| 1. |
- Alkhori, Liza, et al.
(författare)
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Hh signalling regulates odorant receptor cilia localization in Drosophila
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hedgehog (Hh) signaling is a key regulatory pathway during development. Here, we show that in adult OSNs the Hh pathway regulate ?dorant receptor transport to cilia and put forward a novel non-developmental function of the pathway as a neuromodulator. We demonstrate that the level of Hh signal modulate the OSNs response to odors. We show that knock down of Hh and Smoothened (Smo), a transmembrane protein that transduce the signal, are required for receptor transport. We further show that the coreceptor, Orco, has an Hh independent transport path and that knock down of Smo segregate OR and Orco to different vesicular compartments. Last, we show that the odor response to the second receptor type in Drosophila olfaction, the ionotropic receptors (IRs), also require Hh signalling. Thus, Hh signalling is a general regulator of the odorant response that fulfils the criteria of being a potential player in Drosophila odorant adaptation.
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| 2. |
- Hermansson, Erik, et al.
(författare)
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The chaperone domain BRICHOS prevents CNS toxicity of amyloid-beta peptide in Drosophila melanogaster
- 2014
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Ingår i: Disease Models and Mechanisms. - : The Company of Biologists. - 1754-8411 .- 1754-8403. ; 7:6, s. 659-665
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of the amyloid-beta peptide (A beta) into toxic oligomers and amyloid fibrils is linked to the development of Alzheimer's disease (AD). Mutations of the BRICHOS chaperone domain are associated with amyloid disease and recent in vitro data show that BRICHOS efficiently delays A beta 42 oligomerization and fibril formation. We have generated transgenic Drosophila melanogaster flies that express the A beta 42 peptide and the BRICHOS domain in the central nervous system (CNS). Co-expression of A beta 42 and BRICHOS resulted in delayed A beta 42 aggregation and dramatic improvements of both lifespan and locomotor function compared with flies expressing A beta 42 alone. Moreover, BRICHOS increased the ratio of soluble: insoluble A beta 42 and bound to deposits of A beta 42 in the fly brain. Our results show that the BRICHOS domain efficiently reduces the neurotoxic effects of A beta 42, although significant A beta 42 aggregation is taking place. We propose that BRICHOS-based approaches should be explored with an aim towards the future prevention and treatment of AD.
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| 3. |
- Kuzhandaivel, Anujaianthi, et al.
(författare)
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Cilia-Mediated Hedgehog Signaling in Drosophila
- 2014
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Ingår i: Cell Reports. - : Elsevier. - 2211-1247. ; 7:3, s. 672-680
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Tidskriftsartikel (refereegranskat)abstract
- Cilia mediate Hedgehog (Hh) signaling in vertebrates and Hh deregulation results in several clinical manifestations, such as obesity, cognitive disabilities, developmental malformations, and various cancers. Drosophila cells are nonciliated during development, which has led to the assumption that cilia-mediated Hh signaling is restricted to vertebrates. Here, we identify and characterize a cilia-mediated Hh pathway in Drosophila olfactory sensory neurons. We demonstrate that several fundamental key aspects of the vertebrate cilia pathway, such as ciliary localization of Smoothened and the requirement of the intraflagellar transport system, are present in Drosophila. We show that Cos2 and Fused are required for the ciliary transport of Smoothened and that cilia mediate the expression of the Hh pathway target genes. Taken together, our data demonstrate that Hh signaling in Drosophila can be mediated by two pathways and that the ciliary Hh pathway is conserved from Drosophila to vertebrates.
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| 4. |
- Schultz, Sebastian, et al.
