A trimeric Rab7 GEF controls NPC1-dependent lysosomal cholesterol export

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van den Boomen, Dick J. H.  ORCID logo  https://orcid.org/0000-0001-6474-3661
Sienkiewicz, Agata 
Berlin, Ilana 
Jongsma, Marlieke L. M. 
van Elsland, Daphne M. 

Abstract: 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.

Article, /631/45/287/1197, /631/80/313, /631/80/313/1624, /631/80/313/2011, /49/47, /14/19, /13/31, /82/58, article
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Nature Communications
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Nature Publishing Group UK
RCUK | Medical Research Council (MRC) (MR/R0009015/1)
Wellcome Trust (Wellcome) (100140, 084957/Z/08/Z)