Whole organism and tissue specific analysis of pexophagy inDrosophila

Abstract

Peroxisomes are essential organelles involved in critical metabolic processes in animals such as fatty acid oxidation, ether phospholipid production and reactive oxygen species detoxification. We have generated transgenicDrosophila melanogastermodels expressing fluorescent reporters for the selective autophagy of peroxisomes, a process known as pexophagy. Using light sheet microscopy, we have been able to obtain a global overview of pexophagy levels, across the entire organism at different stages of development. Tissue specific control of pexophagy is exemplified by areas of peroxisome abundance but minimal pexophagy observed in clusters of oenocytes, which are the major site of long chain fatty acid synthesis. They are surrounded by epithelial cells where pexophagy is much more evident. Enhancement of pexophagy was achieved by feeding flies with the iron chelator deferiprone, in line with past results using mammalian cells. Specific drivers were used to visualise pexophagy in neurons, in which we tested the role of two proteins proposed to regulate pexophagy. Firstly, depletion of CG8814, theDrosophilahomologue of the yeast protein Atg37, had no noticeable impact on pexophagy. In contrast, specific depletion in the larval central nervous system of Hsc70-5, theDrosophilahomologue of the chaperone HSPA9/Mortalin, led to a substantial elevation in pexophagy.

New insights into the functions of ACBD4/5-like proteins using a combined phylogenetic and experimental approach across model organisms

“…Human ACBD5 has initially also been linked to pexophagy (Nazarko et al, 2014), but other studies did not reveal an involvement of ACBD5 in peroxisome degradation (Ferdinandusse et al, 2017; Yagita et al, 2017; Barone et al, 2023b). Similar observations were also recently made for D. melanogaster Acbd4/5 (Barone et al, 2023a). Interestingly, we noticed that overexpression of Hs_ACBD4, but not Hs_ACBD5, in H9C2 myoblasts reduced peroxisome number ( Fig.…”

“…3A, B ), indicating conserved physicochemical properties for the peroxisomal targeting of the ACBD4/5 homologs. Indeed, peroxisomal targeting of Acbd4/5 was recently confirmed in D. melanogaster (Barone et al, 2023a). Interestingly, expression of Dm_Acbd4/5, but not Um_Acbd4/5, induced peroxisome elongation in COS-7 cells ( Fig.…”

“…Notably, the ACBD4/5 homolog in the yeast P. pastoris (Atg37), which is required for the formation of the pexophagic receptor complex linking peroxisomes to the autophagic machinery, appears to be regulated by palmitoyl-CoA (Nazarko et al, 2014). Drosophila Acbd4/5 and human ACBD5 do not appear to impact peroxisome degradation (Ferdinandusse et al, 2017;Yagita et al, 2017;Barone et al, 2023a;. We therefore suggest that H. sapiens ACBD4 and fungal/yeast ACBD4/5-like proteins may share a role in the regulation of peroxisome number.…”