Tampere University of Technology

TUTCRIS Research Portal

High-content imaging and structure-based predictions reveal functional differences between Niemann-Pick C1 variants

Research output: Contribution to journalArticleScientificpeer-review

Details

Original languageEnglish
Pages (from-to)386-397
Number of pages12
JournalTraffic
Volume21
Issue number5
DOIs
Publication statusPublished - 1 May 2020
Publication typeA1 Journal article-refereed

Abstract

The human Niemann-Pick C1 (NPC1) gene encoding a 1278 amino acid protein is very heterogeneous. While some variants represent benign polymorphisms, NPC disease carriers and patients may possess rare variants, whose functional importance remains unknown. An NPC1 cDNA construct known as NPC1 wild-type variant (WT-V), distributed between laboratories and used as a WT control in several studies, also contains changes regarding specific amino acids compared to the NPC1 Genbank reference sequence. To improve the dissection of subtle functional differences, we generated human cells stably expressing NPC1 variants from the AAVS1 safe-harbor locus on an NPC1-null background engineered by CRISPR/Cas9 editing. We then employed high-content imaging with automated image analysis to quantitatively assess LDL-induced, time-dependent changes in lysosomal cholesterol content and lipid droplet formation. Our results indicate that the L472P change present in NPC1 WT-V compromises NPC1 functionality in lysosomal cholesterol export. All-atom molecular dynamics simulations suggest that the L472P change alters the relative position of the NPC1 middle and the C-terminal luminal domains, disrupting the recently characterized cholesterol efflux tunnel. These results reveal functional defects in NPC1 WT-V and highlight the strength of simulations and quantitative imaging upon stable protein expression in elucidating subtle differences in protein function.

Keywords

  • cholesterol transport, gene variants, late endosomes, lipid droplets, lysosomal storage diseases, Niemann-Pick C1