diffusion in cells with disrupted SJs. Taken together, these results show that Pasiflora1 and Pasiflora2 are novel integral components of the SJ and implicate a new family of tetraspan proteins in the function of these ancient and crucial cell junctions (Deligiannaki, 2015).
- Pez
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The conserved Hippo signaling pathway acts in growth control and is fundamental to animal development and oncogenesis. Hippo signaling has also been implicated in adult midgut homeostasis in Drosophila. Regulated divisions of intestinal stem cells (ISCs), giving rise to an ISC and an enteroblast (EB) that differentiates into an enterocyte (EC) or an enteroendocrine (EE) cell, enable rapid tissue turnover in response to intestinal stress. The damage-related increase in ISC proliferation requires deactivation of the Hippo pathway and consequential activation of the transcriptional coactivator Yorkie (Yki) in both ECs and ISCs. This study identified Pez, an evolutionarily conserved FERM domain protein containing a protein tyrosine phosphatase (PTP) domain, as a novel binding partner of the upstream Hippo signaling component Kibra. Pez function (but not its PTP domain) is essential for Hippo pathway activity specifically in the fly midgut epithelium. Thus, Pez displays a tissue-specific requirement and functions as a negative upstream regulator of Yki in the regulation of ISC proliferation (Poernbacher, 2012).
- shrub
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Abscission is the final step of cytokinesis that involves the cleavage of the intercellular bridge connecting the two daughter cells. Recent studies have given novel insight into the spatiotemporal regulation and molecular mechanisms controlling abscission in cultured yeast and human cells. The mechanisms of abscission in living metazoan tissues are however not well understood. This study shows that ESCRT-III component Shrub are required for completion of abscission during Drosophila female germline stem cell (fGSC) division. Loss of ALIX or Shrub function in fGSCs leads to delayed abscission and the consequent formation of stem cysts in which chains of daughter cells remain interconnected to the fGSC via midbody rings and fusome. ALIX and Shrub interact and that they co-localize at midbody rings and midbodies during cytokinetic abscission in fGSCs. Mechanistically, this study shows that the direct interaction between ALIX and Shrub is required to ensure cytokinesis completion with normal kinetics in fGSCs. It is concluded that ALIX and ESCRT-III coordinately control abscission in Drosophila fGSCs and that their complex formation is required for accurate abscission timing in GSCs in vivo (Eikenes, 2015).
- Spinophilin
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Assembly and maturation of synapses at the Drosophila neuromuscular junction (NMJ) depend on trans-synaptic Neurexin/Neuroligin signalling, which is promoted by the scaffolding protein Syd-1 binding to Neurexin. This study reports that the scaffold protein spinophilin binds to the C-terminal portion of Neurexin and is needed to limit Neurexin/Neuroligin signalling by acting antagonistic to Syd-1 (RhoGAP100F). Loss of presynaptic spinophilin results in the formation of excess, but atypically small active zones. Neuroligin-1/Neurexin-1/Syd-1 levels are increased at spinophilin mutant NMJs, and removal of single copies of the neurexin-1, Syd-1 or neuroligin-1 genes suppresses the spinophilin-active zone phenotype. Evoked transmission is strongly reduced at spinophilin terminals, owing to a severely reduced release probability at individual active zones. It is concluded that presynaptic Spinophilin fine-tunes Neurexin/Neuroligin signalling to control active zone number and functionality, thereby optimizing them for action potential-induced exocytosis (Muhammad, 2015).
- uninflatable
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Cell fate decision during asymmetric division is mediated by the
biased partition of cell fate determinants during mitosis. In the case
of the asymmetric division of the fly sensory organ precursor cells,
directed Notch signaling from pIIb to the pIIa daughter endows pIIa with
its distinct fate. Previous studies have shown that Notch/Delta
molecules internalized in the mother cell traffic through Smad anchor for receptor activation (Sara) endosomes
and are directed to the pIIa daughter. This study shows that the
receptor Notch itself is required during the asymmetric targeting of the
Sara endosomes to pIIa. Notch binds Uninflatable, and both traffic
together through Sara endosomes, which is essential to direct asymmetric
endosomes motility and Notch-dependent cell fate assignation. The data
uncover a part of the core machinery required for the asymmetric
motility of a vesicular structure that is essential for the directed
dispatch of Notch signaling molecules during asymmetric mitosis
(Loubery, 2014).
- Zyxin
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Coordinated multicellular growth during development is achieved by the sensing of spatial and nutritional boundaries. The conserved Hippo (Hpo) signaling pathway has been proposed to restrict tissue growth by perceiving mechanical constraints through actin cytoskeleton networks. The actin-associated LIM proteins Zyxin (Zyx) and Ajuba (Jub) have been linked to the control of tissue growth via regulation of Hpo signaling, but the study of Zyx has been hampered by a lack of genetic tools. A zyx mutant was generated in Drosophila using TALEN endonucleases, and this was used to show that Zyx antagonizes the FERM-domain protein Expanded (Ex) to control tissue growth, eye differentiation, and F-actin accumulation. Zyx membrane targeting promotes the interaction between the transcriptional co-activator Yorkie (Yki) and the transcription factor Scalloped (Sd), leading to activation of Yki target gene expression and promoting tissue growth. Finally, this study shows that Zyx's growth-promoting function is dependent on its interaction with the actin-associated protein Enabled (Ena) via a conserved LPPPP motif and is antagonized by Capping Protein (CP). These results show that Zyx is a functional antagonist of Ex in growth control and establish a link between actin filament polymerization and Yki activity (Gaspar, 2015).
date revised: 5 January 2016
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