Disease pathogenesis explained by basic science: lysosomal storage diseases as autophagocytic disorders

Area of Science:

• Biochemistry
• Cell Biology
• Genetics

Background:

• Lysosomal storage diseases (LSDs) are characterized by the accumulation of undegraded metabolites within lysosomes, stemming from deficient lysosomal enzyme activity.
• The precise mechanisms linking metabolite accumulation to disease pathology in LSDs remain incompletely understood.
• Defects in sulfatase enzymes contribute to several LSDs, with mutations in the sulfatase modifying factor 1 (SUMF1) gene causing multiple sulfatase deficiency (MSD).

Purpose of the Study:

• To investigate the pathological mechanisms underlying lysosomal storage diseases (LSDs), specifically focusing on the role of autophagy.
• To explore the connection between lysosomal storage, impaired autophagosome-lysosome fusion, and disease progression in mouse models of LSDs.
• To determine if LSDs can be characterized as disorders of autophagy and explore potential therapeutic overlaps with neurodegenerative diseases.

Main Methods:

• Utilized a Sumf1 knockout mouse model to study multiple sulfatase deficiency (MSD), a representative LSD.
• Examined disease pathology in mouse models of MSD and mucopolysaccharidosis (MPS) Type IIIA.
• Quantified and analyzed autophagosome levels and autophagosome-lysosome fusion in affected mouse models compared to wild-type controls.

Main Results:

• Sumf1 knockout mice exhibited phenotypes mirroring human MSD, including lysosomal storage, inflammation, and apoptosis.
• Both MSD and MPS Type IIIA mouse models displayed a significant increase in autophagosome accumulation compared to wild-type mice.
• Evidence suggests impaired autophagosome-lysosome fusion, potentially leading to a functional absence of autophagy in these LSD models.

Conclusions:

• Lysosomal storage diseases may be fundamentally disorders of autophagy due to impaired autophagosome-lysosome fusion.
• The pathological pathways in LSDs share similarities with those in common neurodegenerative diseases.
• Understanding LSDs as autophagy disorders offers new avenues for developing therapeutic strategies for both LSDs and neurodegenerative conditions.