CRISPR screens for lipid regulators reveal a role for ER-bound SNX13 in lysosomal cholesterol export

Abstract

We report here two genome-wide CRISPR screens carried out to identify genes that when knocked out, alter levels of lysosomal cholesterol or bis(monoacylglycero)phosphate. In addition, these screens were also carried out under conditions of NPC1 inhibition to identify modifiers of NPC1 function in lysosomal cholesterol export. The screens confirm tight co-regulation of cholesterol and bis(monoacylglycero)phosphate levels in cells, and reveal an unexpected role for the ER-localized, SNX13 protein as a negative regulator of lysosomal cholesterol export. In the absence of NPC1 function, SNX13 knockout decreases lysosomal cholesterol, and is accompanied by triacylglycerol-rich lipid droplet accumulation and increased lysosomal bis(monoacylglycero)phosphate. These experiments provide unexpected insight into the regulation of lysosomal lipids and modification of these processes by novel gene products.

Loss of the GARP but not EARP protein complex drives Golgi sterol overload during dendrite remodeling

“…However, beyond the coordinated function of Npc1 and 2, other routes for sterol egress from endolysosomes remain poorly understood. Several recent studies in mammalian cells have focused on identifying mechanisms for sterol metabolism, and sterol transport specifically, in control cells and/or in cells in which Npc1 is either genetically or pharmacologically inhibited (Scott et al ., 2015; Trinh et al ., 2020; van den Boomen et al ., 2020; Lu et al ., 2021). We suggest that, given their unique reliance on dietary sterol, Drosophila is an ideal model in which to study mechanisms of sterol egress from the endolysosomal pathway.…”