An “Exacerbate-reverse” Strategy in Yeast Identifies Histone Deacetylase Inhibition as a Correction for Cholesterol and Sphingolipid Transport Defects in Human Niemann-Pick Type C Disease

Abstract

Niemann-Pick type C (NP-C) disease is a fatal lysosomal lipid storage disorder for which no effective therapy exists. A genome-wide, conditional synthetic lethality screen was performed using the yeast model of NP-C disease during anaerobiosis, an auxotrophic condition that requires yeast to utilize exogenous sterol. We identified 12 pathways and 13 genes as modifiers of the absence of the yeast NPC1 ortholog (NCR1) and quantified the impact of loss of these genes on sterol metabolism in ncr1⌬ strains grown under viable aerobic conditions. Deletion of components of the yeast NuA4 histone acetyltransferase complex in ncr1⌬ strains conferred anaerobic inviability and accumulation of multiple sterol intermediates. Thus, we hypothesize an imbalance in histone acetylation in human NP-C disease. Accordingly, we show that the majority of the 11 histone deacetylase (HDAC) genes are transcriptionally up-regulated in three genetically distinct fibroblast lines derived from patients with NP-C disease. A clinically approved HDAC inhibitor (suberoylanilide hydroxamic acid) reverses the dysregulation of the majority of the HDAC genes. Consequently, three key cellular diagnostic criteria of NP-C disease are dramatically ameliorated as follows: lysosomal accumulation of both cholesterol and sphingolipids and defective esterification of LDL-derived cholesterol. These data suggest HDAC inhibition as a candidate therapy for NP-C disease. We conclude that pathways that exacerbate lethality in a model organism can be reversed in human cells as a novel therapeutic strategy. This "exacerbatereverse" approach can potentially be utilized in any model organism for any disease.

Niemann-Pick C disease and mobilization of lysosomal cholesterol by cyclodextrin

“…HDAC inhibitors have already been approved for clinical use in humans for treatment of certain cancers. A clinically approved HDAC inhibitor decreased HDAC expression in NPC1-defi cient cells and reduced cholesterol accumulation in LEs/Ls ( 160,161 ). Interestingly, however, treatment of NPC2-defi cient human fi broblasts with an HDAC inhibitor did not reduce cholesterol storage in LEs/Ls ( 161 ).…”

“…The ED 50 for the therapeutic effect of CYCLO is 0.5 mg/ kg ( 100,170 ). The concentration of CYCLO required to mobilize LE/L cholesterol in NPC1-defi cient cells in either peripheral tissues or in the CNS of Npc1 Ϫ / Ϫ mice is <1 mM, ( 160,161 ). Because HDAC inhibitors increase the amount of NPC1 protein ( 162 ), these inhibitors might be useful in NPC patients in which residual NPC1 activity remains or where partially active NPC1 protein is mislocalized ( 163 ).…”

The yeast Pmp3p has a significant role in plasma membrane organization

“…Couthouis et al suggest that the toxicity of M8 comes from its propensity to be inserted in phospholipid membranes and to hamper membrane fission, leading to vesicular trafficking poisoning, mostly at the endosome and vacuole (Couthouis et al, 2010). Munkacsi et al have shown that the double deletion mutant pmp3Δ ncr1Δ has a growth defect when grown under anaerobic conditions compared to the single deletion mutants and the wild type (Munkacsi et al, 2011). NCR1 has been suggested to be responsible for mannoseinositol-phosphoceramide (MIPC) recycling out of the vacuole (Malathi et al, 2004).…”

A Murine Niemann-Pick C1 I1061T Knock-In Model Recapitulates the Pathological Features of the Most Prevalent Human Disease Allele

“…Overexpression of NPC1 I1061T protein results in lysosomal localization of mutant protein and complementation of the mutant phenotype, likely caused by a small proportion of NPC1 I1061T protein that assumes proper conformation and escapes ER quality control checkpoints (Gelsthorpe et al, 2008). Recently, histone deacetylase (HDAC) inhibitors have been shown to increase synthesis of NPC1 I1061T protein and cholesterol egress from lysosomes (Kim et al, 2007;Munkacsi et al, 2011;Pipalia et al, 2011). These findings raise the possibility that small moleculebased proteostatic therapies might stabilize mutant NPC1 proteins and have the potential to provide clinical benefit.…”

“…I1061T fibroblasts (Kim et al, 2007;Munkacsi et al, 2011;Pipalia et al, 2011). Together with the biochemical and immunofluorescence analysis of the NPC1 I1061T protein in the mouse tissues, these data indicate that the cellular behavior of the mutant protein closely models that of the most common disease-causing mutation in the human NPC1 locus (Gelsthorpe et al, 2008) and provide proof of concept that the mouse model will respond similarly to interventions that stabilize the human NPC1…”