Ceramides And Stress Signalling Intersect With Autophagic Defects In Neurodegenerative Drosophila blue cheese (bchs) Mutants

Abstract

Sphingolipid metabolites are involved in the regulation of autophagy, a degradative recycling process that is required to prevent neuronal degeneration. Drosophila blue cheese mutants neurodegenerate due to perturbations in autophagic flux, and consequent accumulation of ubiquitinated aggregates. Here, we demonstrate that blue cheese mutant brains exhibit an elevation in total ceramide levels; surprisingly, however, degeneration is ameliorated when the pool of available ceramides is further increased, and exacerbated when ceramide levels are decreased by altering sphingolipid catabolism or blocking de novo synthesis. Exogenous ceramide is seen to accumulate in autophagosomes, which are fewer in number and show less efficient clearance in blue cheese mutant neurons. Sphingolipid metabolism is also shifted away from salvage toward de novo pathways, while pro-growth Akt and MAP pathways are down-regulated, and ER stress is increased. All these defects are reversed under genetic rescue conditions that increase ceramide generation from salvage pathways. This constellation of effects suggests a possible mechanism whereby the observed deficit in a potentially ceramide-releasing autophagic pathway impedes survival signaling and exacerbates neuronal death.

Drosophila BEACH domain autophagic adaptorblue cheeseshuttles between vesicle populations and is required for an early step in autophagy

“…12, left). Such a role for Bchs is also consistent with the greatly increased quantity of p62/Ref (2)p marker we documented in an earlier publication 39 . Our epistasis studies additionally show that even in a strong bchs loss of function background, an excess of Atg7 can rescue degeneration (see Fig.…”

“…Bchs' possible role in vesicle trafficking and membrane dynamics, in the context of its recently reported genetic interactions with sphingolipid lipases 39 will be an interesting avenue to investigate in the future.…”

Ceramide-Protein Interactions Modulate Ceramide-Associated Lipotoxic Cardiomyopathy

“…To test the effects of blocking de novo ceramide synthesis on cardiac function, we examined lace and schlank KD flies, as well as wild-type flies administered myriocin, an SPT inhibitor with known efficacy in flies (Figure 2A) (Hebbar et al, 2015). In contrast to the Cdase and SK1/2 RNAi lines that have a dilated cardiac phenotype, flies with global KD of lace and schlank exhibited a constricted heart, with reduced diastolic and systolic diameters but unchanged fractional shortening (Figures 2B–2D and S1B–S1D).…”

Lipid metabolic perturbation is an early-onset phenotype in adultspinmutants: aDrosophilamodel for lysosomal storage disorders

“…Ultrastructural defects as well as lipofuscin accumulation were used to score the extent of the degenerative phenotype against spin mutant alone. Reducing slab levels (with slab 2 heterozygosity; slab 2 /+) in the background of spin mutant, and consequently further pushing ceramide levels higher (documented for slab 2 /+ in [33], correlated with an intensification of these degenerative phenotypes. This effect is most clearly evidenced (at day 4 of adulthood) by the increased presence of ultrastructural defects ( Fig.…”

“…Mutants and overexpression lines of slab exhibit altered levels of ceramides as characterized by MS measurements [31,32]. slab heterozygotes and overexpression of Cdase specifically in neurons showed an increase and decrease of brain ceramides by over 200% and 30% respectively (Hebbar et al, 2015). Therefore, these genetic tools were combined in the background of spin mutants.…”