JIMD Reports - Volume 12 by Johannes Zschocke K. Michael Gibson Garry Brown Eva Morava & Verena Peters

Author:Johannes Zschocke, K. Michael Gibson, Garry Brown, Eva Morava & Verena Peters
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Abbreviations

CD2-hydroxypropyl-β-cyclodextrin

Cer/cholceramide/cholesterol

LSDlysosomal storage disease

PBSphosphate buffered saline

TEMtransmission electron microscopy

WTwild type

Competing interests: None declared

Authors Natalia Santos Ferreira and Michal Goldschmidt-Arzi contributed equally to this study

Introduction

Farber disease (Farber lipogranulomatosis: OMIM # 228000) is a lysosomal storage disease (LSD) caused by mutations in the acid ceramidase (ASAH1) gene, which results in intracellular ceramide accumulation (Levade et al. 2009). As with most LSDs, patients display a wide variety of symptoms, with the most severely affected displaying central nervous system involvement (Levade et al. 2009). Seven clinical subtypes of the disease are known which are associated with 17 distinct mutations in the ASAH1 gene (Zhang et al. 2000; Bär et al. 2001; Muramatsu et al. 2002; Devi et al. 2006). The subtypes are categorized according to the age of onset, symptom severity, and the tissue where lipid accumulation appears (Levade et al. 2009). Types 1 and 5 are the most common forms, with patients displaying nervous system dysfunction and an average age of death between 2 and 3 years (Eviatar et al. 1986; Scriver 1995). Types 2 and 3 are milder forms with death occurring in the second or third decade of life (Ehlert et al. 2007). Type 4 is a very severe form, with patients displaying neurological deterioration, hepatosplenomegaly at birth, and granulomatous infiltrations in the liver, spleen, lymphoid tissue, thymus, and lungs; death typically occurs in the first years of life (Schafer et al. 1996) Type 6 disease has only been described once (Fusch et al. 1989). Type 7 Farber disease, which displays a very severe phenotype (Levade et al. 2009), is not due to mutations in the ASAH1 gene but rather due to mutations in the gene encoding prosaposin D, which may serve as an activator for ASAH1 (Levade et al. 2009).

Ceramide accumulation is common to all Farber disease types. Surprisingly, despite wide interest in ceramide in both intracellular signaling pathways (Hannun and Obeid 2008) and as a structural component of membrane lipid microdomains/rafts (Schenck et al. 2007; Lingwood and Simons 2010), only a few studies have used Farber cells to examine the effect of ceramide accumulation on cell function (Levade et al. 1993; Tardy et al. 2004). We now take advantage of a newly developed tool, namely, a monoclonal antibody that was raised and selected to recognize a mixed monolayer phase composed of 60:40 mol% cholesterol:C16-ceramide, at which molar ratio, the two lipids form an ordered and homogeneous phase when deposited as a monolayer at the air-water interface and as a single hydrated bilayer (Ziblat et al. 2012). This anti-C16-ceramide/cholesterol (anti-C16-Cer/Chol) antibody interacts specifically with C16-ceramide/cholesterol and does not bind to pure cholesterol or ceramide monolayers (Scheffer et al. 2006). Using this antibody, we have previously demonstrated that C16-Cer/Chol domains are found at high levels in late endosomes in a variety of cultured cells (Goldschmidt-Arzi et al. 2011). We now use this antibody to determine the levels and localization of C16-Cer/Chol domains in Farber disease patient fibroblasts, and demonstrate that types 4 and 7 fibroblasts display high levels of the domains, which can be abrogated either by reduction of ceramide or of cholesterol levels.

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