ABSTRACT
The amyloid-ß (Aß) peptide, produced from amyloid precursor protein (APP) by ß and γ-secretases, has been implicated in the etiology of Alzheimer's disease (AD). However, the precise intracellular trafficking pathway of APP and its subcellular locations to produce Aß have remained unclear. To address these issues, we established fly AD models that recapitulated multiple AD-like symptoms by expressing human APP in the Drosophila nerve system. The ESCRT (endosomal sorting complexes required for transport) machinery regulates the sorting and trafficking of endocytosed proteins, yet its role in AD pathogenesis has not been explored in vivo. We found that knockdown of distinct ESCRT components ameliorated APP-induced morphological and behavioral defects, including impaired wing expansion, eye degeneration, dopamine neuron loss, locomotor disability, lifespan shortening, and cognitive deficits. Mechanistically, we showed that impaired ESCRT impeded APP's intracellular transportation from early endosomes to late endosomes, resulting in reduced Aß production and amyloid deposit load. These data suggest that APP undergoes ESCRT-mediated endocytic trafficking, and Aß is generated mainly in late endosomes. Our data provide the first in vivo evidence to support a physiological role of ESCRT in AD pathogenesis, suggesting that interfering with ESCRT machinery might be an alternative therapeutic strategy for AD.
Subject(s)
Alzheimer Disease , Amyloid beta-Protein Precursor , Endosomal Sorting Complexes Required for Transport , Animals , Humans , Alzheimer Disease/pathology , Amyloid beta-Peptides/genetics , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/metabolism , Amyloid Precursor Protein Secretases/metabolism , Drosophila/metabolism , Endosomal Sorting Complexes Required for Transport/genetics , Protein Transport/physiologyABSTRACT
Dysregulation of autophagy is associated with the neurodegenerative processes in Alzheimer's disease (AD), yet it remains controversial whether autophagy is a cause or consequence of AD. We have previously expressed the full-length human APP in Drosophila and established a fly AD model that exhibits multiple AD-like symptoms. Here we report that depletion of CHIP effectively palliated APP-induced pathological symptoms, including morphological, behavioral, and cognitive defects. Mechanistically, CHIP is required for APP-induced autophagy dysfunction, which promotes Aß production via increased expression of BACE and Psn. Our findings suggest that aberrant autophagy is not only a consequence of abnormal APP activity, but also contributes to dysregulated APP metabolism and subsequent AD pathogenesis.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Protein Precursor/metabolism , Autophagy/genetics , Drosophila Proteins/metabolism , Drosophila/metabolism , Nuclear Proteins/metabolism , Alzheimer Disease/pathology , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/toxicity , Animals , Aspartic Acid Endopeptidases/metabolism , Brain/metabolism , Cognitive Dysfunction/genetics , Disease Models, Animal , Dopaminergic Neurons/metabolism , Down-Regulation , Drosophila Proteins/genetics , Eye/growth & development , Eye/metabolism , Learning Disabilities/genetics , Locomotion/genetics , Longevity/genetics , Nuclear Proteins/genetics , Presenilins/metabolism , RNA Interference , Wings, Animal/metabolism , Wings, Animal/pathologyABSTRACT
Reproductive behaviour is important for animals to keep their species existing on Earth. A key question is how to generate more and healthier progenies by choosing optimal mates. In Drosophila melanogaster, males use multiple sensory cues, including vision, olfaction and gustation, to achieve reproductive success. These sensory inputs are important, yet not all these different modalities are simultaneously required for courtship behaviour to occur. Moreover, the roles of these sensory inputs for male courtship choice remain largely unknown. Here, we demonstrate that males court younger females with greater preference and that olfactory inputs are indispensable for this male courtship choice. Specifically, the olfactory receptor Or47b is required for males to discriminate younger female mates from older ones. In combination with our previous work indicating that gustatory perception is necessary for this preference behaviour, our current study demonstrates the requirement of both olfaction and gustation in Drosophila males' courtship preference, thus providing new insights into the role of sensory cues in reproductive behaviour and success.
Subject(s)
Drosophila Proteins/metabolism , Drosophila melanogaster/physiology , Receptors, Odorant/metabolism , Animals , Courtship , Drosophila melanogaster/metabolism , Female , Male , Olfactory Receptor Neurons/metabolismABSTRACT
The amyloid precursor protein (APP) has been implicated in the pathogenesis of Alzheimer's disease (AD). Despite extensive studies, little is known about the regulation of APP's functions in vivo. Here we report that expression of human APP in Drosophila, in the same temporal-spatial pattern as its homolog APPL, induced morphological defects in wings and larval NMJ, larva and adult locomotion dysfunctions, male choice disorder and lifespan shortening. To identify additional genes that modulate APP functions, we performed a genetic screen and found that loss of Polo, a key regulator of cell cycle, partially suppressed APP-induced morphological and behavioral defects in larval and adult stages. Finally, we showed that eye-specific expression of APP induced retina degeneration and cell cycle re-entry, both phenotypes were mildly ameliorated by loss of Polo. These results suggest Polo is an important in vivo regulator of the pathological functions of APP, and provide insight into the role of cell cycle re-entry in AD pathogenesis.
