Hydroxylated sphingolipid biosynthesis regulates photoreceptor apical domain morphogenesis

Abstract

Apical domains of epithelial cells often undergo dramatic changes during morphogenesis to form specialized structures, such as microvilli. Here, we addressed the role of lipids during morphogenesis of the rhabdomere, the microvilli-based photosensitive organelle of Drosophila photoreceptor cells. Shotgun lipidomics analysis performed on mutant alleles of the polarity regulator crumbs, exhibiting varying rhabdomeric growth defects, revealed a correlation between increased abundance of hydroxylated sphingolipids and abnormal rhabdomeric growth. This could be attributed to an up-regulation of fatty acid hydroxylase transcription. Indeed, direct genetic perturbation of the hydroxylated sphingolipid metabolism modulated rhabdomere growth in a crumbs mutant background. One of the pathways targeted by sphingolipid metabolism turned out to be the secretory route of newly synthesized Rhodopsin, a major rhabdomeric protein. In particular, altered biosynthesis of hydroxylated sphingolipids impaired apical trafficking via Rab11, and thus apical membrane growth. The intersection of lipid metabolic pathways with apical domain growth provides a new facet to our understanding of apical growth during morphogenesis.

The role of plasmalogens, Forssman lipids, and sphingolipid hydroxylation in modulating the biophysical properties of the epithelial plasma membrane

“…33 They play a key role in the formation of the apical epithelial membrane and apical trafficking. 34 In addition, the variation in hydroxylation patterns of hydroxylated sphingolipids can influence phase transition temperatures and nanoscale assemblies with glycerophospholipids and sterols. 35,36 Given the distinct lipid composition, morphology, and functions of the apical epithelial plasma membrane, its nanoscale lipid dynamics and membrane biophysical properties are of significant interest.…”

Vitamin A Deficiency Alters the Phototransduction Machinery and Distinct Non-Vision-Specific Pathways in the Drosophila Eye Proteome

“…Lipid analysis was performed as previously described [ 26 , 27 ]. Briefly, whole adult eyes (N = 10) were separated with a thin blade and placed in 40 µL of 150 mM ammonium bicarbonate buffer containing 10% of isopropanol in a 2 mL Eppendorf tube, snap-frozen in liquid nitrogen, and stored at −80 °C or processed immediately.…”

Mutations in the splicing regulator Prp31 lead to retinal degeneration in Drosophila

“…For vitamin A depletion experiments, animals were raised and maintained from embryonic stages onward on carotenoid free food (10% dry yeast, 10% sucrose, 0.02% cholesterol, and 2% agar) as described ( Pocha et al, 2011 ). The protocol for BLICS assays was as described in Hebbar et al, 2020 doi: ). Briefly, flies were raised on carotenoid free food and upon eclosion, they were placed in the dark containing carotenoid-free food or food supplemented with all-trans retinal.…”