November 28
PROGRAM

01

Glycoscience : diversity and integration

Glucosylceramide :From a simple glycosphingolipid toa complex disease
Tony Futerman, PhD
Professor, Department of Biological Chemistry,Weizmann Institute of Science, ISRAEL

Tony Futerman
ProfileProfessor Tony Futerman received his BSc
degree in biochemistry at the Universityof Bath, England (1981), and obtained his
PhD from the Weizmann Institute in 1986,
where he discovered that acetylcholinesterase is attached to the cell membrane via
a GPI anchor. From 1987-1990, he was a
postdoctoral fellow at the Carnegie Institution (Baltimore, Maryland, USA) withRichard Pagano, and in 1990 he joined thestaff of the Weizmann Institute where heis currently the Joseph Meyerhoff Professor of Biochemistry and the director of theNella and Leon Benoziyo Center for Neurological Diseases. He is a member of theEditorial Board of the Journal of BiologicalChemistry, and was the chair of the 2006
Gordon Conference on Glycolipid andSphingolipid Biology and of the 2011 Gordon Conference on Lysosomal Diseases.
He currently runs a laboratory of ~20 scientists, postdoctoral fellows and students,and has multiple international collaborations. Prof. Futerman's research focuseson the cell biology and biochemistry ofsphingolipids and the roles that they playin health and disease. He works on two
major issues, namely understanding thebiology of ceramide and how ceramide issynthesized, and the mechanisms underlying neuronal dysfunction in sphingolipid storage diseases such as Gaucher andTay-Sachs diseases, two genetic disorders
found at high levels in Ashkenazi Jewish
populations, in which glycosphingolipids
accumulate. In particular, he wishes tounderstand how the brain is affected inthese diseases, and has provided some data
which may explain why nerve cells in thebrain are damaged.

Lysosomal storage disorders (LSDs) arecaused by the defective activity of lysosomal proteins, which results in intracellular accumulation of undegraded metabolites. Sphingolipid (SL) storage disorders
are a sub-group of LSDs, in which unmetabolized SLs and glycosphingolipids accumulate. Research over the past few years
has demonstrated that SL storage can result in multiple direct or indirect effects on
various cellular compartments and on biochemical pathways. SL storage disorders
are normally associated with devastatingneurodegeneration and death at early age.
Gaucher disease (GD), the most common
LSD, is caused by the defective activity ofglucosylceramidase (glucocerebrosidase,GlcCerase), the lysosomal hydrolase responsible for glucosylceramide (GlcCer)
degradation. As a result of this autosomal,
recessive genetic defect, the glycosphingolipids, GlcCer and glucosylsphingosine
accumulate intracellularly. Tissue macrophages engorged with glycolipid-laden lysosomes (‘Gaucher cells’) are the hallmarkof the disease.
Generation of animal models that faithfully recapitulate the three clinical sub-types
of GD has proved to be more of a challenge
than first anticipated. The first mouse to
be produced died within hours after birth
due to skin permeability problems, andmice with point mutations did not display
symptoms correlating to human disease
and also died soon after birth. Recently,conditional knockout mice (the ‘Karlssonmouse’) that mimic some features of thehuman disease have become available, andthis mouse has been of huge importancefor advancing our understanding of theneurological changes that occur in neuronal forms of GD.
The rare neuronopathic forms of GD arecharacterized by profound neurologicalimpairment and neuronal cell death, butlittle is known about the neuropathologi-20

the 20th Anniversary of the Mizutani Foundation for Glycosciencecal changes that underlie these events. We
systematically examined the onset andprogression of various neuropathologicalchanges (including microglial activation,astrogliosis and neuron loss), and documented the brain areas that are first affected, which may reflect vulnerability of theseareas to GlcCerase deficiency. We havealso identified neuropathological changes
in several brain areas and pathways, suchas the substantia nigra reticulata, reticulotegmental nucleus of the pons, cochlear
nucleus and the somatosensory system,
which could be responsible for some of theneurological manifestations of the humandisease. In addition, we have establishedthat microglial activation and astrogliosis are spatially and temporally correlatedwith selective neuron loss.
We have also delineated the role of neuroinflammation in the pathogenesis ofneuronopathic GD and demonstrated significant changes in levels of inflammatory
mediators in the brain. Levels of mRNA
expression of interleukin-1β, tumor necrosis factor-α, tumor necrosis factor-α
receptor, macrophage colony-stimulating
factor and transforming growth factor-β
were elevated by up to ~30-fold, with thetime-course of the increase correlatingwith the progression of disease severity. The most significant elevation wasdetected for the chemokines CCL2, CCL3
and CCL5. Blood-brain barrier disruption was also evident in neuronopathic
GD mice. Finally, extensive elevation ofnitrotyrosine, a hallmark of peroxynitrite
formation, was observed, consistent withoxidative damage caused by macrophage/
microglia activation. Together, our results
suggest a cytotoxic role of activated microglia in neuronopathic GD. We suggestthat once a critical threshold of GlcCer
storage is reached in neurons, a signalingcascade is triggered that activates microglia, which in turn releases inflammatory
cytokines that amplify the inflammatory
response, contributing to neuronal death.

