Different Niemann-Pick C1 Genotypes Generate Protein Phenotypes that Vary in their Intracellular Processing, Trafficking and Localization

• Published in: Scientific reports 2019-03, Vol.9 (1), p.5292, Article 5292
• Main Authors: Shammas, Hadeel, Kuech, Eva-Maria, Rizk, Sandra, Das, Anibh M., Naim, Hassan Y.
• Format: Article
• Language: English
• Subjects: 14; 14/19; 631/45/2783; 692/4017; Animals; Ataxia; Biomarkers - analysis; Biomarkers - metabolism; Brain diseases; Calnexin; Calnexin - analysis; Calnexin - metabolism; Chlorocebus aethiops; Cholesterol; Cholesterol - metabolism; COS Cells; Dystonia; Endocytosis - genetics; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Genetic disorders; Genotypes; Humanities and Social Sciences; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Intravital Microscopy; Liver diseases; Localization; Lysosomal protein; Lysosomal storage diseases; Lysosomal-Associated Membrane Protein 2 - analysis; Lysosomal-Associated Membrane Protein 2 - metabolism; Lysosomes; Lysosomes - metabolism; Mammalian cells; Metabolic disorders; Microscopy, Confocal; multidisciplinary; Mutagenesis, Site-Directed; Mutants; Mutation; Niemann-Pick disease; Niemann-Pick Disease, Type C - diagnosis; Niemann-Pick Disease, Type C - genetics; Niemann-Pick Disease, Type C - therapy; Npc1 protein; Paralysis; Phenotypes; Precision Medicine - methods; Protein Binding - genetics; Protein Domains - genetics; Proteins; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-41707-y

Niemann-Pick Type C (NP-C) is an inherited neurovisceral lysosomal storage disease characterized by a defect in the trafficking of endocytosed cholesterol. In 95% of patients the gene encoding NPC1 is affected. The correlation of the genetic background in NP-C with the clinical phenotype such as, severity and onset of liver dysfunction, ataxia, dystonia and vertical gaze palsy, has not been elucidated at the molecular level. We have designed strategies to investigate the effect of different mutations in the NPC1 gene at the protein and cellular levels. The NPC1 mutants were expressed in mammalian cells and their structural features, maturation pathways and subcellular localization elucidated. Interestingly, three classes of NPC1 mutants could be identified and further characterized. The first group comprised mutants in which the NPC1 protein revealed virtually similar structural features to the wild type species. It was trafficked to the lysosomes and colocalized with the lysosomal protein marker Lamp2. The second class of NPC1 mutants was only partially trafficked to the lysosomes, but predominantly localized to the endoplasmic reticulum (ER). In the third group with the most severe phenotype, NPC1 mutants were entirely retained in the ER, colocalizing with the ER-protein marker calnexin. In conclusion, this study relates NPC1 mutations to the trafficking behavior of the NPC1 mutants along the secretory pathway. The findings are essential for a comprehensive understanding of the pathogenesis of NP-C and propose a mutation-based personalized therapeutical approach.