title: Ryanodine receptor antagonists adapt NPC1 proteostasis to ameliorate lipid storage in Niemann-Pick type C disease fibroblasts.
abstract: Niemann-Pick type C disease is a lysosomal storage disorder most often caused by loss-of-function mutations in the NPC1 gene. The encoded multipass transmembrane protein is required for cholesterol efflux from late endosomes and lysosomes. Numerous missense mutations in the NPC1 gene cause disease, including the prevalent I1061T mutation that leads to protein misfolding and degradation. Here, we sought to modulate the cellular proteostasis machinery to achieve functional recovery in primary patient fibroblasts. We demonstrate that targeting endoplasmic reticulum (ER) calcium levels using ryanodine receptor (RyR) antagonists increased steady-state levels of the NPC1 I1061T protein. These compounds also promoted trafficking of mutant NPC1 to late endosomes and lysosomes and rescued the aberrant storage of cholesterol and sphingolipids that is characteristic of disease. Similar rescue was obtained using three distinct RyR antagonists in cells with missense alleles, but not with null alleles, or by over-expressing calnexin, a calcium-dependent ER chaperone. Our work highlights the utility of proteostasis regulators to remodel the protein-folding environment in the ER to recover function in the setting of disease-causing missense alleles.
authors.affiliation: Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.forename: Chan
authors.initials: C
authors.lastname: Chung
authors.forename: Dongbiao
authors.initials: D
authors.lastname: Shen
authors.forename: Haoxing
authors.initials: H
authors.lastname: Xu
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Lieberman
mesh_terms: D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D011992:Endosomes / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D050356:Lipid Metabolism / Q000187:drug effects*; D008247:Lysosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D000077296:Niemann-Pick C1 Protein; D052556:Niemann-Pick Disease, Type C / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; D000077296:Niemann-Pick C1 Protein; D020543:Proteome; D019837:Ryanodine Receptor Calcium Release Channel