title: Reduction of TMEM97 increases NPC1 protein levels and restores cholesterol trafficking in Niemann-pick type C1 disease cells.
abstract: Niemann-Pick type C disease (NP-C) is a progressive lysosomal lipid storage disease caused by mutations in the NPC1 and NPC2 genes. NPC1 is essential for transporting cholesterol and other lipids out of lysosomes, but little is known about the mechanisms that control its cellular abundance and localization. Here we show that a reduction of TMEM97, a cholesterol-responsive NPC1-binding protein, increases NPC1 levels in cells through a post-transcriptional mechanism. Reducing TMEM97 through RNA-interference reduces lysosomal lipid storage and restores cholesterol trafficking to the endoplasmic reticulum in cell models of NP-C. In TMEM97 knockdown cells, NPC1 levels can be reinstated with wild type TMEM97, but not TMEM97 missing an ER-retention signal suggesting that TMEM97 contributes to controlling the availability of NPC1 to the cell. Importantly, knockdown of TMEM97 also increases levels of residual NPC1 in NPC1-mutant patient fibroblasts and reduces cholesterol storage in an NPC1-dependent manner. Our findings propose TMEM97 inhibition as a novel strategy to increase residual NPC1 levels in cells and a potential therapeutic target for NP-C.
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg.|Division of Pediatric Neurology and Metabolic Medicine, Department of Pediatrics, Heidelberg University Hospital, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany.
authors.forename: Darius
authors.initials: D
authors.lastname: Ebrahimi-Fakhari
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg.|Division of Pediatric Neurology and Metabolic Medicine, Department of Pediatrics, Heidelberg University Hospital, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany.
authors.forename: Lara
authors.initials: L
authors.lastname: Wahlster
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg.
authors.forename: Fabian
authors.initials: F
authors.lastname: Bartz
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Werenbeck-Ueding
authors.affiliation: Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Praggastis
authors.affiliation: Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Jessie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Joggerst-Thomalla
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg.
authors.forename: Susanne
authors.initials: S
authors.lastname: Theiss
authors.affiliation: Center for Infectious Diseases/Virology, BioQuant BQ0030, Heidelberg, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Grimm
authors.affiliation: Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Ory
authors.affiliation: Institute of Human Genetics, Ruprecht-Karls-University Heidelberg heiko.runz@merck.com.|Molecular Medicine Partnership Unit (MMPU), Ruprecht-Karls-University Heidelberg/European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Runz
mesh_terms: D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D002784:Cholesterol / Q000235:genetics* / Q000378:metabolism; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology; D055785:Gene Knockdown Techniques; D006023:Glycoproteins / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008247:Lysosomes / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation; D000077296:Niemann-Pick C1 Protein; D052556:Niemann-Pick Disease, Type C / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C106881:NPC1 protein, human; C104585:NPC2 protein, human; D000077296:Niemann-Pick C1 Protein; C516615:TMEM97 protein, human; D033921:Vesicular Transport Proteins; D002784:Cholesterol