(författare)
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Drosophila Melanogaster as a Model System for Studies of Islet Amyloid Polypeptide Aggregation
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Recent research supports that aggregation of islet amyloid polypeptide (IAPP) leads to cell death and this makes islet amyloid a plausible cause for the reduction of beta cell mass, demonstrated in patients with type 2 diabetes. IAPP is produced by the beta cells as a prohormone, and proIAPP is processed into IAPP by the prohormone convertases PC1/3 and PC2 in the secretory granules. Little is known about the pathogenesis for islet amyloid and which intracellular mechanisms are involved in amyloidogenesis and induction of cell death.Methodology/Principal Findings: We have established expression of human proIAPP (hproIAPP), human IAPP (hIAPP) and the non-amyloidogenic mouse IAPP (mIAPP) in Drosophila melanogaster, and compared survival of flies with the expression driven to different cell populations. Only flies expressing hproIAPP in neurons driven by the Gal4 driver elavC(155,Gal4) showed a reduction in lifespan whereas neither expression of hIAPP or mIAPP influenced survival. Both hIAPP and hproIAPP expression caused formation of aggregates in CNS and fat body region, and these aggregates were both stained by the dyes Congo red and pFTAA, both known to detect amyloid. Also, the morphology of the highly organized protein granules that developed in the fat body of the head in hIAPP and hproIAPP expressing flies was characterized, and determined to consist of 15.8 nm thick pentagonal rod-like structures.Conclusions/Significance: These findings point to a potential for Drosophila melanogaster to serve as a model system for studies of hproIAPP and hIAPP expression with subsequent aggregation and developed pathology.
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| 5. |
- Schultz, Sebastian, et al.
(författare)
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Fly model of type 2 diabetes: processing of proIAPP makes a difference
- 2010
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Ingår i: Amyloid. - : Informa Healthcare. - 1350-6129 .- 1744-2818. ; 17:S1, s. 44-45
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Patients with type 2 diabetes have a marked reducedbeta cell mass and fail to produce sufficient amounts of insulin required for regulation of glucose home- ostasis. Recent research supports that intracellular aggregation of islet amyloid polypeptide (IAPP) leads to cell death and therefore makes IAPP aggregation a plausible cause for the beta cell reduction. Little is known about the mechanisms that precede amyloid formation or which cellular pathways are involved in this process. To gain better understanding we haveestablished a Drosophila melanogaster model, where GAL4 drives expression of UAS-targeted transgenes in a cell or tissue specific pattern. The fruit fly offers a unique option to manipulate any cellular pathway with different genetic tools. The knowledge that*70% of all Drosophila melanogaster genes have anorthologue in humans stress the potential for path- ways found in D. melanogaster to be of importance in humans as well. Transgenic flies expressing human proIAPP (the precursor of IAPP) and IAPP and the non-amyloidogenic mouse IAPP (mIAPP) have been generated. Expression of proIAPP in the brain reduced the lifespan of the fly whereas neither IAPP nor mIAPP expression influenced survival. Immu- nolabelling with an antibody raised against human IAPP and that cross-reacts with murine IAPP labelled neurons in all three strains, whereas a concomitant loss of cell nuclei only appeared during proIAPP and IAPP expression. Furthermore, we detected an early potentiated activation of the autophagy pathway in proIAPP flies. Interestingly, even though IAPP expression was not related to a shorter lifespan, both IAPP and proIAPP expression in the central nervous system led to amyloid deposition in the fat body of the head as shown with Congo red and pFTAA, a newly synthesised luminescent conjugated polymer. Our results de- monstrate that D. melanogaster has a great potential as a model for studies of proIAPP and IAPP expression with subsequent amyloid formation and connected cellular response mechanisms. The find- ing that proIAPP aggregation seems to exert a more toxic impact at a cellular level is in line with ourresults from mammalian cell lines.
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| 6. |
- Schultz, Sebastian, et al.
