Báo cáo khoa học: Missense mutations as a cause of metachromatic leukodystrophy Degradation of arylsulfatase A in the endoplasmic reticulum

Missense Mutations as a Cause of Metachromatic Leukodystrophy: Degradation of Arylsulfatase A in the Endoplasmic Reticulum

Authors: Peter Poeppel, Matthias Habetha, Ana Marcão, Heinrich Büssow, Linda Berna, and Volkmar Gieselmann

Field: Biochemistry / Molecular Biology

Document Summary: This study investigates the molecular mechanisms underlying metachromatic leukodystrophy (MLD), a lysosomal storage disorder caused by arylsulfatase A (ASA) deficiency. The research focuses on how missense mutations in the ASA gene lead to misfolding and subsequent degradation of the enzyme within the endoplasmic reticulum (ER). By analyzing various mutant ASA enzymes using structure-sensitive monoclonal antibodies (mAbs), the study reveals that these mutations often result in folding deficits, leading to retention in the ER. The findings suggest a sequential folding process for ASA, where early-forming epitopes are prerequisites for the maturation of late-forming epitopes. The degradation of ER-retained enzymes is shown to involve the proteasome, and inhibitors of the proteasome can reduce this degradation. However, inhibiting the degradation pathway does not enhance the enzyme’s exit from the ER. The study concludes that while ER-associated degradation plays a significant role in MLD pathogenesis, it may not be a straightforward therapeutic target for enhancing enzyme secretion.

Detailed Table of Contents:

• Introduction to Metachromatic Leukodystrophy and Arylsulfatase A
• Biosynthesis of Wild-Type ASA
• Recognition of Amino Acid-Substituted ASAs by mAbs
• Degradation of Amino Acid-Substituted ASAs via the Proteasome
• Effects of Protease or Phosphatase Inhibitors on the Stability of Mutant ASAs
• Effects of Glycosidase Inhibitors on the Stability of Amino Acid-Substituted ASAs
• Influence of ER α1,2-mannosidase I Inhibition on ER Exit of Amino Acid-Substituted ASAS
• Discussion
• Experimental Procedures
• Acknowledgements
• References