Figure 1. Proposed mechanism for the role of neuroinflammation in nGD. Upon GlcCer accumulationin neurons, neurons signal to the surrounding microglia (1) and as a result, resting microglia become
activated (2). Activated microglia initiate a neuroinflammatory cascade involving elevation of cytokines,
release of neurotoxic agents (3) and reactive oxygen/nitrogen species (4), and BBB permeabilization (5).
The persistence of GlcCer accumulation in neurons and continuous glial activation results in chronic
inflammation, which contributes to neuronal cell death (6).

Finally, Parkinson's disease is associatedwith mutations in the GlcCerase gene. We
performed an exhaustive literature search
and found that additional LSDs might
be associated with Parkinson's disease,
based on case reports, the appearance ofpathological features such as α-synuclein
deposits in the brain, and substantia nigra

pathology. Our findings suggested that thesearch for biochemical and cellular pathways that link Parkinson's disease with
LSDs should not be limited exclusively tochanges that occur in GD, such as changes
in GlcCerase activity or in GlcCer levels,
but rather include changes that might
be common to a wide variety of LSDs.

Moreover, we propose that additional genetic, epidemiological and clinical studies
should be performed to check the precise
incidence of mutations in genes encoding
lysosomal proteins in patients displaying
Parkinson’s symptoms.

References1) 	Kacher, Y., Brumshtein, B., Boldin-Adamsky, S., Toker, L., Shainskaya, A.,Silman, I., Sussman, J.L. and Futerman, A.H. (2008). Acid-β-glucosidase:
Insights from structural analysis and relevance to Gaucher disease therapy.
Biological Chemistry, 389, 1361-1369.
2) 	Farfel-Becker, T., Vitner, E., Dekel, H., Leshem, N., Berglin-Enquist, I., Karlsson, S. and Futerman. A.H. (2009) No evidence for activation of the unfolded
protein response in neuronopathic models of Gaucher disease. Hum. Mol.
Genet., 18, 1482-1488.
3) 	Farfel-Becker, T. and Futerman, A.H. (2010) Cellular pathogenesis in sphingolipid storage disorders: the quest for new therapeutic approaches. ClinicalLipidology, 5, 255-265.
4) 	Vitner, E., Dekel, H., Zigdon, H., Shachar, T., Farfel-Becker, T., Eilam, R.,
Karlsson, S. and Futerman, A.H. (2010) Altered expression and distributionof cathepsins in neuronopathic forms of Gaucher disease and in other sphingolipidoses. Hum. Mol. Genet., 19, 3583-3590.
5) 	Vitner, E., Platt, F.M. and Futerman, A.H. (2010) Common and uncommon

pathogenic cascades in lysosomal storage diseases. J. Biol. Chem., 285, 2042320427.
6) 	Farfel-Becker, T., Vitner, E.B., Pressey, S.N.R., Eilam, R., Cooper, J.D. andFuterman. A.H. (2011) Spatial and temporal correlation between neuron loss
and neuroinflammation in a mouse model of neuronopathic Gaucher disease. Hum. Mol. Genet., 26, 1593-604.
7) 	Shachar, T., Lobianco, C., Recchia, A., Wiessner, C., Raas-Rothschild, A. andFuterman, A.H. (2011) The association between Parkinson's disease and lysosomal storage disorders might not be limited to Gaucher disease. Movement Disorders, 26,1593-604.
8) 	Farfel-Becker, T., Vitner, E.B. and Futerman. A.H. (2011) Animal models for
Gaucher disease research. Disease Models and Mechanisms, 4, 746-752.
9) 	Vitner, E.B., Biton, I., Farfel-Becker, T. and Futerman, A.H. (2012) Contribution of brain inflammation to neuronal cell death in neuronopathic forms ofGaucher disease. Brain, 135, 1724-1735.

Commemorative Symposium

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