The role of sphingolipids in health and disease
The cell surface is decorated with proteins and lipids that mediate cell-cell contacts and trigger signalling pathways. An important class of lipids enriched at the plasma membrane are glycosphingolipids (GSLs), which play critical roles in membrane structure, host–pathogen interactions, cell–cell recognition and modulation of membrane protein function. Imbalances in GSL homeostasis cause a range of early-onset diseases often involving rapid, fatal neurodegeneration and are implicated in later-onset diseases including cancer and diabetes. While the importance of these lipids is highlighted by the catastrophic diseases caused by GSL imbalances, the molecular details of how they contribute to cellular phenotypes remains poorly understood. I seek to define the molecular mechanisms by which altered GSL metabolism perturbs cellular functions causing disease.
The role of GSLs in neurodegenerative disease
Several monogenic diseases affecting enzymes in the GSL metabolic pathway result in severe, early-onset neurodegenerative diseases. The lysosomal enzyme galactosylceramidase (GALC) degrades the major lipid component of the myelin sheath, galactosylceramide (GalCer), to ceramide and defects in GALC cause the severe neurodegenerative disorder Krabbe disease. Using a combination of biochemical and cellular approaches we have identified specific molecular mechanisms driving disease pathogenesis in GALC variants, highlighting therapeutic opportunities and providing insights into fundamental lipid-processing complexes.
The role of GSLs in immune presentation
Our work on GALC identified the mechanism by which GSLs are presented to lysosomal hydroalses (Hill, et al. Nat. Commun. 2018). This mechanism involves the lipid-binding saposin proteins. Interestingly, saposins also load lipids onto the antigen-presenting molecules CD1 for immune surveillance. Our ongoing work is addressing how saposins transfer GSLs into the lipid-binding groove of CD1.
The role of sphingolipids in host-pathogen pathways
Several pathogens rely on host sphingolipids to promote their virulence. For example, pathogens bind ceramide-rich membrane domains and surface-exposed GSLs during cell invasion, and they manipulate host sphingolipid pathways to promote their intracellular growth. Bacterial hijacking of host pathways has been a long-term interest in the lab and recently we have expanded this work, via a collaborative project, looking at viral hijacking of sphingolipid pathways.
Key papers:
Hay IM, Fearnley GW, Rios P, Köhn M, Sharpe HJ & Deane JE. The receptor PTPRU is a redox sensitive pseudophosphatase. Nat. Commun. In press (2020)
Shamin M, Benedyk TH, Graham SC & Deane JE. The lipid transfer protein Saposin B does not directly bind CD1d for lipid antigen loading. Wellcome Open Res. 2019, 4:117 (2019)
Hill CH, Cook GM, Spratley SJ, Fawke S, Graham SC & Deane JE. The mechanism of glycosphingolipid degradation revealed by a GALC-SapA complex structure. Nat. Commun. 9:151 (2018)
Spratley SJ, Hill CH, Viuff AH, Edgar JR, Skjødt, K & Deane JE. Molecular mechanisms of disease pathogenesis differ in Krabbe disease variants Traffic 17:908-22 (2016)
Hill CH, Viuff AH, Spratley SJ, Salamone S, Christensen SH, Read RJ, Moriarty NW, Jensen HH & Deane JE. Azasugar Inhibitors as Pharmacological Chaperones for Krabbe Disease. Chem. Sci. 6, 3075-3086, DOI: 10.1039/C5SC00754B (2015)
Hill CH, Graham SC, Read RJ & Deane JE. Structural snapshots illustrate the catalytic cycle of β-galactocerebrosidase, the defective enzyme in Krabbe disease. Proc. Natl Acad. Sci. USA. 110, 20479–20484 (2013)
