A trimeric Rab7 GEF controls NPC1-dependent lysosomal cholesterol export.

Cholesterol import in mammalian cells is mediated by the LDL receptor pathway. Here, we perform a genome-wide CRISPR screen using an endogenous cholesterol reporter and identify >100 genes involved in LDL-cholesterol import. We characterise C18orf8 as a core subunit of the mammalian Mon1-Ccz1 guanidine exchange factor (GEF) for Rab7, required ...
for complex stability and function. C18orf8-deficient cells lack Rab7 activation and show severe defects in late endosome morphology and endosomal LDL trafficking, resulting in cellular cholesterol deficiency. Unexpectedly, free cholesterol accumulates within swollen lysosomes, suggesting a critical defect in lysosomal cholesterol export. We find that active Rab7 interacts with the NPC1 cholesterol transporter and licenses lysosomal cholesterol export. This process is abolished in C18orf8-, Ccz1- and Mon1A/B-deficient cells and restored by a constitutively active Rab7. The trimeric Mon1-Ccz1-C18orf8 (MCC) GEF therefore plays a central role in cellular cholesterol homeostasis coordinating Rab7 activation, endosomal LDL trafficking and NPC1-dependent lysosomal cholesterol export.
Mesh Terms:
Biological Transport, CRISPR-Cas Systems, Cholesterol, Cholesterol, LDL, Endosomes, Fluorescent Dyes, Genome, Human, Guanine Nucleotide Exchange Factors, HEK293 Cells, HeLa Cells, Homeostasis, Humans, Hydroxymethylglutaryl-CoA Synthase, Intracellular Signaling Peptides and Proteins, Lysosomes, Models, Biological, Multiprotein Complexes, Protein Binding, Protein Multimerization, rab GTP-Binding Proteins
Nat Commun
Date: Dec. 03, 2019
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