(författare)
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HIAPP and hproIAPP triggers elective autophagy and inhibit the neuro-protective effect of autophagy
- 2010
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Amyloid formation is associated with cell death and islet amyloid is thought to participate in the 50-60% β-cell reduction detected in patients with type 2 diabetes. Islet amyloid polypeptide (IAPP) is the main amyloid protein in the islets of Langerhans. Initial IAPP-amyloid formation is intracellular and part of this amyloid constitutes of proIAPP. Material & methods: We have established a new model in Drosophila melanogaster where expression of hproIAPP and IAPP results in the formation of amyloid. With this model, we have investigated the effect of protein aggregation on pathways such as ER-stress, unfolded protein response (UPR), apoptosis and autophagy. Important steps in the different pathways were manipulated by RNAi-technique or over- expression of endogenous Drosophila proteins. Results: Expression of hproIAPP and hIAPP driven to the pdf-neurons led to cell death, but this was without activation of ER-stress, UPR or apoptosis. Aggregated hproIAPP and IAPP, labeled with antibodies against ubiquitin and p62 were accumulated intracellular, a finding that points to an involvement of autophagy. HproIAPP and hIAPP were shown to exert their toxic activity by an intracellular mechanism in contrary to Aβ42 and Aβ42 E22G that exhibit an extracellular toxic activity. Conclusion: Studies on toxicity suggest that hproIAPP and hIAPP aggregates can occupy the autophagy pathway and prevent maintenance of basal cellular homeostasis. Comparison of proIAPP/IAPP and Aβ42 toxicity shows that amyloid proteins of separate origin can exhibit different toxicity.
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| 7. |
- Schultz, Sebastian
(författare)
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Studies on Islet Amyloid Polypeptide Aggregation : From Model Organism to Molecular Mechanisms
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The proper folding of a protein into its defined three--‐dimensional structure is one of the many fundamental challenges a cell encounters. A number of tightly controlled pathways have evolved to assist in the proper folding of a protein, but also to aid in the removal of misfolded proteins. Despite the presence of these pathways accumulation of misfolded proteins can still occur. Amyloid deposits consist of misfolded proteins with a characteristic highly ordered fibrillar structure that will exert affinity for the amyloid dye Congo red and has a unique X-ray diffraction pattern. Currently 27 different proteins have been identified as amyloid forming proteins in human, however the exact role of amyloid in the pathogenesis of the connected disease is most often unclear.Islet amyloid is made up of the beta cell derived hormone islet amyloid polypeptide (IAPP) and is associated with the development of type 2 diabetes. Propagation of IAPP-fibrils is believed to be one important cause of the pancreatic beta cell death detected in patients with type 2 diabetes. IAPP is a naturally occurring polypeptide hormone stored and secreted together with insulin. IAPP and insulin arise from posttranslational processing of their biological inactive precursors proIAPP and proinsulin. In addition to human, cat and monkey IAPP will form amyloid deposits in conditions resembling human type 2 diabetes. However, IAPP from mouse and rat do not form amyloid as a result of the differences in amino acid sequence.My main research goal was to establish a unique model system suitable to study the effects of proIAPP and IAPP aggregation. I selected Drosophila melanogaster due to its many suitable characteristics as a model organism and its superior genetic toolbox. I have demonstrated that over--‐expression of hproIAPP and hIAPP in the central nervous system (CNS) results in aggregate formation in the brain and neighbouring fat body. Consistent with previous studies, expression of mIAPP does not result in the formation of aggregates. To investigate the intracellular effects of hproIAPP and hIAPP aggregation on a specific population of neurons, we targeted the expression of these peptides specifically to 16 neurons in the brain, the pdf- neurons. These pdf-neurons are divided into 2 clusters of 8 cells per brain hemisphere. First I showed that expression of aggregation prone hIAPP and hproIAPP resulted in significant death of the 8 cells, whereas expression of mIAPP had no such effect. In efforts to pinpoint the mechanisms behind the observed cell death I demonstrated that hproIAPP and hIAPP both pass the ERs quality control for protein folding and that the initiated cell death does not occur through classical apoptosis. Instead, selective autophagy is activated by hIAPP and hproIAPP. This activation counteracts the usually neuro-protective effects of autophagy and contributes to cell death. Strikingly, I also showed that Aâ, the amyloid protein implicated in Alzheimer’s disease, does not exhibit any intracellular toxicity when expressed in pdf-cells. This supports the existence of separate toxic pathways for different amyloid proteins.
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