|Cancer||Cell death||Cell cycle||Cytoskeleton||Exo/endocytosis||Differentiation||Division||Organelles||Signalling||Stem cells||Trafficking|
Proteasome inhibition induces developmentally deregulated programs of apoptotic and autophagic cell death during Drosophila melanogaster oogenesis
Panagiotis D Velentzas, Athanassios D Velentzas, Vassiliki E Mpakou, Issidora S Papassideri, Dimitrios J Stravopodis12 and Lukas H Margaritis1
Faculty of Biology, Department of Cell Biology and Biophysics, University of Athens, Panepistimiopolis 157 84, Athens, Greece
Ubiquitin/proteasome-mediated degradation of eukaryotic proteins is critically implicated in a number of signalling pathways and cellular processes. To specifically impair proteasome activities, in vitro developing Drosophila melanogaster egg chambers were exposed to the MG132 or epoxomicin proteasome inhibitors, while a GAL4/UAS binary genetic system was employed to generate double transgenic flies overexpressing β2 and β6 conditional mutant proteasome subunits in a cell type-specific manner. MG132 and epoxomicin administration resulted in severe deregulation of in vitro developing egg chambers, which was tightly associated with precocious induction of nurse cell-specific apoptotic and autophagic death programmes, featured by actin cytoskeleton disorganization, nuclear chromatin condensation, DRICE caspase activation and autophagosome accumulation. In vivo targeted overexpression of β2 and β6 conditional mutants, specifically in the nurse cell compartment, led to a notable up-regulation of sporadic apoptosis potency during early and mid-oogenesis ‘checkpoints’, thus reasonably justifying the observed reduction in eclosion efficiency. Furthermore, in response to the intracellular abundance of β2 and β6 conditional mutant forms, specifically in numerous tissues of third instar larval stage, the developmental course was arrested, and lethal phenotypes were obtained at this particular embryonic period, with the double transgenic heterozygote embryos being unable to further proceed to complete maturation to adult flies. Our data demonstrate that physiological proteasome function is required to ensure normal oogenesis and embryogenesis in D. melanogaster, since targeted and cell type-dependent proteasome inactivation initiates developmentally deregulated apoptotic and autophagic mechanisms.
Key words: Drosophila melanogaster, epoxomicin, GAL4/UAS, MG132, oogenesis, programmed cell death
Abbreviations: CLSM, Confocal Laser Scanning Microscope, DRICE, interleukin-1β-converting enzyme Drosophila homologue, GFP, green fluorescent protein, PCD, programmed cell death, TEM, transmission electron microscopy, TUNEL, terminal transferase-mediated dUTP nick end labelling
1Dimitrios J. Stravopodis and Lukas H. Margaritis contributed equally to this work.
2To whom correspondence should be addressed (email firstname.lastname@example.org).
Received 22 March 2010/12 July 2010; accepted 6 September 2010
Published as Cell Biology International Immediate Publication 6 September 2010, doi:10.1042/CBI20100191
© The Author(s) Journal compilation © 2011 Portland Press Limited